snhl compiled by bijay bhattarai

ETIOLOGY OF SENSORINEURAL HEARING LOSS

(SNHL) IN CHILDEREN

BY: BIJAY BHATTARAI

ROLL: LX111O1410

GRADE: IV

Sensorineural hearing loss (SNHL) :

Sensorineural hearing loss (SNHL) occurs when there is damage to the inner ear (cochlea), or to the nerve pathways from the inner ear to the brain. Most of the time, SNHL cannot be medically or surgically corrected. This is the most common type of permanent hearing loss. There are characteristic features of SNHL/ which differentiate it from conductive hearing loss .

Sensorineural hearing loss can be: mild moderate & severe, including total deafness.

EPIDEMIOLOGY

SNHL is the most common sensory deficit in moredeveloped societies. In the USA, congenital SNHLoccurs about three times more frequently than Down’ssyndrome, six times more frequently than spina bifida,and over 50 times more frequently thanphenylketonuria. An estimated 4000 infants are borneach year with severe to profound bilateral hearingLoss, and another 8000 are born with unilateral ormild to moderate bilateral SNHL

CAUSES OF SNHLCONGENITAL

• GENETIC

• NON GENETIC

ACUIRED

•Idiopathic SSNHL Perinatal asphyxia and kernicterus

•Labyrinthitis Presbyacusis

•Ototoxicity Suppurative otitis media

•Cochlear otosclerosis Endolymphatic hydrops

•Trauma to inner ear Acoustic neuroma

CONGENITAL SNHL

• Genetic

Syndromic

Non Syndromic: -More common than Syndromic

Autosomal dominant SNHL

X-linked SNHL

Autosomal recessive SNHL-more common

• Non genetic (Embryopathies):•Aplasia - Michel, Mondini, Scheibe, Alexander•Viral- mumps, measles,•Ototoxocity•Trauma to labyrinth & cranial nerve VIII in fractures of temporal bone & ear surgery

Congenital SNHL

Genetic SNHL in infants and young children•The relative contribution of genetics to the total number of infants and young children with SNHL is unknown.

•Inherited hearing loss diagnosed among children of these age-groups is congenital hearing loss that was present but missed during the neonatal period.

• Negligible or mild congenital hearing loss that was undetectable by available screening methods but has become more serious and thus detectable, or late-onset SNHL.

• In children with late-onset and progressive hearing loss, dilatation of the vestibular aqueduct must be considered.

Acquired SNHL in infants and children prevalence.It is most commonly caused by bacterial meningitis. Altogether, bacterial meningitis accounts for about 6% of all cases of SNHL in children. The prevalence is about 7/100,000 with a heavy age bias for younger children. 75% of affected children are younger than 2 years, 15% are aged 2–5 years, and 10% are older than 5 years. 62 Postmeningitic SNHL can be unilateral or bilateral.

OTOTOXICITY

Definition:

Tendency of certain therapeutic agents to cause functional impairment of inner ear as a side effect of pharmacotherapy

Route of administration:

Topical- creams, ointments, drops, sprays, inhalation, irrigation Systemic- IM/ IV

a) Cytomegalovirus

b) Lymphocytic choriomeningitis virus

c) Rubella virus

d) Toxoplasma gondii

e) Treponema pallidum

f) Acquired infections

g) Borrelia burgdorferi

h) Epstein-Barr virus

i) Haemophilus influenzae

j) Lassa virus

k) Measles virus

l) Mumps virus

m) Neisseria meningitidis

n) Non-polio enteroviruses

o) Plasmodium falciparum

p) Streptococcus pneumoniae

q) Varicella zoster virus

INFECTIOUS PATHOGENS IMPLICATED IN SNHL IN CHILDREN ARE VIZ;

DRUG / CHEMICALS

1. Aminoglycosides high risk permanent

2. Cytotoxic agents - Cisplatin high risk permanent

3. Industrial chemicals-Toluene, benzene high risk Permanent

4. Polypeptide antibiotics - Vancomycin low risk permanent

5. Macrolides low risk temporary

6. Loop diuretics- low risk temporary

7. Salicylates low risk temporary

8. Quinine derivatives unknown Temporary

9. Others-

a. Anticonvulsants c. Barbiturates,

b. Beta-blockers, d. Muscle relaxants

•MECHANISM OF AMINOGLYCOSIDE : Affect on sensory neuro-epithelium of the inner ear especially outer hair cells of the organ of Corti and type I hair cells of Crista ampulli

Causes of hearing loss in the paediatric population are numerous and varied, often making evaluation and management of the condition quite challenging for otolaryngologists. Imaging plays a central role in the work-up of childhood SNHL because it depicts anomalies in the structures of the inner ear, frequently provides clues as to the aetiology of the hearing loss, and may detect associated co morbid conditions. Although CT and MR imaging are both viable imaging choices, we prefer MR imaging due to its ability to directly assess not only the inner ear but also the cranial nerves and brain. In cases of congenital hearing impairment, inner ear malformations and CND are fairly common, and identification of these anomalies is critical when surgical intervention is being considered because they may complicate or even preclude cochlear implantation in a child with SNHL.

Conclusions

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