Ruptured peripheral superior cerebellar artery dissecting aneurysms associated with primitive trigeminal artery: a case report

Persistent primitive trigeminal artery (PPTA) is a remnant of the carotid-vertebrobasilar anastomoses in the embryo. Although PPTAs are discovered incidentally in most cases, altered hemodynamics may lead to increased risk of stroke. To the best of our knowledge, no reports of PPTA associated with superior cerebellar artery (SCA) dissecting aneurysms have been published in the English language. We describe the case of a patient who presented with subarachnoid hemorrhage (SAH) due to ruptured peripheral SCA dissecting aneurysms in association with PPTA. Additionally, we discuss the relationship between PPTA and peripheral SCA aneurysms and the treatment of peripheral SCA aneurysms. A 43-year-old woman presented with acute onset of headache and nausea and admitted to our hospital. She was diagnosed with SAH due to ruptured left SCA dissecting aneurysm(s) and had undergone digital subtraction angiography. The left vertebral angiography showed aneurysmal dilatations of the left S2 segment (lateral pontomesencephalic segment) along with dissection through the segments of S2 and S3 (cerebellomesencephalic segment). It also showed ipsilateral PPTA. The left vertebral artery (VA) had normal caliber and the basilar artery segment proximal to the orifice of the left PPTA was not hypoplastic. The patient underwent proximal parent artery occlusion at the S2 segment via the left VA and was successfully treated with no neurological deficits having lasted 5 months. The flow alteration with PPTA may have influenced the formation of SCA dissection in this patient. Further studies are needed to understand the etiology and treatment outcomes of peripheral SCA aneurysms better.