Somatosensory evoked potentials and sensory involvement in multiple sclerosis: comparison with clinical findings and quantitative sensory tests

Sensory disturbances are one of the most common findings in patients with multiple sclerosis (MS). However, they are usually assessed at the standard neurological examination only. Quantitative Sensory Tests (QSTs) for temperature and vibratory sense allow a more objective evaluation. In a group of 19 clinically definite MS patients, we compared vibratory and temperature thresholds with sensory symptoms or signs at clinical neurological examination and somato sensory evoked potentials (SEPs) at the four limbs. The frequency of abnormalities of clinical symptoms/signs, vibration threshold and median SEPs were 69%, 33% and 55%, respectively. Correlation between degree of abnormality of SEPs and clinically assessed vibration sense (V) was statistically significant (P<0.007; Spearmann rank coefficient), as well as between SEPs and vibration perception threshold (P<0.02). Clinical evaluation of thermal sense did not show false positive results compared to quantitative thermal threshold, but false negative findings (35%). This study suggests that the combined use of vibration threshold and SEPs allows a better objectivation of sensory function, allowing the detection of subclinical abnormalities and possibly reducing the number of false positive results introduced by clinical assessment. Moreover, QSTs are to be preferred to clinical evaluation in the assessment of thermal sense, due to their superior sensitivity.