Hearing Loss in Adults
Summary
Hearing loss affects 1 in 6 adults and is a major cause of reversible disability and social isolation. Clinically, it is divided into Conductive Hearing Loss (CHL) (pathology of the external or middle ear preventing sound transmission) and Sensorineural Hearing Loss (SNHL) (pathology of the cochlea or auditory nerve). Presbycusis (age-related SNHL) is the most common cause. While most hearing loss is gradual and benign, Sudden Sensorineural Hearing Loss (SSNHL) is an otological emergency requiring urgent steroid treatment (the "Heart Attack of the Ear"). Asymmetrical SNHL requires MRI imaging to exclude a Vestibular Schwannoma (Acoustic Neuroma). [1,2]
Key Facts
- Conductive vs Sensorineural:
- CHL: Volume is turned down. Quality is good if volume increased. Bone Conduction > Air Conduction.
- SNHL: Volume AND Quality (Clarity) are affected. "I can hear people talking but can't understand the words". Air Conduction > Bone Conduction.
- Dementia Link: Untreated hearing loss is the single largest modifiable risk factor for dementia (Lancet Commission).
- Otosclerosis: Common cause of CHL in young women (often worsened by pregnancy). Fixation of the stapes footplate.
- Presbycusis: High frequencies go first. Consonants (f, s, t, th) are high frequency. Vowels (a, e, i, o, u) are low frequency. Patients hear the vowels (volume) but miss the consonants (clarity).
Clinical Pearls
The "Hum Test": A quick way to confirm your Weber test. Ask the patient to hum.
- If they hear it louder in the BAD ear -> CHL (Occlusion Effect).
- If they hear it louder in the GOOD ear -> SNHL.
Sudden Hearing Loss: If a patient says "I woke up deaf in one ear", do NOT assume it is wax. Check the canals. If clear, treat as SSNHL immediately. Every day matters.
Noise Notch: Noise-induced hearing loss typically causes a dip in the audiogram specifically at 4 kHz (the resonance frequency of the ear canal).
Prevalence
- 11 million people in the UK (1 in 6).
- Rises with age: >40% of over 50s; >70% of over 70s.
Causes
- Conductive: Wax, Otitis Externa/Media, TM Perforation, Otosclerosis, Cholesteatoma.
- Sensorineural: Presbycusis, Noise, Meniere's, Ototoxic drugs (Gentamicin/Cisplatin), Acoustic Neuroma.
Mechanisms
- Conductive: Mechanical block. The ossicular chain cannot vibrate the oval window.
- Sensorineural:
- Cochlear: Loss of Hair Cells (Organ of Corti). Once lost, they do not regenerate.
- Retro-cochlear: Nerve compression (Tumour).
- Central: Brain processing.
Symptoms
Red Flags
Otoscopy
- Canal: Wax? Osteoma? Otitis Externa?
- Drum: Perforation? Retraction pocket? Fluid (Glue ear)? Red reflex (Otosclerosis - Schwartze sign)?
Tuning Fork Tests (512 Hz) --- The Essential Skill
| Test | Method | Normal | Conductive Loss (CHL) | Sensorineural Loss (SNHL) |
|---|---|---|---|---|
| Rinne | Fork on mastoid (BC) then in front of ear (AC) | AC > BC (Positive) | BC > AC (Negative) | AC > BC (False Positive) |
| Weber | Fork on forehead | Midline | Lateralises to BAD ear | Lateralises to GOOD ear |
Investigation Note: A patient with severe SNHL in the Right ear will appear to have BC > AC on the right (Negative Rinne) because the vibration crosses the skull to the good Left ear (False Negative Rinne). Use Weber to decide.
Audiometry
- Pure Tone Audiometry (PTA):
- Air Conduction (AC): Headphones. Measures whole system.
- Bone Conduction (BC): Vibrator on mastoid. Bypasses middle ear. Measures Cochlea only.
- Air-Bone Gap: If BC is better than AC by >10dB = Conductive Loss.
- No Gap: If AC and BC are equal but below normal = Sensorineural Loss.
- Tympanometry: Measures compliance of the drum.
- Type A: Normal pressure.
- Type B: Flat line (Fluid/Glue Ear or Perforation).
- Type C: Negative pressure (Eustachian tube dysfunction).
