Sudden onset hearing loss (SOHL)

Sudden Onset Hearing Loss (SOHL) is characterized by the patient’s subjective experience of hearing loss in one or both ears. To objectively confirm the presence and severity of hearing loss, a Pure Tone Audiogram (PTA) is necessary.

A thorough clinical assessment can help differentiate between:

• Conductive Hearing Loss (CHL): The most common type, usually due to obstruction or mechanical issues in the ear.
• Sensorineural Hearing Loss (SNHL): Caused by damage to the inner ear structures or the auditory nerve.
• Sudden Sensorineural Hearing Loss (SSNHL):
  • Defined as a loss of ≥30 dB across at
  • least three consecutive frequencies
  • occurring within 72 hours.
  • It can range from mild impairment to complete deafness and may be temporary or permanent.

In most cases of SSNHL, no identifiable cause is found, and it is classified as Idiopathic SSNHL. For these patients, high-dose oral prednisolone initiated early can significantly improve the hearing outcome. Regardless of the cause or severity of hearing loss, rapid assessment and timely treatment are crucial for optimal prognosis.

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Aetiology of SOHL	clinical
Outer ear (conductive hearing loss)
Foreign body Wax Otitis externa Other ear canal pathology (eg. exostoses) Trauma (syringing)	Non-distorted sound Features of external ear pathology Volume of voice remains normal and hearing improves in noisy environment
Middle ear (conductive hearing loss)
Otitis media with effusion Haemotympanum Ossicular chain discontinuity Trauma Barotrauma Iatrogenic (post-operative) Tympanic membrane perforation Cholesteatoma
Inner ear (sensorineural hearing loss)
Idiopathic Noise Exposure: – Prolonged exposure to loud noises (e.g., machinery, music) causing damage to hair cells. Aging (Presbycusis): – Natural degeneration of the auditory system with age. Infective: – viral/bacterial ([HIV], [CMV], [HSV], mumps, rubella, syphilis) Trauma (temporal bone fracture) Ototoxic drugs (e.g., aminoglycoside antibiotics, chemotherapy agents) Autoimmune – SLE – Wegener – Cogan syndrome – relapsing polychondritis – ulcerative colitis Tumour – vestibular schwannoma – leukaemia – myeloma Vascular (cerebrovascular disease, sickle cell disease) Perilymphatic fistula Barotrauma Neurological – multiple sclerosis – cerebrovascular accident – migraine) Other (diabetes mellitus, sarcoidosis)Non-organic hearing loss	Distorted sound +/- tinnitusNo features of external ear pathology Volume of voice is loud, hearing worsens in noisy environment and high frequencies lost preferentially

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Red Flags Associated with Sudden Onset Hearing Loss

Unilateral Hearing Loss

• Sudden hearing loss in one ear could indicate a serious underlying condition, such as an acoustic neuroma or stroke.

Associated Neurological Symptoms

• Vertigo: Sudden onset of intense dizziness or spinning, which may suggest a central or vestibular pathology.
• Facial Weakness: Can indicate cranial nerve involvement, potentially due to a stroke or tumor.
• Severe Headache: Could point to a cerebrovascular event or space-occupying lesion.
• Diplopia (Double Vision): Suggestive of a central nervous system issue.

Recent Trauma

• Head Trauma: Recent head injury may lead to perilymph fistula or temporal bone fracture.
• Barotrauma: Sudden changes in pressure, such as during diving or flying, can cause hearing loss.

Otologic Symptoms

• Otorrhea (Ear Discharge): May indicate an infection, such as otitis media or cholesteatoma.
• Ear Pain (Otalgia): Suggests an infection or inflammatory condition.
• Tinnitus: Sudden ringing in the ears, particularly unilateral, can indicate a range of pathologies.

Infectious Symptoms

• Fever: Could suggest a systemic infection or meningitis.
• Recent Upper Respiratory Infection: Might be associated with viral labyrinthitis.

History of Otologic Disease

• Chronic Ear Infections: May increase the risk of complications such as cholesteatoma.
• Previous Ear Surgery: Raises the possibility of complications or recurrent disease.

Systemic Symptoms

• Rash: Vesicular rash may indicate herpes zoster oticus (Ramsay Hunt syndrome).
• Weight Loss/Night Sweats: Possible indication of malignancy or chronic infection.

Medication Use

• Ototoxic Drugs: Recent use of ototoxic medications (e.g., aminoglycosides, cisplatin) can lead to sudden hearing loss.

Autoimmune Conditions

• Sudden Bilateral Hearing Loss: May indicate autoimmune inner ear disease.

Family History

• Genetic Predisposition: Family history of hearing loss or genetic syndromes can also be relevant.

