It is one of three type of hearing loss Hearing loss due to defect in the sensory apparatus cochlea (sensory) Or in the pathway of conduction of nerve impulses to the brain (neural) Neural causes can be peripheral:8 nerve Central:auditory pathway or cortex

1. Neuroscience(NS)
Farah Talib Nayef
Second stage
University of Baghdad /Gollege of medicine

2. Content :-
◦ Introduction
◦ Epidemiology
◦ Pathophysiology
◦ Sign and symptoms
◦ Complication and investigations
◦ Evaluation
◦ Diagnosis
◦ Prevention and management
◦ Treatment
◦ Prognosis
◦ Sudden sensorineural hearing loss
◦ Summary
◦ Reference
1

3. Introduction
Sensorineural hearing loss is one of three types of hearing loss (conductive hearing loss,
sensorineural deafness and mixed hearing loss ) and essentially refers to damage of the
inner ear[1]. It can be categorised as mild,moderate, moderate-severe, severe,or profound .
It is a common problem and it is estimated that there are more than 10 million people (1in
6) in the UK with some degree of hearing loss [2]. It is often develops with age but can be
caused by repeated exposure to loud sounds,infection of the ear , genetics ,illness and
trauma [3]. A commone condition that results in hearing loss is chronic ear infections ,
certain infection during pregnancy such as syphilis and rubella may also cause hearing loss
,it is diagnosed when hearing testing finds that a person is unable to hear 25 decibels in at
least one ear [4]. Testing for poor hearing is recommended for all newborns [5].
Hearing loss can occur suddenly but develops gradually [6] .
Most often ,can be treated successfully with hearing aids or cochlear implants. However ,a
thorough ear examination and customized treatment plan is vital [7].Half of hearing loss is
preventable , this includes by immunization ,proper care around pregnancy ,avoiding loud
noise,and avoiding certain medication, the world health organization recommends that
young people limit the use of personal audio players to an hour a day in an effort to limit
exposure to noise . early identification and support are particularly important in children
[8]. A deaf person has little to no hearing ,may occur in one or both ears , such that a
person is unable to understand speech even in the presence of amplification ,In profound
deafness even the loudest sound produced by an audiometer (an instrument used to
measure hearing by producing pure tone sounds through a range of frequencies) may not
be detected , in total deafness ,no sounds at all ,regardless of amplification or method of
production ,are heard . speech perception -another aspect of hearing involves the
perceived clarity of word rather than the amplitude of sound made the by the word [9]. In
humans, that aspect is usually measured by tests of speech perception ,these tests measure
one’s ability to understand speech not to merely detect sound [10].In children hearing
problem can affected the ability to learn spoken language and in adults it can cause work
related difficulties ,In some people , particularly older people , hearing loss can result in
loneliness .Hearing loss can be temporary or permanent [11].Human hearing extends in
frequency from 20-20,000 Hz, and in amplitude from 0 dB to 130dB or more .0dB dose not
represent absence of sound ,130dB represent the threshold of pain .But the ear dose not
hear all frequencies equally well, hearing sensitivity peaks around 3000HZ [12].
2

4. Figure 1
3

5. Epidemiology
A total of 117 children ,55girles and 62 boys with a median age of 8 years ,range 2-12 years
,was retrospectively evaluated in consideration of : [13]
1- the prevalence rate and characteristics of permanent hearing loss (defined as the average
of 500,1000 and 2000Hz greater than or equal to 35dB HL on the better hearing ear .
2- the aetiology of the hearing impairment .
3- the basis for the aetiological diagnosis in the individual child .
4-the value of non audiological investigation . The overall prevalence of permanent hearing
loss was 1.4% in this geographical area .In 91% the hearing loss was sensorineural ,in
4%conductive and in 5% mixed .conductive/sensorineural in63% the hearing loss had been
confirmed and assessed at the age of 3years while in 31% the hearing loss was ascertained
after the age of 3 years .85% were considered to suffer from congenital /early acquired
hearing loss[14].
4

6. Pathophysiology
Sensorineural hearing loss (SNHL) may result from disruptions in transmission after the
cochlea .These distruptions may be a result of hair cell destruction in cochlea or damage to
the eighth cranial nerve or the auditory tracts of the brainstem .If higher level of the
auditory tract are affected this is known as central deafness [15].Central deafness may
present as sensorineural deafness but should be distinguishable from the history and
audiological testing [16].Sounds perceived by the brain are both diminished and distorted
.the degree of distortion is independent of the degree of hearing loss ,for example ,it is
possible to have only mild hearing loss yet have very poor speech discrimination [17].
Auditory dyssynchronous should be considered in the setting of no auditory brainstem
respons ,no middle ear muscle response ,normal otoacoustic emission or normal cochlear
microphonics[18].
Cochlear dead regions in sensory hearing loss:
hearing impairment may be associated with damage to the hair cells cochlea. sometimes
there may be complete loss of function of inner hair cells over a certain region of the
cochlea this is called dead region .The region can be define in terms of the range of
characteristic frequencies of inner hair cell and/or neurons immediately adjacent to the
dead region[19].
Hair cell damage:
SNHL is most commonly caused by damage to the OHCs and the IHCs .there are two
method by which they might become damaged firstly ,the entire hair might die .secondly
the stereocilia might become distorter destroyed [19].Damage to cochlea can occur in
several ways. The auditory system is highly complex and disruptions at the level of the
middle ear cochlea and central nervous system can result in variable degrees of hearing
loss [20].
Hearing also depends on precise biochemical ,metabolic,vascular,hematologic,endocrine
function [21]. Disruption in any of these systems can profoundly affect the auditory system
.The pathophysiology differs with each type of syndromic hearing loss [22].
5

