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Issues Affecting the Hearing

Hearing impairment occurs commonly as part of the mitochondrial disease phenotype and may be present in up to half of all cases (Chinnery, 2000). It is usually due to cochlear or sensorineural hearing loss, though the source of concern may be even more central in origin when there is active brain involvement (Chinnery, 2006). However, in some patients and in those with some degree of immune dysfunction, recurrent ear infections may occur leading to a conductive hearing loss.

Hearing loss related to mitochondrial mutations may be syndromic and non-syndromic in nature (Fischel-Ghodsian, 2003). The 1555 A-G 12S tRNA mutation is associated with slowly progressive, high-frequency, sensorineural hearing loss; sudden worsening can occur with exposure to aminoglycoside antibiotics (Usami, 1997). Some component of acquired hearing loss with age may be related to mitochondrial dysfunction related to an accumulation over time of a significant load of mtDNA mutations (Fischel-Ghodsian, 2003).

In some cases, the problem may not be with hearing as much as it is a delay in auditory processing related with lethargy or fatigue. As the fatigue resolves, the patient generally recovers to his/her baseline. Persistent issues with processing are more likely to be associated with developmental or learning issues (which may or may not be due to the underlying energy disorder).

Mitochondrial Differential Diagnosis

1. Sensorineural hearing loss -

a. Syndromic hearing loss (e.g., MELAS or Kearns-Sayre syndromes);

b. Non-syndromic hearing loss (e.g., A1555G mutation);

c. Associated with aging;

2. Conductive hearing loss (e.g., from recurrent infections);

3. Auditory processing problems (or hearing inattention) -

a. Due to the underlying mitochondrial disease;

b. Related to fatigue or lethargy.

Assessment

1. If the patient seems to demonstrate hearing inattention, determine what symptoms are associated with the hearing loss and whether or not there are any trigger factors (such as fatigue or infections);

2. If not variable in its course, is there a family history?

3. Is there a history of frequent infections?

4. Is there a history of aminoglycoside use?

5. Is there a safety concern related to the hearing impairment?

Recommendations

1. Refer to audiologist if there are concerns about hearing loss. Patients with mitochondrial disease should have regular hearing assessments given the increased risk for developing sensorineural hearing loss.

2. Refer to otolaryngologist as appropriate, especially if there is a history of recurring otitis media or related sinusitis.

3. Consider testing for mtDNA mutations associated with hearing loss (A1555G).

4. Consider hearing aids or cochlear implants when appropriate.

5. A developmental or neuropsychological assessment might be necessary if auditory processing is considered to be the issue and is not secondary to fatigue or lethargy.

References 

Chinnery PF, Elliott C, Green GR, et al. The spectrum of hearing loss due to mitochondrial DNA defects. Brain 2000; 123(Pt1):82-92

Chinnery PF, Griffiths TD. Mitochondrial otology. In Mitochondrial Medicine. DiMauro S, Hirano M, Schon EA, eds. Informa Healthcare, Abingdon UK, 2006, 161-78.

Donovan LE, Severin NE. Maternally inherited diabetes and deafness in a North American kindred: Tips for making the diagnosis and review of unique management issues. J Clin Endocrinol Metab 2006;91(12):4737-42.

Fischel-Ghodsian N. Mitochondrial deafness. Ear Hearing 2003;24(4):303-13.

Forli F, Mancuso M, Santoro A, et al. Auditory neuropathy in a patient with mitochondrial myopathy and multiple DNA deletions. J Laryngol Otol 2006;120(10):888-91.

Hill D, Wintersgill S, Stott L, et al. Cochlear implantation in a profoundly deaf patient with MELAS syndrome. J Neurol Neurosurg Psychiatr 2001;71(2):281.

Keats BJ. Genes and syndromic hearing loss. J Communication Dis 2002;35(4):355-66.

Tawankanjanachot I, Channarong NS, Phanthumchinda K. Auditory symptoms: A critical clue for the diagnosis of MELAS. J Med Assoc Thailand 2005;88(11):1715-20.

Usami S, Abe S, Kasai M, et al. Genetic and clinical features of sensorineural hearing loss associated with the 1555 mitochondrial mutation. Laryngoscope 1997;107(4):483-90.

Yasumura S, Aso S, Fujisaka M, Watanabe Y. Cochlear implantation in a patient with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes syndrome. Acta Otolaryngol 2003;123(1):55-8.

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