SAH and P1 Posterior Cerebral Artery Aneurysm in a Young Adult

We report the case of a young woman with a history of cocaine use who presented with subarachnoid hemorrhage secondary to rupture of an aneurysm of the P1 segment of the posterior cerebral artery, treated via intracranial vascular microsurgery. A 29-year-old woman presented with sudden onset of headache, nausea, vomiting, and nuchal rigidity (Hunt & Hess grade II). The patient was a cocaine user and had a positive FTA-Abs and Wasserman reaction, indicative of acute syphilis. Computed tomography of the head was consistent with a Fisher grade 3 subarachnoid hemorrhage (SAH). CT angiogram revealed an aneurysm of the P1 segment of the posterior cerebral artery (Figures 1 & 2). Figure 1: CT angiogram showing left posterior cerebral artery aneurysm (posterior-anterior view). Figure 2: CT angiogram showing left posterior cerebral artery aneurysm (lateral view). Discussion The P1 segment of the posterior cerebral artery has a mean length of 6.8mm (range, 2.8-12.2mm) and a mean diameter of 1.85mm (range, 0.8-4.5mm). On average, there are 3.35 branches per segment arising from the postero-superior aspect of P1; in 96.4% of cases, they are the most proximal branches [4]. The literature on P1 segment aneurysms is scarce, consisting solely of small case series. Yonekawa et al. [2] reported seven cases of posterior cerebral artery aneurysms out of 1,027