Apogeotropic Positional Nystagmus in Pontine Infarction

Son, Hye Ran; Jung, Jae Yun; Suh, Myung Whan

Abstract

It is thought that horizontal canal benign paroxysmal positional vertigo (BPPV) is the most common cause of apogeotropic direction-changing positional nystagmus (DCPN). But there are many reports about cerebellar or brainstem lesions as the cause of apogeotropic DCPN. We also report a 72-year-old male patient who showed apogeotropic DCPN, but was proven to have a pontine infarction. The patients complained of disequilibrium which has lasted for 3-4 years and aggravated recently. The symptom was present only when he stood up, and was absent as soon as he sat down. He was not able to successfully perform the Romberg test and tandem gait on physical examination. Vestibular function test revealed apogeotropic DCPN without spontaneous nystagmus. Rotation chair test and caloric test results were all within normal limit. On the brain magnetic resonance imaging, newly detected infarction in the left basal ganglia, pons and right parietal lobe was found. Although horizontal canal BPPV is the most common cause of apogeotropic DCPN, we should be aware that there can be patients with central origin DCPN. In this report, we present the detailed history of this patient and tried to point out the clues to suspect central lesion in patients with apogeotropic DCPN.