Lateral Supracerebellar Infratentorial Approach for Resection of a Tegmental Midbrain Cavernous Malformation:...

Brainstem cavernous malformations present a surgical challenge because of their deep location and proximity to critical structures. However, for lesions with recurrent hemorrhage, the risks of surgery may be lower than observation. Brainstem safe entry zones are well-established corridors through which intrinsic brainstem lesions such as cavernous malformations can be resected,¹ even when they do not present to the pial surface. The safe entry zone in the lateral mesencephalic sulcus is an established route to lesions of the lateral peduncle and tegmentum.¹ Here we present a case of a 43-year-old patient with multiple brainstem cavernous malformations who presented with multiple symptomatic hemorrhages and growth of a right tegmental midbrain² lesion. We performed a lateral supracerebellar infratentorial approach through a 2-piece modified retrosigmoid craniotomy to resect this lesion (Video 1). Key surgical steps included cerebrospinal fluid drainage from the cisterna magna, opening of the ambient cistern with mobilization of the trochlear nerve inferiorly, entry into the lateral mesencephalic sulcus, and circumferential dissection with piecemeal resection of the cavernous malformation. The patient tolerated the procedure well and was discharged home with postoperative imaging confirming a complete resection. Overall, the lateral supracerebellar infratentorial approach provides reliable access to the lateral mesencephalic safe entry zone for resection of midbrain cavernous malformations not amenable to subtemporal or paramedian posterior corridors. The patient consented to the procedure and to participation in research. Because of the retrospective nature of this report, institutional review board approval was not required.