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Although clinical head CT images are typically interpreted qualitatively, automated methods applied to routine clinical head CTs enable quantitative assessment of brain volume, brain parenchymal fraction, brain radiodensity, and brain radiomass. These metrics gain clinical meaning when viewed relative to a reference database and expressed as quantile regression values. Quantitative imaging data can aid in objective reporting and in the identification of outliers, with possible diagnostic implications. The comparison to a reference database necessitates standardization of head CT imaging parameters and protocols. Future research is needed to learn the effects of virtual monochromatic imaging on the quantitative characteristics of head CT images.

BACKGROUND AND PURPOSE: The majority of brain growth and development occur in the first 2 years of life. This study investigated these changes by analysis of the brain radiodensity histogram of head CT scans from the clinical population, 0–2 years of age. MATERIALS AND METHODS: One hundred twenty consecutive head CTs with normal findings meeting the inclusion criteria from children from birth to 2 years were retrospectively identified from 3 different CT scan platforms. Histogram analysis was performed on brain-extracted images, and histogram mean, mode, full width at half maximum, skewness, kurtosis, and SD were correlated with subject age. The effects of scan platform were investigated. Normative curves were fitted by polynomial regression analysis. RESULTS: Average total brain volume was 360 cm3 at birth, 948 cm3 at 1 year, and 1072 cm3 at 2 years. Total brain tissue density showed an 11% increase in mean density at 1 year and 19% at 2 years. Brain radiodensity histogram skewness was positive at birth, declining logarithmically in the first 200 days of life. The histogram kurtosis also decreased in the first 200 days to approach a normal distribution. Direct segmentation of CT images showed that changes in brain radiodensity histogram skewness correlated with, and can be explained by, a relative increase in gray matter volume and an increase in gray and white matter tissue density that occurs during this period of brain maturation. CONCLUSIONS: Normative metrics of the brain radiodensity histogram derived from routine clinical head CT images can be used to develop a model of normal brain development.

Prior studies of post-operative stereotactic radiosurgery (SRS) have not distinguished between Adjuvant SRS (ARS) versus Adjuvant SRS to residual/recurrent disease (ARD). In this study, we defined ARS and ARD and investigated local control (LC), overall survival (OS), distant development of brain metastases (DBF), and leptomeningeal disease (LMD). We retrospectively identified BM patients who received surgical resection and SRS for BM from an IRB approved database between Jan 2009-Aug 2015. Patients were stratified into two groups: ARS and ARD. LC was determined by follow-up MRI studies and OS was measured from the date of surgery. LC and OS were assessed using the Kaplan-Meier method. 70 cavities underwent surgical resection of BM and received SRS to the post-operative bed. 41 cavities were classified as ARS and 29 as ARD. There was no significant difference in 12-month LC between the ARS and ARD group (71.4 vs. 80.8%, respectively; p = 0.135) from the time point of SRS. The overall 1-year survival for ARS and ARD was 79.9 and 86.1%, respectively (p = 0.339). Mean time to progression was 6.45 and 8.0 months and median follow-up was 10 and 15 months for ARS and ARD, respectively. 11.8% of ARS patients and 15.4% of ARD patients developed LMD, p = 0.72. 29.4% of ARS and 48.0% of ARD patients developed DBF, p = 0.145. Our findings suggest that observation after surgical resection, with subsequent treatment with SRS after the development of local failure, may not compromise treatment efficacy. If validated, this would spare patients who do not recur post-surgically from additional treatment.

Acute leukemia can present with a wide range of symptoms and with no classic osseous findings on radiographs. Recognizing subtle imaging abnormalities and raising the possibility of a lymphoproliferative or hematologic pathology may facilitate early diagnosis. Described here is a case of a 4-year-old with back pain that was found to have acute lymphoblastic leukemia with diffuse loss of vertebral body height on plain film radiographs, and with prominent discs, and diffusely abnormal marrow signal on magnetic resonance imaging.

