Dr. Ghulam SaqulainM.B.B.S., D.L.O, F.C.P.S

Head of Department of E.N.TCapital Hospital

Hearing is one of the five special senses

Definition:“It is the perception of sound”

Collection and conduction of sound waves by the external and middle ear

Conversion of Mechanical Energy to Electrical Energy in the inner ear

Interpretation in the brain

TYPES :

◦ Conductive, ◦ Sensori-neural, or ◦ Mixed

Impaired conduction of sounds Causes:

◦ A) Congenital Conductive Deafness Atresia of ear Absence of ear Ossicular abnormalities

◦ B) Acquired Conductive Deafness In External Ear

Wax Otitis Externa Foreign body

In Middle Ear: Effusion Chronic Infection Perforation Cholesteatoma Traumatic Ossicular disruption

Results from damage to cochlea or 8th nerve. There is no perception of sound.

A) Congenital:◦ Genetic◦ Non Genetic:Rubella

B) Acquired:◦ Natal: Hypoxia, Jaundice◦ Trauma: Surgical, Head Injury◦ Inflammatory: Otitis, Meningitis, Measles,

mumps, syphilis

◦ Degenerative: Presbycusis◦ Ototoxic:Aminoglycosides and cytotoxics◦ Neoplastic: Acoustic neuroma◦ Idiopathic: Meniere’s disease.

Endogenous causes Originating or produced within an organism or one of

its part Exogenous causes Originating outside the organism

Etiology according to patient’s age at onset:

Prenatal causes Perinatal causes Postnatal cause

Factors causing HL occurring during pregnancy before the child is born

Adverse effect on the normal development of the cochlea

Congenital hearing loss Sometimes difficult to determine extent of genetic vs.

environmental factors

1) Multifactorial genetic considerations: combinations of hereditary and environmental factors, it results into multifactorial hereditary disorders

2) Congenital hearing loss: the person inherit a hearing loss he/she is born with it

3) Hereditodegenerative hearing loss: the person inherit the tendency for hearing loss to occur after birth (congenital hearing loss not shown until later in life)

1) Autosomal dominant◦ Only one gene from one parent is required for a trait to

be shown◦ Each child have a 50 % chance of inheriting the disorder◦ Family pattern can be observed

2) Autosomal recessive

◦ Constitutes 80 % of profound genetic HL – half of them are associated with syndromes

◦ Usually have two parents with normal hearing who are carriers of the recessive gene

◦ 25 % chance of that gene being passed on with each pregnancy to the child

◦ Each normal hearing child have a two in three chance of being a carrier

3) X-linked◦ Many recessive alleles for HL are X-linked

Female X chromosome carry considerable genetic info Male Y chromosome contains only info required to

produce the male sex ◦ Female child (having an allele for HL) from one

parent will not show the trait ◦ A male child (not having the corresponding normal

gene) will probably develop the HL◦ Female who is heterogonous for an X-linked

recessive HL will not have a genetic hearing loss but will be a carrier and produce sons each of whom will have a 50 % chance of having the HL and daughters each of whom will have a 50 % chance of being a carrier

◦ Males with X-linked HL have sons who don’t show the trait daughters who would be carriers

Chromosomes are missing, or extra material is found

i.e. Trisomy: an extra (third) chromosome is present

Parents may be perfectly normal but the fetus may have difficulty surviving the pregnancy or may be severely impaired

Women getting pregnant above the age of 40, have an increased risk of having children with trisomic chromosomal disorders

Example; Down Syndrome

Occurs in patients with no associated abnormalities Occurs in patients in association with:

Skull Facial deformities (cleft palate) Optic disorders (changes in the eye, hair and skin

pigmentation) Thyroid diseases Heart disorders Musculoskeletal anomalies Mental retardation Balance disorders Other sensory and motor deficits

Syndrome: a combination of signs and symptoms

which are considered together for the diagnosis of a particular disorder

Hereditary HL have different audiometric configuration

Flat moderate to severe bilateral HL Predominantly HF or LF pattern Unilateral HL

Rh (rhesus) Factor / Rh Incompatibility The fetus blood contains the protein molecule

called Rh factor The mother doesn’t have the factor The mother’s body produces antibodies for

protection against the harmful effects of the Rh factor

This antibody count increases with succeeding pregnancies

Causes HL as well as other abnormalities (i.e. cerebral palsy)

Rubella / German Measles/ Maternal Rubella

Anoxia

Human immunodeficiency virus (HIV)

Cytomegalovirus (CMV)

Anoxia

Prematurity (low birth weight < 1500 grams = 3.5 pounds)

High noise levels from infants Incubators

Head trauma (violent uterine contractions or the use of high forceps)

Factors causing HL occurring after birth

Usually starts as a CHL then patient develop MHL (SN component is added)

