Inner ear dysfunction in myotonic dystrophy type 1

Myotonic dystrophy type 1 is associated with various oculomotor, vestibular, and auditory abnormalities. However, auditory system investigation has been mainly performed with the subjective method of pure-tone audiometry. In this study, a detailed vestibular and audiological evaluation was undertaken, including the objective and more sensitive method of transiently evoked otoacoustic emissions (TEOAEs).

Twenty-four patients with genetically diagnosed myotonic dystrophy type 1 and 21 controls were studied. Audiological and vestibular investigations included pure-tone audiometry, tympanometry, auditory brainstem responses (ABRs), TEOAEs, and electronystagmography.

Hearing impairment was evident in 15 (62.5%) patients and in nine of them (37.5%) ABR abnormalities were found. However, subclinical cochlear damage was found in all patients, as evidenced by absent emissions or lower otoacoustic emission amplitude. Vestibular hypesthesia was found in nine patients (37.5%), accompanied by spontaneous nystagmus in four of them (15.6%).

Auditory and vestibular abnormalities are quite common in patients with myotonic dystrophy type 1. However, it appears that subclinical cochlear damage is an ubiquitous finding of the disease.