Hearing loss can be conductive, sensorineural, or mixed. Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal or middle ear. Sensorineural hearing loss involves damage to the inner ear or auditory nerve. Hereditary and noise-induced hearing loss are common causes of sensorineural hearing loss. Other causes include traumatic injury, infection, ototoxic drugs, presbycusis, and idiopathic conditions. Hearing is evaluated through tests like tuning fork tests, pure tone audiometry, speech audiometry, and tympanometry.

1. HEARING LOSS
Zagada, Timothy M.

2. HEARING LOSS

3. 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

4. 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

5. KNOWN CAUSES

6. 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

7. 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

9. 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

10. 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

11. LABYRINTHITIS
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

12. LABYRINTHITIS
• 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

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

14. UNKNOWN CAUSES

15. PRESBYACUSIS
• 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)

16. 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

17. 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

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

19. 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

22. 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.

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

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

25. • Mixed hearing loss

26. 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.

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