BACKGROUND AND PURPOSE: Though CT is a highly calibrated imaging modality, head CT is typically interpreted qualitatively. Our aim was to initiate the establishment of a reference quantitative database for clinical head CT. MATERIALS AND METHODS: An automated segmentation algorithm was developed and applied to 354 clinical head CT scans with radiographically normal findings (ages, 18–101 years; 203 women) to measure brain volume, brain parenchymal fraction, brain radiodensity, and brain parenchymal radiomass. Brain parenchymal fraction was modeled using quantile regression analysis. RESULTS: Brain parenchymal fraction is highly correlated with age (R(2) = 0.908 for men and 0.950 for women), with 11% overall brain volume loss in the adult life span (1%/year from 20 to 50 years and 2%/year after 50 years of age). Third-order polynomial quantile regression curves for brain parenchymal fraction were rationalized and statistically validated. Total brain parenchymal radiodensity shows a decline as a function of age (14.9% for men, 14.7% for women; slopes not significantly different, P = .760). Age-related loss of brain radiomass (the product of volume and radiodensity) is approximately 20% for both sexes, significantly greater than the loss of brain volume (P

Objective: To investigate the effects of beam hardening by the skull on the measured radiodensity of the brain. To test a hypothesis that these effects of beam hardening are decreased using a monochromatic energy source. Methods: Selected clinical cases were reviewed in illustration. An anthropomorphic skull and brain phantom was created and scanned in a clinical CT scanner with skull, without skull, and with hemicraniectomy. The effects of beam hardening were illustrated by scanning the phantom with mono- and poly-chromatic X-ray sources. Results: In clinical cases, the HU values of the brain were consistently lower when the X-ray beam traversed the skull than when it did not. An anthropomorphic skull-and-brain phantom further demonstrated these effects, which were evident with a polychromatic energy source and absent with a virtual monochromatic energy source. Conclusions: Beam hardening by the skull lowers the measured HU values of the brain. The effects, which can impact quantitative imaging, may be mitigated by a virtual monochromatic energy source. Advances in knowledge: Beam hardening by the skull lowers the measured radiodensity of the brain. The effects may be mitigated by a virtual monochromatic energy source.

Purpose To validate the T1- and T2-weighted (T1w/T2w) MRI ratio technique in evaluating myelin in the neonatal brain. Materials and Methods T1w and T2w MR images of 10 term neonates with normal-appearing brain parenchyma were obtained from a single 1.5 Tesla MRI and retrospectively analyzed. T1w/T2w ratio images were created with a postprocessing pipeline and qualitatively compared with standard clinical sequences (T1w, T2w, and apparent diffusion coefficient [ADC]). Quantitative assessment was also performed to assess the ratio technique in detecting areas of known myelination (e.g., posterior limb of the internal capsule) and very low myelination (e.g., optic radiations) using linear regression analysis and the Michelson Contrast equation, a measure of luminance contrast intensity. Results The ratio image provided qualitative improvements in the ability to visualize regional variation in myelin content of neonates. Linear regression analysis demonstrated a significant inverse relationship between the ratio intensity values and ADC values in the posterior limb of the internal capsule and the optic radiations (R2 = 0.96 and P

OBJECTIVE The aim of this study was to investigate the use of one magnetic resonance image-processing tool, FSL, in its ability to perform automated segmentation of computed tomographic images of the brain. METHODS Head computed tomography (CT) images were brain extracted and segmented using the FSL tools BET and FAST, respectively. The products of segmentation were analyzed by histogram. The impact of image intensity inhomogeneity correction was investigated using simulated bias fields, 14 routine head CT scans, and selected illustrative clinical cases. RESULTS FSL FAST performs direct segmentation of head CT images, permitting quantitation of gray and white matter densities and volumes, achieving a more complete segmentation than masking methods. "Bias field correction" reduced the covariance of image signal intensities of the total brain and gray matter images (P < 0.01). Correction is larger when the effects of beam hardening and radiation scatter are larger, resulting in improved segmentation. CONCLUSIONS FSL FAST enables direct segmentation of head CT images.