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History and Examination for Sudden Onset Hearing Loss

History

• Which Ear?: Determine if the loss is unilateral or bilateral.
  • Bilateral loss is rare and may be associated with conditions like autoimmune diseases, syphilis, trauma, neoplasia, or vascular disorders.
• Onset: Was it sudden or gradual?
  • Gradual loss may point to underlying conditions such as Ménière’s disease.
  • Wax Impaction: Water exposure may precipitate wax buildup.
• Trauma: Physical trauma or acoustic exposure can cause:
  • CHL: Due to ossicular discontinuity.
  • SNHL: From extreme noise exposure or brain injury.
• Straining/Excessive Pressure: Excessive straining may cause a perilymph fistula, often accompanied by tinnitus and vertigo.
• Associated Symptoms:
  • Tinnitus and Dizziness: Nonspecific but often present in both CHL and SNHL.
  • Coryzal Symptoms, Fever, Discharge, Otalgia: Presence of these symptoms provides clues to the etiology.
• Past Medical History:
  • History of autoimmune disease, diabetes, sarcoidosis, or vascular disease.
  • Use of ototoxic drugs such as aminoglycosides, frusemide, NSAIDs, chemotherapeutic agents (e.g., cisplatin), quinine, and high doses of salicylates.

Examination

• Head, Neck, and Lymph Nodes:
  • Check for lymphadenopathy, which could indicate malignancy or a middle ear infection affecting the facial nerve.
• Cranial Nerve Examination:
  • Assess for abnormalities which may indicate intracranial lesions such as acoustic neuromas, malignancy, or multiple sclerosis.
• Otoscopic Examination:
  • Look for signs of otitis externa (discharge or pain when moving the pinna).
  • Check for mastoiditis (mastoid tenderness or fluctuance).
  • Evaluate the external ear canal for:
    • Foreign bodies, wax, discharge, or masses.
    • Inspect for tympanic membrane perforation, especially if there is a history of trauma or infection.

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Tuning fork tests

• The 512 Hz tuning fork is commonly used in clinical practice to assess hearing because it provides reliable results for both bone and air conduction tests. Below is a summary of how to perform and interpret Rinne’s and Weber’s tests.
• Rinne’s Test
  • Procedure:
    • Place a vibrating 512 Hz tuning fork firmly on the mastoid process to test bone conduction. Ensure firm contact by applying pressure to the opposite side of the head.
    • Ask the patient to indicate when they can no longer hear the sound.
    • Move the tuning fork in front of the external auditory meatus to test air conduction.
    • Ask the patient if they can hear the sound again.
  • Interpretation:
    • Normal Hearing (Rinne’s Positive):
      • Air conduction (AC) is better than bone conduction (BC).
      • The patient hears the sound when the tuning fork is moved in front of the ear after it can no longer be heard on the mastoid.
    • Conductive Hearing Loss (Rinne’s Negative):
      • Bone conduction (BC) is better than air conduction (AC).
      • The patient hears the tuning fork longer on the mastoid than in front of the ear.
    • Sensorineural Hearing Loss:
      • Rinne’s test remains positive (AC > BC), but the patient may have a ‘false negative’ if they cannot hear anything in the affected ear; bone vibrations might be transmitted to the unaffected ear.
• Weber’s Test
  • Procedure:
    • Tap a 512 Hz tuning fork and place it in the midline of the forehead.
    • Ask the patient “Where do you hear the sound?”
  • Interpretation:
    • Normal Hearing:
      • Sound is heard equally in both ears (midline).
    • Conductive Hearing Loss:
      • Sound localizes to the affected ear.
      • The affected ear has less environmental noise and low-frequency sounds are trapped within the inner ear, increasing loudness.
    • Sensorineural Hearing Loss:
      • Sound localizes to the unaffected ear.
• Additional Notes
  • The 512 Hz tuning fork is preferred due to its balance between decay time and minimizing tactile vibration.
  • Rinne’s Test Sensitivity: While useful, it has low sensitivity, and results should be interpreted in conjunction with other clinical findings.
  • Demonstration of Conductive Loss: Speaking or humming and then occluding one ear can illustrate how conductive loss causes increased loudness in the occluded ear.

	Rinne’s test	Weber’s test
Normal	Air conduction > bone conduction  (Positive Rinne’s)	Heard in the midline
Conductive hearing loss	Bone conduction > Air conduction (Negative Rinne’s)	Heard in the bad ear
Sensorineural hearing loss	Air conduction > bone conduction (Positive Rinne’s)	Heard in the good ear

Free field testing 

• sensitivity of 90–100%
• specificity of 70–87%
• The examiner tests the patient’s hearing with whispered, conversational and loud voice (indicating higher sound thresholds) while standing 60 cm behind the seated patient. If responses are poor, then the test can be repeated at 15 cm from the patient. Free field testing does not differentiate the type of hearing loss, but can be useful in the consulting room where audiology is not available.

