Stereotactic Surgery. Stereotactic surgery uses precision apparatus (often computer guided) to assist the surgeon to precisely target an area of the brain (Fig. 57-19). Stereotactic biopsy can be performed to obtain tissue samples for histologic examination. CT scanning and MRI are used to image the targeted tissue. With the patient under general or local anesthesia, the surgeondrills a burr hole or creates a bone flap for an entry site and then introduces a probe and biopsy needle. Stereotactic procedures are used for removal of small brain tumors and abscesses, drainage of hematomas, ablative peocedures for extrapyramidal diseases (e.g.,Parkinson’s disease), and repair of arteriovenous malformations. A major advantage of the stereotactic approach is a reduction in damage to surrounding tissue.