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OBJECTIVEDespite significant advances in diagnostic and surgical techniques, the surgical management of Chiari malformation type I (CM-I) with associated syringomyelia remains controversial, and the type of surgery performed is surgeon dependent. This study’s goal was to determine the feasibility of a prospective, multicenter, cohort study for CM-I/syringomyelia patients and to provide pilot data that compare posterior fossa decompression and duraplasty (PFDD) with and without tonsillar reduction.METHODSParticipating centers prospectively enrolled children suffering from both CM-I and syringomyelia who were scheduled to undergo surgical decompression. Clinical data were entered into a database preoperatively and at 1–2 weeks, 3–6 months, and 1 year postoperatively. MR images were evaluated by 3 independent, blinded teams of neurosurgeons and neuroradiologists. The primary endpoint was improvement or resolution of the syrinx.RESULTSEight clinical sites were chosen based on the results of a published questionnaire intended to remove geographic and surgeon bias. Data from 68 patients were analyzed after exclusions, and complete clinical and imaging records were obtained for 55 and 58 individuals, respectively. There was strong agreement among the 3 radiology teams, and there was no difference in patient demographics among sites, surgeons, or surgery types. Tonsillar reduction was not associated with > 50% syrinx improvement (RR = 1.22, p = 0.39) or any syrinx improvement (RR = 1.00, p = 0.99). There were no surgical complications.CONCLUSIONSThis study demonstrated the feasibility of a prospective, multicenter surgical trial in CM-I/syringomyelia and provides pilot data indicating no discernible difference in 1-year outcomes between PFDD with and without tonsillar reduction, with power calculations for larger future studies. In addition, the study revealed important technical factors to consider when setting up future trials. The long-term sequelae of tonsillar reduction have not been addressed and would be an important consideration in future investigations.

Background and purpose Cervical spine tapering affects cerebrospinal fluid dynamics. Cervical spine taper ratios derived from anteroposterior diameters reportedly differ between patients with syringomyelia and controls. We attempted to verify the differences in diameter and to show differences in cross-sectional area between syringomyelia and controls. Methods Cervical spine magnetic resonance images in syringomyelia patients (idiopathic or Chiari I related) and control patients were examined. In each subject, the anteroposterior diameter of the spinal canal was measured at each cervical level, and C1–C4, C4–C7, and C1–C7 taper ratios were calculated. Differences in taper ratio between groups were tested for statistical significance with the t-test. Cross-sectional areas of the spinal canal were measured at each cervical spinal level, and tapering was calculated. Results Eighteen patients with idiopathic syringomyelia, 28 with Chiari I, and 29 controls were studied. Chiari and syringomyelia patients had significantly steeper diameter-based taper ratios than controls. The dural sac areas tapered proportionally with the diameter-based taper ratio in all groups. Conclusions Cervical spine anteroposterior diameter tapering and dural sac cross-sectional areas tapering differ between syringomyelia patients and controls.

Purpose How fluid moves during the cardiac cycle within a syrinx may affect its development. We measured syrinx fluid velocities before and after craniovertebral decompression in a patient and simulated syrinx fluid velocities for different heart rates, syrinx sizes and cerebrospinal fluid (CSF) flow velocities in a model of syringomyelia. Materials and methods With phase-contrast magnetic resonance we measured CSF and syrinx fluid velocities in a Chiari patient before and after craniovertebral decompression. With an idealized two-dimensional model of the subarachnoid space (SAS), cord and syrinx, we simulated fluid movement in the SAS and syrinx with the Navier-Stokes equations for different heart rates, inlet velocities and syrinx diameters. Results In the patient, fluid oscillated in the syrinx at 200 to 210 cycles per minute before and after craniovertebral decompression. Velocities peaked at 3.6 and 2.0 cm per second respectively in the SAS and the syrinx before surgery and at 2.7 and 1.5 cm per second after surgery. In the model, syrinx velocity varied between 0.91 and 12.70 cm per second. Increasing CSF inlet velocities from 1.56 to 4.69 cm per second increased peak syrinx fluid velocities in the syrinx by 151% to 299% for the three cycle rates. Increasing cycle rates from 60 to 120 cpm increased peak syrinx velocities by 160% to 312% for the three inlet velocities. Peak velocities changed inconsistently with syrinx size. Conclusions CSF velocity, heart rate and syrinx diameter affect syrinx fluid velocities, but not the frequency of syrinx fluid oscillation. Craniovertebral decompression decreases both CSF and syrinx fluid velocities.

Background Spinal canal tapering, which can be measured as taper ratios, affects cerebrospinal fluid flow dynamics. We calculated the tolerance interval for normal cervical spine taper ratios to facilitate the detection of abnormal taper ratios. Methods We collected a series of patients who had cervical spine magnetic resonance studies reported as normal. We measured anteroposterior diameters of the cervical spine and calculated C1–C4, C4–C7, and C1–C7 taper by standard methodology. We calculated the normal tolerance limits for taper ratios and compared results of this study with data in previous reports on taper ratios. Results We enrolled 78 patients aged 2–55 years. The 99% tolerance limits for the taper ratios for C1–C4, C4–C7, and C1–C7 were −0.31 to +0.09, −0.11 to +0.14, and −0.13 to +0.05 cm/level, respectively. Age and sex were not significant variables for taper ratios. Taper ratios in this study agreed with those reported for controls in previous studies. Patients with syringomyelia in previous reports tended to have taper ratios outside the normal tolerance limits. Conclusion Normal limits of the cervical taper ratios are reported.

Purpose The relationship between syringomyelia and presyrinx, characterized by edema in the spinal cord, has not been firmly established. Patients with syringomyelia have abnormal spinal canal tapering that alters cerebrospinal fluid flow dynamics, but taper ratios in presyrinx have never been reported. We tested the hypothesis that presyrinx patients have abnormal spinal canal tapering. Materials and methods At six medical institutions, investigators searched the PACS system for patients with Chiari I and spinal cord edema unassociated with tumor, trauma, or other evident cause. In each case taper ratios were calculated for C1 to C4 and C4 to C7. In two age- and gender-matched control groups, Chiari I patients with no syringomyelia and patients with normal MR scans, the same measurements were made. Differences between groups were tested for statistical significance with t tests. Results The study enrolled 21 presyrinx patients and equal numbers of matched Chiari I and normal controls. C4 to C7 taper ratios were positive and steeper in presyrinx patients than in the normal controls ( p = 0.04). The upper cervical spine, C1 to C4, tapered negatively in cases and controls without significant differences between the groups. The difference in degree of tonsillar herniation was statistically significant between presyrinx patients and Chiari I controls ( p = 0.01). Conclusions Presyrinx patients have greater than normal positive tapering in the lower cervical spine and greater degree of tonsillar herniation than the controls.

