Hearing Loss Undergraduate

8/7/2019 Hearing Loss Undergraduate

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Hearing loss & Tinnitus

by

Professor Hassan Wahba

Professor of OtoRhinoLaryngology

Ain Shams UniversityPrivileges of hearing:

Functions all the time

Auditory field is very large

First special sense to function (intra uterine)

Special sense responsible for development of speech & communication

The means of education is through hearing

Auditory Pathway:

1. Sound is collected by the auricle

2. Sound passes through the external auditory canal3. Sound vibrates the tympanic membrane

4. Sound is transmitted along the auditory ossicles to the oval window

5. Sound passes into the inner ear as a fluid wave and vibrates the basilar membrane

6. Hair cells convert sound to an electrical nerve impulse

7. The cochlear nerve transmits the nerve impulse to the cochlear nuclei in the brain

stem along the auditory pathway to the auditory center in the temporal lobe

The function of the tympano-ossicular system of the middle ear is to convert a mechanical vibration

wave in air to a mechanical vibration wave in the fluid of the inner ear. This action involves

transmitting the sound wave into the inner ear as well as amplifying the sound wave to compensate

for any energy loss.

The organ of Corti in the inner ear is responsible for the creation of an electrical nerve impulse by

an intricate mechanism that relies on vibration of the basilar membrane to and from the tectorial

membrane with the hair cells collecting the electrical stimulus. The organ of Corti is the region

were the volume of sound is determined by the amplitude of the vibration of the basilar membrane

and the frequency of sound is determined by the site of vibration along the length of the cochlea;

hence, the cochlea is the site were the physical properties of sound are analyzed and are send along

the cochlear nerve in a ready format to the auditory center.

Binaural hearing (hearing with both ears) is necessary for the determination of the source of sound

and is important in life especially when crossing the road.

Hearing loss when complete is called deafness. Some sources may use the word deafness to

describe a hearing loss.

Types of hearing loss are:

Conductive hearing loss

Sensorineural hearing loss

Central hearing loss

Mixed hearing loss

Malingerer Hysterical

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Clinical detection of hearing loss:

The patient uses his hand to direct the auricle towards the speaker while bringing his

head closer

The patient shouts in a raised non-modulated voice this indicates a sensorineural

hearing loss

The patient complains of hearing loss and raises the radio or TV and asks speakers to

raise their voice but has a low well-modulated voice this indicates a conductive hearing loss

Tuning fork tests:

Rinne

Weber

Schwabach

ABC

Audiometry:

Pure tone audiometry

Speech audiometry

Tympanometry

Neonatal screening for hearing loss:

Auropalpebral reflex

Auditory brainstem response (ABR)

Otoacoustic emission (OAE)

Degrees of hearing loss:

Normal hearing: 0-25dB

Mild hearing loss: 26-40dB unable to hear soft sounds problems with speech clarity

Moderate hearing loss: 41-55dB unable to hear soft and moderately loud sounds problems withspeech clarity especially with background noise

Severe hearing loss: 56-90dB can hear some loud sounds needs hearing aid for recognition and

understanding speech

Profound hearing loss: +91dB relies on other means of communication (lip reading or sign language

and needs cochlear implantation

Causes of conductive hearing loss:

External auditory canal:

Congenital aural atresia

Foreign body

Large furuncle

External otitis

Exostosis

WAX commonest cause

Tympanic membrane:

Traumatic rupture

Pathological perforation due to otitis media

Tympanosclerosis

Myringitis

Middle ear: Atresia

Longitudinal fracture of the temporal bone

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Otitis media

Glomus tumor

Otosclerosis

Ossicular disruption

Eustachian tube:

Otitic barotrauma Otitis media with effusion commonest cause for conductive hearing loss in

children

Factors affecting hearing loss in tympanic membrane perforation:

Size

Exposure of round window

Presence of ossicular discontinuity

Sensorineural hearing loss:

Cochlear:

