Auditory brainstem responses (ABR) in multiple sclerosis

Thirty-two multiple sclerosis (MS) patients, 10 males and 22 females, aged between 21 and 55, underwent pure-tone audiometry and testing of auditory brainstem response (ABR). Thirteen were classified as 'definite', 12 as 'probable' and 7 as 'possible', according to the McAlpine criteria. Each ear of each patient was tested monoaurally. The most common alterations were seen in the parameters of the cross-correlation between the normal template and the template of the individual MS patient. The second most altered parameters were those concerning the V wave which was absent in most cases but, when present, rarely showed latency-amplitude values falling outside the 90% confidence limit ellipses. Test-retest replicability and stimulations with increasing numbers of stimuli per second were useful in detecting intra-individual variability of waveform characteristics. When considering all the tests performed, 88% of the 'definite', 71% of 'probable' and 64% of 'possible' MS patients' ears showed ABR abnormalities. We stress the importance of a separate evaluation of the two ears due to the frequent unilateral alterations, and of an accurate evaluation of the ABR characteristics. We conclude that brainstem audiometry is a more reliable test for detecting demyelinating processes than is usually described in the literature.