The cervical spine in Chiari I patient with syringomyelia has significantly different anteroposterior diameters than it does in Chiari I patients without syringomyelia. We tested the hypothesis that patients with idiopathic syringomyelia (IS) also have abnormal cervical spinal canal diameters. The finding in both groups may relate to the pathogenesis of syringomyelia. Local institutional review boards approved this retrospective study. Patients with IS were compared to age-matched controls with normal sagittal spine MR. All subjects had T1-weighted spin-echo (500/20) and T2-weighted fast spin-echo (2000/90) sagittal cervical spine images at 1.5 T. Readers blinded to demographic data and study hypothesis measured anteroposterior diameters at each cervical level. The spinal canal diameters were compared with a Mann-Whitney U test. The overall difference was assessed with a Friedman test. Seventeen subjects were read by two reviewers to assess inter-rater reliability. Fifty IS patients with 50 age-matched controls were studied. IS subjects had one or more syrinxes varying from 1 to 19 spinal segments. Spinal canal diameters narrowed from C1 to C3 and then enlarged from C5 to C7 in both groups. Diameters from C2 to C4 were narrower in the IS group (p

Background Investigators use phase-contrast magnetic resonance (PC-MR) and computational fluid dynamics (CFD) to assess cerebrospinal fluid dynamics. We compared qualitative and quantitative results from the two methods. Methods Four volunteers were imaged with a heavily T2-weighted volume gradient echo scan of the brain and cervical spine at 3T and with PC-MR. Velocities were calculated from PC-MR for each phase in the cardiac cycle. Mean pressure gradients in the PC-MR acquisition through the cardiac cycle were calculated with the Navier-Stokes equations. Volumetric MR images of the brain and upper spine were segmented and converted to meshes. Models of the subarachnoid space were created from volume images with the Vascular Modeling Toolkit. CFD simulations were performed with a previously verified flow solver. The flow patterns, velocities and pressures were compared in PC-MR and CFD flow images. Results PC-MR images consistently revealed more inhomogeneous flow patterns than CFD, especially in the anterolateral subarachnoid space where spinal nerve roots are located. On average, peak systolic and diastolic velocities in PC-MR exceeded those in CFD by 31% and 41%, respectively. On average, systolic and diastolic pressure gradients calculated from PC-MR exceeded those of CFD by 11% and 39%, respectively. Conclusions PC-MR shows local flow disturbances that are not evident in typical CFD. The velocities and pressure gradients calculated from PC-MR are systematically larger than those calculated from CFD.

SUMMARY: Flow imaging with cardiac-gated phase-contrast MR has applications in the management of neurologic disorders. Together with computational fluid dynamics, phase-contrast MR has advanced our understanding of spinal CSF flow. Phase-contrast MR is used to evaluate patients with Chiari I malformation who are candidates for surgical treatment. In theory, abnormal CSF flow resulting from the abnormal tonsil position causes syringomyelia and other neurologic signs and symptoms in patients with Chiari I. CSF flow imaging also has research applications in syringomyelia and spinal stenosis. To optimize MR acquisition and interpretation, neuroradiologists must have familiarity with healthy and pathologic patterns of CSF flow. The purpose of this review is to update concepts of CSF flow that are important for the practice of flow imaging in the spine.

The flow of cerebrospinal fluid (CSF) in a patient-specific model of the subarachnoid space in a Chiari I patient was investigated using numerical simulations. The pulsating CSF flow was modeled using a time-varying velocity pulse based on peak velocity measurements (diastole and systole) derived from a selection of patients with Chiari I malformation. The present study introduces the general definition of the Reynolds number to provide a measure of CSF flow instability to give an estimate of the possibility of turbulence occurring in CSF flow. This was motivated by the fact that the combination of pulsating flow and the geometric complexity of the spinal canal may result in local Reynolds numbers that are significantly higher than the commonly used global measure such that flow instabilities may develop into turbulent flow in these regions. The local Reynolds number was used in combination with derived statistics to characterize the flow. The results revealed the existence of both local unstable regions and local regions with velocity fluctuations similar in magnitude to what is observed in fully turbulent flows. The results also indicated that the fluctuations were not self-sustained turbulence, but rather flow instabilities that may develop into turbulence. The case considered was therefore believed to represent a CSF flow close to transition.

Computational studies are used to demonstrate the effect of oscillating CSF flow on pressures within the spinal cord. We tested the hypothesis that the central canal in the spinal cord affects spinal cord pressure gradients resulting from oscillatory CSF flow. Two computational models of the spinal cord were created with the same dimensions. Model 1 had a homogeneous porous structure. Model 2 had the same structure with the addition of a central fluid filled space, representing the central canal of the cord. We simulated oscillatory flow in the fluid space using standard computational fluid dynamics tools. For all phases of the CSF flow cycle and for specific projections through the model we calculated pressure gradients and fluid movement in the cord models. Pressures in the models varied through the flow cycle. Model 1 had linearly varying pressure along its long axis that varied with the cycle and had no pressure gradients across the cord. Model 2 had nonlinear varying pressure along its long axis varying with the time in the cycle and had transient centrifugal and centripetal pressure gradients with a central fluid space. The radial pressures varied linearly with distance from the fluid space. Centrifugal and centripetal pressure gradients resulted in radially directed fluid flow in the cord. The central canal within the spinal cord alters the pressure fields occurring during oscillatory CSF flow and creates centrifugal and centripetal fluid flux in the cord.

According to some theories, obstruction of CSF flow produces a pressure drop in the subarachnoid space in accordance with the Bernoulli theorem that explains the development of syringomyelia below the obstruction. However, Bernoulli's principle applies to inviscid stationary flow unlike CSF flow. Therefore, we performed a series of computational experiments to investigate the relationship between pressure drop, flow velocities, and obstructions under physiologic conditions. We created geometric models with dimensions approximating the spinal subarachnoid space with varying degrees of obstruction. Pressures and velocities for constant and oscillatory flow of a viscid fluid were calculated with the Navier-Stokes equations. Pressure and velocity along the length of the models were also calculated by the Bernoulli equation and compared with the results from the Navier-Stokes equations. In the models, fluid velocities and pressure gradients were approximately inversely proportional to the percentage of the channel that remained open. Pressure gradients increased minimally with 35% obstruction and with factors 1.4, 2.2 and 5.0 respectively with 60, 75 and 85% obstruction. Bernoulli's law underestimated pressure changes by at least a factor 2 and predicted a pressure increase downstream of the obstruction, which does not occur. For oscillatory flow the phase difference between pressure maxima and velocity maxima changed with the degree of obstruction. Inertia and viscosity which are not factored into the Bernoulli equation affect CSF flow. Obstruction of CSF flow in the cervical spinal canal increases pressure gradients and velocities and decreases the phase lag between pressure and velocity.

Chiari I patients have increased CSF velocities in the foramen magnum due hypothetically to increased pressure gradients or reduced flow resistance. We calculated flow resistance in the cervical spinal canal in a group of subjects with and without the Chiari malformation. Eight subjects including healthy volunteers and Chiari I patients were studied. From 3D high resolution MR images of the cervical spine mathematical models of the subarachnoid spaces were created by means of standard programs for segmentation and discretization. Oscillatory flow through the subarachnoid space was simulated. Cross-sectional area of the subarachnoid space was computed at each level from C1 through C4 and the length of this spinal canal segment was measured. Peak caudad CSF flow velocity at each level was plotted against cross-section area. CSF volumetric flux and resistance were calculated for each subject. The correlation between velocity and resistance was calculated. In all subjects, peak velocities increased progressively from C1 to C4 by 0.6 to 0.7 cm/s per level. Spinal canal areas diminished from C1 to C5 in each subject at a rate of 0.25 to 0.29 cm2per level. Resistance averaged 4.3 pascal/ml/s in the eight subjects; 3.8 pascal/ml/s in patients with tonsilar herniation and 6.0 pascal/ml/s in volunteers. Velocity correlated inversely with resistance (R2= 0.6). CSF velocities correlated inversely with the flow resistance in the upper cervical spinal canal. Resistance tends to be lower in Chiari I patients than in healthy volunteers.

