Ruptured Cerebellar Micro-AVM Presenting with Lobar (Semilunar Lobe) Hemorrhage Causing Deep Coma: Surgical Evacuation of the Hemorrhage Followed by Embolization Utilizing a Wedged Flow-Directed Microcatheter and Concentrated nBCA Mixture; Main Feeder, Nidus, and Draining Vein Occlusion Leading to Cure and Excellent Clinical Evolution

Abstract

Arteriovenous malformations (AVMs) in the pediatric population are relatively rare but are reportedly associated with a higher rupture rate than AVMs in adults. This could be because most pediatric AVMs are only detected after rupture. Since pediatric AVMs are usually discovered because of devastating intracranial hemorrhage, and the overall mortality rate after initial hemorrhage is as high as 25%, the proper management of such conditions is critical.

This 9-year-old girl with an unremarkable medical past presented to the emergency room after a sudden episode of headaches, profuse vomits, and rapid loss of consciousness. Intubated by paramedics at her home, she was admitted to the emergency room in a deep coma. Upon arrival, the neurological evaluation revealed bilateral fixed, dilated pupils, a fixed gaze, and bilateral decerebration posturing (Glasgow Coma Score (GCS) 4). Cranial CT showed a large right hemispheric, lobar cerebellar hemorrhage centered at the semilunar lobule with extra-axial extension exerting mass effect on the midline and collapsing the fourth ventricle. CT angiography showed abnormal vessels, suggesting a vascular malformation located at the anterolateral (petrous) and superior (tentorial) hemorrhage borders. The patient was urgently brought to the operating room for hematoma evacuation. Midline suboccipital craniotomy allowed evacuation of the hemorrhage and alleviation of mass effect. Abnormal vessels were coagulated, but no specimen was taken for pathological examination. At the end of the procedure, external ventricular drainage was placed to monitor the patient’s intracranial pressure and control the risk for postoperative obstructive hydrocephalus. The patient evolved satisfactorily and was extubated after 72 h, and the ventriculostomy was removed on postoperative day 6. Cerebral angiograms obtained on day 12 showed a cerebellar micro-AVM supplied by hemispheric branches of the caudal trunk of the right superior cerebellar artery (SCA) and draining through a middle hemispheric vein into the anterior hemispheric venous tributary of the superior petrosal vein. Endovascular embolization required identification of the small AVM feeder branching off of the distal caudal trunk of the left SCA and navigation of a flow-directed microcatheter placed at the nidus origin. Embolization was carried out using a highly concentrated n-butyl cyanoacrylate (nBCA)/Lipiodol mixture. The mixture was injected with the microcatheter wedged in the main feeding artery, achieving antegrade penetration into the nidus and the draining vein with no reflux, and it’s low viscosity facilitated a relatively slow rate of polymerization. We hypothesized that this prolongation was due to the wedged position of the catheter, which limited exposure of the mixture to blood. The patient evolved satisfactorily, and a follow-up angiogram after 2 months confirmed the persistent complete exclusion of the micro-AVM.

This chapter illustrates the management of a pediatric patient who arrived at the emergency department in a deep coma due to acute cerebellar hemorrhage originating from a micro-AVM. The placement of a ventriculostomy followed the urgent surgical evacuation of the hemorrhage. At a subacute stage, the patient underwent endovascular embolization of the AVM utilizing a wedged flow-directed microcatheter and concentrated nBCA/Lipiodol injection. The procedure led to complete occlusion of the cerebellar AVM and allowed complete clinical recovery. Pediatric AVM, the anatomy of the SCA and fissures veins, and technical considerations of nBCA embolization are the main themes of this chapter.