Bilateral Upper Cerebellar Hemorrhage Due to Pial Arteriovenous Fistula and Its Pathophysiological Insight

Objectives: Bilateral upper cerebellar hemorrhage is extremely rare clinical entity but relatively known as postoperative neurosurgical complication with as-yet unknown etiology. Here, we report a case of bilateral upper cerebellar hemorrhage due to pial arteriovenous fistula (pAVF) and discuss the possible pathophysiology of this bleeding pattern. Case Description: A 4-year-old boy who was previously healthy presented with a sudden onset of headache, vomiting, and gait instability. Computed tomography revealed atypical bleeding in the sulci of bilateral cerebellar hemispheres facing the tentorium. Despite the symmetric distribution of bleeding, T2-weighted magnetic resonance imaging showed flow void adjacent to the lateral margin of bleeding. Diffusion-weighted magnetic resonance imaging showed increased apparent diffusion coefficient value in the hemorrhagic lesion, suggesting vasogenic edema. Vertebral angiogram revealed a pAVF, which was fed by the hemispheric branch of superior cerebellar artery. It drained via the venous varix, inferiorly into the tortuous and engorged inferior hemispheric vein, indicating venous congestion. On the venous phase of vertebral angiogram, the superior vermian vein, which is one of the main drainers of the superior part of the cerebellum, was not opacified. Transarterial n-butyl-2-cyanoacrylate embolization was performed to prevent rebleeding, and the pAVF was treated successfully. The patient's follow-up has been uneventful for 3 years. Conclusions: We reported an extremely rare case of cerebellar pAVF presenting as bilateral upper cerebellar hemorrhage. Severe congestion of upper cerebellar veins seemed to be a possible pathophysiology of this specific bleeding pattern.