Intermittent positional downbeat nystagmus of cervical origin.

Intermittent positional down beat nystagmus (p-DBN) is rare. We describe an unusual case of intermittent p-DBN which was induced by rotation, anteflexion, and lateral flexion of the neck. A 59-year-old man complained of loss of consciousness and lightheadedness. Positional testing revealed the p-DBN. The evoked p-DBN had latency and the patient had a feeling of passing out while the p-DBN was present. There were no abnormal findings in the vestibular functional examinations. Findings of the MRI were negative. MRA revealed no stenosis of the vertebral artery bilaterally, but there was an anatomical difference. The p-DBN characteristics were documented by electronystagmography during the positional test. The p-DBN lasted intermittently while maintaining the provoking position. It was found that p-DBN occurred with not only the rotation of the neck, but also in the anteflexion and lateral flexion of the neck. There was no stenosis of the vertebral artery (VA) on angiography, but we speculated that the cause of the p-DBN was the VA occlusion due to rotation, anteflexion, and lateral flexion of the neck.