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Retroclival arachnoid cyst is a rare mass lesion, with only seven cases previously reported in literature. MR is the imaging modality of choice in its evaluation and in its differentiation from epidermoid cyst. The case reported here was surgically proved and had an uncharacteristic MR signal intensity that was higher than that of cerebrospinal fluid due to previous hemorrhage.

Intraoperative computed tomography (CT) with a dedicated, therapeutic scanner facilitated resection of intracranial tumors in nine patients. Major benefits of intraoperative CT included exact, multiplanar lesion localization, maximal surgical resection and immediate recognition of potential intraoperative complications such as intracranial hemorrhage. Three cases are presented in detail to demonstrate the surgical technique. No complications related to the use of intraoperative imaging occurred. Although total resection of malignant brain neoplasms remained an unrealized goal, intraoperative CT increased the surgical accessibility of malignant and benign lesions located in critical areas of the brain.

The recording of compound action potentials (CAPs) from peripheral nerves is a routine clinical investigative procedure in the operating room. Parameters such as amplitude, area, conduction velocity, and latency are used as measures for the functional integrety of the nerve. Pathology produces reduction in conduction velocities, desynchronization of compound nerve action potentials and, in severe disease, complete conduction block, leading to observable changes in these measurements. A number of technical difficulties exist which produce distortions in this data. For example, reliable and repeatable measurements of these parameters require careful electrodes placement. Also, changes in nerve moistness produces conductivity changes. These factors affect the amplitudes of the CAPs producing errors in the measured data (Wikswo et al, 1985).

A C-ring radiolucent head holder was designed to facilitate intraoperative computed tomography (CT) during resection of various intracerebral lesions. Important features of the procedure include rigid skull and CT table fixation, cranial access, and low artifact CT imaging performed during and after operation. A case of CT-assisted resection of an arteriovenous malformation is described.