Involvement of the audiovestibular system in multiple sclerosis. An otoneurologic and audiologic study

This study was performed on a material of 70 patients, who fulfilled the criteria of definitive MS. All the patients were examined by an otologist, a neurologist and a neuro-ophthalmologist. A wide range of audiologic and otoneurologic tests were used to obtain a good understanding of the respective disorders in MS, to gain a better knowledge of the role of otology in MS, to correlate the results with the clinical findings in order to find the most useful tests to detect MS lesions and to describe pathophysiologic aspects of central lesions using MS as a model. The material consisted of MS cases representing mild or moderate stages of disability (Hyllested classification 1.-4); 32 belonged to Hyllested group 1., 19 to group 2., 7 to group 3. and 12 to group 4. The age and sex distribution were similar with materials described earlier, as were most of the clinical neurologic findings. The material can thus be considered representative. The neuro-ophthalmologic examination served to rule out causes other than MS for abnormalities observed in the tests. Besides the clinical neurologic and otoneurologic evaluation a number of additional tests were performed. The ENG tests consisted of registration for spontaneous and positional nystagmus, of smooth pursuit and saccadic eye movements, optokinetic nystagmus and caloric reactions. The audiologic evaluation was based on the following tests: pure tone audiograms, speech reception thresholds, discrimination scores, filtered speech test, stapedius reflex thresholds, stapedius reflex decay and auditory brainstem responses. The clinical otologic examination revealed little abnormalities, which is well in accordance with the pathophysiology of MS. In addition the clinical examination ruled out peripheral lesions as reasons for observed abnormalities. Numerous abnormalities were found during the otoneurologic examination of the cranial nerves. The amount of abnormal findings in the otoneurologic examination were surprisingly high: only one patient exhibited normal results in all the tests used. The abnormalities most often encountered were those of smooth pursuit (96%), followed by saccadic eye movements (76%), optokinetic nystagmus (53 %), and abnormalities in the caloric reactions such as dysrhythmia (40%) and defective visual suppression of the nystagmus (43%). When comparing the results obtained with ENG with those of clinical findings seen during the neuro-ophthalmologic examination, a good intercorrelation was found. Yet, in many ENG tests a number of cases with subclinical abnormalities only, were observed, which stresses the importance of exact and objective methods for the registration of eye movements.(ABSTRACT TRUNCATED AT 400 WORDS)