Hearing Loss
Hearing loss refers to the reduced ability to hear and can be broadly classified into conductive hearing loss or sensorineural hearing loss.
This updated UKMLA guide to hearing loss is based on NICE NG98 and NICE CKS, which covers conductive vs sensorineural hearing loss, causes, investigations and management.
Types and Causes
There are 2 main types of hearing loss: [Ref]
| Conductive hearing loss | Caused by mechanical disturbances along the sound conduction pathway (external auditory canal → tympanic membrane → middle ear) |
| Sensorineural hearing loss | Caused by dysfunction of the inner ear, usually the cochlea or cochlear nerve |
Conductive Hearing Loss Causes
Grouped by clinical categories: [Ref]
| Paediatric / congenital causes |
|
| Acute / transient causes | |
| Chronic / irreversible causes |
|
Same list of causes but grouped by anatomical categories: [Ref]
| External auditory canal |
|
| Tympanic membrane |
|
| Middle ear cavity |
|
Sensorineural Hearing Loss Causes
Key causes: [Ref]
| Paediatric / congenital causes | Genetic factors:
Acquired causes
|
| Acute / transient causes |
|
| Chronic / irreversible causes |
|
Be aware that BPPV and vestibular neuronitis do NOT cause hearing loss.
Assessment and Investigation
The work-up of hearing loss / impairment primarily involves:
- Clinical tests with a tuning fork (to perform the Rinne and Weber tests)
- Pure-tone audiometry
Rinne and Weber Tests
How The Tests Are Performed
A 512 Hz tuning fork should be used (rather than the larger 128 Hz tuning fork).
- Memory aid: 5 + 1 + 2 = 8 → cranial nerve 8 (vestibulocochlear nerve) – the nerve for hearing
| Rinne test |
|
| Weber test |
|
Interpretation
The classic interpretation table :
| Test | Normal hearing | Conductive hearing loss | Sensorineural hearing loss |
|---|---|---|---|
| Rinne | AC > BC (+ve test) | BC > AC (-ve test) | AC > BC (+ve test) |
| Weber | No lateralisation | Lateralises to the affected ear | Lateralises to the unaffected ear |
AC: air conduction; BC: bone conduction
High-yielding practical interpretation:
| Test | Normal hearing | Conductive hearing loss | Sensorineural hearing loss |
|---|---|---|---|
| Rinne | AC > BC (+ve test)
The patient continues to hear the tuning fork after moved next to the ear canal |
BC > AC (-ve test)
The patient no longer hears the tuning fork when moved next to the ear canal, but hears it again on the mastoid process |
AC > BC (+ve test)
The patient continues to hear the tuning fork after moved next to the ear canal |
| Weber | No lateralisation
Sound is heard equally in both ears |
Lateralises to the affected ear
Sound is heard louder in the affected ear |
Lateralises to the unaffected ear
Sound is heard louder in the unaffected ear |
Pure Tone Autiometry
Interpretation:
| Feature | Conductive hearing loss | Sensorineural hearing loss |
|---|---|---|
| Air conduction | Reduced | Reduced |
| Bone conduction | Normal | Reduced |
| Audiogram pattern | Bone conduction > air conduction → air-bone gap | Both air and bone conduction are reduced together |
Some key cause-specific audiogram findings:
| Cause | Hearing loss type | Audiogram findings |
|---|---|---|
| Noise-induced trauma | Sensorineural (bilateral) | Primarily affecting the higher frequencies, with a classic 4 KHz notch |
| Presbycusis (age-related hearing loss) | Sensorineural (bilateral) | Primarily affecting the higher frequencies |
| Otosclerosis | Conductive (bilateral) | Primarily affecting the lower frequencies, may show a Carhart notch at ~2 kHz on bone conduction |
| Vestibular schwannoma (acoustic neuroma) | Sensorineural (unilateral) | Often high-frequency |
| Ménière disease | Sensorineural (unilateral) | Primarily affecting the lower frequencies (rising audiogram pattern) in early stages |
Management
Referral Criteria
Immediate Referral
Refer within 24 hours to ENT or to emergency department if any of the following:
- Sudden onset (<72 hours) unexplained hearing loss, that occurred within the past 30 days
- Unilateral hearing loss + focal neurological deficits
- Hearing loss associated with head / neck injury
- Hearing loss + serious infective cause (e.g. malignant otitis externa)
Urgent Referral
Refer to ENT within 2 weeks if any of the following:
- Sudden onset (<72 hours) unexplained hearing loss, that occurred more than 30 days ago
- Rapidly progressive unexplained hearing loss (over 4-90 days)
Suspected Cancer Pathway Referral
- Person of Chinese or Southeast Asian family, with
- Hearing loss and a middle ear effusion,
- That is not associated with URTI
Idiopathic Sudden Sensorineural Hearing Loss (SSNHL)
Refer within 24 hours to ENT
1st line: steroids (oral steroids and/or intratympanic steroid injections)
- Rationale: Steroids may reduce inflammation and oedema in the cochlea, which are thought to contribute to the pathogenesis of SSNHL
Hearing Loss Without Reversible Causes (Adults)
Interventions should be offered if hearing loss affects the patient’s ability to:
- Communicate
- Hear
- Awareness of warning sounds and environment
- Appreciation of music
Choice of interventions:
- 1st line: hearing aids
- 2nd line: cochlear implants
- Recommended if there is severe to profound deafness without adequate benefit from acoustic hearing aids
- Although not stated by NICE, some major contraindications to cochlear implantation are
- Absence / damage to cochlear nerve
- Congenital malformations of the inner ear
- Chronic active middle ear infection / cholesteatoma
If deafness is caused by damage to vestibulocochlear nerve (due to surgery / tumour) → auditory brain stem implants are an option
References