Direction-changing positional nystagmus: incidence and meaning.

Direction-changing positional nystagmus (DCPN) is a nystagmus that changes its direction with different body and head positions. Many authors consider that it indicates the presence of a central nervous system lesion. Of 1,196 patients whose abnormal electronystagmographic (ENG) traces were reviewed, 46 (3.8 per cent) showed DCPN. Of these, ten (22 per cent) had central neurologic diseases, 14 (30 per cent) had peripheral vestibular diseases, and for 22 (48 per cent) there was no definite clinical diagnosis. Nineteen patients (41 per cent) with DCPN had ENG findings suggesting a peripheral vestibular lesion, while only five (11 per cent) had ENG findings suggesting a central vestibular lesion. Four of 44 control subjects exhibited DCPN. Thus, the presence of DCPN does not necessarily indicate disease of the vestibular system and definitely does not localize the site of a lesion in the vestibular pathways, but more often indicates a peripheral vestibular site. As with spontaneous nystagmus, lack of suppression with fixation suggests a central lesion.