Hearing impairment classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:

Overview

Classification is based on laterality, severity, cause, anatomy of ear, symmetry, clinical characteristics, age of onset, and associated symptoms.

Classification

Hearing losses can be classified according to:

1. Laterality
2. Symmetry
3. Clinical characteristic (syndromic or not)
4. Time of onset (congenital, perinatal, or postnatal)
5. Hereditary (genetic or not)
6. Time of manifestation (prelingual, perilingual, or post-lingual)
7. Intensity (mild, moderate, severe, and profound)

CLASSIFICATION BASED OF SEVERITY OF DISEASE

	MILD	MODERATE	SEVERE	DISABLING
HEARING LOSS	26–40 dB HL	41–60 dB HL	61–80 dB HL	>80 dB HL
DESCRIPTION	Patient hears fine	Hear with some difficulty People Mumble	Difficulty in hearing	Patients rely on reading lips. The term deaf is often used by persons with profound hearing loss with >80 dB HL.
INTERVENTION	Communication strategies	Communication strategies Amplification	Communication strategies Hearing aids Cochlear implant	Communication strategies Hearing aids Cochlear implant Sign language Lip reading

CLASSIFICATION BASED ON ANATOMY OF EAR

CONDUCTIVE	SENSORINEURAL	MIXED
CHL occurs when sound is not conducted efficiently through the outer ear canal to the middle ear due to any cause.	SNHL occurs when there's damage to the internal ear or to the nerve pathways from the ear to the brain that is vestibulocochlear nerve or sensory relay center for auditory stimulus. So injury at the cochlea or proximal to the cochlea is termed as SNHL.	Mixed HL is defined as CHL and SNHL.
CHL accounts for 90%–95% of all childhood HL.	SNHL is more common in adults.
With pure conductive hearing loss, the quality of hearing and speech discrimination is good.
Often only mild and is never worse.	It can be mild, moderate, or severe, including complete deafness.
Common causes in adults include: Cerumen impaction Otosclerosis Cholesteatoma Otitis media with effusion. Ear canal obstruction Middle-ear abnormalities Tympanic membrane Ossicles	If SNHL takes hours or days to develop it can be due to: Labyrinthitis Meniere disease If hearing loss develops in weeks: Drug-induced ototoxicity If happens in years: Noise-induced loss

CLASSIFICATION BASED ON CAUSE

CONGENITAL

ACQUIRED

Syndromes Dysplasia: Children with skeletal dysplasias were more likely to have abnormal tympanometry, reflecting the greater likelihood of middle ear disease. Infections: Cytomegalovirus (CMV), rubella virus, Toxoplasma gondii, herpes virus, and HIV Malformations

Infections: Bacterial meningitis, particularly from Streptococcus pneumoniae, has been reported to be one of the most common postnatal causes of hearing loss in children. Traumatic Autoimmune: Systemic diseases that cause hearing loss include systemic lupus erythematosus, rheumatoid arthritis, myasthenia gravis, and Hashimoto's thyroiditis Neoplastic: Direct compression of the cochlear nerve by the tumor, occlusion or vascular compression of the internal auditory artery, intratumor bleeding, internal auditory channel occlusion, and toxic substances produced by the tumor that result in degeneration of the inner ear.