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Otorhinolaryngology
Lec: 02
Deafness
Definition
Partial or total loss of hearing in one or both ears.
Types
Conductive
Sensorineural
Mixed
Causes
1- Congenital
a- Genetic : Syndromal (part of syndrome as down s., Treacher
Collin s. , achondroplasia) or
Non-syndromal (deafness is the only complain), either autosomal
dominant, recessive or x-linked.
b- Non-genetic:
i- intrauterine infection
ii- maternal DM or hypertension
iii- ototoxic drugs during pregnancy
iv- perinatal anoxia, hyperbilirubinemia or birth trauma.
2- Acquired (postnatal):
Conductive:
a- external ear
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b- tympanic membrane
c- middle ear
Sensorineural:
a- sensory : damage to the sensory cell of the inner ear due to:
Trauma (Head injury or surgical trauma)
Noise induced
Blast injury
Endolymphatic hydrops
Presbyacusis
Autoimmune disease
Ototoxic drugs
b- neural: damage to cochlear nerve or auditory centers in the
brain due to:
Trauma
Infection
Tumours
Vascular
Multiple sclerosis
Approach
1- History
Age of presentation
Progression
Events during pregnancy
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Birth trauma
Neonatal infections
Other ear symptoms
Loud noise exposure
Drug history
Past medical and surgical history
Family history
2- Examination:
Ear , nose and throat : thorough exam.
General examination :stigmata of congenital anomaly.
Examination of other systems : including CNS, Cranial nerves, CVS .
3- Investigations
Should be selected in logical manner
1- auditory tests: allow qualitative and quantitative hearing
assessment. Could be subjective or objective. Include :
A-pure tone audiometry (PTA)
Adults and children above 4 years
Both air and bone conduction tested using pure tones applied
using special headphone and the results represented graphically.
The pure tones are of different frequencies (Hz) and intensities
(dB). Normal persons can hear pure tones at 20-25 dB or less.
Greater than this is considered as hearing impairment which could
be mild, mild-moderate, moderate, sever or profound.
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B- speech audiometry: phonetically balanced words presented to
the patient at different intensities and the patient asked to repeat
these words. Normally 100% of the words can be repeated at 40
dB and 50% at 25%. This is called speech discrimination score.
C- Tympanometry :graphical representation of the middle ear
pressure and compliance. Could be:
1- normal called type A. in which there is a peak of 0.4-1.3 ml with
ME pressure between -100 to +50 mmH2o.
2- type B: flat curve with no peak. Occurs in patient with otitis
media with effusion or tympanic membrane perforation.
3- type C : the point of maximum compliance below -100 mmH2o (
negative ME pressure). Occur in Eustachian tube dysfunction.
4- hypercompliant : greatly increased peak more than 3.5 ml as in
ossicular disconnection.
D- Electric response audiometry:
Hearing generates action potentials along the auditory nerve and
central connections. These potentials can be picked up using
special electrodes placed externally on the skull or through the
tympanic membrane from the cochlea and represented
graphically.
These tests allow estimation of hearing threshold and localizing of
the site of the lesion, and are mainly useful in young children and
mentally handicapped patients and can be done under local or
general anesthesia.
2- Blood tests : full blood count, ESR, bleeding profile
3- Biochemistry: sugar, urea, ceatinine, electrolytes, thyroid
hormones.
4- Serological : for syphilis. TORCH (toxoplasmosis, rubella,
cytomegalovirus, herpes virus).
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5- Autoimmune profile: rheumatoid factor, antinuclear factor.
6- Urine analysis
7- Radiological : skull, mastoids, and sinuses as indicated using
plain, CTS, and MRI.
4- Treatment
1- treat the underlying cause
2- general measures:
a- avoid exposure to loud noise
b- vasodilators : as betahistine, Ca channel blockers, low
molecular weight dextran.
c- steroids
3- hearing aids : provide help in most types of deafness whether
conductive or sensorineural .
Hearing aids is an electronic, sound amplifying device. It consists
of the following parts:
a- microphone: transduce sound or acoustic energy into
electricity.
b- amplifier: increases the electrical signal.
c- receiver or ear phone (loud speaker): transduce the electrical
signal back into acoustic energy.
Types of hearing aids
1- body worn HA : the device attached to the clothes and
connected to the ear phone by flexible wire. It is big sized and
conspicuous.
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2- ear level HA : or called behind the ear HA. The most widely
used in which the whole device fits behind the auricle. It is more
comfortable and less conspicuous than body worn but its
amplifying power is less.
Both body worn and ear level hearing aids are air conduction HA.
3- bone conduction HA : the transducer press against the mastoid
bone. It is useful in patient with atresia of the external auditory
canal or chronically discharging ear. In both cases air conduction
HA cannot be used.
4- cochlear implantation
One of the new advances in the management of hearing loss. It is
indicated in patients with bilateral sever or profound hearing loss
in whom a trial of at least 6 months period with a hearing aid
show no benefit.
The device consists :
a- external part : consists of a microphone( picks up sound from
environment) , speech processor( filters sound into channel
according to the frequency) and a transmitter (coil which
transmits the processed sound signals into the internal device by
electromagnetic induction.
b- internal part : implanted surgically in the mastoid bone and
consists of a receiver and stimulator which converts the signals
into electrical impulses and send them into the cochlea (scala
tympani) through electrodes.