Post-Caloric Nystagmus by Positional Change

We investigated the postcaloric nystagmus that is related to positional change in 24 patients with spinocerebellar degeneration (SCD) and compared it with that in normal subjects. Six ears of 3 patients exhibited no evaluable caloric response. In 42 ears of 21 patients, the primary phase of caloric nystagmus was definitely observed. In 37 of 42 (88%) ears, postcaloric nystagmus was observed. The postcaloric nystagmus from a positional change in patients with SCD was significantly larger than that in control subjects. Furthermore, it was significantly exaggerated in patients with brainstem and cerebellar lesions in comparison with patients with pure cerebellar lesions. The degree of disturbance coming from visual suppression had only a limited correlation with the exaggerated postcaloric nystagmus. Also discussed are possible other factors affecting the exaggerated postcaloric nystagmus.