u,' The authors describe a novel stereotaxic method for the removal of minute lesions of the central nervous system (CNS). With the development and refinement of computerized tomography (CT), such small lesions can be detected by noninvasive (x-ray) scanning with computer processing of the data. Using a G E 7800 scanner system and a PDP 11/45 computer, data processing of various kinds is possible. Multiple computer programs have been developed to enhance regions of interest on CT scans by magnification, threedimensional reconstruction, and digital processing. These data are then used to calculate a stereotaxic approach to a CNS lesion. A head fixation system has been devised to enable information transfer from a CT scan to the stereotaxic surgical system. Newly developed instruments are mounted on a micromanipulator for guidance at the operative site. These include stereo endoscopes with xenon arc illumination, a tissue expander for exposing the operative area, a radiation tracer probe, a rotary extractor, and instruments for operating and removal of blood from a small intracerebral hemorrhage. The micromanipulator for guiding the tactical instruments is, in turn, mounted on a stereotaxic guide mechanism which accurately defines all areas of the cranium in three-dimensional coordinates. The combination enables the site of the lesion, the three-dimensional coordinates of which have been located by CT scan, to be accurately approached by the stereotaxic guide/micromanipulator assembly.

The authors update a novel method recently utilized in humans with various CNS pathology for stereotactic localization, removal, and adjuvant therapy of small CNS lesions using additional computer processing of the data from a GE 8800 CT Scanner. Multiple computer algorithms developed at Cal Tech enhance regions of interest by filtering, magnifying, color-coding and 3-dimensional reconstruction based on routine CT scans. This stereotactic approach is calculated by the computer and coordinates are mated to a modified head fixation system; small lesions can be removed with the apparatus described herein under direct binocular vision with minimal tissue damage. This technique may offer the possibility of successful secondary application of adjuvant therapy to, particularly, a CNS glioma site.

The authors report a case of bilateral posttraumatic middle cerebral artery occlusion. Previously reported unilateral cases are reviewed and possible pathophysiological mechanisms disscussed.

The authors report a case of primary osteogenic sarcoma of the brain. Negative autopsy findings, complete bone radiographs, and bone-scanning techniques were consistent with a primary tumor focus in the right temporopietal region of the brain. The authors suggest an origin from a primitive multipotential mesenchymal cell.

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