The 'corkscrew' sign: an indirect MRI hint for intracranial venous hypertension

Dural arteriovenous fistulas (DAVFs) are intracranial vascular abnormalities in which one or more meningeal arteries shunt into a venous structure, either a cortical vein or a venous sinus, causing cerebral venous hypertension and risk of haemorrhage. Imaging diagnosis and characterisation are of paramount importance to grade the haemorrhagic risk and direct management. Non-invasive vascular neuroimaging might pose a diagnostic suspicion, but invasive catheter digital subtraction angiography (DSA) is usually required. We present the case of a patient with an atypical acute cerebral haemorrhage in which admission imaging with CT angiography (CTA) and MR angiography (MRA) was unremarkable, while advanced morphological MR with susceptibility-weighted imaging (SWI) revealed specific findings suggesting unilateral chronic venous hypertension. Successively, DSA detected a small DAVF that was treated with endovascular embolization. This case report raises awareness on subtle but important conventional imaging findings that suggest the presence of an AV shunt, to avoid misdiagnosis and delayed treatment.