ORIGINAL ARTICLES   

Otorinolaringologia 1998 December;48(4):177-81

Copyright © 2000 EDIZIONI MINERVA MEDICA

language: English

ENG investigations about after optokinetic nystagmus in man

Taborelli G., Pasquale G., D’Agostino R., Melagrana A.

From the Divisione ORL, Istituto «G. Gaslini» Genova Quarto

Back­ground. We car­ried out ­research ­regarding the pres­ence, in man, of opto­ki­netic ­after nys­tagmus (­OKAN) fol­lowing ­OKAN1 and ­OKAN2 (respec­tively homo­lat­eral and coun­ter­lat­eral opto­ki­netic ­after nys­tagmus to the ­former OKN: opto­ki­netic nys­tagmus).
­Methods. We exam­ined 50 ­patients ­with a com­pletely neg­a­tive oto­ves­tib­ular neu­ro­log­ical and oph­tal­mo­logic anam­nesis. We sub­mitted ­each ­patient to an ­unbroken OKN stim­u­la­tion (at an ­angular ­velocity of 30 ­degrees/sec.) ­which ­lasted 30 min­utes.
25 ­patients ­were stim­u­lated by clock­wise OKN and 25 by coun­ter­clock­wise OKN, in 27 ­cases the OKN was of “­stare” ­type and in 23 ­cases it was of “­look” ­type.
We ­recorded the ­OKAN al ­least 15 min­utes ­after extin­guishing the ­light ­with a Ton­nies elec­tro­nis­tag­mo­graph.
­Results. We ­observed the com­par­ison of ­OKAN1 in all ­patients (100%) ­while ­OKAN2 was ­clear in 23 ­cases (46%). In 7 ­patients (14%) we ­point out ­OKAN3 and ­OKAN4 (respec­tively con­tra­lat­eral and homo­lat­eral opto­ki­netic ­after nys­tagmus to the ­OKAN2).
Con­clu­sions. ­Unlike mon­keys the ­modest ­results ­obtained in man ­could be jus­ti­fied by a ­lower ­adopted opto­ki­netic stim­u­la­tion and by a ­great devel­op­ment of the ence­phalic ­cortex ­which car­ries out a reg­u­lating and mod­ulator and per­haps inhib­i­tory ­action of the evo­ca­tion of ­OKAN.
In the ­cases in ­which ­OKAN2, ­OKAN3 and ­OKAN4 ­have not ­been ­observed we ­could sup­pose the evo­ca­tion of a ­cyclic ­course reac­tion, a ­sort of nys­tag­mus­be­reits­chaft ­which, how­ever ­does not ­express a ­real nys­tagmus.