Genetic malformations Transverse fracture of the temporal bone

Labyrinthitis (viral, otogenic, meningitis commonest cause in Egyptian children,

syphlytic)

Ototoxicity

Metabolic (diabetes mellitus, thyroid disorders)

Meniere's disease

Presbyacusis (senile hearing loss commonest cause in adults)

Cochlear nerve:

Acoustic neuroma (must be suspected in case of unilateral SNHL with tinnitus)

Congenital sensorineural hearing loss:

Dating since birth or develops later on in life due to genetic or hereditary cause

Endogenous:

Genetic syndromal disorders

Cochlear malformations

Exogenous:

Prenatal (german measles)

Natal (fetal hypoxia)

Postnatal (erythroblastosis fetalis)

Sound is what we hear & Noise is an uncomfortable sound

Acoustic trauma:

Acute noise exposure

Chronic noise exposure (occupational)

Labyrinthine insult:

Secondary to meningitis (commonest cause of SNHL in Egyptian children)

Secondary to otitis media

Secondary to viral infections (measles & mumps)

Syphilis

Metabolic (diabetis mellitus, thyroid gland dys.) Transverse fracture temporal bone

Labyrinthine concussion

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Vascular (embolism, hemorrhage or thrombosis)

Menieres disease

Otosclerosis (cochlear type - commonest cause of mixed hearing loss)

Ototoxicity

Ototoxic drugs

Aminoglycosidesgentamicin streptomycin tobramycin neomycin amikacin kanamycin

erythromycin, loop diuretics, acetyl salicylic acid

Central hearing loss:

Encephalitis

Vascular lesion especially in hypertensive and diabetics

Brain tumors

Multiple sclerosis

Psychogenic causes

Kernectrus

Epilepsy Brain injury

Post operative after brain surgery

Sudden SNHL:

Viral or Vascular or Acute acoustic trauma

Treatment according to the cause:

Viral: antivirals and steroids

Vascular: vasodilators, hyperbaric oxygen and steroids

Noise trauma: good prognosis so wait and steroids

Otologic work up for hearing loss patients:

Associated otologic complaint (symptom):

Otorhea:

Pure pus cholesteatoma furuncle

Mucopus acute supp OM tubotympanic OM

Blood glomus carcinoma

CSF temporal bone fracture

Tinnitus:

Low pitched CHL

High pitched SNHL

Pulsating vascular lesion as glomusVertigo:

Attacks Menieres disease

Continuous labyrinthitis

Earache:

Severe increases with TMJ movement external otitis

With fever acute otitis media

After air flight otitic barotrauma

Itching otomycosis

Otologic examination:

External auditory canal: Aural atresia

Wax

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Furuncle

Exostosis

Foreign body

Tympanic membrane:

Perforated acute & chronic OM traumatic rupture aural polyp

Not perforated:

Normal otosclerosis SNHL: history and genetic Abnormal:

1. Retracted OME

2. Chalky patches tympanosclerosis

3. Flamingo red otosclerosis

4. Bulging Acute OM

5. Bullae bullous myringitis

Incident preceding hearing loss:

Placing a foreign body in the ear

After a bath or shower wax

A slap to the ear traumatic perforation A car or cycling accident skull base fracture

Pregnancy otosclerosis

Air plane flight otitic barotrauma

Post adenoidectomy Eustachian tube trauma

Exposure to loud noise acoustic trauma

Use of ototoxic drugs

Straining perilymph fistula

Common cold acute OM or viral labyrinthitis

Psychic trauma hysterical

Fevers meningitis mumps measles Surgery to the ear operative trauma

Tinnitus:

Hearing loss is accompanied by tinnitusSubjective tinnitus (patient only):

Hypo & hypertension

Anemia

Thyroid dysfunction

Atherosclerosis

Spondylosis

MenopauseObjective tinnitus (patient & examiner):

Aneurysms

Vascular tumors (glomus)

AV fistula

Myoclonus

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Hearing Loss Undergraduate

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