The corpus callosum is the largest white matter tract in the brain, connecting the 2 hemispheres. The functions of the corpus callosum are many and varied, and lesions frequently cause only subtle clinical findings. The range of diseases that can affect the corpus callosum is vast and includes all potential white matter disease. The distribution of lesions in the corpus callosum is disease specific in only a few entities such as Susac syndrome and Marchiafava-Bignami disease. Group studies have found significant differences of diffusivity metrics in the corpus callosum in preterm infants, patients suffering seizure activity, and patients with early-onset Alzheimer's disease. Given the challenges that multiple orientation of fibers within the callosum presents, advanced postprocessing methods may be required to reveal ultrastructural disease.

Magnetic resonance imaging technology allows for in vivo visualization of fiber tracts of the central nervous system using diffusion-weighted imaging sequences and data processing referred to as "diffusion tensor imaging" and "diffusion tensor tractography." While protocols for high-fidelity diffusion tensor imaging of the brain are well established, the spinal cord has proven a more difficult target for diffusion tensor methods. Here, we review the current literature on spinal diffusion tensor imaging and tractography with special emphasis on neuroanatomical correlations and clinical applications.

OBJECTIVE. The purpose of this article is to review recent advances in diffusion-tensor imaging (DTI) and tractography of the cranial and peripheral nerves. CONCLUSION. Advances in MR data acquisition and postprocessing methods are permitting high-resolution DTI of the cranial and peripheral nerves in the clinical setting. DTI offers information beyond routine clinical MRI, and DTI findings have implications for the diagnosis and treatment of nerve disease.

MR morphometric studies have suggested that structural brain abnormalities including corpus callosum enlargement may, in part, explain cognitive deficits in children with neurofibromatosis type 1 (NF-1). Diffusion tensor imaging (DTI) metrics of the corpus callosum in adults with NF-1 have recently been reported, but such studies in children with NF-1 are needed. The purpose of this study was to quantify the DTI metrics at 3 T of different regions of the corpus callosum in children with NF-1.DTI metrics from seven consecutively identified patients with NF-1 (6 boys and 1 girl; age range, 3-17 years; average age, 7.0 years) were compared with 11 age- and sex-matched control subjects (10 boys and one girl; age range, 3-17 years; average age, 7.1 years) at 3 T. Fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were calculated in different sections of the corpus callosum as well as whole-brain mean diffusivity.Comparing children with NF-1 to control subjects, there were statistically significant decreases in fractional anisotropy in the genu, anterior body, and isthmus of the corpus callosum and significant increases in radial diffusivity in the genu and anterior body. Whole-brain mean diffusivity histograms revealed significant increases in whole-brain mean diffusivity in children with NF-1.Children with NF-1 have abnormal DTI metrics, particularly in the genu, and elevated whole-brain mean diffusivity. NF-1-related microstructural abnormalities of the corpus callosum are detectable in childhood and likely persist through myelination maturation.

To validate the T1- and T2-weighted (T1w/T2w) MRI ratio technique in evaluating myelin in the neonatal brain.T1w and T2w MR images of 10 term neonates with normal-appearing brain parenchyma were obtained from a single 1.5 Tesla MRI and retrospectively analyzed. T1w/T2w ratio images were created with a postprocessing pipeline and qualitatively compared with standard clinical sequences (T1w, T2w, and apparent diffusion coefficient [ADC]). Quantitative assessment was also performed to assess the ratio technique in detecting areas of known myelination (e.g., posterior limb of the internal capsule) and very low myelination (e.g., optic radiations) using linear regression analysis and the Michelson Contrast equation, a measure of luminance contrast intensity.The ratio image provided qualitative improvements in the ability to visualize regional variation in myelin content of neonates. Linear regression analysis demonstrated a significant inverse relationship between the ratio intensity values and ADC values in the posterior limb of the internal capsule and the optic radiations (RThe T1w/T2w ratio accentuates contrast between myelinated and less myelinated structures and may enhance our diagnostic ability to detect myelination patterns in the neonatal brain.2 Technical Efficacy: Stage2 J. MAGN. RESON. IMAGING 2017;46:690-696.

The increasing availability of magnetic resonance imaging (MRI) and the high sensitivity of MRI for soft tissue injury are resulting in the increased use of MRI for the evaluation of acute trauma. As cervical spine injury can have a devastating consequence, MRI is being more commonly used to evaluate cervical spine injury in the acute setting, necessitating emergent interpretation by the on-call radiologist. Unless one is formally trained in a trauma center, the MRI findings of soft tissue and ligamentous cervical spine injury may not be fully appreciated. The goal of this pictorial review is to familiarize the reader with some of the more common soft tissue, vascular, and ligamentous injuries seen on MRI of the cervical spine in the emergent setting.

