Positional nystagmus of central origin.

Audiometric, electrophysiologic, and radiographic findings for a 68-year-old male with an "imbalance" concern are presented. This paper has a two-fold purpose: (1) to present an unusual electronystagmography case study and (2) to highlight the importance of test conditions in lesion localization. The specific disease pathophysiology remains obscure. Repeated hearing tests documented a known hearing impairment with worsening word-recognition ability of the right ear. An initial electronystagmographic exam was normal except for a mild ageotropic direction-changing positional nystagmus with eyes open and fixed. No repeatable click-evoked auditory brainstem response waveforms could be collected. A magnetic resonance imaging of the brain documents diffuse ischemic white matter disease. A repeated vestibular examination some months later supports the initial findings. The case illustrates the importance of following diagnostic protocol, of repeated measures, and of using both a visual fixation and a nonfixation condition for select electronystagmographic subtests.