[Accessory nerve paralysis due to compression of the fenestrated vertebral artery].

Neurological involvement due to fenestrated vertebral artery has not yet been reported, although fenestration formation by vertebral arteries is not rare. Reported here is one such rare case. In this case accessory nerve paralysis developed due to fenestrated vertebral artery. A 51-year-old woman was admitted to our department with tilting of the head to the right side as her chief complaint. This had gradually developed over a period of approximately one year. Neurological examination on admission showed the presence of marked atrophy of the left sternocleidomastoid muscle with hyperactive deep tendon reflexes in her four limbs. Metrizamide CT scan showed compression of the upper cervical cord at the left side, and an abnormal small high density area was found at the same site on contrast enhanced CT scan. Left vertebral angiogram showed fenestration formation of the left vertebral artery at C1 level. Surgical decompression for the left accessory nerve and high spinal cord was planned because of the occurrence of symptoms due to compression of the fenestrated vertebral artery. C1 and C2 laminectomy was performed and the dura was opened in prone position. The fenestrated vertebral artery of the intraspinal portion was confirmed to be compressing the spinal root of the accessory nerve and high cervical cord. Initially, trapping of the fenestrated vertebral artery was attempted in the hope of sufficiently relieving compression on the accessory nerve and high cervical cord. This attempt resulted in failure, since auditory evoked response became definitely abnormal within two minutes following interruption of this abnormal artery. Because of this, insertion of Ivaron sponges between the abnormal artery and the accessory nerve was all that could be done.(ABSTRACT TRUNCATED AT 250 WORDS)