SENSORINEURAL HEARING LOSS
Definition: This hearing loss results due to involvement of the cochlea, vestibulocochlear nerve or central auditory pathways. Aetiology: Sensorineural hearing loss may be congenital or acquired. Congenital
- Birth trauma.
- Prenatal and perinatal factors.
- Labyrinthine infections viral and / or bacterial.
- Ototoxic drugs.
- Systemic diseases like diabetes, hypothyroidism, alcoholism.
- Meniere’s disease.
- Acoustic neuroma.
- Noise induced hearing loss.
- Traumatic skull base fractures.
- Viral labyrinthitis: Infections such as mumps, measles, rubella destroys the stria vascularis of the inner ear. Bacterial infections such as meningitis damage the membranous labyrinth.
- Ototoxic drugs can be vestibulotoxic or cochleotoxic. The sensory hair cells in the vestibule and inner and outer hair cells of the cochlea are damaged. Common ototoxic drugs are aminoglycosides, diuretics, anti-malarial and cytotoxic drugs.
- Noise induced hearing loss causes damage to outer and inner hair cells. High frequency hearing loss is seen.
Clinical assessment of hearing loss:
- Tuning fork tests
- a) Rinne test: Air conduction is better than bone conduction in sensorineural hearing loss. It is also called Rinne positive. It is done with 256 Hz, 512 Hz and 1024 Hz tuning forks.
- b) Weber test: It is done with 512 Hz tuning fork. The sound lateralizes to better ear in sensorineural hearing loss.
- c) Absolute bone conduction test: This test is a measure of cochlear function. In sensorineural deafness, the patient hears the fork for a shorter duration.
- Pure tone audiometry: It is a qualitative and quantitative analysis of patients hearing. It is also helpful for medicolegal purposes.
- Brainstem Evoked Response Audiometry (B.E.R.A).
- Treat the systemic causes, like tuberculosis, syphilis, diabetes.
- Vasodilators- Oral or Intravenous.
- Steroids, oral and intravenous in sudden onset sensorineural hearing loss. However, the results can be variable.
- Hyperbaric Oxygen therapy has been tried in patients with sudden onset SN loss with limited success.
- Hearing aids.