Microsurgical resection of brainstem, thalamic, and basal ganglia angiographically occult vascular malformations

OBJECTIVE: To evaluate the clinical results for patients who underwent rese ction of angiographically occult vascular malformations (AOVMs) of the brai nstem, thalamus, or basal ganglia. METHODS: Between January 1990 and May 1998, 56 patients with 57 deep AOVMs underwent 63 operations, at Stanford University Medical Center, to treat AO VMs of the brainstem (42 AOVMs), thalamus (5 AOVMs), or basal ganglia (10 A OVMs). The surgical approach was suboccipital midline (27 operations), far lateral suboccipital (10 operations), transsylvian (9 operations), interhem ispheric transcallosal or infracallosal (8 operations), infratentorial supr acerebellar (6 operations), or subtemporal (3 operations). Four patients ex perienced recurrent bleeding from the same lesion after surgical resection, requiring a second operation. One patient required a planned second operat ion, using a different approach, to completely resect the lesion, and one p atient underwent two surgical procedures to resect two separate brainstem A OVMs. One patient initially underwent exploration but not resection of her AOVM, because it did not present to a pial or ependymal surface. The AOVM w as successfully resected after it exhibited rebleeding and presented to a p ial surface. RESULTS: The immediate outcomes after surgery were unchanged for 31 patient s (55%), worsened for 16 (29%), and improved for 9 (16%). The long-term out comes were unchanged for 24 patients (43%), compared with their presenting grade, worse for 3 (5%), and improved for 29 (52%). Patients who had underg one previous radiotherapy or radiosurgery to treat these lesions experience d more difficult postoperative courses, and radiation necrosis was observed for two patients. CONCLUSION: AOVMs of the brainstem, thalamus, and basal ganglia can be safe ly removed, with a long-term neurological morbidity rate of only 5% and a c omplete lesion resection rate of 93% after the initial planned resection. T he use of cranial base surgical approaches and intraoperative electrophysio logical monitoring contributes to successful clinical outcomes.