Abstract
Head shaking nystagmus (HSN) is a pathological afternystagmus. It has been known that HSN manifests itself mainly on the basis of vestibular asymmetry. We analyzed 94 patients with vertigo of peripheral origin for the most part, in whom both bithermal caloric and horizontal head shaking stimulations were performed at the initial clinical examination. All patients had a follow-up period of at least two months with repeated head shaking tests. All nystagmus was observed with Frenzel's spectacles in darkness. The main results obtained are as follows : 1. Horizontal HSN reflects very well caloric canal paresis, but it is also subject to the influence of various factors other than canal paresis, such as presumably the directional preponderance of the vestibular system or latent spontaneous nystagmus. 2. Horizontal HSN may reverse its direction in the course of months. This occurs especially in endolymphatic hydrops, as in Meniere's disease, or in recurrent vestibular vertigo, occasionally also in patients with central lesions.
