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Purpose: Considering the rapidly increasing number of clinical high-field MR imagers and the lack of data regarding interference with magnetically adjustable cerebrospinal fluid (CSF) shunt valves, valve safety was assessed with regard to magnetic field interactions: imaging artifacts, heating, magnetic forces, and functional changes in a phantom study at 3.0 Tesla using explanted devices as a realistic model for in vivo conditions., Materials and Methods: Sixteen explanted Codman-Medos and Sophy-SU8 shunt valves, all in perfect working order, were selected and exposed to a 3.0 T static magnetic field. Valve-induced imaging artifacts and signal drop-outs and the heating experiments were evaluated using standard diagnostic MR sequences with different SAR values. Translational attraction for the adjustable valves was assessed using the deflection angle method. To test adjustability and function, the spherical phantom containing the valve was placed in the isocenter of the MR scanner and exposed to a static magnetic field of 3.0 T for 0.25 to 12 hours (repeated exposure 1-12 times), including typical entrance and move-out procedures., Results: The diameters of imaging artifacts ranged from 10-70 mm and were most prominent on T2*w sequences. There was no relevant MR-imaging-related heating. Magnetic forces were not critical. Reproducible adjustment failures occurred in 6 valves., Conclusion: Until suggestions can be made concerning the exposure of hydrocephalic patients to 3.0 T-MRI, further testing is necessary., (Copyright (c) Georg Thieme Verlag KG Stuttgart-New York.)

Direct or indirect injury of craniocervical vessels may be the consequence of an accident, may result from tumor arrosion, or may even occur spontaneously. Many of these vascular lesions can be detected using modern non-invasive vascular imaging techniques such as CT angiography and MR angiography. These traumatic vascular lesions can usually be treated using endovascular techniques. This overview describes neuroradiological findings for traumatic lesions of cervical and cranial vessels as well as endovascular treatment options.

Infectious diseases of the central nervous system have often to be considered in differential diagnosis, particularly in immunocompromised persons. Neuroimaging, specifically advanced techniques such as diffusion-weighted MRI and perfusion MRI contribute much to the differentiation of various brain infections and to delineation of brain infections from other, for instance, neoplastic diseases. In this review we present the imaging criteria for the most important brain infections in adults and discuss in detail differential diagnostic aspects.

Purpose: Functional magnetic resonance imaging (fMRI) localizes Broca's area (B) and Wernicke's area (W) and the hemisphere dominant for language. In clinical fMRI, adapting the stimulation paradigms to each patient's individual cognitive capacity is crucial for diagnostic success. To interpret clinical fMRI findings correctly, we studied the effect of varying frequency and number of stimuli on functional localization, determination of language dominance and BOLD signals., Materials and Methods: Ten volunteers (VP) were investigated at 1.5 Tesla during visually triggered sentence generation using a standardized block design. In four different measurements, the stimuli were presented to each VP with frequencies of 1/1 s, (1/2) s, (1/3) s and (1/6) s., Results: The functional localizations and the correlations of the measured BOLD signals to the applied hemodynamic reference function (r) were almost independent from frequency and number of the stimuli in both hemispheres, whereas the relative BOLD signal changes (DeltaS) in B and W increased with the stimulation rate, which also changed the lateralization indices. The strongest BOLD activations were achieved with the highest stimulation rate or with the maximum language production task, respectively., Conclusion: The adaptation of language paradigms necessary in clinical fMRI does not alter the functional localizations but changes the BOLD signals and language lateralization which should not be attributed to the underlying brain pathology.

Purpose: To assess whether MRI can detect atrophy of the trigeminal nerve in patients with trigeminal neuralgia., Materials and Methods: A prospective MRI study was conducted in 39 patients (trigeminal neuralgia, trigeminal neuropathy, or atypical facial pain) and 25 volunteers. Using a coronal orientation (T1 Flash 3D; T2 CISS 3D), regions of interest were delineated in the cisternal part of the trigeminal nerve along the border of the nerve to calculate the volume of the nerve. The volume of the nerve was compared side-by-side in each patient (t-test, p < 0.05) and the volume difference compared between patients and volunteers., Results: The volume of the compromised trigeminal nerve in patients with trigeminal neuralgia was lower than on the contralateral healthy side, with the difference between healthy and compromised side statistically significant (p < 0.05). In all other patients and in all volunteers, no significant difference was found between the volume of the healthy and compromised nerve. The volume difference between the healthy and compromised side in patients with trigeminal neuralgia was significantly higher (p < 0.05) than in all other patients and volunteers., Conclusion: Atrophy of the trigeminal nerve caused by a nerve-vessel conflict can be detected by MRI. Only patients with trigeminal neuralgia show this unilateral atrophy. Therefore, it is possible to demonstrate the result of the nerve-vessel conflict and to determine the consequences of such a conflict.