This chapter uses magnetic resonance imaging phase-contrast cerebrospinal fluid (CSF) flow measurements to predict which clinical normal-pressure hydrocephalus (NPH) patients will respond to shunting as well as which patients with Chiari I are likely to develop symptoms of syringomyelia. Symptomatic NPH patients with CSF flow (measured as the aqueductal CSF stroke volume) which is shown to be hyperdynamic (defined as twice normal) are quite likely to respond to ventriculoperitoneal shunting. The hyperdynamic CSF flow results from normal systolic brain expansion compressing the enlarged ventricles. When atrophy occurs, there is less brain expansion, decreased aqueductal CSF flow, and less likelihood of responding to shunting. It appears that NPH is a “two-hit” disease, starting as benign external hydrocephalus in infancy, followed by deep white-matter ischemia in late adulthood, which causes increased resistance to CSF outflow through the extracellular space of the brain. Using computational flow dynamics (CFD), CSF flow can be modeled at the foramen magnum and in the upper cervical spine. As in the case of NPH, hyperdynamic CSF flow appears to cause the signs and symptoms in Chiari I and can provide an additional indication for surgical decompression. CFD can also predict CSF pressures over the cardiac cycle. It has been hypothesized that elevated pressure pulses may be a significant etiologic factor in some cases of syringomyelia.

MR imaging of the lumbar spine often is requested to identify the cause of back or radicular pain. Official reports of lumbar spine images tend to focus on changes in the disk margin that may cause nerve root compression. The potential role of the dark disk, in back pain has not been adequately emphasized. The purpose of this review is to discuss the dark disk that has not produced nerve root compression. On T2-weighted images, a disk that has diminished signal intensity is called a dark disk or a dehydrated disk. It corresponds to a stage III disk in the Pfirrmann or the Thompson scale. Such a disk has specific morphologic, chemical and biomechanical properties, which will be reviewed in this presentation. The goal is to suggest the clinical significance of finding a dark disk on an MR image.

BACKGROUND AND PURPOSE: T2 relaxation times provide a continuous measure of changes in intervertebral disk biochemistry. The purpose of this study was to correlate T2 relaxation times in lumbar disks with patient age and stage of degeneration. MATERIALS AND METHODS: Sagittal T1- and T2-weighted images and axial images were acquired in 20 patients referred for MR imaging for back pain or radiculopathy. Two readers inspected these images and assigned a Pfirrmann grade to each disk. An additional sagittal multiecho FSE image sequence was obtained, and T2 relaxation times were calculated for a each lumbar disk. T2 relaxation times were correlated with Pfirrmann grade. T2 relaxation times in nondegenerated disks were correlated with patient age. Statistical significance was tested by ANOVA, ad hoc tests, and Pearson coefficients. RESULTS: T2 relaxation times were calculated for 95 lumbar disks in 19 patients and discarded for 5 disks in 1 patient due to motion artifacts. Forty-four disks were classified as Pfirrmann grade II; 34, as grade III; 14, as grade IV; and 3, as grade V. Mean T2 relaxation times of the central region decreased from 108 ms for grade II to 53 ms for grade IV disks. T2 relaxation times correlated significantly with Pfirrmann grade. For grade II disks, T2 relaxation times of the central region decreased significantly from an average of 132 ms for patients in their 20s to 86 ms for those in their 60s. CONCLUSIONS: T2 relaxation times in lumbar disks correlate with stage of degeneration and patient age.

PCMR, widely used for the evaluation of blood flow, has been adopted for the assessment of cerebrospinal fluid flow in a variety of disorders. The purpose of this study was to evaluate the accuracy and reproducibility of 2 fast PCMR techniques for measuring CSF flow.Velocities were calculated from RPC and CPC images of fluid flowing in a tube at a constant velocity. Error and the COV were computed for average and peak velocities. Additionally, measurements of sinusoidally fluctuating flow and of CSF flow in 5 healthy volunteers were acquired with the RPC and CPC acquisitions.For constant velocity experiments, error for the RPC and CPC acquisitions averaged +1.15% and +8.91% and COVs averaged 1.29% and 3.01%, respectively. For peak velocities ofor=12.6 cm/s, error with RPC or CPC ranged from -33.3% to -36.9% and COVs were 0%-4% for RPC and 1%-7% for CPC. For peak velocities ofor=6.4 cm/s, RPC and CPC overestimated velocity by250%. For fluctuating flow, both acquisitions showed similar flow patterns. In volunteer studies, peak systolic and diastolic velocities were not significantly different.The RPC and CPC sequences measure velocities on the order of CSF flow with an average error ofor=9%. The 2 techniques significantly overestimate peak velocities6.4 cm/s, with maximum errors of 209% and 276% and maximum COVs of 100% and 73% for the RPC and CPC sequences, respectively. Measurements of CSF velocities in human volunteers and of sinusoidally fluctuating phantom velocities did not differ significantly between the 2 techniques.

Study design Reliability study comparing computed tomography (CT) to biomechanics. Objective To measure the accuracy and precision of such measurements in comparison with a standard method. Summary of background data Rotations of lumbar spinal motion segments can be measured with dynamic CT imaging. This may be a useful tool to measure intersegmental motion. Validation of its use is lacking. Methods Human cadaveric lumbar spines were fixed in a rigid rotation device and rotated, whereas rotation at each level was measured with extensiometers. Rotation at each level was calculated as a percent of total rotation. The spines were placed in a CT scanner and imaged after rotation of the spine in each direction. The percent of total rotation that occurred at each level was calculated with a software program. Accuracy of the CT method was calculated as the average difference between methods. Precision was measured as the standard deviation of the CT measurement. Biomechanical testing and CT were repeated after the posterior anulus fibrosus at L3-L4 was incised with a scalpel. The power of the CT method to detect a change in rotation was tested by calculating the difference between the pre- and postsurgery rotation at L3-L4 and testing it for significance with a Student t test of paired samples. Results Differences between CT and biomechanical measurements averaged 0.2%. Precision was 6.0% (Table 1). Postanular injury, percent rotation at the L3-L4 level increased, whereas it decreased at the other 4 levels. The change at L3-L4 was statistically significant (P = 0.047). Conclusion Dynamic CT measures vertebral rotations sufficiently accurately to study the effect of a radial tear on axial rotation can.

BACKGROUND AND PURPOSE:Stenosis of the carotid artery may be a cause of reduced cognitive performance that can be ameliorated with placement of a stent. The goal of this study was to measure cognitive performance and speed of psychomotor performance prospectively before and after carotid stent placement. MATERIALS AND METHODS:Patients referred for stent placement for a unilateral carotid artery stenosis were enrolled in the study. Neuropsychologic testing was performed with a Mini-Mental State Examination, an extended mental status examination, a subjective cognitive status measure, and a psychomotor performance test for speed. The severity of the stenosis was measured on angiograms performed before stent placement. Three months after stent placement, CT angiograms were performed and the neuropsychologic testing was repeated. Differences in neuropsychologic test scores before and after stent placement were calculated and tested for significance with a Student t test. RESULTS:Seventeen patients with a single unilateral carotid stenosis of more than 50% completed the study. Stenosis of the carotid artery averaged 80% before treatment and 18% after treatment. After stenting, the scores from the extended mental status examination improved significantly. The scores from the subjective cognitive status measure also improved. No significant change was noted in the scores from the Mini-Mental State Examination or in the speed of psychomotor performance. CONCLUSION:Carotid stent placement in patients with a unilateral stenosis of the carotid artery resulted in significant improvement in cognitive test scores in this highly selected patient group. Further studies are needed to confirm these preliminary observations.

