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Indexed/Abstracted in: EMBASE, Scopus
Online ISSN 1827-188X
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.