1. Otitis media

Bacteria toxins in the ME might enter IE through OW OR RW

2. Bacterial Meningitis: ◦ Inflammation of the meninges ◦ May cause total deafness when the

labyrinth is full with pus3. Measles (Rubeola):

◦ Rash◦ Heart defects◦ CNS disorders ◦ In severe cases can cause death◦ Sudden HL

4. Mumps (Parotitis):◦ Inflammation of the parotid (salivary)

gland located on either side of the neck near the ear

◦ Lump in the neck◦ Causes bilateral as well as unilateral HL

5. Syphilis:◦ May be prenatal or acquired◦ Its symptoms resembles other symptoms

of different systemic diseases, that is why it is called “great imitator”

◦ Can cause brain damage◦ Cochlea might get involved

6. Labyrinthitis: ◦ Infection of the labyrinth◦ May affect both auditory and vestibular

mechanisms◦ Cause HL & vertigo◦ Unknown causes

7. Ototoxicity: ◦ Cochlear damage resulted from

medications◦ Some medications are known to be

toxic to the cochlea◦ In most cases, the effect will be on the

HFs range ◦ Infections of the kidneys might result in

deposits of toxic substances in the IE◦ Kidney disease might prevent

medications from being excreted thereby raising their levels in the blood resulting in ototoxicity

8. Diabetes: ◦ Linked with cochlear damage

Cochleotoxic: medications causing HL◦ HL range from mild to profound◦ i.e. Dihydrostreptomycin, viomycin,

neomycin and kanamycin Vestibulotoxic: medications affecting

the vestibular organs◦ i.e. Streptomycin & gentamycin

Others:◦ Aspirin, certain diuretics, nicotine and

alcohol ◦ Cause HL when taken in large amounts and

over prolonged periods of time

Specific criteria for identification of toxicity Timely identification of at risk patients Pretreatment counseling regarding potential

cochleotoxic effects Valid baseline measures (hearing tests)

performed before treatment or shortly after treatment begins

Periodic monitoring evaluations at intervals timed to document progression of hearing loss

Follow-up evaluations to determine post-treatment effects

A disease of bony labyrinth that causes a CHL when the new bone growth affects either OW or RW

If it involves the cochlea, a SNHL or MHL will result

Could be unilateral or bilateral

Audiometric configuration generally flat

Speech recognition is not severely affected

Sudden changes in ME pressure (as in diving or violent sneezing) usually cause CHL

May cause a rupture of RW or a tearing of the annulus of the OW

Fistula (perilymph leak) can result Can be surgically repaired and may reverse a

permanent of fluctuating cochlear HL and or vertigo

May produce mild to profound HL

HL from intense noise may result from: Brief exposure to high-level sounds with subsequent

partial or complete hearing recovery Repeated exposure to high-level sounds, with

permanent hearing impairment

Temporary threshold shift (TTS): hearing thresholds improve after an initial impairment following noise

Permanent threshold shift (PTS): irreversible hearing impairment after noise exposure

The degree of SNHL depends on The intensity of the noise The spectral composition of the noise The duration of exposure Individual susceptibility

Noise notch Cummulative Progressive

Loss of hair cells & their supporting structures in the basal turn

Nerve degeneration in the osseous lamina

Biological changes in the sensory cells

Physical dislodging of hair cells Changes in cochlear blood supply Alterations in the function of stria

vascularis Loss of OHCs Rupture of Reissner’s membrane Detachment of organ of Corti

from BM Tinnitus

Other effects:

Increased anxiety levels Loss of ability to

concentrate Increased blood pressure

levels Higher divorce rates Greater incidence of illness Loss of sleep

Increasing hearing awareness among school-age children

Limit exposure to loud noise Use protective earplugs or muffs Periodic hearing examination to monitor

progression If NIHL is suspected; hearing should

always be tested at 3000 Hz and 6000 Hz even if sensitivity at adjacent octave and midoctave frequencies is normal

Occupational safety and Health Administration (OSHA) and National Institute of Occupational Safety and Health (NIOSH) Recommends a scale on which the time that a worker may be safely exposed to intense sounds is decreased as the intensity of the noise is increased Max. exposure level is 85 dBA for an 8 hours work day For every 5 dB increase in noise, half the time is allowedi.e. four hours for 90 dBA, two hours for 95 dBA Other guidelines (noise monitoring, noise exposure limits, hearing monitoring practices and training of audiometric technicians)

Preemployement physical examination now include pure tone audiometry

Often happens when surgeon is trying to improve hearing with corrective surgery for the ME (i.e. Stapedectomy)

HL often unilateral that may develop over the course of a few days or occur seemingly instantaneously

many patients claiming that they awoke from sleep in the morning to find that their hearing had changed

Can occur at any age, most frequent in adults

Suggested etiologies: Autoimmune disease Viral infection (if respiratory infection has

preceded the HL) Other infections Rupture of BM Vascular disorder Tumors Other neurological disorders