To determine the sensitivity and specificity of cerebrospinal fluid (CSF) flow imaging in distinguishing between patients with symptomatic Chiari I malformation and those with asymptomatic tonsilar ectopia by using a neurosurgeon's overall clinical determination as the reference standard.The institutional review board of the University of Wisconsin Hospital and Clinics approved our HIPAA-compliant retrospective study and granted a waiver for informed consent. Seventeen patients (five male, 12 female; aged 4-43 years) with tonsils extending more than 5 mm below the foramen magnum were classified by the neurosurgeon as symptomatic for Chiari I malformation or asymptomatic for tonsilar ectopia. The CSF flow images of the two groups were read independently in blinded fashion by four neuroradiologists. Reader agreement was calculated as percentage of readings in each patient that agreed with the neurosurgeon's classification. Sensitivity and specificity were respectively calculated as the percentage of abnormal readings in symptomatic patients and the percentage of normal readings in asymptomatic patients.Of 17 patients, nine were classified by the neurosurgeon as symptomatic Chiari I malformation and eight as asymptomatic tonsilar ectopia. Agreement between pairs of readers was 63%-44%. For sagittal and transverse images, reader sensitivity for finding abnormal flow in symptomatic Chiari I malformation patients averaged 76% and specificity for normal flow in patients with asymptomatic tonsilar ectopia averaged 62%. The number of positive readings in the symptomatic patient group was significantly greater than that in the asymptomatic group (P.02).Readers detected an abnormal CSF flow pattern significantly more often in patients with symptomatic Chiari I malformation than in patients with asymptomatic tonsilar ectopia.

Cardiac-gated Phase Contrast MR (PC MR) is used in the evaluation of the Chiari I malformation to assess the CSF flow though the foramen magnum. Images may show reduced CSF flow posterior to the spinal cord in patients with a Chiari I malformation. MR images however do not differentiate with sufficient accuracy between symptomatic and asymptomatic Chiari I malformations. In the presence of the Chiari I malformation, CSF velocities are elevated. Measuring the velocity of flow and determining the degree of inhomogeneity in CSF flow aid in the detection of clinically significant flow abnormalities.

One possible cause of back pain in patients with intervertebral disk degeneration is decreased stability of the motion segment. Axial rotations between lumbar spinal vertebrae can be measured noninvasively with CT. We tested the hypothesis that larger axial rotations are found in motion segments with disks that test positive for concordant pain, which is considered by some investigators to be a reasonable, accurate predictor of spinal instability.Between October 2002 and March 2004, all patients undergoing discography were evaluated for inclusion in the study, with the approval of the institutional review board. All patients in whom concordant pain was detected at discography were enrolled in the study. The patients were placed supine in the CT scanner on a table that rotated the pelvis 8 degrees clockwise and then counterclockwise with respect to the thorax. CT images were obtained with the patient in the two positions of rotation. An automated program calculated the amount of rotation between each lumbar vertebra as a result of the table rotations. Rotations were stratified by disk level and by disk classification (concordant pain, nonconcordant pain, no significant pain).We recorded the axial rotations of 94 disks in 16 consecutive patients (10 women, six men; age range, 26-53 years) after two disks were excluded because of a previous fusion. There were 68 normal disks by MRI and discography, six disks with nonconcordant pain, and 20 disks with concordant pain. Rotation averaged 0.6 degrees for the normal disks, 1.4 degrees for disks with nonconcordant pain, and 1.8 degrees for disks with concordant pain. The differences were significant (analysis of variance, p0.001). Disks at L3-L4 with concordant pain rotated on average 1.2 degrees , whereas disks classified as normal or nonconcordant pain rotated on average 0.7 degrees (significant at p = 0.005). Disks at L4-L5 with concordant pain rotated on average 1.9 degrees , and those without concordant pain rotated on average 1.4 degrees (significant at p = 0.05). Disks with concordant pain at L5-S1 had an average rotation of 2.2 degrees , whereas disks without concordant pain had an average rotation of 1.5 degrees (marginally significant difference at p = 0.07).Concordant pain at discography predicts increased axial rotation at a lumbar disk level.

The Hooper Visual Organization Test (VOT), a commonly applied neuropsychological test of visual spatial ability, is used for assessing patients with suspected right hemisphere, or parietal lobe involvement. A controversy has developed over whether the inferences of this test metric can be assumed to involve global, lateralized, or regional functionality. In this study, the characteristic visual organization and object naming aspects of the VOT task presentation were adapted to a functional MR imaging (fMRI) paradigm to probe the neuroanatomic correlates of this neuropsychological test. Whole brain fMRI mapping results are reported on a cohort of normal subjects. Bilateral fMRI responses were found predominantly in the posterior brain, in regions of superior parietal lobules, ventral temporal-occipital cortex, and posterior visual association areas, and to a lesser extent, the frontal eye fields bilaterally, and left dorsolateral prefrontal cortex. The results indicate a general brain region or network in which VOT impairment, due to its visuospatial and object identification demands, is possible to be detected. Discussion is made of interpretive limitations when adapting neuropsychological tests to fMRI analysis. (JINS, 2004, 10, 939–947.)

To measure spatial and temporal variations in cerebrospinal fluid (CSF) flow through the cardiac cycle and throughout the subarachnoid space at magnetic resonance (MR) imaging in volunteer subjects with no known neurologic or spinal problems and in patients with Chiari I malformation.A cardiac-gated phase-contrast MR technique was used to acquire images at 14 time points evenly spaced through the cardiac cycle in 10 volunteers and eight patients with Chiari I malformation. Instantaneous CSF velocities were displayed as temporal and spatial plots and examined for homogeneity, differences between flow anterior and flow posterior to the spinal cord, synchronous bidirectional flow, and equivalence of the caudad flow and craniad flow in each voxel. Indexes for flow homogeneity, synchronous bidirectional flow, and preferential flow direction were calculated, and differences between the patient and volunteer groups were tested for significance with a t test of the means.In volunteers, diastolic velocity peaked in two regions in the anterior paramedial subarachnoid space. Patients had greater inhomogeneity of flow than volunteers. They had substantially increased flow (jets) in the anterior paramedial locations. Synchronous bidirectional flow was seen in six of the patients and in none of the volunteers. Cephalad flow in the jets or nodes (P =.05), proportion of cephalad and caudad flow in the anterior compartment (P.005 for both), and the fraction of voxels with flow directionality (P =.03) differed significantly between patients and volunteers.CSF flow in symptomatic patients with Chiari I malformation, unlike that in volunteer subjects, is characterized by flow jets, regions with a preponderance of flow in one direction, and synchronous bidirectional flow.

Clinical applications of functional MR imaging include mapping of brain functions in relationship to intracranial tumors, seizure foci, or vascular malformations to determine the risk for performing surgical excision, the need for intraoperative mapping during excision, and selecting the optimal surgical approach to a lesion. A variety of paradigms are used to produce a blood-oxygen-level-dependent response in various brain regions, which can be identified with functional MR imaging. The paradigms used include active motor, language, or cognitive tasks, and passive tactile, auditory, or visual stimuli. Activation usually indicates the location of eloquent cortex. Lack of function in a region cannot be assumed when functional MR imaging shows absence of activation within the region.

An automated method for determination of arterial input function (AIF) for rapid determination of cerebral perfusion with dynamic susceptibility contrast magnetic resonance (MR) imaging was derived. In 100 patients, the automated method was used to create images of relative blood flow, relative cerebral blood volume, and mean transit time. In 20 patients, the voxel chosen with the automated AIF correlated with a large cerebral artery and exhibited less partial-volume averaging when compared with an AIF chosen manually. It is possible to reliably determine the AIF at dynamic susceptibility contrast MR imaging and eliminate the need for operator input and lengthy postprocessing.

