Pontine cavernous malformations (CMs) are difficult to reach and pose a higher risk of symptomatic rehemorrhage compared with their supratentorial counterparts. Resection of CMs along the floor of the fourth ventricle has been associated with worse functional outcomes. Complete resection of the CM and evacuation of the hematoma can provide the patient with relief of some of the presenting symptoms and a chance for long-term cure.
Pontine cavernous malformations (CMs) located on a peripheral pontine surface or the fourth ventricular floor are resectable lesions, but those deep within the pons away from a pial surface are typically observed.
In a video from Cohen-Gadol, the author attempts to describe technical nuances for resection of large posterior pontine CMs. He presents the case of a 32-year-old man who presented with 2 brainstem hemorrhages within a 2-month interval related to his newly diagnosed pontine CM near the floor of the 4th ventricle. The lesion was resected through a midline suboccipital craniotomy and telovelar approach. The floor of the 4th ventricle was mapped using a monopolar probe and the facial nucleus was noted to be displaced more medially. A small incision within the lateral floor of the ventricle allowed exposure of the CM and drainage of the hematoma. Bipolar coagulation was kept to a minimum to protect the brainstem fiber tracts, and the CM was debulked and removed piecemeal. Arterial feeders were coagulated and cut while the associated developmental venous abnormality was protected. The CM was removed in a gross total fashion as confirmed by postoperative MRI. The patient suffered from transient worsening of his facial weakness (House-Brackmann III → IV) immediately after surgery. However, his neurologic deficits had significantly improved by the 1-month follow-up examination 1).
Favorable surgical outcomes can be predicted in brainstem CM patients with early age at presentation, pontine location of the cavernoma, favorable preoperative mRS and those undergoing early surgery. The outcomes at long-term follow-up were associated with location of the CM in the brainstem, size of the CM and the preoperative mRS 2).
An endoscopic, endonasal, transclival approach is a novel and effective approach to cavernous malformations presenting to the ventral surface of the pons. Recently developed techniques for closure and repair of the skull base defect have minimized but have not eliminated the risk of CSF leak in these procedures 3).