HEARING LOSS ENT

Topics: Ear, Auditory system, Middle ear Pages: 11 (964 words) Published: December 4, 2014
HEARING LOSS
BY: NURRASHIDAH BT ABDURAHMAN
NABILAH IFFAH BT MD. ARIF

ANATOMY OF EAR

The ear is made up of three parts
1.
Outer ear – consists of pinna and
external auditory canal
2.
middle ear – consists of tympanic
membrane and ossicles (3 tiny bones
that are attached to the tympanic
membrane which are malleus, incus and
stapes)
3.
inner ear – consists of oval window,
semicircular ducts, cochlea and auditory
tube


HEARING – transduction of sound to neural
impulses and its interpretation by the CNS
 HEARING LOSS – defect of any level from
transduction of sound to the interpretation
of sound


NORMAL HEARING PHYSIOLOGY
Conductive Pathway
Neural Pathway

Conductive Pathway
(External auditory canal to
cochlea)

Neural Pathway
(nerve to brain)
Stimulation of
bipolar neurons in
the spiral ganglion
of the cochlear
division of CN VIII

Sylvian fissure
of temporal
lobe

Cochlear
nucleus

Superior
olivary nucleus

Inferior
colliculus

Lateral
leminiscus

TYPES OF HEARING LOSS









-

CONDUCTIVE HEARING LOSS (CHL)
The conduction of sound to the cochlea is
impaired
Can be caused by external and middle ear
diseases
SENSORINEURAL HEARING LOSS (SNHL)
Due to a defect in the conversion of sound into
neural signs or in the transmission of those
signal to the cortex
Can be caused by the disease in cochlea,
acoustic nerve(CN 8), brainstem or cortex
MIXED HEARING LOSS
The conduction of sound to the cochlea is
impaired, as well as transmission through
cochlea to the cortex

CAUSES OF HEARING LOSS
CONDUCTIVE HEARING LOSS
1.
EXTERNAL EAR CANAL
 Impacted earwax
 Otitis externa
 Foreign body
 Congenital atresia
2.
MIDDLE EAR
 Acute otitis media
 Otitis media with effusion
 Perforation of tympanic membrane
 Otosclerosis
 Tumour (cholesteatoma)


SENSORINEURAL HEARING LOSS
1.
CONGENITAL
 Hereditary defects
 TORCH infection
 Perinatal and postnatal infection
2.
ACQUIRED
 Presbycusis
 Noise induced hearing loss
 Meniere’s disease
 Ototoxic drug
 Sudden SNHL
 Labyrinthitis


HISTORY TAKING







Onset
Rate of progression
Associated symptoms like pain, discharge,
tinnitus, dizziness, vertigo
Any noise exposure history
Drug history
Family history

PHYSICAL EXAMINATION

Auditory acuity
 Whispered voice test : Mask one ear and
whisper into the other


Tuning fork tests (512Hz)
- Rinne
-Weber



Otoscopy

Tuning Fork Test

Examples

Weber

Rinne

Normal or bilateral 
sensorineural hearing loss

Central 

AC>BC (+) bilaterally

R conductive hearing loss
Normal L ear

Lateralizes to 
R

BC>AC (­) R

R sensorineural HL
Normal L ear

Lateralizes to L AC>BC (+) bilaterally

*These tests are not valid if the ear canals are obstructed with cerumen (i.e will create conductive hearing loss

Otoscopy
Inspect the
concha and
surrounding

Inspect Ear canal and then insert the
otoscope
- Cartilaginous canal skin
-bony canal skin
Tympanic membrane
-silver/grey in colour
-transluscent/opaque
-handle of malleus
-light reflex (anterior, inferior aspect)
- any scarring or perforation
Check for
-effusion from the middle ear
-ai bubble or air fluid level

INVESTIGATION
Auditory Brainstem Response (ABR)
Otoacoustic Emissions (OAE)
Audiometry

Auditory Brainstem Response
(ABR)


Stimulus- Sound clicks are presented to each ear,
and 2 electrodes placed on the scalp record brainwave activity.



Electrographic activity followed from the ear to
central areas of the brain.



Cannot be used to distinguish CHL from SNHL



Prematurity or seizure disorders may cause failing
results



Delay in brainstem response suggests
cochlear or retrocochlear abnormalities

Otoacoustic Emissions (OAE)


Concept : Certain sounds generated by the inner
ear can be recorded. These...
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