Study of the Cochlear Function in Patients with Myotonic Dystrophy Type 1

Abstract

Objectives: Myotonic Dystrophy type 1 is a progressive autosomal dominant multisystem disorder, the second most common form of muscular dystrophy. The disease is associated with various vestibular, oculomotor, and auditory disorders. The aim of the present study was to undertake a detailed vestibular and audiological evaluation, and specifically to analyze the cochlear function using transiently evoked otoacoustic emissions. Methods: 24 patients with genetically diagnosed myotonic dystrophy type 1 were studied during the past 4 years in Eginition hospital of Athens. Twenty-one normal subjects were used as controls. Testing included pure-tone audiometry, tympanometry, auditory brainstem responses (Abr), transiently evoked otoacoustic emissions, and nystagmography. Results: Tympanograms were normal in most patients. 15 (62.5%) patients had a varying degree of sensorineural hearing loss, with no conductive element. In 9 of them (37.5%), ABR abnormalities were found, such as absence of wave I or increased latencies of waves III and V, compatible with sensorineural hearing loss (5 patients), as well as increased I-III and I-V interpeak latencies, compatible with retrocochlear involvment of the auditory pathways (4 patients). Subclinical cochlear damage was found in all patients, as evidenced by absent otoacoustic emissions or lower otoacoustic emission amplitude. Vestibular hypersthesia was found in 9 patients (37.5%), accompanied by spontaneous nystagmus in 4 of them (15.6%). Conclusions: Audiovestibular abnormalities are quite common in patients with myotonic dystrophy type 1. We have found that subclinical cochlear damage is a common finding of the disease, as concluded from the absence or decrease of otoacoustic emissions in these patients.