持続型方向交代性上向性眼振例の検討

Persistent type of apogeotropic direction-changing positional nystagmus

はじめに

　外側半規管型BPPVのなかで，減衰型方向交代性下向性眼振を示すものは，半規管結石症（canalolithiasis）と考えられており^1），Lempert法^2）などの浮遊耳石置換法が有効であることはすでによく知られている。一方，持続型で方向交代性上向性眼振を示すものは，議論はあるが，外側半規管のクプラ結石症（cupulolithiasis）で説明されている^1,3）。今回，当科で経験した持続型方向交代性上向性眼振を示した症例を検討し，その病態につき，若干の文献的考察を加え報告する。

　We evaluated 13 patients with persistent type of apogeotropic direction-changing positional nystagmus（DCPN）retrospectively. The duration of nystagmus lasted more than 1 minute and the neutral position in which the nystagmus ceases was identified in all cases. Three cases showed apogeotropic DCPN converted to transient geotropic DCPN, which was cured by barbecue rotation and forced prolonged position. It was thought that persistent apogeotropic DCPN was probably caused by otolithic factor. On the other hand, in the cases whose nystagmus disappeared naturally, we guess they were caused by a cupula denser than the endolymph, as the late phase of positional alcohol nystagmus.