NYSTAGMUS is a rapid involuntary oscillation of the eyeballs. It can be the result of an impulse from the labyrinthine nerve endings to the ocular muscle nuclei in the brain stem. When linear acceleration occurs, endolymphatic fluid in a semicircular canal pushes against the cupula thus distorting the normal position of the hair cells. The movement of the hair cells changes the polarity of the sensory cells and thus initiates nerve impulses to the brain. Via reflex arcs to eye muscle centers these impulses cause movement of the eyeballs. The flow of endolymph resulting from head or body movement may therefore cause nystagmus, the direction of which will depend on the direction of the endolymphatic stream.
Measurement of nystagmus is important because it can give the clinician or researcher an objective modality for the measurement of vertigo. Frequency, amplitude, velocity, and duration are some of the parameters which can be
Norris C. Notes on Nystagmography: Method and Calibration. Arch Otolaryngol. 1967;85(3):265–268. doi:10.1001/archotol.1967.00760040267006
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