Objective: To evaluate the progression of peripheral vestibular dysfunction in patients with an A-to-G point mutation at nucleotide pair 3243 in mitochondrial DNA (A3243G mutation).
Study design: Retrospective patient series.
Setting: Tertiary referral center.
Patients: Six unrelated patients with an A3243G mutation (four mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes; and two maternally inherited diabetes and deafness; five females and one male; average age 41 ± 11.3 yr old), who underwent repeated vestibular examinations, were included (average interval between the first and second examinations: 5.7 ± 2.1 yr).
Intervention: Diagnostic.
Main outcome measure: Results of caloric testing and cervical vestibular evoked myogenic potential testing in response to air-conducted sound were analyzed.
Results: All the patients except one, who was already completely deaf in both ears at the first examination, showed progression of hearing loss (average 4.0 ± 6.3 dB per year). Five of the six patients had vestibular symptoms at the first examination. The other patient developed dizziness later. Caloric responses were abnormal in four patients at the first examination and in five patients at the second examination. Cervical vestibular evoked myogenic potential responses were bilaterally absent in three patients at the first examination and in five patients at the second examination.
Conclusions: The A3243G mutation causes progression of peripheral vestibular dysfunction as well as that of hearing loss.