Hyperventilation-Induced Downbeat Nystagmus in a Cerebellar Disorder

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: 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. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: This patient presented with a chronic progressive cerebellar degeneration 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 https://collections.lib.utah.edu/ark:/87278/s6g77x3f