[Bow hunter's syndrome with spontaneous improvement].

A 74-year-old man complained of near loss of consciousness when he rotated his head to the left side. The symptom was reversed by returning his head to a neutral position. Transcranial Doppler studies with the patient's neck rotated into the left side revealed reduction of flow in his left vertebral artery. Vertebral angiography revealed a hypoplastic right vertebral artery and occlusion of the left vertebral artery at the C6 level on head rotation. We diagnosed him bow hunter's syndrome and treated him conservatively. Six months later, he was symptom-free on head rotation. Transcranial Doppler and vertebral angiography demonstrated the disappearance of the vertebral artery occlusion at the neck rotation. Some patient without any definite cause can be treated conservatively, and surgical interventions for bow hunter's syndrome should be carefully decided.