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Introduction

Deafness is a partial or total inability to hear. WHO defines deafness as hearing threshold of 20dB or better in both ears.

Classification

[Deafness] may be classified according to WHO into 5 subtypes/groups:

• Mild- Hearing losses between 26 and 40 dB
• Moderate- Hearing losses between 41 and 55 dB
• Moderately severe- Hearing losses between 56 and 70 dB
• Severe - Hearing losses between 71 and 90 dB
• Profound - Hearing losses greater than 91 dB

Causes

Common causes of hearing loss include: Based on location

• External Ear
  • Congenital atresia of external auditory meatus (EAC)
  • Infection- Otitis externa
  • Trauma
  • Tumour
  • Benign Polyp
  • Cerumen
• Middle Ear
  • Atresia or malformation of ossicular chain
  • Eustachian tube dysfunction
  • Infection- Otitis media
  • Cholesteatoma
  • Otosclerosis
  • Jugulotympanic paragangliomas (glomus tumors)
  • Middle ear barotrauma-sudden, large change in ambient pressure, often during diving or flying
• Inner Ear
  • Congenital malformation of cochlea
  • Presbycusis- old age related hearing loss
  • Infection- Viral cochleitis
  • Meniere disease
  • Noise exposure
  • Inner ear barotrauma
  • Ototoxic drugs
  • Systemic diseases- diabetic vasculopathy can cause cochlear ischemia
  • Tumors- acoustic neuroma

Epidemiology and Demographics

The incidence of hearing loss increases with age In the Beaver Dam cohort in the United States, the prevalence of hearing loss, defined by audiometry:

●3 percent ages 21 to 34

●6 percent ages 35 to 44

●11 percent ages 44 to 54

●25 percent ages 55 to 64

●43 percent ages 65 to 84

World Health Organization estimates that hearing loss affects 538 million people worldwide.