Investigations

Pure tone audiogram

• Gold Standard: Definitive method for diagnosing SSNHL.
• If unavailable: Treatment should not be delayed while waiting for an audiogram as time is crucial for effective management.
• Use of Smartphone Apps:
  • The Real RazorTM app: Shown to be a reliable substitute for a tuning fork, with >97% agreement in conducting the Weber test
• Understanding the Audiogram Layout
  • Axes:
    • Horizontal Axis (X-Axis): Represents the frequency (pitch) of sounds, measured in Hertz (Hz). It typically ranges from 250 Hz to 8000 Hz.
    • Vertical Axis (Y-Axis): Represents the hearing threshold level, measured in decibels (dB). It usually ranges from -10 dB to 120 dB. The higher the number, the louder the sound.
  • Symbols:
    • Right Ear: Represented by a red “O”.
    • Left Ear: Represented by a blue “X”.
    • Bone Conduction Right Ear: Typically represented by a red “<“.
    • Bone Conduction Left Ear: Typically represented by a blue “>”.
• Interpreting the Results
  • Thresholds:
    • The points marked on the graph where the person begins to hear the sound at various frequencies. The lower the mark on the audiogram, the better the hearing at that frequency.
  • Hearing Levels:
    • Normal Hearing: -10 to 20 dB
    • Mild Hearing Loss: 21 to 40 dB
    • Moderate Hearing Loss: 41 to 55 dB
    • Moderately Severe Hearing Loss: 56 to 70 dB
    • Severe Hearing Loss: 71 to 90 dB
    • Profound Hearing Loss: 91+ dB
  • Shape of the Audiogram:
    • Flat: Similar loss across all frequencies.
    • Sloping: Better hearing at low frequencies, worse at high frequencies.
    • Rising: Worse hearing at low frequencies, better at high frequencies.
    • Notched: A significant dip at certain frequencies (often seen in noise-induced hearing loss).
• Steps to Read an Audiogram
  • Identify the Symbols:
    • Red: Right ear results.
    • Blue: Left ear results.
    • Bone conduction thresholds: Represented by symbols such as < and >.
    • Air conduction thresholds: Represented by symbols such as O (right ear) and X (left ear).
  • Examine the Frequency (X-Axis):
    • Start from the left (low frequencies) and move to the right (high frequencies).
  • Check the Hearing Thresholds (Y-Axis):
    • Note the dB level at which the person starts to hear each frequency.
    • The marks closer to the top of the graph indicate better hearing.
  • Assess the Hearing Loss Type:
    • Conductive Hearing Loss:
      • bone conduction thresholds are 15 dB or better than air conduction thresholds
      • bone conduction thresholds are 15 dB or less.
    • Sensorineural Hearing Loss:
      • if the difference between air conduction (AC) and bone conduction (BC) thresholds is less than 15 dB
      • both thresholds are worse than 15 dB
    • Mixed Hearing Loss: Combination of both conductive and sensorineural loss.
  • Look for Patterns:
    • Note any specific patterns like notching, which could indicate noise-induced hearing loss.
  • Example of Reading an Audiogram
    • Normal Hearing: Thresholds at or above 20 dB across all frequencies.
    • Noise-Induced Hearing Loss: Notching pattern at 4000 Hz, indicating a dip in hearing sensitivity typical of exposure to loud sounds

• Tympanometry
  • assesses tympanic membrane mobility and middle ear function. 
  • Fluid in the middle ear is represented as a ‘flat’ trace (type B tympanogram), and is consistent with CHL.
• Flexible nasoendoscopy
• Blood tests
  • Full blood count
  • Erythrocyte sedimentation rate (ESR)
  • Urea and electrolytes        
  • Fasting blood glucose
  • Fasting cholesterol/triglycerides
  • Viral titres (HIV, CMV, HSV, mumps, rubella)
  • FTA-abs for syphilis (or VDRL)
  • Lyme titres (this is rare and could be considered in patients returning from endemic areas)
  • Thyroid function tests/anti-thyroid antibodies
  • Angiotensin-converting enzyme (ACE)
  • Anti-neutrophil cytoplasmic antibodies (ANCA)
  • Antinuclear antibodies (ANA)
  • Rheumatoid factor (RF)
  • Anti-cyclic citrullinated peptide (anti-CPP)
  • Anti-phospholipid antibodies

Imaging

• MRI
  • Suspect vestibular schwannoma : if unilateral or asymmetrical SNHL (>15 dB)
  • demyelination, typically seen in multiple sclerosis, and small vessel ischaemic changes.
• CT
  • can exclude large acoustic neuromas in SNHL
  • evaluate the middle ear/ossicular chain in conductive hearing loss. 
• chest X-ray
  • suspicion of sarcoidosis with mediastinal involvement.