7. Sign and symptoms
Permanent hearing loss occurs when inner ear nerves become damaged and do not
properly transmit their signals to the brain [23]. those who suffer from this condition may
complain that people seem to mumble or that they hear ,but do not understand ,what is
being said [24]. Since the inner ear is not directly accessible to instruments ,identification is
by patient report and audiometric testing [25]. Of those who present to their doctor with
sensorineural hearing loss ,90% report having diminished hearing ,57%report having
plugged feeling in ear and 49% report having ringing in ear (tinnitus) about half report
vestibular (vertigo) problems [26]. Sensorineural hearing loss may be genetic or acquired
as consequence of disease [27].In addition to aging, sensorineural hearing loss may be
caused by : injury , excessive noise exposure , viral infection , ototoxic drugs , meningitis ,
diabetes ,stroke , high fever ,menieres disease , acoustic tumors ,people may have a hearing
loss from birth (congenital) or the hearing loss may come on later [28].Hearing lose can be
inherited more than 40genes have been identified to cause deafness there are 300syndromes
with related hearing loss and each syndrome may have caustive genes Recessive ,dominant
,X-linked or mitochondrial genetic mutation can affect the structure or metabolism of the
inner ear .some may be single point mutations whereas others are due to chromosomal
abnormalities. Some genetic causes give rise to a late onset hearing loss[29].Congenital
hearing loss may be cause by human cytomegalovirus ,congenital rubella syndrom
,toxoplasmosis,and hypoplastic auditory nerves or abnormalities of the cochlea[30].
6

8. Complication
-In patient with chronic otitis media and acute otitis media [31].
-Kawasaki disease is an acute systemic vasculitis of unknown etiology in which the main
complication is corony arteritis[32].
Investigation
-Molecular analysis of the Pds gene in pendred syndrome (sensorineural hearing loss and
goitre) : is an autosomal recessive disorder characterized by the association between
sensorineural hearing loss and thyroid swelling and is likely to be the most common form
syndromic deafness [33].This would support the use of molecular analysis of the PDS gene
in the assessment of families with congenital hearing loss. [34].
-Magnetic resonance imaging : high resolution T2-weight magnetic resonance imaging has
been proposed as a rapid , inexpensive deafness ,particularly to exclude vestibular
schwannomas [35].
-Genetic investigation of autosomal recessive distal renal tubular acidosis evidence for
early sensorineural hearing loss associated with mutation in the ATP6V0A4 gene[36].
-Temporal bone computed tomography findings in bilateral sensorineural hearing loss :all
childern with SNHL should undergo radiological investigation of petrous bones/inner ear
[37].
-Bacterial meningitis and sensorineural hearing loss : to prospectively assess the incidence
of sensorineural hearing loss associated with bacterial meningitis; to evaluate the onest and
degree of SHL and to describe the audiometric pattern [38].Steroid use in idiopathic
sudden sensorineural hearing loss and you can use electromagnetic hearing aid for
moderate to severe sensorineural hearing loss[39].
7

9. Evaluation
Advances in both the medical/surgical and nonmedical treatment of sensorineural hearing
loss have drastically increased the need for more precise evaluation of inner ear disorders
and their differentiation from retrocochlear sites of lesion[40]. Consider, for example, the
tremendous strides made in the application of cochlear implants to patients with severe to
profound hearing loss who are unable to derive sufficient or adequate benefit from hearing
aids. Equally impressive are the improvements made recently in the area of assistive
listening technology[41].The newest hearing aid devices are smaller in addition to being
capable of greater fidelity, and contain digital circuitry making them more flexible and
responsive to a patient's auditory needs [42].A challenge for hearing healthcare
professionals today is to successfully address the needs of the millions of hearing impaired
individuals in the United States who are currently not adequately served, either medically
or nonmedically, for their hearing problem[43].
Diagnosis
Before examination ,a case history provides guidance about the context of the hearing loss
:[44]
-major concern
-pregnancy and childern information
-medical history
-development history
-family history
8

