Third-nerve palsy heralding dissecting aneurysm of posterior cerebral artery: digital subtraction angiography and magnetic resonance appearance

Dissections of intracranial arteries are rare and occur most commonly in the vertebrobasilar system.1 Isolated dissecting aneurysms of the posterior cerebral artery (PCA) are very uncommon. We report a case of subarachnoid haemorrhage (SAH) heralded by a 3-month history of diplopia due to dissection of the right PCA documented with digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and angiography (MRA). The patient was treated conservatively, with a good outcome. A 58-year-old male farm worker was found unconscious in the countryside and admitted to hospital. His medical history was unremarkable except for treated arterial hypertension and diplopia for 3 months. On admission, he had a Glasgow Coma Scale (GCS) score of 14 and a complete right third-nerve palsy. Vision and corneal reflexes were normal. A computed tomography scan showed diffuse SAH and intraventricular haemorrhage with hydrocephalus (fig 1A). Soon after arrival, he became less responsive and underwent temporary external ventricular drainage. DSA disclosed a fusiform dilatation of the P1–P2 segment of the right PCA with a focal “blister”, suggesting a dissecting aneurysm (fig 1B). Figure 1  Computed tomography scan at admission showing extensive subarachnoid haemorrhage (SAH) (A). Digital subtraction angiography (DSA; anteroposterior projection) showing a fusiform ectasia of the P1–P2 segment of the right posterior cerebral artery (PCA) with a …