What is sensorineural hearing loss?
Sensorineural hearing loss results due to involvement of the Auditory nerve pathway.It can involve the cochlea, vestibulocochlear nerve or central auditory pathways.
What are the causes of sensorineural hearing loss?
Sensorineural hearing loss may be:
- 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
What is the pathology of acquired sensorineural hearing loss?
- Viral labyrinthitis: Infections such as mumps, measles, rubella destroy 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.
How is sensorineural hearing loss clinically diagnosed?
Clinical assessment of hearing loss:
- Rinne's test: This test is Rinne's positive indicating that air conduction is better than bone conduction. It is done with 256, 512 and 1024 Hz, tuning forks
- Weber's test: It is done with 512 tuning fork and lateralises to the better ear
- Pure tone audiometry: It is a qualitative and quantitative analysis of the patients hearing. It is also useful for medico legal purposes
- Brainstem Evoked Response Audiometry (B.E.R.A)
- Absolute bone conduction test: It helps to diagnose the sensorineural hearing loss.
How is sensorineural hearing loss treated?
- Treat the systemic cause like tuberculosis, syphilis, diabetes
- Steroids, oral and intravenous in sudden onset sensorineural hearing loss. However their results can be variable
- Hearing aids
- Transtympanic Injections of steroids .However the results of this procedure and debatable.