Download MBBS Hearing Loss Causes Lecture PPT

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Hearing
loss
Organic

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Non
organic
Conductive
Sensory
neural

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Sensorineural
sensory
Neural
Peripheral
Central

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8th nerve

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Any disease process which interferes with the
conduction of sound to reach cochlea causes
conductive hearing loss

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Negative Rinne test, i.e. BC > AC.
Weber lateralized to poorer ear
Normal absolute bone conduction
Low frequencies affected more
Audiometry shows bone conduction better than

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air conduction with air-bone gap
Loss is not more than 60 dB.
Speech discrimination is good

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Congenital

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Meatal atresia
Fixation of stapes footplate
Fixation of malleus head
Ossicular discontinuity
Congenital cholesteatoma

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Any obstruction in the ear canal, e.g. wax, foreign
body, furuncle, acute inflammatory swelling, benign
or malignant tumour or atresia of canal
Perforation of tympanic membrane, traumatic or

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infective
Fluid in the middle ear, e.g. acute otitis media, serous
otitis media or haemotympanum
Mass in middle ear, e.g. benign or malignant tumour
Disruption of ossicles, e.g. trauma to ossicular chain,

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chronic suppurative otitis media, cholesteatoma
Fixation of ossicles, e.g. otosclerosis,
tympanosclerosis, adhesive otitis media
Eustachian tube blockage, e.g. retracted tympanic
membrane, serous otitis media

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Sensorineural hearing loss (SNHL) results from lesions
of the cochlea, VIIIth nerve or central auditory
pathways
A positive Rinne test, i.e. AC > BC

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Weber lateralized to better ear.
Bone conduction reduced on Schwabach and absolute
bone conduction tests.
More often involving high frequencies.
No gap between air and bone conduction curve on

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audiometry
Loss may exceed 60 dB.
Speech discrimination is poor. 8. There is difficulty in
hearing in the presence of noise

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PRENATAL CAUSES
Infant factors
Scheibe dysplasia-Dysplasia is seen in the cochlea
and saccule
Alexander dysplasia-It affects only the basal turn of

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membranous cochlea
Bing?Siebenmann dysplasia. There is complete
absence of membranous labyrinth.
Michel aplasia. There is complete absence of bony
and membranous labyrinth.

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Mondini dysplasia. Only basal coil is present or
cochlea is 1.5 turns
Enlarged vestibular aqueduct.
Semicircular canal malformations

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Waardenburg syndrome-White forelock
Heterochromia iridis ,Vitiligo ,Dystopia
canthorum

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Usher syndrome-Retinitis pigmentosa ,Night
blindness
Pendred syndrome-Goitre ,Perchlorate discharge
test shows defect in organic binding of iodine
Alport syndrome-Hereditary progressive

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glomerulonephritis ,Corneal dystrophy

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Infections during pregnancy. -toxoplasmosis,
rubella, cytomegaloviruses, herpes type 1 and 2
and syphilis

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Drugs during pregnancy. Streptomycin,
gentamicin, tobramycin, amikacin, quinine or
chloroquine
Radiation to mother in the first trimester
Nutritional deficiency, diabetes, toxaemia and

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thyroid deficiency

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Anoxia
Prematurity and low birth weight
Birth injuries

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Neonatal jaundice
Neonatal meningitis
Sepsis
Time spent in neonatal ICU
Ototoxic drugs

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Genetic-Deafness may occur alone as in familial
progressive sensorineural deafness or in
association with certain syndromes, e.g. Alport,
Klippel-Feil, Hurler

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Nongenetic
Viral infections (measles, mumps, varicella,
influenza), meningitis and encephalitis.
Secretory otitis media.
Ototoxic drugs.

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Trauma, e.g. fractures of temporal bone, middle ear
surgery or perilymph leak.
Noise-induced deafness

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Infections of labyrinth--viral, bacterial or spirochaetal

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Trauma to labyrinth or VIIIth nerve, e.g. fractures of
temporal bone or concussion of the labyrinth or the ear
surgery
Noise-induced hearing loss
Ototoxic drugs

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Presbycusis
M?ni?re's disease
Acoustic neuroma
Sudden hearing loss
Familial progressive SNHL

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Systemic disorders, e.g. diabetes, hypothyroidism, kidney
disease, autoimmune disorders, multiple sclerosis, blood
dyscrasias.

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INFLAMMATIONS OF
LABYRINTH
Viral labyrinthitis
Measles, mumps and cytomegaloviruses
Viruses usually reach the inner ear by blood stream

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Bacterial
Bacterial infections reach labyrinth through the middle
ear (tympanogenic) or through CSF (meningogenic)

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Syphilitic
Sensorineural hearing loss is caused both by

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congenital and acquired syphilis
M?ni?re's syndrome
Hennebert's sign. A positive fistula sign in the
absence of a fistula. This is due to fibrous
adhesions between the stapes footplate and the

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membranous labyrinth
Tullio phenomenon

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It is a genetic disorder in which there is

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progressive degeneration of the cochlea
starting in late childhood or early adult life.
Hearing loss is bilateral with flat or basin-
shaped audiogram but an excellent speech
discrimination

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Various drugs and chemicals can damage the
inner ear and cause sensorineural hearing loss,
tinnitus and sometimes vertigo
Eg: Aminoglycoside, Diuretics,Salicylates

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NOISE TRAUMA
Acoustic trauma
Permanent damage to hearing can be caused
by a single brief exposure to very intense sound
without this being preceded by a temporary

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threshold shift
explosion, gun fire or a powerful cracker and
may reach or cross 140 dB

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Noise-induced hearing loss
chronic exposure to less intense sounds

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Temporary threshold shift (TTS). The
hearing is impaired immediately after
exposure to noise but recovers after an
interval of a few minutes to a few hours
even up to 2 week

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Permanent threshold shift (PTS). The
hearing impairment is permanent and does
not recover at all.

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Immune-mediated inner ear disease causes
progressive bilateral sensorineural hearing loss.
It occurs between 40 and 50 years with equal
incidence in both sexes.
Nearly 50% of patients also experience vestibular

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symptoms like disequilibrium, motion intolerance,
positional or episodic vertigo
15% of patients have evidence of other
autoimmune disorder such as ulcerative colitis,
systemic lupus, rheumatoid arthritis or multiple

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sclerosis

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No Organic lesion
Malingering or Psychogenic
Claim compensation

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THANK YOU

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