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A Journal on Otorhinolaryngology, Head and Neck Surgery,
Plastic Reconstructive Surgery, Otoneurosurgery

Indexed/Abstracted in: EMBASE, Scopus




Otorinolaringologia 1998 June;48(2):67-71

language: English

The influ­ence of ­repeated sinu­soidal ­stimuli on a fol­lowing opto­ki­netic ­response

Taborelli G., Favata E., Melagrana A., D'Agostino R.

From the Otorh­i­nol­a­ryn­gology Depart­ment «Gian­nina Gas­lini» Insti­tute Genoa, ­Italy


Back­ground. ­Some ­authors ­assert ­that opto­ki­netic nys­tagmus (OKN) ­increases (or de­creases) a homo­di­rec­tional (or coun­ter­di­rec­tional) ves­tib­ular nys­tagmus ­evoked ­some ­time ­after its inter­rup­tion. ­They ­also ­state the oppo­site: an ­evoked OKN nei­ther ­increases nor ­decreases 10 ­min ­after the ­last of 10 coun­ter­clock­wise ­stop-­tests at 180°/sec. In ­this ­study, ­unlike all the ­other ­reports ­reviewed, we ­intend to ­observe if a ­very pro­longed and ­strong ves­tib­ular bidi­rec­tional rot­a­tory stim­u­la­tion can inter­fere ­with an OKN ­evoked ­some ­time ­after.
­Methods. In ­order to deter­mine ­whether the pre­vious state­ment may be pos­sible, 2 ­groups of 9 sub­jects ­each under­went ­very ­strong and pro­longed ves­tib­ular ­stimuli. In ­both ­groups of sub­jects sinu­soidal ­angular accel­er­a­tions ­test, of 10 and 20 ­min, respec­tively ­were ­applied. In ­every ­single ­group we eval­u­ated the pos­sible pres­ence of a sta­tis­tical dif­fer­ence ­between the ­basal and ­final (­look or ­stare) OKN ­either ­homo — or coun­ter­di­rec­tional to the ves­tib­ular nys­tagmus.
­Results. ­Both “­stare” OKN ( ­first ­group) and “­look”. OKN (second ­group) ­evoked 10 min ­after the inter­rup­tion of the sinu­soidal ­angular accel­er­a­tion ­test ­increase com­pared to the cor­re­sponding ­basal OKN, but ­such an ­increase is sig­nif­i­cant (“t”-­test on ­paired dif­fer­ences) ­only for “­look” ampli­tude and ­slow ­speed component. So we sug­gest ­that ­also a ves­tib­ular stim­u­la­tion (­which ­should be ­very ­strong and pro­tracted) can inter­fere ­with a fol­lowing OKN.
Con­clu­sions. We ­think ­that (in the clin­ical ­field) a suit­ably ­long ­time ­interval ­between ves­tib­ular and opto­ki­netic ­tests is nec­es­sary in ­order to ­avoid inter­fer­ences ­which ­might ­change the nys­tagmic ­response and ­lead to a ­wrong diag­nosis.

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