Imaging
- MRI IAM (Internal Acoustic Meatus): To rule out Vestibular Schwannoma in asymmetrical SNHL (>15dB difference at 2 frequencies).
Management Algorithm
HEARING LOSS
↓
OTSOCOPY & TUNING FORKS
↓
┌─────────┴─────────┐
CONDUCTIVE SENSORINEURAL
(BC > AC) (AC > BC)
↓ ↓
Treat Cause SUDDEN?
(Wax/Perf) ↓ ↓
↓ YES NO (Gradual)
Persistent? ↓ ↓
Consider Surgery Rx HEARING AIDS
(BAHA/Stapes) Steroids
1. Management of Conductive Loss
- Wax: Microsuction / Irrigation.
- Otitis Media: Antibiotics / Observation.
- Otosclerosis: Stapedectomy (replace stapes with piston) or Hearing Aid.
- Bone Anchored Hearing Aid (BAHA): For patients who cannot wear conventional aids (e.g., no ear canal / chronic discharge). Vibrates the skull directly.
2. Management of Sensorineural Loss
- Digital Hearing Aids: Mainstay. Programmed to amplify specific frequencies lost.
- Cochlear Implants: For severe-profound deafness where aids provide no benefit. Bypasses hair cells and stimulates auditory nerve directly.
- Assistive Devices: Loop systems, vibrating alarms.
3. Sudden SNHL (Emergency)
- Definition: >30dB loss in 3 frequencies over less than 3 days.
- Treatment:
- Oral Steroids: Prednisolone 1mg/kg (60mg) for 1 week. Start immediately.
- Intratympanic Steroids: Injection through eardrum (Salvage therapy).
- MRI: Mandatory to rule out tumour.
- Prognosis: 1/3 recover fully, 1/3 partially, 1/3 not at all.
- Social Isolation: Withdrawal from conversations.
- Balance: Vestibular system often co-affected.
- Dementia: Auditory deprivation accelerates cognitive decline.
- Presbycusis: Progressive but manageable.
- Sudden SNHL: Time-critical. Poor prognosis if treated >2 weeks.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| NG98 | NICE (2018) | Refer sudden onset immediately. Screen for dementia in hearing loss. |
| Sudden Loss | AAO-HNS | Steroids are the only proven therapy. Antivirals/Vasodilators have no evidence. |
Landmark Knowledge
1. Carhart's Notch
- On PTA in Otosclerosis, there is a dip in Bone Conduction at 2kHz. It is an artifact of stapes fixation, not true cochlear loss. It disappears after surgery.
2. Harvey Fletcher (1920s)
- Defined the "Speech Banana" (the frequencies where speech sounds sit).
Why can I hear noise but not words?
Imagine a piano where the high keys are broken. You can hear the low "boom" of the bass notes (vowels) loud and clear, but the crisp high notes (consonants like T, S, F) are missing. So "Fish" sounds like "Ish". Volume isn't the problem; clarity is.
Do hearing aids just turn the volume up?
Old ones did. Modern digital ones are smart. They selectively turn up the high keys (treble) that you are missing, without making the background noise deafening.
Why do I need to see a specialist for one-sided deafness?
It is usually nothing serious, but rarely, a benign growth on the hearing nerve can cause it. We do an MRI scan just to be safe.
Primary Sources
- NICE Guideline NG98. Hearing loss in adults: assessment and management. 2018.
- Chandrasekhar SS, et al. Clinical Practice Guideline: Sudden Hearing Loss (Update). Otolaryngol Head Neck Surg. 2019.
- Livingston G, et al. Dementia prevention, intervention, and care. Lancet. 2017.
Common Exam Questions
- ENT: "Rinne negative on Right. Weber lateralises to Right. Diagnosis?"
- Answer: Right Conductive Hearing Loss.
- Emergency: "Sudden deafness left ear. Treatment?"
- Answer: High Dose Oral Steroids.
- Audiology: "Dip at 4kHz on audiogram?"
- Answer: Noise Induced Hearing Loss.
- Pharmacology: "Antibiotic causing deafness?"
- Answer: Gentamicin (Aminoglycoside).
Viva Points
- Masking: What is it? Playing white noise into the "good" ear during testing to prevent it from "helping" the bad ear hearing the sound (cross-over).
- Recruitment: A phenomenon in SNHL where loud sounds become rapidly uncomfortable (narrow dynamic range).
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.