Brainstem Cavernous Malformations

Brainstem cavernous malformations (CMs) continue to present a considerable source of controversy in the neurosurgical community, with an accumulating volume of literature detailing their natural history and their surgical and radiosurgical management. As part of a systematic review of the literature, 12 natural history studies, 52 surgical series, and 14 radiosurgical series were tabulated. Annual bleeding rates for brainstem CMs ranged from 2.3% to 4.1% in natural history studies and from 2.68% to 6.8% in surgical series before intervention. Rebleed rates as high as 21.5% in natural history studies and greater than once per year in surgical series were reported. A total of 684 of 745 CMs (92%) were documented as completely resected in 46 series that provided specific information on resection rates. Early postoperative morbidity ranged from 29% to 67% in larger surgical series, although it was often transient. Thirty of 61 partially resected lesions rebled; 4 of these rebleeds were fatal. Twelve additional patients died from surgically related causes for a combined postoperative rebleeding and surgically related mortality rate of 1.9%. Across 45 series (683 patients), 85% of patients were reported as the same or improved, 14% were worse, and 1.9% died from surgically related causes at long-term follow-up. Patients with anterolateral pontine lesions generally appeared to have a better functional recovery, whereas those requiring excision via the floor of the fourth ventricle had relatively worse long-term outcomes. Radiosurgical series demonstrated conflicting data; some reported a statistically significant decrease in CM rebleeding rates after 2 years, whereas others did not, partially related to dosimetry. Postradiosurgical morbidity was nonetheless significantly greater for CMs than for arteriovenous malformations.