Septo-optic dysplasia (SOD) refers to a heterogeneous group of midline brain developmental anomalies, with optic nerve hypoplasia (ONH) being one of the morphologic correlates of the condition. Traditionally, ONH has been diagnosed on fundoscopic exam. Conventional MRI is used in cases of suspected ONH to identify associated brain abnormalities and to compare findings to the fundoscopic exam. Advances in magnetic resonance diffusion tensor imaging (MRDTI) permit in vivo, noninvasive, quantitative characterization of the entire visual pathway at 3.0 T. To investigate the feasibility of MRDTI at 3.0 T in children with SOD to evaluate the entire visual pathway. MRDTI at 3T was performed in two children with SOD and seven age-matched controls. Manual region-of-interest analysis was used to evaluate the tensor metrics of the optic nerves. Deterministic tractography was used to evaluate the tensor metrics of the optic radiations. The SOD patients demonstrated a significant decrease in anisotropy and increase in mean diffusivity of the optic nerves and radiations compared to the control subjects. This study demonstrates the feasibility of MRDTI to evaluate the entire visual pathway in children, and it demonstrates pre- and post-chiasmatic diffusion tensor abnormalities in SOD patients.

The purpose of this study was to retrospectively assess the outcomes of temporal MRI follow-up of indeterminate cystic lesions of the pineal region.Cases of indeterminate pineal lesions were identified by a computerized search of radiology reports at our institution from 1998 to 2007. Twenty-six indeterminate pineal lesions, one each in 26 patients (six males and 20 females), were followed in the current study. Cases were included in the study if the radiology report detailed an incidentally noted but indeterminate or worrisome cystic lesion of the pineal region and if temporal follow-up MRI was recommended by the interpreting neuroradiologist. For a case to be included in our data set, a follow-up MRI study must have been obtained at least 6 months after the initial study.Follow-up imaging ranged from 7 months to 8 years. Lesions ranged in description and appearance from "probable benign cyst" with typical cystic imaging features to "pineal mass" with features of solid enhancement. We found that, within the limitations of the technique, there were no significant changes in the size or character of any indeterminate pineal region lesion followed at our institution over the time interval of 1998-2007.In our study, all pineal lesions found incidentally and for which follow-up imaging had been recommended were stable over time. These data suggest that neoplastic lesions of the pineal region either are too rare or grow too slowly to be identified by traditional temporal imaging follow-up. With increasing interest in optimal allocation of health care resources, our findings suggest that incidentally identified pineal region cystic lesions, both typical and atypical, can be followed clinically.

Background/Aims: As a preoperative planning tool, conventional magnetic resonance (MR) imaging may have limited value in differentiating tumors from white matter tracts. MR diffusion tensor imaging (MRDTI) has become a useful tool for evaluating white matter tracts in relation to surrounding structures and has been used in surgical planning for brain tumors involving white matter. We investigated the use of DTI of the optic nerves in surgical planning for pediatric suprasellar tumors. Methods: We present findings in 10 pediatric control patients and 2 cases of pediatric suprasellar tumors in which a routine 6-direction DTI of the brain was performed at 3 T. Postprocessing permitted the study of the diffusion tensor parameters, as well as the tractography, of the optic nerves. Results: The control patients demonstrated the optimization of the technique and permitted the quantitation of fractional anisotropy and apparent diffusion coefficient values. The tumor cases demonstrated the utility of optic nerve DTI to differentiate between optic nerves and suprasellar/chiasmatic brain tumors. Conclusions: A routine 6-direction DTI of the pediatric brain at 3 T permits a detailed DTI study of the optic nerves. Optic nerve tractography can be used to aid in the evaluation and treatment of pediatric brain tumors in the area of the optic chiasm.

The objective of this article is to detail the indications, techniques, risks, and benefits of fluoroscopically guided lumbar puncture (LP).Familiarity with the details of fluoroscopically guided LP can aid in the work flow, increase the success rate, and minimize the complications of the procedure.

