Irreversible cochlear damage in myasthenia gravis -- otoacoustic emission analysis

Acta Neurol Scand. 2006 Jan;113(1):46-54. doi: 10.1111/j.1600-0404.2005.00541.x.

Abstract

Objective: Acetyl choline (ACh) is the main neurotransmitter of the efferent auditory system. This study is aimed to evaluate cochlear function in myasthenia gravis (MG), a neuromuscular transmission disorder caused by ACh receptor autoantibodies.

Methods: This prospective study included 16 myasthenic patients, tested audiologically twice, first after improvement from myasthenic crisis or acute oropharyngeal dysfunction (1 week from admission) and then 2 months later. We detected the effect of contralateral acoustic stimulation (CAS) on patients' transient and distortion product otoacoustic emissions (TEOAE and DPOAE).

Results: Compared with controls, patients reported significant reduction in overall echo response and amplitude of TEOAEs at 1-2 kHz and at 1-6 kHz of DPOAE with marked reduction at 5 kHz. In the control group, CAS produced amplitude reduction in TEOAEs and DPOAEs at 1-4 kHz. Utilizing masking effect, patients reported amplitude reduction in TEOAEs at 1.5-4 kHz while DPOAEs did not reach significant level except at 1.5 and 5 kHz. After 2 months, no changes were observed compared with early assessment.

Conclusions: It is clear that disease progression is associated with irreversible cochlear damage. Lack of improvement in patients' emissions despite partial non-audiometric improvement in relation to receptors needs to be considered.

Publication types

  • Controlled Clinical Trial

MeSH terms

  • Adolescent
  • Adult
  • Auditory Threshold
  • Chronic Disease
  • Cochlea / pathology
  • Cochlea / physiopathology*
  • Diagnostic Techniques, Otological*
  • Female
  • Follow-Up Studies
  • Hearing Loss, Sensorineural / diagnosis*
  • Hearing Loss, Sensorineural / etiology
  • Hearing Loss, Sensorineural / physiopathology
  • Humans
  • Male
  • Middle Aged
  • Myasthenia Gravis / complications*
  • Myasthenia Gravis / physiopathology
  • Otoacoustic Emissions, Spontaneous*
  • Prospective Studies