Galvanically induced asymmetric optokinetic after-nystagmus

• The effect of an asymmetric vestibular input on the symmetry of horizontal optokinetic after-nystagmus (OKAN) was studied in twenty healthy subjects. Optokinetic nystagmus (OKN) was elicited by a whole-field optokinetic drug, rotating at 90 degrees/s, and eye-movements were recorded by a DC electro-oculographic technique (EOG). The ratio of OKAN following right and left-beating OKN respectively was computed. An asymmetric vestibular input was generated by a continuous bi-polar, bi-aural galvanic stimulus (1 mA) to the vestibular nerves during the optokinetic stimulation and the recording of the OKAN. During galvanic stimulation the relation between left and right-beating OKAN was asymmetric, compared with the OKAN found after optokinetic stimulation only. The galvanic stimulus caused a preponderance for OKAN with the fast phase beating toward the cathode. Thus, the small vestibular asymmetry induced by the galvanic stimulus, which was not strong enough to produce nystagmus by itself, caused an asymmetric OKAN. These findings suggest that examination of OKAN may be of value to detect small vestibular asymmetries in peripheral vestibular disorders in man.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Oto-rhino-laryngologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Otorhinolaryngology (hsv//eng)

Keyword

Adult

Electric Stimulation

Electrooculography

Female

Humans

Male

Middle Aged

Nystagmus, Physiologic

Vestibular Nerve

Journal Article

Research Support, Non-U.S. Gov't

Publication and Content Type

art (subject category)

ref (subject category)