Objective: To evaluate possible applications of microsurgical extirpation to arteriovenous malformations (AVMs) involving the brainstem.
Methods: We retrospectively reviewed clinical records of 25 patients with AVMs involving brainstems who were admitted to our institute from 1984 to 2004. We defined a brainstem AVM as an AVM in which some part was located within the brainstem. The main location of the nidus was classified into ventral midbrain (n = 3), dorsal midbrain (n = 10), pons (n = 5), cerebellopontine angle (n = 6), and medulla oblongata (n = 1). Bleeding risks from the AVMs were calculated, and applied treatment modalities, respectability, and clinical outcomes were analyzed.
Results: The annual bleeding and rebleeding risks of brainstem AVMs were 15.1 and 14.2%, respectively. Total resection was successfully performed in 0 out of 3, 6 out of 10, 2 out of 5, 6 out of 6, and 0 out of 1 in each of the groups, respectively. Stereotactic radiosurgery was applied as a main treatment modality in three patients (two ventral midbrain AVMs and one pontine AVM), and after microsurgery in one patient with a medulla oblongata AVM. Microsurgery-related permanent neurological complications were observed in five patients (one postoperative bleeding, one hemiparesis, three hearing deterioration, one abducens nerve palsy). During a follow-up period of 8 years (range, 8 mo-15 yr), one patient with an untreated pontine AVM died owing to hemorrhage and one patient with a subtotally resected dorsal midbrain AVM died owing to an unknown etiology 4 years later.
Conclusion: Surgical resection can be applied with considerable, but acceptable, morbidity and mortality in some groups of brainstem AVMs with hemorrhagic presentation, particularly dorsal midbrain and cerebellopontine angle types, in which most parts of the nidus located sub- or extrapially.