Object. Injury to the supplementary motor area (SMA) is thought to be responsible for transient motor and speech deficits following resection of tumors involving the medial frontal lobe. Because direct intraoperative localization of SMA is difficult, the authors hypothesized that functional magnetic resonance (fMR) imaging might be useful in predicting the risk of postoperative deficits in patients who undergo resection of tumors in this region. Methods. Twelve patients who had undergone fMR imaging mapping while performing speech and motor tasks prior to excision of their tumor, that is, based on anatomical landmarks involving the SMA, were included in this study. The distance between the edge of the tumor and the center of SMA activation was measured and was correlated with the risk of incurring postoperative neurological deficits. In every patient, SMA activation was noted in the superior frontal gyrus on preoperative fMR imaging. Two speech and two motor deficits typical of SMA injury were observed in three of the 12 patients. The two speech deficits occurred in patients with tumors involving the dominant hemisphere, whereas one of the motor deficits occurred in a patient with a tumor in the nondominant hemisphere. The risk of developing a postoperative speech or motor deficit was 100% when the distance between the SMA and the tumor was 5 mm or less. When the distance between SMA activation and the lesion was greater than 5 mm, the risk of developing a motor or a speech deficit was 0% (p = 0.0007). Conclusions. Early data from this study indicated that fMR imaging might be useful in localizing the SMA and in determining the risk of postoperative deficits in patients who undergo resection of tumors located in the medial frontal lobe.

Object The effect of craniovertebral decompression surgery on CSF flow dynamics in patients with Chiari malformation Type I (CM-I) has been incompletely characterized. The authors used computational fluid dynamics to calculate the effect of decompression surgery on CSF flow dynamics in the posterior fossa and upper cervical spinal canal. Methods Oscillatory flow was simulated in idealized 3D models of the normal adult and the CM-I subarachnoid spaces (both previously described) and in 3 models of CM-I post–craniovertebral decompressions. The 3 postoperative models were created from the CM model by virtually modifying the CM model subarachnoid space to simulate surgical decompressions of different magnitudes. Velocities and pressures were computed with the Navier-Stokes equations in Star-CD for multiple cycles of CSF flow oscillating at 80 cycles/min. Pressure gradients and velocities were compared for 8 levels extending from the posterior fossa to the C3–4 level. Relative pressures and peak velocities were plotted by level from the posterior fossa to C3–4. The heterogeneity of flow velocity distribution around the spinal cord was compared between models. Results Peak systolic velocities were generally lower in the postoperative models than in the preoperative CM model. With the 2 larger surgical defects, peak systolic velocities were brought closer to normal model velocities (equal values at C-3 and C-4) than with the smallest surgical defect. For the smallest defect, peak velocities were decreased, but not to levels in the normal model. In the postoperative models, heterogeneity in flow velocity distribution around the spinal cord increased from normal model levels as the degree of decompression increased. Pressures in the 5 models differed in magnitude and in pattern. Pressure gradients along the spinal canal in the normal and CM models were nonlinear, with steeper gradients below C3–4 than above. The CM model had a steeper pressure gradient than the normal model above C3–4 and the same gradient below. The postoperative models had lower pressure gradients than the CM model above C2–3. The most conservative decompression had lower pressure gradients than the normal model above C2–3. The two larger decompression defects had CSF pressure gradients below those in the normal model above C2–3. These 2 models had a less steep gradient above C-3 and a steeper gradient below. Conclusions In computer simulations, craniovertebral surgical defects generally diminished CSF velocities and CSF pressures.

STUDY DESIGN A biomechanical and anatomic study with human cadaveric lumbar spine. OBJECTIVES The purpose of this study is to examine the morphologic changes in the intervertebral foramen during flexion, extension, lateral bending, and axial rotation of the lumbar spine and to correlate these changes with the flexibility of the spinal motion segments. SUMMARY OF BACKGROUND DATA Previous studies showed morphologic changes in the intervertebral foramen during flexion and extension; however, those changes during lateral bending and axial rotation were not well known. METHODS There were 81 motion segments obtained from 39 human cadaveric lumbar spines (mean age 69 years). The motion segments were imaged with CT scanner with 1-mm thick consecutive sections. For biomechanical testing each motion segment was applied with incremental pure moments of flexion, extension, lateral bending, and axial rotation. Rotational movements of the motion segment were measured using VICON cameras. After application of the last load, the specimens were frozen under load, and then CT was performed with the same technique described above. Six parameters of the intervertebral foramen were measured, including foraminal width (maximum and minimum), foraminal height, disc bulging, thickness of ligamentum flavum, and cross-sectional area of the foramen. RESULTS Flexion increased the foraminal width (maximum and minimum), height, and area significantly while significantly decreasing the disc bulging and thickness of ligamentum flavum (P < 0.05). However, extension decreased the foraminal width (maximum and minimum), height, and area significantly. Lateral bending significantly decreased the foraminal width (maximum and minimum), height, and area at the bending side, whereas lateral bending significantly increased the foraminal width (minimum), height, and area at the opposite side of bending. Likewise, axial rotation decreased the foraminal width (minimum) and area at the rotation side significantly while significantly increasing the foraminal height and foraminal area at the opposite side. The percent change in the foraminal area was found significantly correlated with the amount of segmental spinal motion except for the extension motion. CONCLUSIONS This study showed that the intervertebral foramen of the lumbar spine changed significantly not only on flexion-extension but also on lateral bending and axial rotation. The percent change in cross-sectional foraminal area was correlated with the amount of segmental motion except for extension motions. Further studies are needed to assess the morphologic changes in the intervertebral foramen in vivo and to correlate clinically.

STUDY DESIGN A biomechanical and imaging study of human cadaveric spinal motion segments. OBJECTIVE To investigate the effect of both disc degeneration and facet joint osteoarthritis on lumbar segmental motion. SUMMARY OF BACKGROUND DATA Spinal degeneration includes the osteoarthritic changes of the facet joint as well as disc degeneration. Disc degeneration has been reported to be associated with spinal motion. The association of facet joint osteoarthritis with lumbar segmental motion characteristics and the combined influence of disc degeneration and facet osteoarthritis has not yet been investigated. METHODS A total of 110 lumbar motion segments (52 female, 58 male) from 44 human lumbar spines were studied (mean age = 69 years). Magnetic resonance images were used to assess the disc degeneration from Grade I (normal) to Grade V (advanced) and the osteoarthritic changes in the facet joints in terms of cartilage degeneration, subchondral sclerosis, and osteophytes. Disc height, endplate size, and facet joint orientation and width also were measured from the computed tomographic images. Rotational movements of the motion segment in response to the flexion, extension, lateral bending, and axial rotational moments were measured using a three-dimensional motion analysis system. RESULTS Female motion segments showed significantly greater motion (lateral bending: P < 0. 001, flexion: P < 0.01, extension: P < 0.05) and smaller endplate size (P < 0.001) than male ones. The segmental motion increased with increasing severity of disc degeneration up to Grade IV, but decreased in both genders when the disc degeneration advanced to Grade V. In male segments, the disc degeneration-related motion changes were significant in axial rotation (P < 0.001), lateral bending (P < 0.05), and flexion (P < 0.05), whereas female segments showed significant changes only in axial rotation (P < 0.001). With cartilage degeneration of the facet joints, the axial rotational motion increased, whereas the lateral bending and flexion motion decreased in female segments. In male segments, however, motion in all directions increased with Grade 3 cartilage degeneration and decreased with Grade 4 cartilage degeneration. Subchondral sclerosis significantly decreased the motion (female: axial rotation, P < 0. 05; extension, P < 0.05 vs.- male:flexion,P < 0.05). Severity of osteophytes had no significant association with the segmental motion. CONCLUSION Axial rotational motion was most affected by disc degeneration, and the effects of disc degeneration on the motion were similar between genders. Facet joint osteoarthritis also affected segmental motion, and the influence differed for male and female spines. Further studies are needed to clarify whether the degenerative process of facet joint osteoarthritis differs between genders and how facet joint osteoarthritis affects the stability of the spinal motion segment.