Hydrocephalus causes changes in the diffusion-tensor properties of periventricular white matter. Understanding the nature of these changes may aid in the diagnosis and treatment planning of this relatively common neurologic condition. Because ventricular size is a common measure of the severity of hydrocephalus, we hypothesized that a quantitative correlation could be made between the ventricular size and diffusion-tensor changes in the periventricular corona radiata. In this article, we investigated this relationship in adult patients with hydrocephalus and in healthy adult subjects.Diffusion-tensor imaging metrics of the corona radiata were correlated with ventricular size in 14 adult patients with acute hydrocephalus, 16 patients with long-standing hydrocephalus, and 48 consecutive healthy adult subjects. Regression analysis was performed to investigate the relationship between ventricular size and the diffusion-tensor metrics of the corona radiata. Subject age was analyzed as a covariable.There is a linear correlation between fractional anisotropy of the corona radiata and ventricular size in acute hydrocephalus (r = 0.784, p0.001), with positive correlation with axial diffusivity (r = 0.636, p = 0.014) and negative correlation with radial diffusivity (r = 0.668, p = 0.009). In healthy subjects, axial diffusion in the periventricular corona radiata is more strongly correlated with ventricular size than with patient age (r = 0.466, p0.001, compared with r = 0.058, p = 0.269).Axial diffusivity of the corona radiata is linearly correlated with ventricular size in healthy adults and in patients with hydrocephalus. Radial diffusivity of the corona radiata decreases linearly with ventricular size in acute hydrocephalus but is not significantly correlated with ventricular size in healthy subjects or in patients with long-standing hydrocephalus.

A noninvasive method to predict aggressiveness of high-grade meningiomas would be desirable because it would help anticipate tumor recurrence and improve tumor management and the treatment outcomes. The Ki-67 protein is a marker of tumor proliferation, and apparent diffusion coefficient (ADC) is related to tumor cellularity. Therefore, we sought to determine whether there is a statistically significant correlation between ADC and Ki-67 values in meningiomas and whether ADC values can differentiate various meningioma subtypes.MRI examinations and histopathology of 68 surgically treated meningiomas were retrospectively reviewed. Mean ADC values were derived from diffusion imaging. Correlation coefficients were calculated for mean ADC and Ki-67 proliferation index values using linear regression. An independent unpaired Student t test was used to compare the ADC and Ki-67 proliferation index values from low-grade and more aggressive meningiomas.A statistically significant inverse correlation was found between ADC and Ki-67 proliferation index for low-grade and aggressive meningiomas (r(2) = -0.33, p = 0.0039). ADC values (± SD) of low-grade meningiomas (0.84 ± 0.14 × 10(-3) mm(2)/s) and aggressive (atypical or anaplastic) meningiomas (0.75 ± 0.03 × 10(-3) mm(2)/s) were significantly different (p = 0.0495). Using an ADC cutoff value of 0.70 × 10(-3) mm(2)/s, the sensitivity for diagnosing aggressive meningiomas was 29%, specificity was 94%, positive predictive value was 67%, and negative predictive value was 75%.ADC values correlate inversely with Ki-67 proliferation index and help differentiate low-grade from aggressive meningiomas.

Long-term cultivation of primary human fetal brain cells has yielded a homogeneous population of glial progenitors of extended life span. These human astrocyte precursor (HAP-1) cells have been in culture for greater than 1 year, are diploid, and do not form colonies in soft agar. The culture was established in 10% fetal calf serum (FCS), although cells greatly increase their proliferative rate when both basic fibroblast growth factor and FCS are present in the culture media. HAP-1 cells express the cytoskeletal proteins glial fibrillary acidic protein, vimentin, and nestin. HAP-1 cells express the AMPA/kainate receptor subunit genes GluRs 1, 3, and 4 and the kainate receptor subunit genes GluR6, KA1, and KA2. Immunohistochemistry confirms the expression of GluR subunit proteins. HAP-1 cells demonstrate a kainate-responsive current found to be blockable by CNQX. HAP-1 cells will serve in the study of human glial cells and ligand-gated ion channels and in the identification of compounds which might act as agonists or antagonists at these receptor-ion channel complexes.

