High resolution MRI of the deep brain vascular anatomy at 8 Tesla: susceptibility-based enhancement of the venous structures.

PURPOSE: The purpose of this work was to describe the deep vascular anatomy of the human brain using high resolution MR gradient echo imaging at 8 T. METHOD: Gradient echo images were acquired from the human head using a transverse electromagnetic resonator operating in quadrature and tuned to 340 MHz. Typical acquisition parameters were as follows: matrix = 1,024 x 1,024, flip angle = 45 degrees, TR = 750 ms, TE = 17 ms, FOV = 20 cm, slice thickness = 2 mm. This resulted in an in-plane resolution of approximately 200 microm. Images were analyzed, and vascular structures were identified on the basis of location and course. RESULTS: High resolution ultra high field magnetic resonance imaging (UHFMRI) enabled the visualization of many small vessels deep within the brain. These vessels were typically detected as signal voids, and the majority represented veins. The prevalence of the venous vasculature was attributed largely to the magnetic susceptibility of deoxyhemoglobin. It was possible to identify venous structures expected to measure below 100 microm in size. Perforating venous drainage within the deep gray structures was identified along with their parent vessels. The course of arterial perforators was more difficult to follow and not as readily identified as their venous counterparts. CONCLUSION: The application of high resolution gradient echo methods in UHFMRI provides a unique detailed view of particularly the deep venous vasculature of the human brain.

Transcochlear repair of persistent cerebrospinal fluid leaks.

OBJECTIVE: The purpose of this study is to demonstrate the utility of a modified transcochlear obliteration of the petrous apex in repair of persistent cerebrospinal fluid (CSF) leaks. A review of temporal bone computed tomography (CT) scans and histological preparations for potential air cells leading to such leaks is also presented. STUDY DESIGN: Retrospective case review in an academic tertiary referral center. METHODS: Patients for inclusion in this study had previously undergone either a suboccipital or translabyrinthine removal of an intracranial tumor with subsequent transmastoid and middle ear obliteration of air cell tracts to stop a CSF leak. Ninety CT scans and 178 temporal bones were reviewed and assessed for peritubal and petrous apex pneumatization. RESULTS: Four patients had initial obliteration of the orifice of the eustachian tube and middle ear that failed to prevent leakage of CSF. The leak was ultimately controlled by a transcochlear petrous apicectomy. From The Ohio State University temporal bone collection, 178 specimens were available for examination. Peritubal pneumatization was found in 42% of the bones examined. The CT scans showed unilateral petrous apex pneumatization in 30% of the specimens and bilateral pneumatization in 11%. CONCLUSIONS: Continuity of air cell tracts from the petrous apex surrounding the internal auditory canal to the medial eustachian tube can provide a path for CSF rhinorrhea that is difficult to stop by conventional means. A modified transcochlear approach successfully terminated persistent leaks in four such patients.