A new approach in studying interregional functional connectivity using functional magnetic resonance imaging (fMRI) is presented. Functional connectivity may be detected by means of cross correlating time course data from functionally related brain regions. These data exhibit high temporal coherence of low frequency fluctuations due to synchronized blood flow changes. In the past, this fMRI technique for studying functional connectivity has been applied to subjects that performed no prescribed task (“resting” state). This paper presents the results of applying the same method to task-related activation datasets. Functional connectivity analysis is first performed in areas not involved with the task. Then a method is devised to remove the effects of activation from the data using independent component analysis (ICA) and functional connectivity analysis is repeated. Functional connectivity, which is demonstrated in the “resting brain,” is not affected by tasks which activate unrelated brain regions. In addition, ICA effectively removes activation from the data and may allow us to study functional connectivity even in the activated regions.

The objective of the two pivotal phase 3 studies was to evaluate the safety and efficacy of OptiMARK (Gd-DTPA-bis(methoxyethylamide) [Gd-DTPA-BMEA]) compared with Magnevist (Gd-DTPA) in magnetic resonance imaging of the central nervous system.Two multicenter, randomized, double-blind, parallel group studies were conducted in 395 patients with known or suspected central nervous system pathology. Subjects were randomized to receive a single 0.1 mmol/kg intravenous injection of either Gd-DTPA-BMEA or Gd-DTPA. The safety of Gd-DTPA-BMEA and Gd-DTPA was monitored for up to 72 hours after study drug administration. Precontrast and postcontrast administration magnetic resonance scans were acquired using identical imaging planes and techniques.No deaths or unexpected adverse events were reported in either group. A comparison of adverse events by intensity and relation demonstrated no statistically significant differences between the two groups. Gd-DTPA-BMEA and Gd-DTPA were equivalent with respect to confidence in diagnosis, conspicuity, and border delineation.Gd-DTPA-BMEA and Gd-DTPA demonstrated comparable efficacy profiles, and the safety profiles were considered similar.

Study design Biomechanical and anatomic study of human cadaveric spinal motion segments. Objectives To measure the stiffness of spinal motion segments by disc type and by load type (flexion, extension, axial rotation, or lateral bending). To compare stiffness in motion segments with and without a high-intensity zone or radial tear in the anulus fibrosus. Summary of background data The high-intensity zone, that is a linear zone of high-intensity on T2-weighted magnetic resonance images corresponding to a radial tear in the anulus fibrosus, is a marker for a painful disc at discography. The high-intensity zone is hypothetically associated with diminished stiffness of the motion segment. Methods Human cadaveric lumbar spinal motion segments with normal disc morphology or a high-intensity zone of the anulus fibrosus were selected on the basis of magnetic resonance imaging. The motion segments were subjected to incremental flexion, extension, rotation, and lateral bending torques. Rotation was measured with a kinematic system. Torque-rotation curves and stiffness were calculated for each motion segment and for each torque. The motion segments were sectioned on a cryomicrotome to verify the disc morphology as normal or as that of a radial tear. Results In four motion segments with normal discs, stiffness was greater in axial rotation (8.4 Nm/degree) than in lateral bending (2.3 Nm/degree), flexion (1.8 Nm/degree), or extension (2.6 Nm/degree). In 16 motion segments with a high-intensity zone, stiffness was 2.4 Nm/degree in axial rotation, and less severely reduced in lateral bending, flexion, and extension. Stiffness in motion segments with a high-intensity zone was significantly less with smaller than with larger axial rotation loads. Conclusions The presence of a high-intensity zone in the intervertebral disc is associated with reduced stiffness of motion segments. The reduction is greater in axial rotation than in other torques. The reduction is more in smaller than in larger axial torques.

Purpose: Our goal was to determine the distribution of auditory and language cortex activation in response to acoustic echo planar scanner noise with functional MRI (fMRI). Method: Acoustic scanner noise and spoken text, reproduced on high output cassette tape, were separately delivered at equivalent intensities to six normal hearing adult volunteers through earphones during fMRI data acquisition. In nine other subjects, taped scanner noise was delivered in five successive iterations of the task to assess the consistency of cortical activation to the noise stimulus. Gyri of the auditory and language system were divided into 10 different subregions for analysis of cortical activation. The number of activated pixels and proportion of volunteers activating each cortical subregion were determined using a cross-correlation analysis. Results: Cortical activation to taped acoustic scanner noise was present within the transverse temporal gyrus (primary auditory cortex) in all subjects, but activation was highly variable between subjects in auditory association and language relevant cortex. Auditory association cortex activation was seen in the planum polari, planum tempo-rali, and middle temporal gyrus/superior temporal sulcus regions in one-half to two-thirds of the volunteers. There was no significant difference in the distribution of cortical activation within individual subjects across five successive iterations of the scanner noise task. Listening to spoken text consistently activated primary and association auditory cortex bilaterally as well as language relevant cortex in some cases. The mean number of activated pixels was significantly greater for text listening than acoustic scanner noise in auditory association and language relevant cortical subregions (p < 0.01), although the distribution of activity was similar between the two tasks. Conclusion: This preliminary investigation suggests that the complex sounds produced by the echo planar pulse sequence can activate relatively large regions of auditory and language cortex bilaterally, with the extent of activation outside the primary auditory cortex being variable between subjects. However, the distribution of activation within individual subjects was relatively constant across several iterations of the scanner noise stimulus.

STUDY DESIGN A comparison of contrast enhancement in the intervertebral disc from two magnetic resonance imaging contrast media in experimental animals. OBJECTIVES To test the effect of molecular weight on the diffusion of ionic contrast media into the intervertebral disc. SUMMARY OF BACKGROUND DATA Intravenously administered gadopentetate diffuses similarly into the fibrocartilage of intervertebral discs and herniated disc fragments. Differentiation between recurrent disc fragments and scar tissue via magnetic resonance imaging is optimized by using contrast media, which result in different contrast enhancement of these two tissues. Contrast media of higher molecular weight diffuse more slowly into cartilage; hypothetically, therefore, such media will produce better contrast between scar tissue and recurrent disc fragments. METHODS Gadopentetate (molecular weight 546) or gadolinium-polylysine (molecular weight 40,000) was injected intravenously into rabbits. The signal intensities of intervertebral disc and muscle tissue were recorded by magnetic resonance imaging at baseline and at pre-determined intervals for 2 hours after injection of the contrast medium. Contrast enhancement in these tissues was calculated in each animal for each contrast medium, and differences in enhancement were tested for significance by a growth-curve model. RESULTS Contrast enhancement in the intervertebral disc was significantly less with gadolinium-polylysine than with gadopentetate. In muscle, no significant difference between the two media was observed. CONCLUSIONS Molecular weight affects the diffusion of paramagnetic contrast media into the intervertebral disc. Contrast media of a high molecular weight may produce better contrast between recurrent herniated disc fragments and scar tissue than contrast media of lower molecular weight. This possibility should be rested in further studies.

PURPOSE: To investigate the feasibility of obtaining clinically useful magnetic resonance (MR) spectra at 0.5 T in cerebral lesions. MATERIALS AND METHODS: Single-voxel localized proton MR spectroscopy was performed at 0.5 T in 18 patients (aged 16-73 years) suspected of having cerebral lesions on MR images who subsequently underwent craniotomy and biopsy and in eight volunteers (aged 21-50 years). The metabolite resonances in the MR spectra were stratified according to the histologic diagnosis. MR spectra demonstrated resonances for choline-containing compounds (Cho), creatine and phosphocreatine, glutamine and glutamate, N-acetylaspartate (NAA), myo-inositol, and lactate. RESULTS: In 14 of 15 patients with cerebral tumors, the Cho-NAA ratio was increased and was greater than 1. In three patients with nonneoplastic cerebral lesions, the ratio did not exceed 1. In healthy control subjects, the average ratio was 0.54. CONCLUSION: H-1 MR spectroscopy at 0.5 T provides clinically useful information in patien...