Bacterial superantigens induce peripheral unresponsiveness in CD4+ T cell populations that express appropriate Vβ chains. We have used Vβ3/Vα11 T cell receptor transgenic (Tg) mice and the Vβ3-specific superantigen staphylococcal enterotoxin A (SEA) to further investigate the mechanisms that contribute to such unresponsiveness. As in other models, in vivo exposure to SEA rendered the Tg CD4+ cells unresponsive to subsequent restimulation in vitro with antigen or mitogens. However, when the SEA-treated CD4+ cells were completely purified away from all other contaminating cells, they regained the ability to proliferate and secrete cytokines. Moreover, enriched CD4−CD8− cells from the SEA-treated mice suppressed the responses of fresh control CD4+ cells in mixed cultures indicating that the apparent “anergy” was both transferable and reversible. Further analysis demonstrated that interferon γ, but not the Fas receptor, played a critical role in the suppression.

Magnetic resonance imaging technology allows for in vivo visualization of fiber tracts of the central nervous system using diffusion-weighted imaging sequences and data processing referred to as "diffusion tensor imaging" and "diffusion tensor tractography." While protocols for high-fidelity diffusion tensor imaging of the brain are well established, the spinal cord has proven a more difficult target for diffusion tensor methods. Here, we review the current literature on spinal diffusion tensor imaging and tractography with special emphasis on neuroanatomical correlations and clinical applications.

Diffusion-weighted imaging is a valuable tool in the assessment of the neonatal brain, and changes in diffusion are seen in normal development as well as in pathological states such as hypoxic-ischemic encephalopathy (HIE). Various methods of quantitative assessment of diffusion values have been reported. Global ischemic injury occurring during the time of rapid developmental changes in brain myelination can complicate the imaging diagnosis of neonatal HIE.To compare a quantitative method of histographic analysis of brain apparent coefficient (ADC) maps to the qualitative interpretation of routine brain MR imaging studies. We correlate changes in diffusion values with gestational age in radiographically normal neonates, and we investigate the sensitivity of the method as a quantitative measure of hypoxic-ischemic encephalopathy.We reviewed all brain MRI studies from the neonatal intensive care unit (NICU) at our university medical center over a 4-year period to identify cases that were radiographically normal (23 cases) and those with diffuse, global hypoxic-ischemic encephalopathy (12 cases). We histographically displayed ADC values of a single brain slice at the level of the basal ganglia and correlated peak (s-sDav) and lowest histogram values (s-sDlowest) with gestational age.Normative s-sDav values correlated significantly with gestational age and declined linearly through the neonatal period (r (2) = 0.477, P 0.01). Six of 12 cases of known HIE demonstrated significantly lower s-sDav and s-sDlowest ADC values than were reflected in the normative distribution; several cases of HIE fell within a 95% confidence interval for normative studies, and one case demonstrated higher-than-normal s-sDav.Single-slice histographic display of ADC values is a rapid and clinically feasible method of quantitative analysis of diffusion. In this study normative values derived from consecutive neonates without radiographic evidence of ischemic injury are correlated with gestational age, declining linearly throughout the perinatal period. This method does identify cases of HIE, though the overall sensitivity of the method is low.

The purpose of this study was to test a hypothesis that routinely performed diffusion-tensor trace imaging is of sufficient image quality and sensitivity for infarct detection to safely and routinely replace standard diffusion-weighted imaging (DWI) in the clinical setting.Both routine DWI and 15-direction diffusion-tensor imaging (DTI) with parallel acquisition technique were obtained on all brain MRI studies from a single 1.5-T MRI scanner at a tertiary care referral center over a 1-year period, permitting direct comparison of the two different diffusion studies on the same patients (2537 studies, 365 infarct-positive studies). A subset of images was assessed for image quality and quantitatively for ability to detect brain infarctions. The total set of positive studies was reviewed qualitatively for ability to detect small cerebral infarctions.Fifteen-direction isotropic DWI (DTI trace images) with parallel acquisition technique resulted in consistently higher image quality with less distortion and higher image detail than routine DWI. Small infarcts were better seen, and in 12 cases, infarcts could only be seen on 15-direction isotropic diffusion-weighted images. The additional scanning time required for 15-direction isotropic DWI did not result in significantly increased motion-related reduction in image quality compared with standard DWI.Diffusion-tensor trace images obtained with parallel acquisition technique are of improved image quality and improved sensitivity for detection of small cerebral infarctions relative to standard DWI. If such DTI data are acquired, routine DWI can be omitted.