Preoperative functional magnetic resonance imaging (fMRI) localizes the primary motor and somatosensory cortex in relation to rolandic brain tumors and determines plastic cortical reorganization. Functional landmarks help to assess the indication for surgery and to plan for safer surgical procedures that protect the functional cortex during resection even when morphologic landmarks are no longer identifiable on anatomic images. Despite its successful application, preoperative fMRI has not yet reached the status of an established clinical diagnostic procedure since special stimulation systems, standardized fMRI protocols and medically approved software are still lacking. Following a brief review of the image display of the functional and morphologic anatomy, the different indications for preoperative fMRI in patients with rolandic brain tumors are presented. A robust preoperative protocol enables clinical MR units with magnetic field strengths of 1.0 Tesla or higher to perform reliable fMRI during contralateral hand movements. Optimized investigation strategies and stimulation modalities are proposed for patients with rolandic tumors distant from the cortical hand representation, for patients with preexisting sensorimotor deficits and for patients with poor compliance. Representative cases illustrate the clinical application. Possibilities and limitations of preoperative fMRI are presented and discussed.

Purpose: Cystic processes are changing the course of the inferior alveolar nerve in the mandible. This study evaluates the possibility of demonstrating the relationship between space-occupying processes and the course of the neurovascular bundle., Materials and Methods: Thirteen patients with cystic processes in the mandible (9 keratocystic lesions, 1 eosinophilic granuloma, 1 plasmocytoma, 2 adamantinomas) were examined by MRI (1.5-T magnet, 8-cm surface coil, PD-gradient-echo-sequences in sagittal and coronal orientation, without enhancement) and the results retrospectively evaluated., Results: The entire course of the nerve could be delineated in all patients. In six patients with minor cystic processes, the nerve was identified in both sagittal and coronal orientation. In seven patients with major cystic lesions, only parts of the nerve were detected in either image orientation, but the nerve could be visualized in its entire length by evaluating coronal and sagittal images side by side., Conclusion: It is possible to delineate the inferior alveolar nerve in its entirety along pathologic mandibular lesions. For large cystic lesions, this requires the evaluation of both coronal and sagittal sections of multidirectional MRI.

Purpose: To compare in a single-blind study the reliability of quantitative measurements and subjective evaluations of contrast enhancement of the facial nerve in patients with idiopathic facial paralysis., Materials and Methods: Magnetic resonance images with a 0.7 mm slice thickness (surface coil) were obtained in patients with idiopathic facial paralysis before and after administration of Gd-DTPA, 0.1 mmol/kg. The five intratemporal segments of the facial nerve were quantitatively measured and subjectively assessed by five radiologists as to the degree of enhancement. The results were compared as to the reliability of both methods., Results: Using the quantitative measuring method, 175 measurements were calculated from a total of 350 regions of interest. At all 35 measured sites, the five quantitative measurements produced identical results. In contrast, the subjective assessment of the five radiologists arrived at a majority consensus in only 16 sites. A complete agreement was not reached for any measured site., Conclusion: The measured quantitative increase in signal intensity after administration of contrast medium is more reliable than subjective assessment. The quantitative method enables reproducible signal intensity measurements even for different window settings and can be easily and swiftly performed at the workstation.

The advent of powerful gradient systems and ultrafast echo-planar imaging (EPI) offers the opportunity to use magnetic resonance imaging to measure and to localize brain function with high spatio-temporal resolution in clinically feasible scanning times. Functional magnetic resonance imaging (fMRI) opens up a new diagnostic field in radiology and neuroradiology with a change from pure morphological brain imaging to the measurement and visualization of brain function. Despite its successful application in neurosurgical, neurological, psychiatric, neuropediatric and pain patients fMRI has not yet reached the status of an established clinical diagnostic procedure. To this end special stimulation systems, standardized fMRI protocols and medically approved software, all dedicated to clinical application, are necessary. The training and teaching of doctors and radiographers will also be crucial for the progress of clinical fMRI. This paper gives an overview of the neurophysiological background, the technical requirements and the data processing strategies that are relevant for the clinical application of fMRI. Presurgical fMRI in patients with brain tumors is used as an example for the clinical relevance of the method.

Purpose: To test the assumption underlying every morphometric twin study that the brains of monozygotic twins are almost identical., Methods: High resolution MRI of the neurocranium of 26 monozygotic twin pairs were acquired and the volumes of 36 cerebral structures were measured. The same twins served as control group after rear-ranging them into non-related pairs of same sex and matching them for age, body height and body weight., Results: For most of the examined structures the correlations within the twins were significant (R = 0.97-0.59). Except for total forebrain volume the controls showed no significant similarity., Conclusions: For almost every measured cerebral structure the assumption, that significant similarities exist between healthy monozygotic twins is correct. Therefore discordant monozygotic twins represent an excellent sample when investigating cerebral correlates of neurologic and psychiatric disorders.