Background A persistent trigeminal artery (PTA) is rare remnant of fetal circulation involving an anastomosis between the carotid and vertebrobasilar system. PTAs are found in only 0.1-0.6% of cerebral angiography. Multiple subtypes of PTA variants have been identified with the first distinction between variants being described by Saltzman in 1959. The Saltzman criteria is used to distinguish between PTAs based on their communication point with the vertebrobasilar system. We discovered an extremely rare Saltzman type IIIa variant of a PTA originating from the pre-cavernous internal carotid artery (ICA) terminating directly into the superior cerebellar artery (SCA) in a patient presenting with non-aneurysmal subarachnoid hemorrhage (SAH). The PTA-SCA variant has an incidence of only 0.37% for cerebral angiography and as low as 0.1% for conventional imaging. PTA and PTA variants are associated with a higher incidence of aneurysms (26%), vascular malformations (4.5%), moya moya disease, and carotid cavernous fistulas. In our case, no identifiable source of rupture was discovered on initial and delayed repeat cerebral angiography. Several authors have hypothesized that hemodynamic stress and defects in the wall of the cavernous ICA or the PTA may account for cases of non-aneurysmal SAH in patients with PTA.

Methods We present a case of a rare anatomical variant of a persistent trigeminal anastomosing directly with the superior cerebellar artery in a patient presenting with non-aneurysmal subarachnoid hemorrhage.

Results No identifiable malformation or aneurysm was discovered to explain the presence of subarachnoid hemorrhage. The patient underwent repeat cerebral angiography on post bleed day 7 which remained negative for aneurysm or source of rupture. The patient recovered fully and was discharged home.

Conclusion To our knowledge, this is the first description of a non-aneurysmal subarachnoid hemorrhage in a patient with an extremely rare Saltzman Type IIIa PTA variant. Recognizing PTA and its variants has important clinical implications especially in patients undergoing endovascular procedures or in patients with atherosclerotic carotid disease.

Disclosures K. Russell: None. S. Pathuri: None. M. Webb: None. L. Birnbaum: None.