Large extracranial vertebral aneurysm with absent contralateral vertebral artery.

The extracranial segment of the vertebral artery is well protected, and the rate of occurrence of extracranial vertebral aneurysms is very low. We describe the case of a 40-year-old woman who presented with a large aneurysm of the left vertebral artery in the angiographic absence of a right vertebral artery. Her medical history included a motorcycle accident at the age of 20, at which time a neck sprain had been diagnosed. Computed tomography of the chest and neck revealed a 6- x 4-cm aneurysm with mural thrombus in the left thoracic outlet and in the first portion of the left vertebral artery before the entrance of the transverse foramen of the 6th cervical vertebra. Angiography of the arch vessels confirmed both the presence of an aneurysm of the left vertebral artery and the absence of a right vertebral artery. Due to the lack of contralateral vertebral flow, we planned to perform a graft interposition under deep hypothermic circulatory arrest, for cerebral protection. Unfortunately, the patient refused the operation and was lost to follow-up. To our knowledge, there has been no previous report of an extracranial vertebral artery aneurysm in the absence of a contralateral vertebral artery. We believe that deep hypothermic circulatory arrest with graft interposition is the best treatment strategy, although we did not, in this case, have opportunity to treat the patient.