66 Brainstem Cavernous Malformations

Of all cavernous malformations (CMs), 4% to 35% are found in the brainstem accounting for 13% of vascular malformations of the posterior fossa. The annual risk of hemorrhage associated with a CM with no history of a previous hemorrhagic episode is very low ranging from 0.6% to 1.1% per year. However, the risk of recurrent hemorrhage after a presenting bleed is significantly higher. There is a correlation between the extent of persistent neurological deficits and the number of recurrent hemorrhages as rehemorrhage increases the rate and severity of neurological deficits. Neurological deficits often improve after a hemorrhagic event spontaneously and sometimes resolve completely. The indication for surgery in patients with brainstem CMs is controversial. Over the years, we have taken a more cautious stance and we often recommend observation in patients after a single symptomatic bleed as most patients return to a good level of functioning after a single bleed. Surgery is recommended for more aggressive lesions usually after a recurrent bleed. In general, given the very low risk of bleeding from truly asymptomatic lesions, surgery should not be considered in these patients. For symptomatic lesions which have presented with hemorrhage, the decision of whether or not to proceed with surgical resection is related to the risk of surgery, patient's disposition and perceived risk of rebleeding. Favorable outcome can be achieved through surgical resection after an appropriate selection of the patients and thorough preoperative surgical planning.