3-Dimensional Exoscope for Far Lateral Approach to Pontomedullary Cavernous Malformation

Brainstem cavernous malformations account for 15%-18% of all central nervous system cavernomas and are histologically characterized by thin-walled, low-pressure capillaries, classically without intervening brain tissue.^1,2 Cavernomas may be sporadic, typically characterized by a single lesion, or inherited. The inherited form is most often autosomal dominant with incomplete penetrance and variable expression. Multiple cavernomas are associated with the familial form; although this is not always the case, genetic workup should be pursued.^3,4 Clinical presentation typically includes focal neurologic deficit related to hemorrhage location, seizures, and rarely obstructive hydrocephalus.^1,2 Indications for surgical management include severe or progressive neurologic dysfunction, lesion size ≥2 cm, recurring hemorrhages, and/or significant mass effect.⁵ Microsurgical resection of a cavernoma is associated with an overall 28% complication rate and perioperative neurologic morbidity upwards of 45% according to some series. Long-term surgical outcomes at 12 months are more reassuring: 84% reported their condition to have improved or remained the same, and the long-term morbidity rate is 14%.^1,6 The location of the lesion dictates the approaches available-cavernomas in the pons or medulla are commonly approached via a retrosigmoid or retrolabyrinthine approach, while more ventral pathologies in this region necessitate a far lateral approach.^1,5,7,8 In Videos 1 and 2, we describe our experience with an exoscope-assisted far lateral approach to a pontomedullary cavernoma in a 10-year-old male presenting with numerous cavernomas and confirmed gene mutation. We demonstrate the exoscope's unparalleled visualization of the anterolateral brainstem, with nominal condylar drilling. The patient and his parents consented to the procedure and publication.