Purpose:To describe an initial experience imaging the human hippocampus in vivo using a 7T magnetic resonance (MR) scanner and a protocol developed for very high field neuroimaging. Materials and Methods:Six normal subjects were scanned on a 7T whole body MR scanner equipped with a 16-channel head coil. Sequences included a full field of view T1-weighted 3D turbo field echo (T1W 3D TFE: time of acquisition (TA) ϭ 08:58), T2*-weighted 2D fast field echo (T2*W 2D FFE: TA ϭ 05:20), and susceptibility-weighted imaging (SWI: TA ϭ 04:20). SWI data were postprocessed using a minimum intensity projection (minIP) algorithm. Total imaging time was 23 minutes.Results: T1W 3D TFE images with 700 m isotropic voxels provided excellent anatomic depiction of macroscopic hippocampal structures. T2*W 2D FFE images with 0.5 mm in-plane resolution and 2.5 mm slice thickness provided clear discrimination of the Cornu Ammonis and the compilation of adjacent sublayers of the hippocampus. SWI images (0.5 mm in-plane resolution, 1.0 mm slice thickness) delineated microvenous anatomy of the hippocampus. Conclusion:In vivo 7T MR imaging can take advantage of higher signal-to-noise and novel contrast mechanisms to provide increased conspicuity of hippocampal anatomy.

We review 160 cases of gliomatosis cerebri from the literature and report an additional three infants and young children who presented with intractable epilepsy, corticospinal tract deficits, and developmental delay in whom a pathologic diagnosis was made. The progressive nature of the encephalopathy in our cases was documented by serial clinical examination, electroencephalograms, magnetic resonance imaging, and positron emission tomographic scans. The natural history of gliomatosis cerebri was determined by a retrospective review of the literature of 160 cases in 85 reports. The most common neurologic symptoms and signs included corticospinal tract deficits (58%), dementia/mental retardation (44%), headache (39%), seizures (38%), cranioneuropathies (37%), increased intracranial pressure (34%), and spinocerebellar deficits (33%). The most commonly involved central nervous system structures were the centrum semiovale and cerebrum (76%), mesencephalon (52%), pons (52%), thalamus (43%), basal ganglia (34%), and the cerebellum (29%). Fifty-two percent of patients were dead within 12 months of onset. Different grades of glial neoplasm may also coexist within gliomatosis cerebri such as astrocytoma with anaplastic astrocytoma, atypical or anaplastic oligodendroglioma, and glioblastoma multiforme. Hypotheses regarding the pathogenesis of gliomatosis cerebri include blastomatous dysgenesis, diffuse infiltration, multicentric origin, in situ proliferation, and "field transformation." The biologic determinants of whether a transformed glial cell behaves as a relatively localized tumor mass or truly loses anchorage dependence to become migratory as well as proliferative are not understood.

Inflammation of the facial nerve in Bell's palsy can be demonstrated on gadolinium-enhanced magnetic resonance imaging. We have studied a series of 17 Bell's palsy patients with gadolinium-enhanced magnetic resonance imaging, and the purpose of this paper is to report our findings and discuss their significance. Most acute Bell's palsy cases demonstrate facial nerve enhancement, usually in the distal internal auditory canal and labyrinthine/geniculate segments. Other segments demonstrate enhancement less often. Gadolinium enhancement occurs regardless of the severity of the paralysis and can persist after clinical improvement of the paralysis. The findings of this study corroborate other evidence that the segments of the facial nerve most often involved in Bell's palsy are the only segments that are most often enhanced with gadolinium-enhanced magnetic resonance imaging. The role of gadolinium-enhanced magnetic resonance imaging in the management of Bell's palsy patients is discussed.

Evaluating contrast-enhancing brain lesions in patients with AIDS by using Toxoplasma serologic testing and positron emission tomography can accurately guide therapy and obviate the need for most brain biopsies in these patients. A larger, national, multicenter study is needed to confirm our findings and to determine the effect of earlier diagnosis and treatment on morbidity and mortality in patients with AIDS and primary central nervous system lymphoma.

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