Postcaloric nystagmus by positional change and other neurootological findings

The postcaloric nystagmus (PCN) by positional change from the supine position to the upright position and other neurootological findings were studied. Twenety-one patients with a clinical diagnosis of spinocerebellar degeneration or Arnold-Chiari malformation were studied. There was a significant negative correlation between maximum slow phase eye velocity in postcaloric nystagmus by positional change (V2) and maximum slow phase eye velocity in optokinetic nystagmus pattern test (r = -0.47; n = 21). Moreover, patients with vertical gaze nystagmus (VN) had significantly larger V2 than patients without VN. However, there was no significant difference for V2 between patients with and without rebound nystagmus. Through these studies, the authors discussed probable mechanisms and responsible lesions for the exaggerated PCN by positional change.