Double origin of the posterior inferior cerebellar artery: association with intracranial aneurysm on catheter angiography.

OBJECTIVE Double origin of the posterior inferior cerebellar artery (PICA) is a congenital anomaly in which the PICA forms from two separate vessels arising from the vertebral artery. The prevalence of double origin of the PICA on catheter angiography is unknown because only four case reports have been published. Because some congenital intracranial vascular oddities are associated with an elevated incidence of aneurysm formation, we sought to determine the association between intracranial aneurysm and double origin of the PICA and to measure the prevalence of double origin of the PICA on catheter angiography. MATERIALS AND METHODS A retrospective review was done over a 27-month period to identify patients with double origin of the PICA. Patients were excluded if both PICAs were not adequately visualized on catheter angiography. The cohort was then divided into two groups consisting of patients with and those without intracranial aneurysm. RESULTS A total of 207 patients (101 males, 106 females) met the inclusion criteria. One or more cerebral aneurysms were found in 35.3% and double origin of the PICA in 1.45% of the patients. Double origin of the PICA was present in 4.1% of the patients with an aneurysm, and none of the patients without an aneurysm had double origin of the PICA (p = 0.043). A majority of the seven known cases of double origin of the PICA described by angiography in the peer-reviewed literature have associated intracranial aneurysm disease. CONCLUSION Our data show that double origin of the PICA is seen in 4.1% of patients with intracranial aneurysm and on 1.45% of catheter angiograms. Double origin of the PICA has an increased association with intracranial aneurysmal disease and may represent a risk factor for subsequent development of intracranial aneurysm.