10.  Otoscopy :
Direct examination of the external canal and tympanic membrane (ear drum ) with an
otoscope ,amedical device inserted into the ear canal that uses light to examine[45][46].
 Tympanometry:
A tympanogram is the result of a test with a tympanometer.it tests the function of the
middle ear and mobility of the ear drum [47].
 Audiometry:
An audiograme is the result of a hearing test .the most common type of hearing test is pure
tone audiometry .it charts the thresholds of hearing sensitivity at a selection of standard
frequencies between 250-8000Hz. [48].
 Differential testing :
Is most useful when there is unilateral hearing loss and distinguishes conductive from
sensorineural loss . These are conducted with a low frequency tuning fork ,usually 512Hz
[49].
-Weber test sound localized to normal ear in unilateral SNHL and localized to affected ear
in conductive loss
-Rinne test : positive rinne test air> bone conductions
negative rinne test bone >air conductions
MRI scans can be usedto identify gross structural causes of hearing loss [50].
9

11. Figure2
Figure3
10

12. Prevention
Any sound above 80 decibels ( the volume of city traffic inside your car ) can potentially
damage your hearing with extended exposure [51]. As the decibel level increase , the
amount of time of safe exposure decrease .That means at 100 decible ( the volume of a rock
concert ), any exposure over 15 minute could damage your hearing [52].
Here are a few tips on how you can protect against hearing loss :[53]
acquired SNHL are largely preventable, especially nosocusis type causes. This would
involve avoiding environmental noise, and traumatic noise such as rock concerts and
nightclubs with loud music. Use of noise attenuation measures like acoustic ear plugs is an
alternative. Presbycucis is the leading cause of SNHL and is progressive and
nonpreventable, and at this time, we do not have either somatic or gene therapy to counter
heredity-related SNHL [54].
Treatment
Treatment modalities fall into three categories: pharmacological, surgical, and
management. As SNHL is a physiologic degradation and considered permanent, there are
as of this time, no approved or recommended treatments[55].
Pharmaceutical:Antioxidant vitamins ,tanakan ,coenzyme Q10, ebselen
Stem cell and gene therapy :hair cell regeneration using stem cell and gene therapy[56].
Proofound or total hearing loss may be amenable to management by cochlear implants
,which stimulate cochlear nerve ending directly [56].
11

13. Management
Management of sensorineural hearing loss involves employing strategies to support existing
hearing such as lip-reading, enhanced communication etc. and amplification using hearing
aids. Hearing aids are specifically tuned to the individual hearing loss to give maximum
benefit[57-58].
Prognosis
Prognosis is affected by multiple factors including duration of hearing loss, presence of
associated vertigo and tinnitus, and co-morbidities such as hypertension and
diabetes[59].prognosis for recovery is dependent on a number of factors, including patient
age, presence of vertigo at onset, degree of hearing loss, audiometric configuration, and
time between onset of hearing loss and treatment (6–8) [60-61].Because the etiology of
SSNHL is usually unknown, treatments have traditionally been empirical. The most
commonly used treatment has been corticosteroids (systemic and/or intratympanic) [62]. A
large array of other treatments such as antivirals, antibiotics, diuretics, vasodilators,
osmotic agents, plasma expanders, anticoagulants, mineral supplements, and hyperbaric
oxygen or carbon dioxide rich gases, among others, have been used[63-64].
12

14. Sudden sensory hearing loss
Sudden SNHL has been called an otologic emergency[65].Early presentation to a physician
and early institution of treatment improves the prognosis for hearing recovery. The
following have been associated with sudden hearing loss:[66-67]
• Information about the onset, time course, associated symptoms, and recent activities may
be helpful.
• Past medical history may reveal risk factors for hearing loss.
• All medications, including over-the-counter products, must be described.
• Aspirin can cause a reversible sensorineural hearing loss, and the list of aspirin-
containing products is extensive.
Physical
Perform a careful head and neck examination, with special attention to the otologic and
neurologic examination[68].Tuning fork tests and a fistula test using pneumatic speculum
must be performed[69].
Causes:[70]
• Infection - Bacterial (eg, meningitis, syphilis), viral (eg, mumps, cytomegalovirus,
varicella/zoster)
• Inflammation – Sarcoidosis, Wegener granulomatosis, Cogan syndrome
• Vascular - Hypercoagulable states (eg, Waldenstrom macroglobulinemia), emboli (eg,
postcoronary artery bypass graft [CABG] surgery), postradiation therapy
• Tumor - Vestibular schwannoma, temporal bone metastases, carcinomatous meningitis
• Trauma - Temporal bone fracture, acoustic trauma, penetrating temporal bone injuries
• Toxins - Aminoglycoside antimicrobials, cisplati.
13

15. Figure4
14

16. Summary
Your ear is made up of three parts— the outer, the middle, and the inner ear.
Sensorineural hearing loss, or SNHL, happens after inner ear damage. Problems with the
nerve pathways from your inner ear to your brain can also cause SNHL. Soft sounds may
be hard to hear. Even louder sounds may be unclear or may sound muffled.This is the most
common type of permanent hearing loss. Most of the time, medicine or surgery cannot fix
SNHL. Hearing aids may help you hear.
15

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Figure List :
Figure 1/ https://en.wikipedia.org/wiki/Sensorineural_hearing_loss
Figure 2/ https://www.kootenayhearingclinic.com/how-do-our-ears-work#
Figure3/https://goo.gi/image/8SrRBG
Figure4/ https://healthfacts.ng/the-inconvenience-of-hearing-loss/
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