Hearing loss

1. HEARING LOSS
PRASANNA DATTA

2. HEARING AND HEARING LOSS
• Hearing- transduction of sound to neural impulses and its interpretation by the
CNS
• Hearing loss- defect at any level from sound transduction to interpretation

3. TYPES OF HEARING LOSS
• Conductive- sound is not conducted efficiently through
the outer ear canal to the eardrum and the tiny bones
(ossicles) of the middle ear
• Sensorineural (SNHL)- damage to the inner ear
(cochlea), or to the nerve pathways from the inner ear
to the brain.
• Mixed
• Central- Problem lies in the central nervous system

4. KNOWN CAUSES

5. HEREDITARY
SENSORINEURAL
HEARING LOSS• Hereditary- 1/3 of all cases of SNHL
• Syndromic- Usually present at birth
usually AR
• Ex; Treacher-Collins syndrome
• Non-syndromic- based on onset
• Congenital form
• Late onset form- more common, tend to
be AD, manifested after birth

6. NOISE INDUCED HEARNG
LOSS
Can cause direct mechanical trauma to cochlea
• Acute acoustic trauma- sudden intense sound event of short
duration
• Exceeds 140 db and pressure rise is very short (<1.5ms)
• Ex; gunshot
• Blast injury- pressure wave from an explosive blast
• Exceeds 140db but duration of pressure rise is longer (>2ms)
• longer frequency spectrum
• Ruptured tympanic membrane

8. NOISE INDUCED HEARNG
LOSS
• Acute noise-induced hearing loss- high levels of
continuous or intermittent noise for seconds to hours
• Often reversible or partially reversible
• muffled sensation and tinnitus
• Ex; loud power tools, rock concerts, engine noise
• Chronic noise-induced hearing loss- irreversible
cochlear hearing loss
• Typical features of sensorneural hearing loss
• Tinnitus can be constant
• Safe if levels below 85db for 8hrs/day

9. TRAUMATIC INJURY TO INNER
EAR
• Functional- labyrinthine concussion
• Structural- labyrinthine contusion
• Temporal bone fracture
• Impact to the skull- accelerating and decelerating
forces
• Barotrauma
• Symptoms: nonspecific vertiginous complaints and
hearing impairment

10. LABYRINTHI
TIS
Infection or inflammatory process affecting the labyrinth or its surrounding 3
routes: Tympanogenic, meningeal and hematogenous
• Tympanogenic- infection/inflammation maybe transmitted through oval or round
window
• Acute toxic (serous labyrinthitis)- labyrinth itself is not infected; becomes
inflamed by substances released in middle ear.
• Acute supporative- bacterial infection of middle ear spreads to
labyrinth.
• Chronic Labyrinthitis- manifested as inner ear damage.
• Chronic otitis media as possible cause

11. LABYRINTHI
TIS
• Meningeal- Labyrinth maybe infected bilaterally (often strep
pneumonia) from intracranial space
• Hematogenous- by viruses and bacteria. Results in hearing loss and
disequilibrium
• Typical causative organisms: mumps, meascles, HIV, CMV,
spirochetes
Symptoms: Cochlear hearing loss, tinnitus, vestibular symptoms (vertigo, disequilibrium,
nystagmus)
Vestibular symptoms in patient with otitis media is a warning sign of labyrinthitis

12. OTOTOXICIT
Y
• Toxic damage to inner ear affects
both cochlear and vestibular
functions
• Endogenous or exogenous
• Effects generally symmetrical
• Symptom: Tinnitus maybe initial
presenting symptom

13. UNKNOWN
CAUSES

14. PRESBYACUS
IS
• Age related (over 50 yr old), symmetrical SNHL
• Ageing process
• Endogenous genetic predisposition
• Cummulative exposure to exogenous factors
• Symptoms: Speech recognition more affected than pure tone
• Diagnosis: Pure tone audiometry- symmetrical SNHL (High tone loss)

15. SUDDEN
SENSORINEURAL
HEARING LOSS• Immediate, unilateral hearing loss with no apparent external cause.
• Symptomatic or Idiopathic
• Idiopathic- cause: Viral, vascular, autoimmune
• Symptoms: within seconds to hours. Mild loss of hearing to sudden deafness
• Vestibular symptoms less common

16. CHRONIC, PROGRESSIVE,
IDIOPATHIC SENSORINEURAL
HEARING LOSS• Bilateral SNHL
• Onset before age 50
• Etiology unknown
• Symptoms: Variable- sudden hearing loss or progress gradually
• Frequently associated by tinnitus
• Vestibular symptoms generally absent

17. • Tuning Fork test
• Pure tone audiometry
• Speech audiometry
• Tympanometry
TEST FOR AUDITORY FUNCTION

18. TUNING FORK
TEST• Differentiate between conductive and SNHL
• Weber and Rinne test
• Weber- TF placed in midline of skull. Vibrations are transmitted by bone conduction
• Normal- Vibrations perceived equally on L+R
• SNHL- Lateralizes to better ear
• CHL-Lateralizes to affected ear
• Rinne- compares level of air and bone conduction in the same ear.
• AC test- TF just outside the ear canal
• BC test- TF firmly against mastoid
• Normal: AC>BC
• CHL: BC>AC
• SNHL: AC>BC but both equally depreciated

21. PURE TONE
AUDIOMETRY• used to identify hearing threshold
levels of an individual, enabling
determination of the degree, type and
configuration of a hearing loss.
• NORMAL HEARING
- both air and bone conduction will
be superimposed at each test
frequency between 0 to 10 dB.

22. • CONDUCTIVE HEARING
LOSS
- air conduction is < normal
bone conduction.

23. • SENSORINEURAL HEARING LOSS
- both air and bone conduction below normal
threshold at any frequency tested

24. • Mixed hearing loss

25. TYMPANOMETRY
• an examination used to test the condition of the middle ear and mobility of the
eardrum (tympanic membrane) and the conduction bones by creating variations of
air pressure in the ear canal.
• Permits a distinction between sensorineural and conductive hearing loss,
when evaluation is not apparent via Weber and Rinne testing.
• Can be helpful in making the diagnosis of otitis media by demonstrating the
presence of a middle ear effusion.

26. • A- Normal
• AD- abnormally compliant
• AS- Stiff (otosclerosis)
• B- Presence of non-compressible
fluid within middle ear space(Otitis
Media)
• C-Eustachian tube dysfunction