BACKGROUND AND PURPOSE (1) To determine the prevalence of vertebral arterial ostial stenosis (VOS) as determined by the “gold standard” of digital subtraction angiography (DSA). (2) To learn the correlation between vertebral ostial stenosis and study indication. (3) To determine the ability of contrast-enhanced magnetic resonance angiography (CE MRA) and computed tomographic angiography (CTA) to reflect the true prevalence of vertebral ostial stenosis as determined by DSA. METHODS Three hundred and twenty-nine patients who underwent DSA had recorded evaluation of 443 vertebral artery origins. Cases were categorized by patient age and study indication. Similar numbers of CTA and MRA studies were assessed. RESULTS The prevalence of VOS in the study population was 5.4%. VOS was not observed in patients under 40 years of age, and was seen in 12.5% of patients over 70 years. CE MRA demonstrated decreased signal at the vertebral origins consistent with stenosis in 20% of patients. CTA estimated VOS at .8%, and yielded 7.3% of studies, which were nondiagnostic for VOS. CONCLUSION The prevalence of VOS as determined by DSA is low and increases with patient age and correlates with factors such as anterior infarct (18.4%), posterior infarct (33.3%), carotid atherosclerosis (30.8%), and vertebrobasilar insufficiency (33%). Patients being evaluated for reasons less closely correlated with atherosclerotic disease, such as arteriovenous malformation (AVM) or hemorrhage showed a lower prevalence of VA stenosis (brain aneurysm or AVM 5/121, 4.1%, brain hemorrhage 5/153, 3.3%). Routine clinical MRA significantly overestimates VOS prevalence, and findings suggest that CTA underestimates the degree and prevalence of VOS.

Hydrocephalus is an uncommon and controversial complication of radiosurgery for vestibular schwannoma (VS). The controversy arises as hydrocephalus can also be associated with untreated vestibular schwannoma. Nevertheless, retrospective review of radiosurgical cases suggest that in a minority of cases of treated vestibular schwannomas, radiosurgery appears to cause or significantly accelerate subsequent hydrocephalus. This chapter discusses the evidence for this claim, and reviews the frequency of this complication, correlating variables, predisposing factors, proposed mechanisms, and patient management options.

Object Cavernous malformations (CMs) can cause symptoms that appear out of proportion to the lesion size, leading one to hypothesize that they may have an effect on adjacent white matter that is not fully explained by local mass effect. The goal of this study was to investigate the diffusion tensor (DT) properties of CMs, the hemosiderin rim, and normal-appearing adjacent white matter. Methods Eighteen cavernous malformations were characterized using standard MR imaging sequences as well as 6-direction DT imaging with single-shot echo planar–gradient echo imaging at 3 tesla. Results Diffusion tensor imaging demonstrated that CMs have a characteristic signature on DT imaging, with low fractional anisotropy (FA) and high mean diffusivity centrally within the lesion. The hemosiderin rim had a high FA value relative to the central lesion or adjacent white matter. Tractography revealed that tracts neatly deviate around CMs. Tracts were typically seen to pass through the hemosiderin rim. Conclusions The hemosiderin rim of CMs was intimately associated with white matter tracts that were deviated by the central lesion. These findings are consistent with histopathological reports that the hemosiderin rim is composed of blood breakdown products deposited in viable white matter.