Functional magnetic resonance (fMR) imaging, like positron emission tomography (PET), shows regions of activation in the brain resulting from the neuronal activity associated with cognitive, sensory, or motor function. An advantage of fMR imaging is that the functional and the reference anatomic images are acquired simultaneously. Additionally, fMR imaging is generally more available than PET or magnetoencephalography. This article reviews the applications of fMR imaging for studying the sensorimotor cortex prior to craniotomy.

Using magnetic resonance (MR) echo–planar imaging (EPI), we recently demonstrated the presence of low-frequency fluctuations (–3) within and across associated regions of the sensorimotor cortex. These fluctuations in MR signal intensity are believed to arise from fluctuations in capillary blood flow and oxygenation. A substantial overlap between the activation map generated by bilateral finger tapping and temporally-correlated voxels from the sensorimotor cortex obtained during rest was observed. In the work reported here, we investigated whether respiratory hypercapnia, which is known to suspend spontaneous oscillations in regional cerebral blood flow, influences these low-frequency fluctuations. The magnitude of low-frequency fluctuations was reversibly diminished during hypercapnia, resulting in a substantial decrease of the temporal correlation both within and across contralateral hemispheres of the sensorimotor cortex. After the breathing mixture was returned to ambient air, the magnitude and spatial extent of the temporal correlation of low-frequency fluctuations returned to normal. Results of this study support the hypothesis that low-frequency physiological fluctuations observed by MR in the human cortex and spontaneous flow oscillations observed in early studies by laser–Doppler flowmetry (LDF) in the cortex of the rat are identical and are secondary to fluctuations in neuronal activity.

STUDY DESIGN In this phantom study, rotations of a vertebral body calculated from computerized tomography (CT) were compared to the actual rotations provided by a specially designed device incorporating a reduction gear. OBJECTIVE The objective was to measure the accuracy of the CT and an automated software program to calculate rotations of lumbar vertebral bodies. BACKGROUND Rotations of individual vertebrae secondary to a change in position or load can be measured in select patients by roentgen stereophotogrammetry or by using CT and a specially constructed table that creates the rotation of the torso. The purpose of this study was to measure the precision and accuracy of rotation measurements made with a CT scanner and an automated program to calculate rotation. METHODS We constructed a phantom with a lumbar vertebra that can be rotated within a CT scanner. CT of the vertebra were obtained at angular positions of 0, 0.360 degrees , 1.080 degrees , 2.520 degrees , 5.400 degrees , 11.160 degrees , 29.160 degrees , 29.340 degrees , 29.520 degrees , 29.610 degrees , 29.700 degrees , 29.790 degrees , 29.880 degrees , and 29.889 degrees . With an automated program based on a pixel-shift algorithm, we calculated rotations of the vertebra between pairs of images. Accuracy was calculated as mean difference between the actual and the calculated rotation, and precision was calculated as the standard deviation of the differences. RESULTS Differences between actual and calculated rotations varied from -0.083 degrees to 0.132 degrees . For rotations less than 15 degrees , mean error (accuracy) was -0.039 degrees , and the standard deviation (precision) was 0.029 degrees . For rotations greater than 15 degrees , the accuracy was 0.086 degrees , and the precision was 0.023 degrees . CONCLUSIONS This study shows that rotations of lumbar vertebrae may be measured with CT, and an automated program to an accuracy and precision better than 0.1 degrees , comparable to that of roentgen stereophotogrammetry.

Study design A cadaveric study was done to analyze the dimensional changes in the spinal canal and intervertebral foramen of the lumber spine with flexion and extension movements. Objectives To investigate the relationship between flexion and extension movements and morphologic changes in the spinal canal and the intervertebral foramen. Summary of background data Previous studies have reported that the dimensions of the spinal canal and the intervertebral foramen may change significantly with motion. The purpose of this study was to assess the quantitative changes in the spinal canal and the intervertebral foramen with segmental flexion-extension movements. Methods Nineteen fresh cadaveric spines yielding 25 motion segments were used. The lumbar motion segments were frozen and then imaged in axial and sagittal projections by a computed tomography scanner. They were thawed then, and the motion segments were loaded to 5.7 Nm in flexion (13 motion segments) and in extension (12 motion segments) specimens. While in flexion or extension, the specimens again were frozen and imaged by computed tomography scan. The frozen specimens than were sliced using a cryomicrotome in the sagittal plane to study the dimensions of the intervertebral foramen. Eighteen other fresh cadaveric spines were sliced sagittally for study in the neutral position. Results The axial computed tomography scans showed that extension significantly decreased the canal area, midsagittal diameter, and subarticular sagittal diameter, whereas flexion had the opposite effects. The sagittal computed tomography scans showed that extension decreased all the foraminal dimensions significantly, whereas flexion increased all the foraminal dimensions significantly. The translational changes were associated with the bulging of the disc and the presence of traction spurs. The cryomicrotome sections showed the cross-sectional area of the foramen to be 12% greater for the flexion group and 15% smaller for the extension group than the cross-sectional area of the neutral group. Nerve root compression in the foramen was found to be 21.0% in neutral, 15.4% in flexion, and 33.3% in extension groups. Conclusions The study supports the concept of dynamic spinal stenosis. In addition to static anatomic changes, careful dynamic studies may be required to evaluate better the central canal and the foramen.

Objective The purpose of this study was to determine the usefulness of functional magnetic resonance imaging (FMRI) to map cerebral functions in patients with frontal or parietal tumors. Methods Charts and images of patients with cerebral tumors or vascular malformations who underwent FMRI with an echoplanar technique were reviewed. The FMRI maps of motor (11 patients), tactile sensory (12 patients), and language tasks (4 patients) were obtained. The location of the FMRI activation and the positive responses to intraoperative cortical stimulation were compared. The reliability of the paradigms for mapping the rolandic cortex was evaluated. Results Rolandic cortex was activated by tactile tasks in all 12 patients and by motor tasks in 10 of 11 patients. Language tasks elicited activation in each of the four patients. Activation was obtained within edematous brain and adjacent to tumors. FMRI in three cases with intraoperative electrocortical mapping results showed activation for a language, tactile, or motor task within the same gyrus in which stimulation elicited a related motor, sensory, or language function. In patients with > 2 cm between the margin of the tumor, as revealed by magnetic resonance imaging, and the activation, no decline in motor function occurred from surgical resection. Conclusions FMRI of tactile, motor, and language tasks is feasible in patients with cerebral tumors. FMRI shows promise as a means of determining the risk of a postoperative motor deficit from surgical resection of frontal or parietal tumors.

Functional magnetic resonance imaging (FMRI) is a new noninvasive technique for imaging cerebral function. Studies of the human central auditory pathway examined responses in eight normal hearing volunteers following auditory stimuli, including narrative speech and pure-tone audiometry. The activation demonstrated by FMRI is modeled on an increase in regional blood flow with increased neuronal activity. The FMRI signals represent deoxyhemoglobin concentration changes in capillaries within the region of the brain that is activated. Brain activation was imaged in the superior temporal gyrus during text reading and pure tones. Activation in both text and pure-tone presentation did not vary with the intensity of the auditory stimulus and elicited a dominant response in the left temporal lobe. These observations demonstrate the capability of FMRI to correlate anatomic and functional relationships in the human central auditory pathway.

