Transcript Hearing Impairment

Hearing Impairment
Dr Ahmad Alamadi FRCS
Consultant Otolaryngologist
Al Baraha Hospital
Objectives
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Basic anatomy
Types of hearing losses
History & Examination
Etiology
Investigations
Management
Introduction
US Annual Incidence
Hearing Loss
280 2000
520
1000
PKU
Cystic Fibrosis
Haemoglobinopathy
Hypothyroid
24000
Introduction
Effects of Hearing Impairment on Development
Has life long effect on
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Language Delay
Literacy
Educational achievement
Vocational Opportunities
Academic difficulties
Psychosocial adjustments and/or difficulties
Anatomy
External Ear
1. concha
2. crus helix
3. helix
4. scaphoid fossa
5. antihelix
6. antitragus
7. tragus
lobule not labeled
Middle Ear
Inner Ear
Organ of corti
Pathophysiology
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Sound waves to the auricle through the external auditory canal to the tympanic membrane.
When they strike the tympanic membrane, the waves cause it to vibrate, setting off a chain
of vibrations along the ossicles (malleus, incus, and stapes) to the membrane of the oval
window at the entrance to the cochlea. This process amplifies the environment sound by
approximately 20-fold.
The cochlea is the end organ of hearing and is shaped like a snail shell with 2.5 turns.
Inside, 2 membranes longitudinally divide the cochlea into 3 sections: the scala tympani, the
scala vestibuli, and the scala media. All 3 are filled with fluid of various ion concentrations
(similar to intracellular and extracellular constituents).
Along one of the membranes in the scala media, or cochlear duct, lie the internal and
external hair cells. Movement of the stapes on the oval window creates a wave or vibration
in the perilymph fluid of the cochlea. This fluid movement, which opens ion channels in the
hair cells, displaces the hair cells, triggering an action potential and causing a nerve in the
cochlea to fire to the brain.
Thousands of nerves representing more than 20,000 frequencies are located along the length
of the cochlea; these nerves account for the hearing range. The microscopic nerves
culminate in the cochlear portion of the eighth cranial nerve. The location of the vibration in
the cochlea is correlated with the frequency of the original pitch. Low-frequency sounds are
near the apex, and high-frequency sounds are near the base.
Types of Hearing Losses
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Conductive hearing loss
Sensori-neural hearing loss
Mixed hearing loss
Central Auditory disorders or Neural hearing
loss
Conductive Hearing Loss
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The loss of sound sensitivity produced by
abnormalities of the outer or middle ear i.e,
conducting mechanism
Sensori-Neural Hearing Loss
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The loss of sound sensitivity produced by
abnormalities of the inner ear.
Mixed Hearing Loss
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The sum of the hearing losses produced by
abnormalities in both the conductive and
sensorineural mechanism of hearing.
Central OR Neural Hearing Loss
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The loss or impairment in
processing of information produced
by abnormality in neural system i.e,
Nerve fiber or central auditory cortex.
Clinical history
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Hearing loss
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Age of onset
Severity
Risk factors
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Family history of congenital or early SNHL
Congenital infection known to be associated with SNHL
Craniofacial anomalies
Birth weight of less than 1500 g (<3.3 lb)
Hyperbilirubinemia over the exchange level
Exposure to ototoxic medications
Bacterial meningitis
Low Apgar scores at birth
Prolonged mechanical ventilation
Findings of a syndrome associated with SNHL
Syndromic Deafness
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DiGeorge sequelae
CHLYesBranchio-oto-facial syndrome
Townes-Brocks syndrome
Miller syndrome
Bixler syndrome
CHARGE syndrome
Jervell Lange-Nielson
Limb-oto-cardiac syndrome
Alport syndrome
Branchio-oto-renal syndrome
Kearns-Sayre syndrome
Epstein syndrome
Barakat syndrome
Noonan syndrome
Killian/Teschler-Nicola syndrome
Clinical history
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Hearing Impairment
Pain
Discharge
Tinnitus
Vertigo
Examination
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Otoscopy
Nose
PNS
Facial nerve
Free field test
Tuning fork tests
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Weber Test
Rinne Test
Investigations
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Lab Studies
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TFT, BUN, CR
ECG
ESR, Rhf, ANA
Connexin 26
Imaging Studies
Tests for Hearing Loss
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PTA
ABR
ASSR
OAE
Etiology
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Genetic causes connexion 26
Syndromic associations
Congenital infections
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Postnatal
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cytomegaloviral
herpes
Rubella
Syphilis
Toxoplasmosis
varicella
Prematurity
low birth weight
anoxia
hyperbilirubinemia
sepsis
meningitis
mumps
ototoxic medications
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major head injury
aminoglycosides
furosemide
Management
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Medical: antibiotics
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Surgical: Ventilation tubes, reconstruction of
middle ear
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Amplification Technology: Analog & digital hearing
aids + Speech and language therapy.
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Surgical+ Amplification Technology: Cochlear
Implants (Severe Sensorineural loss or greater)