INVESTIGATIONS OFSENSORINEURAL HEARING LOSS

(SNHL)BY: KAREEM HUSSIEN

SNHL INVESTIGATIONS

1. HISTORY

2. PHYSICAL EXAMINATION

• Examination of the ear & other structures

• Evaluation with a tuning fork

3. AUDIOLOGICAL EVALUATION

• Pure tone audiometry (PTA)

• Speech discrimination audiometry.

• Tympanometry

• Otoacoustic emissions (OAE) test screening

• Auditory brainstem response

• Electrocochleography (ECoG)

4. IMAGING STUDIES

• CT

• MRI

HISTORY

• duration of deafness

• the nature of the onset (sudden or insidious)

• the rate of progression (rapid or slow)

• involvement of the ear (unilateral or bilateral)

• presence or absence of other conditions: tinnitus, vertigo, imbalance, aural fullness, otorrhea,

headache, facial nerve dysfunction, and head and neck paresthesia

PHYSICAL EXAMINATION

• Examination of the ear

• Examination of other structures

Evaluation with a tuning fork

• Rinne's test

• Weber's test

AUDIOLOGICAL EVALUATION

1. PURE TONE AUDIOMETRY (PTA)

2. SPEECH DISCRIMINATION AUDIOMETRY.

• The ability to understand speech is obviously reduced with all hearing loss but particularly with

sensorineural loss in which the high tones are involved

• Sensory score 70-90%

• Neural scores are very poor (0-50%)

3.TYMPANOMETRY

• measuring the pressure in the middle

ear & the compliance of the TM

• Test result is usually normal in case if

SNHL

(If cochlear or retrochochlear)

(not on top of mid ear disease)

• Type A, As and Ad

• Type B

• Type C

4.OTOACOUSTIC EMISSIONS (OAE) TEST

• It is widely used for neonatal screening of hearing loss

• This phenomenon measures the active sounds produced by the outer hair cells which are

recorded in response to tone clicks applied to the ear

• This test measures the function of the cochlea

5. AUDITORY BRAINSTEM RESPONSE ABR

• The ABR is generally used to evaluate for a retrocochlear process, or

pathology that occurs downstream of the auditory process from the

cochlea.

• the signal electrodes are positioned to measure the components of the

pathway

• The signals are measured after an acoustic stimulus, usually a “click,”

and filtered to record five specific ABR waves.

IMAGING STUDIES

• CT scans

• caliber of the external auditory canal, the integrity of the ossicular chain

• presence or absence of middle ear or mastoid disease

• detecting inner ear malformations

• measurement of the cochlear height, lateral semicircular canal bony island width, and the vestibular

aqueduct

• detection of bone erosion often seen in the presence of chronic otitis media and cholesteatoma.

• MRI

It is superior for imaging

retrocochlear pathology such as

vestibular schwannomas,

meningiomas, other lesions of

the cerebellopontine angle that

may present with hearing loss,

demyelinating lesions of the

central nervous system, and

brain tumors.