Spontaneous and positional nystagmus in healthy persons demonstrated only by electronystagmography: Physiological spontaneous nystagmus or ?functional scar??

Abstract

We wanted to ascertain whether a physiological horizontal vestibular spontaneous nystagmus is existent, or whether the spontaneous and positional nystagmus seen in clinically healthy persons in the electronystagmogram -- when fixation had been excluded completely -- was always the result of earlier damages to the vestibular system (Jatho). For this purpose we tried to detect a spontaneous and positional nystagmus in 102 healthy persons from 6 age groups (17 each) between 11 and 70 years of age. When the ENG was registered with open eyes in darkness, 63 out of the 102 test persons had a horizontal spontaneous or positional nystagmus, however, under the Frenzel glasses there was a nystagmus in only 2 out of these test persons. With open eyes in darkness, the frequency and intensity was the same in all age groups. With this, we believe to have proved that a physiological horizontal vestibular nystagmus does exist. We share Kornhuber's opinion that the examination with the Frenzel glasses in a dark room, together with the head shaking test and positional test, at the present time represents the best method for differentiating between physiological and pathological spontaneous nystagmus.

Spontaneous Nystagmus in Normal Subjects

“…Although monothermal cold caloric testing alone does not indicate reduced vestib ular function [6], a right-left difference of more than 40% was observed in 3 of 5 subjects with spontaneous nystag mus. Although Coats [7] and Mulch and Lewitzki [13] found normal caloric responses in subjects with sponta neous nystagmus, other studies [6. 14] found that the right-left difference in caloric response varied greatly, even among normal subjects.…”

“…In the present study, the SPEV of spontaneous nystagmus was less than 6°/s in all but 1 subject. In the studies by Coats [7] and Mulch and Lewitzki [ 13], the SPEV of spon taneous nystagmus was less than 6°/s in most subjects. Sills et al [14] reported that it was less than 5°/s.…”

“…In addition, some authors [2,4,13] did not differ entiate spontaneous nystagmus from positional nystag mus. Mulch and Lewitzki [13] defined spontaneous nys tagmus as the occurrence of at least 3 consecutive nystag mus beats; Bos et al [4], Coats [7] and Eviatar et al [8] defined it as nystagmus lasting for 30 s, and Fluur and Eriksson [ 1 ] defined it as nystagmus lasting for 60 s. In the present study, we defined spontaneous nystagmus as nys tagmus that was unaffected by posture and was present in one or the other of 3 conditions: with the eyes closed, with the eyes open in darkness, and with the eyes open and fixed in the primary position; Eviatar et al [8], Stahle [ 16] and Coats [17] also defined nystagmus thus. We consid ered nystagmus significant if consecutive nystagmus beats lasting at least 30 s were recorded.…”

“…This raises the question whether transient spontaneous nystagmus has pathophysiological signifi cance. Coats [7] and Mulch and Lewitzki [13] regarded nystagmus as idiopathic and physiological, while Hinchcliffe [6] reported that it was not always pathological. Milojevic [5] considered nystagmus to have pathological significance.…”

Nystagmus Findings in Healthy Subjects Examined with Infrared Videonystagmoscopy

“…When it comes to positional nystagmus most studies concern ENG recordings in darkness. For example Mulch and Lewitzki [6] found positional nystagmus in lateral positions in about 30% of the subjects. In head hanging position the frequency of nystagmus was similar (28%), however the presence of torsional or oblique components in this position was not mentioned.…”