Microsurgery of midbrain lesions.

Of 41 patients with midbrain lesions, 25 underwent definitive surgical exploration. In 16 patients surgical exploration was not warranted, since the patients had only slight neurological deficits and longstanding histories or consent was not given. The infratentorial supracerebellar approach proved to be the ideal method of exposure in 20 patients, in whom the lesion was located in the more dorsal aspect of the midbrain. In 6 of these patients the mass lesion extended from the cerebellum into the midbrain and, therefore, a transcerebellar route was also needed for exposure. In 5 patients the subtemporal approach was chosen. Three patients died as a result of the operation, but in the other 22 patients no increase in morbidity after surgery was apparent and the immediate postoperative course was normal. Five patients with malignant tumors died from recurrence despite radiotherapy. The remaining 17 patients have been doing well up to 14 years after surgery, but 3 had only limited follow-up. This experience with surgical exploration and total resection or evacuation of midbrain lesions in 25 patients should prove the safety of modern microsurgical techniques. Emphasis is placed on the benefit of microtopographic considerations in the choice of the most suitable approach to these deep-seated lesions.