Microsurgical Resection of Tonsillar Arteriovenous Malformation: Operative Video.

Cerebellar arteriovenous malformation (AVM) comprises 10%-15% of intracranial AVMs. Rupture often leads to devastating brainstem compression, with mortality reported as high as 67%. AVM can be a challenging disease, especially when large in size. AVMs can be treated by 1 or a combination of treatment modalities, namely embolization, radiosurgery, or microsurgical resection. Arterial adhesions to tonsilobulbar and telovelonsilar segments of posterior inferior cerebellar artery (PICA) can be a challenge, increasing bleeding and ischemic risk. We present a 2-dimensional video case of a tonsillar AVM. The patient, a previously healthy female in her 20s, presented with a chronic headache. She had no medical history. Initial magnetic resonance imaging revealed a tonsillar AVM classified as Spetzler-Martin grade II. It received its supply from the tonsilobulbar and telovelotonsilar segments of the PICA and drained directly into the precentral vein, transverse sinus, and sigmoid sinus. An angiogram revealed severe venous engorgement-the source of the patient's headache. The AVM was partially embolized 1 month preoperatively. A medial suboccipital telovelar approach was chosen to reduce the working distance and afford a wider corridor to expose the suboccipital surface of the cerebellum. Complete resection of the AVM was achieved with no additional morbidity. Microsurgery in experienced hands offers the best chance of cure for AVMs. In Video 1, we demonstrate the relationships among the tonsila, biventral lobule, vallecula cerebelli, PICA, and cerebellomedullary fissure as an important anatomic landmark in a safe total resection of a tonsillar AVM.