✓ A safe technique is described for performing a lateral posterior fossa craniotomy to gain access to the cerebellopontine angle. The method makes use of currently available high-speed air drills. Thus, it is possible to replace the removed bone at the conclusion of the procedure and to re-establish normal tissue planes while providing rigid protection to the posterior fossa.
Christopher S. Ogilvy and Robert G. Ojemann
Christopher S. Ogilvy, Roberto C. Heros, Robert G. Ojemann and Paul F. New
✓ Eight cases of histopathologically proven arteriovenous malformations (AVM's) which were not visualized on angiography are presented. As is typical with these lesions, most of the patients in this series presented with hemorrhage, seizures, or episodic or progressive neurological symptoms suggestive of a neoplasm. The diagnosis of angiographically occult AVM was highly suspected preoperatively in each case based on the combination of computerized tomography (CT) and magnetic resonance (MR) findings. The CT scans in all cases showed moderately hyperdense lesions which enhanced mildly or moderately in a nonhomogeneous pattern with administration of contrast material. The MR image showed one or more bright areas interspersed with areas of low or absent signal peripherally or centrally on both T1- and T2-weighted images. The AVM was totally excised in seven patients and partially excised in one patient, with favorable results in all. The clinical management and differential diagnosis of angiographically occult AVM's are discussed. In patients with a clinical course and radiological studies suggestive of an occult AVM, removal of the lesion, if accessible, should be performed in order to rule out a neoplasm and prevent subsequent hemorrhage and progression of symptoms.
Stephen B. Tatter, Christopher S. Ogilvy, Jeffrey A. Golden, Robert G. Ojemann and David N. Louis
✓ Two cases are reported of third ventricle masses that were clinically and radiographically indistinguishable from pure colloid cysts. A 21- and a 36-year-old man presented with 5-year and 10-day histories of headache, respectively. Magnetic resonance (MR) imaging revealed smooth, homogeneous masses in the anterior third ventricle that were iso- to hyperintense on T1-weighted MR images and hyperintense on T2-weighted images. There was little enhancement with intravenous contrast material. In both patients, craniotomies were performed and histopathological examination revealed xanthogranulomas of the choroid plexus with only microscopic foci of colloid cyst-like structures. These cases illustrate that xanthogranulomas of the third ventricle may clinically and radiologically mimic pure colloid cysts, that a range of MR imaging signals can be seen, and that craniotomy rather than stereotactic aspiration is the indicated treatment.