Audiological findings in the Charcot-Marie-Tooth Disease

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Brazilian Journal of Otorhinolaryngology

4115 - Vol. 77 / Ed 1 / in 2011

Audiological findings in the Charcot-Marie-Tooth Disease

Authors:

Fukushima1; Sens2; Ernani Lambert3

Keywords: charcot-marie-tooth disease, hearing loss, polyneuropathies.

INTRODUCTION

Charcot-Marie-Tooth disease (CMT) is one of a group of clinically and

genetically heterogeneous polyneuropathies. The prevalence is 1:2,500. It is

characterized by peripheral nerve degeneration, which results in distal muscle

atrophy, loss of sensitivity, and hand and foot deformities; deep reflexes are

also affected.1,2 The most common form is autosomal dominant.3

A clinically distinct condition is the association of this disease with hearing

loss, suggesting an abnormal expression on the PMP22 gene.1

OBJECTIVE

The purpose of this study was to report a case of a patient with

Charcot-Marie-Tooth disease, highlighting its importance in the differential

diagnosis of hearing loss.

CASE REPORT

A female patient aged 42 years complained of difficulties in understanding

speech, especially in noise environments, developing within the last 2 years. An

electromyography was done in 1992 because of pain associated with absent deep

reflexes in the lower limbs, and valgus knees; this test revealed marked chronic

mixed peripheral axonal-demyelinating polyneuropathy (sensitive and motor) in

the four limbs, which suggested type 1 CMT disease.

The pain progressed and affected the upper limbs and right shoulder; lower limb

hypoesthesia, paresthesia and weakness were also present.

The otorhinolaryngological physical examination was normal. Auditory thresholds

were within normal limits. Acoustic immittance testing demonstrated type A

tympanograms, and bilaterally absent ipsilateral and contralateral acoustic

reflexes. Responses were bilaterally absent in the brainstem auditory evoked

potential (BAEP) test. Otoacoustic emissions were altered, and an assessment of

auditory processing revealed decoding disorders and non-verbal deficits.

DNA studies of the patient and her parents (PCR and Southern blot methods) found

no duplication or mutation on the PMP22 gene in the chromosome 17 (which

explains most cases of type 1 CMT); these studies, however, do not preclude

another form of CMT disease.

DISCUSSION

Musiek et al.2 reported a similar case in which the only complaint was

difficulty in understanding speech; the tests yielded similar results to our

case, suggesting that an association between hearing loss and CMT disease is

rare. However, we found reports in the literature of families diagnosed with CMT

disease, including family members with hearing loss; the attending physicians

were advised to carry out auditory testing for patients with CMT disease.3,4 In

these families, the onset of hearing loss occurred at an earlier age in

subsequent generations.

There is no single reported feature for hearing loss in CMT disease. Kovach et

al.4 described sensorineural tests of limbs in a family, which ranged from

normal results to profound losses. Papadakis et al.3 described a case of sudden

hearing loss with profound bilateral sensorineural loss associated with CMT

disease.

As with our patients, several authors reported altered acoustic reflexes and

abnormal BAEP, in which wave latencies were increased or absent.4-6

Kovach et al.1 found altered BAEP and otoacoustic emissions results in the study

family, which were similar to those in our case, suggesting that there are

audiological differences between families with CMT disease and dysacusis. The

mechanism of cochlear involvement, however, remains unclear. Starr et al.6

reported 8 subjects with CMT disease that presented absent BAEP and normal

otoacoustic emissions, which were characterized as auditory neuropathy.5

As our case had altered otoacoustic emissions, the diagnosis of auditory

neuropathy did not apply; however, BAEP and otoacoustic emissions changes were

probably due to demyelinated auditory pathways because of CMT disease.

COMMENTS

CMT disease is relevant in the differential diagnosis of sensorineural hearing

loss, particularly if hereditary hearing loss is suspected. Specialists should

be aware of the possible association between hearing loss and CMT disease, to

support appropriate treatment for patients.

REFERENCES

1. Kovach MJ, KCM, Herman K, Waggoner B, Gelber D, et al. Antecipation

in a unique family Charcot-Marie-Tooth Syndrome and deafness: delineation of

clinical features and review of the literature. Am J Med

Genet.2002;108(4):295-303.

2. Musiek FE, Weider DJ, Mueller RJ. Audiologic findings in Charcot-Marie-Tooth

disease. Arch Otolaryngol.1982;108(9):595-9.

3. Papadakis CE, Hajiioannou JK, Kyrmizakis DE, Bizakis JG. Bilateral sudden

sensorioneural hearing loss caused by Charcot-Marie-Tooth disease. J Laryngol

Otol.2003;117(5):399-401.

4. Kovach MJ, Lin J, Boyadjiev S, K, Mazzeo L. A unique point mutation

in the PMP22 gene is associated with Charcot-Marie-Tooth disease and deafness.

Am J Hum Genet.1999;64(6):1580-93.

5. Raglan E, Prasher DK, Trinder E, Rudge P. Auditory function in hereditary

motor and sensory neuropathy (Charcot-Marie-Tooth disease). Acta

Otolaryngol.1987;103:50-5.

6. Starr A, Picton TW, Sininger Y, Hood LJ, Berlin CI. Auditory neuropathy.

Brain.1996;119:741-53.