To investigate the feasibility of routine clinical DTI of the lower spinal cord using high-field-strength MRI and parallel imaging, and to evaluate the utility of diffusion tensor imaging and tractography as tools for study of lower cord pathology. Three patients with diastematomyelia, one patient with tethered cord, and six normal volunteers underwent MR imaging of the lower spine at 3 T. A 15-channel spine coil and parallel imaging were used with a six-direction single-shot echo-planar gradient echo technique. In normal volunteers, tractography delineated the conus and cauda equina. Tractography software permitted assessment of fractional anisotropy of the distal cord and nerve roots. In cases of tethered cord, tractography correlated with anatomical imaging. Tractography also correlated with the anatomical pathological findings in cases of diastematomyelia. The methods described enable routine DTI and tractography of the lower spinal cord at 3 T. Compared with conventional imaging, tractography offers additional information that may prove useful in the characterization and surgical planning for congenital lesions involving the lower spinal cord.

A 5-year-old girl presented with intractable seizures and nonfocal hemispheric slowing on EEG. Blood, urine, and CSF laboratory values were all normal. MR imaging of the brain demonstrated diffuse volume loss of the entire left hemisphere. Clinical and imaging findings were consistent with the diagnosis of Rasmussen encephalitis. Diffusion tensor imaging demonstrated increased ADC values and decreased fractional anisotropy (FA) of the affected (left) hemisphere. Tractography data showed decreased numbers of lines drawn in the affected hemisphere, with fewer lines drawn at higher FA thresholds, relative to the contralateral hemisphere, or to normal age-matched controls. Diffusion tensor imaging offers an adjunct MR imaging modality in diagnosis and monitoring of this rare condition.

The purpose of this study was to determine the discrepancy rates of radiology residents interpreting emergent neck and Circle of Willis magnetic resonance angiography (MRA) studies and to detect any adverse clinical outcomes. Three hundred seventeen MRA studies given preliminary reading by radiology residents were retrospectively reviewed over a 2-year period. Discrepancies were classified as either false negatives (failure to diagnose abnormalities) or false positives (misinterpreting normal scans as abnormal). The overall discrepancy rate was 12.1% for Circle of Willis MRA and 7.9% for neck MRA. Fourth-year residents had the lowest discrepancy rates (7.7%), but this was not statistically significant. The most common misses were stenosis greater than 70% (n = 9) and aneurysm (n = 12). No adverse clinical outcome was detected mainly due to rapid turnaround time for final reporting.

cDNAs encoding a novel nAChR structural subunit (GFn alpha-3) and a ligand-binding subunit (GF alpha-3) have been isolated from a goldfish retina cDNA library. The protein encoded by GFn alpha-3 shares 88% amino acid similarity with that encoded by GFn alpha-2, a structural subunit gene previously identified to be expressed in this system (Cauley et al., 1989). The ligand-binding subunit (GF alpha-3) is likely the goldfish homolog of the rat alpha-3 gene (Boulter et al., 1986). Northern blots and S1 protection experiments show that GFn alpha- 3 and GF alpha-3 genes are expressed in retina and brain. GFn alpha-3 identifies multiple RNAs differing in their 3′ untranslated regions. In situ hybridization analysis demonstrates GFn alpha-3, GFn alpha-2, and GF alpha-3 expression by cells of the retinal ganglion cell layer. Unlike GFn alpha-2 and GF alpha-3, GFn alpha-3 is expressed at highest levels by cells of the retina's inner nuclear layer. In the optic tectum, both GF alpha-3 and GFn alpha-3 genes are expressed by cells of the periventricular zone, as well as more superficial layers. These results suggest the presence of multiple nAChR systems in retina and tectum. In addition, they indicate that tectal nAChRs may arise from remote (ganglion cell) as well as local (tectal cell) synthesis.

Polyadenylated messenger RNA was isolated from goldfish retinas at various times following unilateral crush of the optic nerve. RNA was translated in a cell-free system and product proteins analyzed by two-dimensional gel electrophoresis and autofluorography. Poly(A)+ mRNA-directed protein synthesis revealed an 8-fold increase in the labeling of polypeptides of about 30 kd Mr and a pI of 5.5 in retinas 2 d following optic nerve crush, compared with control retina mRNA translation products. In vitro labeling of retinal proteins revealed the enhanced synthesis of comparable 30 kd proteins in 2 d post-crush retinas. Evidence presented suggests that this 30 kd protein cluster may correspond to fish 30 kd stress or heat-shock proteins (hsp-30).