A hazard of combining the infratentorial supracerebellar and the cerebellomedullary fissure approaches: cerebellar venous insufficiency.

The infratentorial supracerebellar approach is a popular technique for exposure of lesions of the superior vermis and pineal region. The cerebellomedullary fissure approach is enjoying increasing application as a technique for exposure of the fourth ventricle. Occasionally, a tumor that arises in the quadrigeminal plate or the superior vermis grows to fill the fourth ventricle, and for such a case a combination of the infratentorial supracerebellar approach and the cerebellomedullary fissure approach might be considered. We report a grave hazard of this combination. Two patients with tumors involving the superior vermis and filling the fourth ventricle were managed with a combined infratentorial supracerebellar/cerebellomedullary fissure approach. The first patient, who underwent a bilateral exposure, died on the sixth postoperative day due to massive hemorrhagic venous infarction of the cerebellum. The second patient, who was explored on one side only, suffered a protracted postoperative course characterized by suboccipital pain, torticollis, feeding difficulties and persisting hydrocephalus. Postoperative imaging showed swelling of the inferior vermis and ipsilateral hemisphere of the cerebellum with unilateral tonsillar herniation. Simultaneous compromise of the galenic and tentorial bridging veins and interruption of collateral pathways between these systems and the petrosal bridging veins, as in the combined infratentorial supracerebellar/cerebellomedullary fissure approach, may cause cerebellar venous insufficiency with venous congestion and possible venous infarction.