A rare venous drainage route from the transverse medullary vein to the inferior retrotonsillar vein on cerebral angiography.

BackgroundIn vascular diseases such as arteriovenous malformations and dural arteriovenous fistulas, rare venous drainage routes can be identified angiographically.Case DescriptionA 50-year-old woman was transported to our hospital after she developed a sudden headache and unconsciousness. Computed tomography showed subarachnoid hemorrhage. A cerebral angiography disclosed an arteriovenous malformation (AVM) at the C2 level and a dural arteriovenous fistula (AVF) at C5/C6. The AVF drained through the posterior spinal vein to the inferior retrotonsillar vein. The AVM drained cranially to the anterior spinal vein flowing into the transverse medullary vein. The transverse medullary vein drained into the inferior retrotonsillar vein through a connecting vein. The connecting vein seemed very unusual.ConclusionsIn this case, a rare collateral vein connecting the transverse medullary vein and inferior retrotonsillar vein was observed.