Hearing Loss

Question 1

Types of hearing loss?

Answer 1

1) Conductive hearing loss - pathology between outer and middle ear.
2) Sensorineural hearing loss - pathology in the cochlear
3) Mixed
4) Auditory Neuropathy Spectrum Disorder - hearing loss due to pathology between cochlear and brain

Question 2

Normal Hearing range?

Answer 2

1) 20dBHL
2) 250Hz - 8000Hz

Speech spectrum: 500Hz -4000Hz

Question 3

Impact of moderate hearing loss (41-70 dBHL)?

Answer 3

1) Poor speech development
2) Mishear information
3) Decreased incidental learning
4) Poorer education levels compared to hearing peers
5) Behavioural difficulties

Question 4

Impact of profound hearing loss (>90 dBHL)?

Answer 4

1) Little or NO speech development
2) Mishear information, decreased incidental learning, poorer educational levels
3) May use British Sign Language

Question 5

Prenatal causes of deafness?

Answer 5

1) Maternal infections - CMV, Toxoplasmosis, Rubella, Herpes simplex
2) Developmental problems - any part of the ear affected, atresia of ear canal/absence of pinna, abnormalities of middle/inner ear, craniofacial abnormalities - cleft palate etc.
3) Hyperbilirubinaemia
4) Genetic problems - Down’s: trisomy 21, hypotonia, developmental delay, sensorineural/mixed/conductive hearing loss, prone to middle ear infections, presbycusis by 2nd decade (age related hearing gloss).
- Waardenberg’s syndrome: auditory-pigmentary syndrome, variable penetrance means you can have the syndrome with/without hearing loss.

Question 6

Perinatal causes of deafness?

Answer 6

1) Hypoxic ischaemic encephalopathy
2) Low Birth weight
3) Preterm
4) Hyperbilirubinaeia
5) Ototoxic drugs: gentamicin, furosemide
6) Noise levels in incubator
7) Respiratory distress syndrome
8) Hyponatraemia

Question 7

Postnatal causes of deafness?

Answer 7

1) Infection - Middle ear disease: OME - commonest cause of conductive hearing loss in children. Mastoiditis.
Meningitis: Pneumococcal, within 24 hours, damage due to suppurative or toxic labrynthitis, direct nerve fibre damage.
Mumps/measles - rare due to MMI
2) Ototoxic drugs - gentamicin, furosemide
3) Noise
4) Trauma - fractured temporal bone

Question 8

Risk factors for deafness?

Answer 8

1) Family history
2) Neurodegenerative/neurodevelopmental disorder
3) Hyperbilirubinaemia - jaundice at or above exchange transfusion level
4) Cleft palate

Question 9

Diagnosis for deafness?

Answer 9

1) TORCH screen - tests for toxoplasmosis, other (syphilis, VZV, parvovirus B19), rubella, CMV, herpes
2) Urine/saliva PCR - for CMV
3) PCR for CMB on Guthrie screen (at 6 days)
4) Newborn hearing screen: - Main purpose to ensure they have adequate hearing to develop speech, impact of bilateral moderate-profound hearing loss is high. MUST have resolved by 6 months to develop normal speech and social development. Aims to identify 90% of MtoP bilateral hearing loss by 8 weeks and 100% by 24 weeks.
- Well babies tested using Automated Otoacoustic Emissions (AOAE) - earphone produces sound which evokes an echo/emission from ear if cholera function normal. AOAE cannot diagnose auditory neuropathy spectrum disorder.
- Babies on the neonatal side are also tested with AOAE and also Automated Auditory Brainstem Response (ABR): computer analysis of EEG waveforms evoked in response to a series of auditory stimuli. ABR is diagnostic for many hearing loss conditions.
5) Visual reinforcement audiometry - 6m to 3yrs:
Good for assessing impairment in infants between 10-18 months. Hearing thresholds are established using visual rewards (illumination of toys) to reinforce the child’s head turn to stimuli of different frequencies.
6) Performance and speech discrimination testing - 18m to 4yrs:
Performance testing using high and low frequency stimuli and speech discrimination testing using miniature toys - McCormick Toy Test
7) Audiometry 4 years:
Threshold audiometry using headphones, where child responds to a pure tone stimulus. Can be used to detect and assess severity of hearing loss in children from 4 yrs onwards.
Any parental concern at all ages regarding hearing warrants further assessment.

Question 10

Treatment of hearing loss?

Answer 10

1) Counselling family
2) Conductive hearing loss: Surgery, medication, hearing aids
3) Sensorineural hearing loss: Hearing aids, cochlear implant, British sign language