Audiological findings in patients with myoclonic epilepsy associated with ragged-red fibres
T Tsutsumi1, H Nishida, Y Noguchi
1Department of Otolaryngology, School of Medicine, Tokyo Medical and Dental University, Tokyo, Japan. tsutsumi.oto@tmd.ac.jp
Abstract:
Sensorineural hearing loss is a common symptom in patients with myoclonic epilepsy associated with ragged-red fibres (MERRF), one of the mitochondrial encephalomyopathies, although the lesion causing hearing loss in such cases remains unknown. Here we describe the audiological features in three MERRF patients, all of whom exhibited a point mutation in their mitochondrial DNA at nucleotide 8344. Pure-tone threshold audiometry revealed bilateral, sloping-type, sensorineural hearing loss in all three patients. Distortion product otoacoustic emissions, electrocochleography, and auditory brainstem responses were variable, even differing between the right and left ears of the same patient. Taken together, our findings suggest that the primary lesion underlying hearing loss in MERRF patients is in the cochlea, although a retrocochlear lesion may be involved in some patients.
Insights
Sensorineural hearing loss is common in myoclonic epilepsy with ragged-red fibres (MERRF). This study suggests the cochlea is the primary site of damage in MERRF patients with hearing loss.
Area of Science:
- Neurology
- Genetics
- Audiology
Background:
- Sensorineural hearing loss is a frequent symptom in mitochondrial encephalomyopathies like myoclonic epilepsy with ragged-red fibres (MERRF).
- The precise location of the auditory system lesion in MERRF patients has not been identified.
- MERRF is associated with specific point mutations in mitochondrial DNA, such as at nucleotide 8344.
Observation:
- Three MERRF patients with the mitochondrial DNA 8344 point mutation were evaluated for audiological features.
- All patients presented with bilateral, sloping-type sensorineural hearing loss.
- Auditory tests including otoacoustic emissions, electrocochleography, and auditory brainstem responses showed variable results, sometimes differing between ears.
Findings:
- The audiological findings in MERRF patients indicate a primary lesion within the cochlea.
- The variability in test results suggests that retrocochlear involvement may also contribute to hearing loss in some individuals.
- A specific mitochondrial DNA mutation (8344) is linked to these audiological characteristics.
Implications:
- These findings help elucidate the pathophysiology of hearing loss in MERRF.
- Understanding the cochlear basis of hearing impairment can guide targeted audiological management and interventions for MERRF patients.
- Further research into retrocochlear contributions may refine diagnostic and therapeutic strategies for this condition.
