Daniel R. Gold, DO, Departments of Neurology, Ophthalmology, Neurosurgery, Otolaryngology - Head & Neck Surgery, Emergency Medicine, and Medicine, The Johns Hopkins School of Medicine
This is a 45-year-old woman with a chronic progressive cerebellopathy of unclear etiology (worsening over at least 10 years) characterized by gait and limb ataxia, gaze-evoked nystagmus, saccadic pursuit and vestibulo-ocular reflex suppression, an esotropia greater at distance, along with very mild downbeat nystagmus (DBN), mainly seen with the ophthalmoscope. This constellation of ocular motor signs localizes well to the flocculus/paraflocculus. Following 40 seconds of hyperventilation, which induces alkalosis and alters intra- and extracellular calcium concentrations, she demonstrated prominent DBN. This finding has been described in patients with cerebellar pathology, and has been theorized to relate to sensitivity of cerebellar voltage-gated calcium channels (e.g., P/Q-type or other abnormal ion channels) to the alkalosis induced by hyperventilation.
1. Walker MF, Zee DS. The effect of hyperventilation on downbeat nystagmus in cerebellar disorders. Neurology 1999;53:1576-1579.
Daniel R. Gold, D.O. Departments of Neurology, Ophthalmology, Neurosurgery, Otolaryngology - Head & Neck Surgery, Emergency Medicine; The Johns Hopkins University School of Medicine
Spencer S. Eccles Health Sciences Library, University of Utah