One hundred lumbar intervertebral foramina from eighteen spines of fresh cadavera were studied to assess the relationship between compression of the nerve root and the height of the intervertebral disc and the morphological characteristics of the intervertebral foramen as determined on cryomicrotome sections. The critical posterior disc height and the critical foraminal height that were associated with entrapment and compression of the nerve root were determined. Significant positive correlations were demonstrated between compression of the nerve root and the posterior disc height, the foraminal height, and the foraminal cross-sectional area for the four intervertebral levels between the second lumbar and first sacral vertebrae. Nerve-root compression was evident in twenty-one of the 100 foramina, in eight of the ten foramina in which the posterior disc height was four millimeters or less, and in four of the five foramina in which the foraminal height was fifteen millimeters or less. These critical dimensions may be indicators of foraminal stenosis in the lumbar spine. However, compression of a spinal nerve root does not always cause sciatica, and the clinical findings must always be taken into account when a diagnosis of stenosis is considered.

BACKGROUND AND PURPOSE: CSF fluid dynamics in healthy subjects and patients with Chiari I have been characterized during rest with phase-contrast MR imaging and CFD. CSF flow velocities and pressures in the nonresting state have not been adequately characterized. We used computer simulations to study CSF dynamics during increased heart rates in the normal and Chiari I subarachnoid space. MATERIALS AND METHODS: Cyclic CSF flow was simulated for multiple cycles in idealized 3D models of the subarachnoid space for normal and Chiari I malformation subarachnoid spaces, with flow cycles corresponding to 80 or 120 heart beats per minute. Flow velocities and pressures were computed by the Navier-Stokes equations. Synchronous bidirectional flow and flow patterns were displayed in Star-CD and inspected visually. Peak velocities and pressure differences in the 2 models were compared for the 2-cycle frequencies. RESULTS: Elevating the cycle rate from 80 to 120 cpm increased peak superior-inferior pressure gradients (top-bottom) by just 0.01% in the normal model and 2% in the Chiari model. Corresponding average pressure gradients increased by 92% and 100%, respectively. In addition, in both models, the range of synchronous bidirectional flow velocities increased. Systolic velocities had smaller increases with faster cycling. For each cycle rate, peak and average pressure gradients in the Chiari model were greater than in the normal model by 11%??6%. CONCLUSIONS: Raising the cycle rate from 80 to 120 cpm increased superior-inferior average pressure gradients and the range of synchronous bidirectional flow velocities in the normal and Chiari I models.

Magnetic resonance (MR) imaging in patients with persistent low back pain and sciatica effectively demonstrates spine anatomy and the relationship of nerve roots and intervertebral disks. Except in cases with nerve root compression, disk extrusion, or central stenosis, conventional anatomic MR images do not help distinguish effectively between painful and nonpainful degenerating disks. Hypoxia, inflammation, innervation, accelerated catabolism, and reduced water and glycosaminoglycan content characterize degenerated disks, the extent of which may distinguish nonpainful from painful ones. Applied to the spine, "functional" imaging techniques such as MR spectroscopy, T1ρ calculation, T2 relaxation time measurement, diffusion quantitative imaging, and radio nucleotide imaging provide measurements of some of these degenerative features. Novel minimally invasive therapies, with injected growth factors or genetic materials, target these processes in the disk and effectively reverse degeneration in controlled laboratory conditions. Functional imaging has applications in clinical trials to evaluate the efficacy of these therapies and eventually to select patients for treatment. This report summarizes the biochemical processes in disk degeneration, the application of advanced disk imaging techniques, and the novel biologic therapies that presently have the most clinical promise.

BACKGROUND AND PURPOSE: Flow simulations in patient-specific models of the subarachnoid space characterize CSF flow in more detail than MR flow imaging. We extended previous simulation studies by including cyclic CSF flow and patient-specific models in multiple patients with Chiari I. We compared simulation results with MR flow measurements. MATERIALS AND METHODS: Volumetric high resolution image sets acquired in 7 patients with Chiari I, 3 patients who had previous craniovertebral decompression, and 3 controls were segmented and converted to mathematical models of the subarachnoid space. CSF flow velocities and pressures were calculated with high spatial and temporal resolution during simulated oscillatory flow in each model with the Navier-Stokes equations. Pressures, velocities, and bidirectional flow were compared in the groups (with Student t test). Peak velocities in the simulations were compared with peak velocities measured in vivo with PCMR. RESULTS: Flow visualization for patients and volunteers demonstrated nonuniform reversing patterns resembling those observed with PCMR. Velocities in the 13 subjects were greater between C2 and C5 than in the foramen magnum. Chiari patients had significantly greater peak systolic and diastolic velocities, synchronous bidirectional flow, and pressure gradients than controls. Peak velocities measured in PCMR correlated significantly ( P = .003; regression analysis) despite differences between them. CONCLUSIONS: In simulations of CSF, patients with Chiari I had significantly greater peak systolic and diastolic velocities, synchronous bidirectional flow, and pressure gradients than controls.

Rationale and Objectives. The purpose of the study was to evaluate the safety, patient tolerance, and diagnostic efficacy of a 0.3 mmol/kg gadodiamide injection in the evaluation of lesions of the central nervous system (CNS) and spine. Methods. A double-blind randomized trial of 0.3 mmol/kg gadodiamide injection in comparison to 0.1 mmol/kg gadopentetate dimeglumine was performed in 187 patients at four medical centers. Gadodiamide was administered to 87 patients at a dose of 0.3 mmol/kg, and gadopentetate dimeglumine was administered to 100 patients at a dose of 0.1 mmol/kg. Adverse reactions, serum chemistry, urinalysis, and neurological examination were monitored. Efficacy was evaluated by determining the number of cases with enhancing lesions, the diagnostic value of the enhancement, the number of lesions demonstrated, and the delineation of the lesions. Results. The study showed a similar safety profile of 0.3 mmol/kg gadodiamide injection and 0.1 mmol/kg gadopentetate dimeglumine with a low incidence of adverse reactions and no significant changes in the serum chemistry, urine, or neurologic parameters monitored. The study showed more enhancement in lesions when the larger dose of contrast medium was used. The greater enhancement was considered diagnostically useful. Conclusion. Gadodiamide injection of 0.3 mmol/kg is safe, well tolerated, and effective for magnetic resonance imaging in cases of CNS and spine lesions.

Functional magnetic resonance imaging (FMRI) detects signal changes in brain that accompany regional changes in neuronal activity. In normal human brain, FMRI shows changes in signal in the postcentral gyrus or superior temporal gyrus that correlate with voluntary motor activity or language processing, respectively. The model used to explain the changes in signal linked temporally with cerebral activity is a reduction in cerebral capillary deoxyhemoglobin concentration due to the increased blood flow that accompanies neuronal activity in the cerebrum. FMRI has been used in normal subjects but not extensively in patients. To determine the feasibility of using FMRI to map cerebral functions in patients with partial epilepsy syndromes, we performed a pilot study, using FMRI to identify signal changes in motor and language areas in response to tasks that activate those areas. Signal changes in epilepsy patients approximated those observed in volunteers. We conclude that FMRI can be developed as a method for functional cerebral mapping in partial epilepsies.

Rationale and objectives Iopromide is a new nonionic monomeric contrast medium for cerebral arteriography. This agent has been approved for sale in over 45 countries; however, it is still undergoing clinical review in the United States. This study evaluated the safety and efficacy of iopromide in comparison with two other nonionic contrast media. Methods A total of 173 patients participated in the study, which was prospective, double-blind, and randomized. In two centers, patients received iopromide or iohexol; in the other three centers, patients received iopromide or iopamidol. Adverse events were monitored by investigators, and efficacy was evaluated by grading the radiographic images. Results Most adverse events were mild or moderate in severity; all resolved completely. Twenty-one percent of patients given iopromide were reported to have a drug-related adverse event, versus 44% of patients given a comparator. No statistically significant difference emerged between iopromide and the comparators with regard to efficacy. Conclusions These study results indicate that iopromide is a safe and effective contrast medium for cerebral angiography.