[Cerebral ischemia originating from rotational vertebral artery occlusion caused by C5/6 spondylotic changes: a case report].

A 68-year-old man presented with sudden onset of left hemiparesis, diplopia and numbness of the left side of the body and was admitted to our hospital. MRI of the brain revealed no abnormality. However, neurological examination on admission strongly suggested ischemia of the brainstem. Under anticoagulation therapy his symptoms gradually disappeared by the fourth hospital day. He had a past history of bouts of unconsciousness caused by right rotation of the head. Dynamic plain roentgenograms of the cervical spine showed spondylotic changes and lateral osteophyte formation at C5/6 without instability. Computed tomography (CT)-angiography demonstrated narrowing of the right vertebral artery due to compression of the lateral osteophyte at C5/6. Vertebral angiography revealed complete occlusion of the right vertebral artery induced by right rotation of the head. The artery-to-artery embolism caused by repeated occlusion of the right vertebral artery due to the neck motion was suggested as the mechanism of ischemic attack in this patient. Osteophytectomy at C5/6 via the anterior approach successfully treated dynamic occlusion of the right vertebral artery. Occlusion of the vertebral artery at C1/2 by the head rotation is well known as Bow-Hunter's syndrome. However, dynamic occlusion due to spondylotic changes at C5/6 is rare. In case of ischemic attack of the posterior circulation with lateral osteophyte formation of the cervical spine, dynamic occlusion mechanisms of the vertebral artery at the lower cervical level should be considered.