Arteriovenous malformations in the brainstem are among the most challenging to manage. They represent between 7% and 15% of all brain arteriovenous malformations (AVMs). The high risk of hemorrhage eloquence and increased susceptibility to adverse radiation effects restricts the management of such cases to experienced centers. 1,2 The latency associated with radiosurgery, poor results from embolization as primary therapy all make surgery a favored option in experience hands. 3 A good understanding of the anatomy, arterial supply, and venous drainage of this region is required to safely manage pathology located here. 4,5 There are 2 main patterns of AVMs seen in the midbrain. A type restricted to the pial with exophytic appearance and a second truly parenchymal location. 6 The goal of surgery is to eliminate the risk of hemorrhage and avoid ocular motility and morbidity. An occipital transtentorial approach is often considered when a steep tentorial angle is encountered. [6][7][8] We present a video case of the surgical resection of an exophytic quadrigeminal plate AVM. The patient, a 42-year-old man, presented with a sudden and intense headache, without neurological deficit. MRI and digital subtraction angiography revealed a 2 cm AVM located in the right inferior colliculi supplied by branches of the posterior cerebral artery with early venous drainage into the vein of Galen. The patient consented to the procedure. We demonstrate the supracerebellar infratentorial corridor with a limited resection of the quadrangular lobule to remove the AVM. The case highlights the key anatomic landmarks required to safely modify this classic approach.

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Arteriovenous malformations (AVM) in the posterior fossa represent 2% to 15% of all brain AVMs, are often smaller, and have a higher risk of hemorrhage. [1][2][3][4] The presence of a single draining vein, venous stenosis, and high-flow fistulae increases hemorrhage risk but also venous congestion. [3][4][5][6] AVM associated with high-flow fistula can be managed surgically, radiosurgically, or endovascularly. 7-10 Embolization of the associated fistula is reported to be safer than embolization of the nidus. 7 Surgery is favored in the symptomatic patient when concerns over the latency from radiosurgery to obliteration and overshooting the shunting zone during embolization predominate. 4,11 For small AVM with high-flow shunts localization of the nidus and fistulous connection is the main challenge. Sinus skeletonization in complex dural arteriovenous fistula is a reported technique. 12 We adapt this technique to delineate and disconnect a subpial posterior fossa AVM with high-flow fistula. We present a video case of an obese male in his 50s with hypertension and end-stage renal disease who presented with a 9-month history of progressive spastic quadriparesis. The patient consented to the procedure. Examination revealed grade 2 power on the left and grade 4 on the right with brisk reflexes. MRI showed T2 signal hyperintensity in the pons, and digital subtraction angiography confirmed an AVM overlying the culmen of the vermis with feeders from the S3 segment of the superior cerebellar artery, draining into the precentral vein. We demonstrated that surgical management of micro-AVMs with associated high-flow fistulae can be safely achieved in experienced hands using technique of vein skeletonization guided by indocyanine green angiography. The patient signed the Institutional Consent Form, which states that he accepts the procedure and allows the use his images and videos for any type of medical publications in conferences and/or scientific articles.

IntroductionDevelopmental venous anomalies (DVAs) are considered variants of normal transmedullary veins. Their association with cavernous malformations is reported to increase the risk of hemorrhage. Expert consensus recommends meticulous planning with MR imaging, use of anatomical “safe zones”, intraoperative monitoring of long tracts and cranial nerve nuclei, and preservation of the DVA as key to avoiding complications in brainstem cavernoma microsurgery. Symptomatic outflow restriction of DVA is rare, with the few reported cases in the literature restricted to DVAs in the supratentorial compartment.CaseWe present a case report of the resection of a pontine cavernoma complicated by delayed outflow obstruction of the associated DVA. A female patient in her 20's presented with progressive left-sided hemisensory disturbance and mild hemiparesis. MRI revealed two pontine cavernomas associated with interconnected DVA and hematoma. The symptomatic cavernoma was resected via the infrafacial corridor. Despite the preservation of the DVA, the patient developed delayed deterioration secondary to venous hemorrhagic infarction. We discuss the imaging and surgical anatomy pertinent to brainstem cavernoma surgery, as well as the literature exploring the management of symptomatic infratentorial DVA occlusion.ConclusionDelayed symptomatic pontine venous congestive edema is extremely rare following cavernoma surgery. DVA outflow restriction from a post-operative cavity, intraoperative manipulation, and intrinsic hypercoagulability from COVID-10 infection are potential pathophysiological factors. Improved knowledge of DVAs, brainstem venous anatomy, and “safe entry zones” will further elucidate the etiology of and the efficacious treatment for this complication.