Oculomotor, auditory, and vestibular responses in myotonic dystrophy

In 13 patients with myotonic dystrophy, oculomotor, auditory, and vestibular tests were performed. All 13 patients showed one or more abnormalities. There was a significant increase in the penetrance of the separate abnormalities with age. Saccadic slowing was found in 10 patients, in a severe form in three. Seven patients had a sensorineural high-tone hearing loss (30 to 85 dB at 8 kHz), which was in excess of that expected for their age, that could be attributed to myotonic dystrophy. Brain-stem auditory evoked potentials showed a significant interwave delay of the I-V interval (0.35 to 0.7 milliseconds). An abnormal vestibulo-ocular reflex was found in six patients; three had vestibular hyperreflexia with increased gain, and three had hyporeflexia with short time constants. This study confirms that in myotonic dystrophy, sensory system involvement can be found on both a peripheral and a central level.