ISSN 1612-3352

Editors in Chief

Prof. Dr. Claus F. Claussen, Neurootological Research Institute of the Research Society for Smell, Taste, Hearing and Equilibrium Disorders at Bad Kissingen (4-G-F). Bad Kissingen, Germany.
Dr. med. Julia M. Bergmann,
Dr. med. Guillermo O. Bertora,
Otoneuroophthalmological Neurophysiology,
Buenos Aires, Argentina.

Production Managers

Dr. med. Julia M. Bergmann,
Dr. med. Guillermo O. Bertora,
Otoneuroophthalmological Neurophysiology,
Buenos Aires, Argentina.


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Electronystagmographic analysis of optokinetic and smooth pursuit eye movement disorders in vestibular lesions

Abstract

The electronystagmographical analysis is very important in most of the vestibular disorders. The analysis of the caloric test is very useful in the differential diagnostic procedure of central and peripheral vestibular lesions. Authors analyzed the results of their 327 patients examined in the last 18 months.
Methods: In the OKN test the target is moving horizontally with 20 degree/seconds. In the smooth pursuit eye movement test the target is moving sinusoidally with 0.2 – 0.7 Hz in a 34 degree screen. Electronystagmography was performed with ICS Chrtr® electronystagmograph. The caloric test was performed with 25 and 50 ˚C air insufflations (5 liter/min, 40 seconds).
The aims of the study were:
1. What are normal caloric test results and normal average slow phase velocities after the irrigation with above mentioned parameters?
2. Comparing the optokinetic or the smooth pursuit eye-movement sensitivity and specificity in several vestibular disorders.
The patients (n= 327) were divided into five groups: right and left unilateral and bilateral peripheral lesions, central vestibular dysfunction, and normal vestibular function.
Results: The average caloric nystagmus in normal vestibular system was 17.4 degree/sec, in unilateral vestibular lesion are 14.65, and in compensated bilateral lesion is decreased (9.56 degree/sec). In the central dysfunctions the average caloric ASPV is increased (19.7 degree/sec)
Optokinetic eye movement was pathological in 9.53% of patients with normal vestibular function. In unilateral lesions, 17.42% of the OKNs were pathological.
In the bilateral peripheral vestibular dysfunction the ratio of the pathological eye-movements was 28%. In central vestibular lesions 22.72% of the patients had abnormal optokinetic eye movements.
The smooth pursuit eye movements were pathological in 8.3% of patients with normal vestibular system. In unilateral peripheral lesions 20.3%, while in bilateral lesions 28% were pathological results. In patients with central vestibular lesions the smooth pursuit eye movement was abnormal in 41.6%.
Conclusions: In unilateral and in bilateral peripheral vestibular lesions mild and moderate decreased caloric nystagmus ASPV can be observed, while in a central vestibular lesions the caloric nystagmus ASPV is increased, presumably because of the lack of central inhibiting mechanisms.
Our results show, that in the unilateral vestibular lesions the smooth pursuit eye movement examination is more sensitive than the OKN test, while in bilateral peripheral vestibular lesions the sensitivity is the same. In central dysfunctions the smooth pursuit eye movement examination seems to be more sensitive than OKN examination.

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