Management of CHL

• Conductive hearing loss
  • Manage wax, foreign bodies or otitis externa,Acute otitis media 
• Tympanic membrane perforations
  • Most tympanic membrane perforations heal spontaneously over several weeks. However, persistent perforations (those lasting longer than 6-8 weeks) may require surgical repair (tympanoplasty).
  • Topical antibiotics are not routinely required unless there is an associated infection.
    • If there is a history of contamination (e.g., water exposure, foreign body), the risk of infection increases
  • The extent of the perforation may correlate with the degree of conductive hearing loss
  • Referral to an ENT surgeon for consideration of repair (tympanoplasty) may be required should the perforation not heal.

Management of SSNHL

Referral Process

• Urgency of Referral:
  • NICE Guidelines: Recommend that an adult presenting with sudden onset hearing loss within the past 30 days should be referred immediately (to be seen within 24 hours) to an ENT specialist or emergency department.
  • Reason for Urgency: Prompt intervention with corticosteroids is critical as treatment effectiveness diminishes significantly with time.

Pharmacological Treatment

• Systemic Corticosteroids:
  • First-Line Therapy: Oral high-dose systemic corticosteroids are the current gold standard for SSNHL treatment.
    • Dosage: Prednisone at 1 mg/kg/day, with a maximum dose of 75 mg, given as a single morning dose for 5 to 7 days.
    • Tapering: Following the initial course, tapering regimens are generally individualized based on clinical response and physician discretion.
  • Therapeutic Window: Initiation of therapy within the first 14 days from symptom onset is vital for optimal recovery. Treatment initiated beyond two weeks is associated with significantly lower success rates in hearing restoration.
• Alternative Routes:
  • Intra-Tympanic Corticosteroids: An option if systemic corticosteroids are contraindicated or in cases that do not respond adequately to oral steroids.
    • Indication: Particularly considered for those patients with hearing loss greater than 30 days duration.

Special Considerations

• Contraindications to Corticosteroids:
  • Diabetes Mellitus: Corticosteroids can exacerbate hyperglycemia; close glucose monitoring is essential.
  • Peptic Ulcer Disease: Use with caution; consider prophylactic proton pump inhibitors.
  • Immunosuppression and Infection: Steroid use in immunocompromised individuals may increase the risk of infections.
• Patient Counselling:
  • Side Effects: Patients should be educated regarding potential side effects of corticosteroids such as insomnia, mood changes, increased appetite, and hyperglycemia.
  • Monitoring: Close monitoring for systemic side effects is warranted during treatment, especially in at-risk populations.

Follow-Up

• Audiological Assessment:
  • Repeat Audiometry: Follow-up audiograms are required at 1-2 weeks, and then again at 3 months to assess improvement or progression.
  • ENT Specialist Review: Continued assessment by an ENT specialist is recommended, especially for those who do not respond to initial corticosteroid therapy.
• Persistent or Late-Presenting SSNHL:
  • Management Options: For cases where the presentation is delayed (>30 days), treatment options such as intra-tympanic steroid injections may still be considered, though outcomes are generally poorer compared to early interventions.

Prognosis

• Factors Affecting Prognosis:
  • Time to Treatment: The single most important prognostic factor is the rapidity of treatment initiation after symptom onset.
  • Severity of Initial Loss: Severe initial hearing loss has a lower chance of full recovery.
  • Presence of Vertigo: Vertigo at onset is generally associated with a worse prognosis.
• Recovery Rates:
  • Spontaneous Recovery: Approximately 30-60% of SSNHL cases recover spontaneously, but early intervention with corticosteroids can significantly enhance the likelihood and extent of recovery.
  • Hearing Outcomes: Patients treated within two weeks of onset have a much better chance of complete or partial recovery compared to those who experience a delayed diagnosis.

Key Takeaway Points

1. SSNHL is a Medical Emergency: Immediate referral and treatment are critical for optimal hearing recovery.
2. Corticosteroid Therapy is the Gold Standard: High-dose systemic corticosteroids should be initiated as soon as possible, even before audiometric confirmation if the diagnosis is strongly suspected.
3. Early Intervention Improves Prognosis: Initiation of corticosteroid treatment within 14 days offers the best outcomes, whereas delays beyond this period drastically reduce the likelihood of hearing restoration.
4. Innovative Diagnostic Solutions: Smartphone applications can provide practical, accessible alternatives in settings where traditional tuning forks are unavailable, supporting timely diagnosis in primary care.