Hearing Loss

Introduction to Hearing Loss for MCCQE1

Hearing loss is a high-yield topic for the MCCQE1, falling under the domains of Otolaryngology (ENT), Family Medicine, and Pediatrics. As a future Canadian physician, you must demonstrate competence in differentiating between conductive and sensorineural hearing loss, identifying red flags (such as sudden sensorineural hearing loss), and managing common conditions like presbycusis and otitis media.

This guide focuses on the Medical Council of Canada (MCC) objectives, emphasizing the CanMEDS roles, particularly the Communicator role, as hearing loss significantly impacts patient-physician interaction and quality of life.

Anatomy and Physiology Review

Understanding the pathway of sound is essential for localizing pathology.

Classification of Hearing Loss

For MCCQE1 preparation, you must be able to distinguish between the three primary types of hearing loss based on history, physical exam, and tuning fork tests.

1. Conductive Hearing Loss (CHL)

Occurs when sound conduction is impeded through the external ear, middle ear, or ossicles.

• Key Feature: Bone conduction > Air conduction.
• Common Causes: Cerumen impaction, Otitis media, Otosclerosis.

2. Sensorineural Hearing Loss (SNHL)

Occurs due to pathology in the cochlea (sensory) or the retrocochlear nerve pathway (neural).

• Key Feature: Air conduction > Bone conduction (but both are reduced compared to normal), often with loss of high-frequency perception.
• Common Causes: Presbycusis, Noise-induced, Meniere’s disease, Acoustic neuroma.

3. Mixed Hearing Loss

A combination of both conductive and sensorineural components.

Etiology and Differential Diagnosis

Clinical Assessment for MCCQE1

Follow this structured approach to maximize your score on the Clinical Decision Making (CDM) component.

Summary Table: Tuning Fork Interpretation

Diagnostic Investigations

Audiometry

The gold standard for diagnosis.

• Pure Tone Audiometry: Measures thresholds for air and bone conduction.
  • Air-Bone Gap: Indicates Conductive Hearing Loss.
• Speech Discrimination: Poor in retrocochlear pathology (e.g., Acoustic Neuroma).

Tympanometry

Assesses tympanic membrane compliance.

• Type A: Normal.
• Type B: Flat (Fluid/OME, Perforation, Cerumen).
• Type C: Negative pressure (Eustachian tube dysfunction).
• Type As: Shallow (Otosclerosis).
• Type Ad: Deep/Disarticulation of ossicles.

Imaging

• MRI with Gadolinium: Gold standard for ruling out Vestibular Schwannoma in cases of asymmetric SNHL.
• CT Temporal Bone: Best for bony pathology (Cholesteatoma, Otosclerosis, Trauma).

Specific Canadian Guidelines and Context

Sudden Sensorineural Hearing Loss (SSNHL)

• Definition: Loss of ≥30 dB in 3 contiguous frequencies occurring over <72 hours.
• Canadian Standard of Care: This is an OTOLOGIC EMERGENCY.
• Management:
  1. Urgent Audiogram.
  2. Systemic Steroids (e.g., Prednisone 1 mg/kg) started immediately (ideally within 2 weeks).
  3. Intratympanic steroid injections (salvage therapy).
  4. MRI to rule out retrocochlear pathology.

Screening Guidelines

• Newborns: Universal Newborn Hearing Screening (UNHS) is standard in most Canadian provinces. Aim to screen by 1 month, diagnose by 3 months, and intervene by 6 months (1-3-6 rule).
• Adults: The Canadian Task Force on Preventive Health Care (CTFPHC) does not recommend routine screening for asymptomatic adults, but physicians should remain alert to patient-reported concerns.

Management Strategies

Conductive Hearing Loss

• Medical: Treat infection (Antibiotics for AOM), remove cerumen, decongestants (limited evidence).
• Surgical: Tympanoplasty (perforation), Stapedectomy (Otosclerosis), Myringotomy tubes (chronic OME).
• Hearing Aids: Bone-anchored hearing aids (BAHA) if surgery is contraindicated.

Sensorineural Hearing Loss

• Presbycusis: Hearing aids (amplification).
• Severe/Profound: Cochlear Implants (bypass hair cells to stimulate the auditory nerve directly).
  • Note: In Canada, candidacy for cochlear implants is determined by provincial health programs based on audiometric criteria.

Key Points to Remember for MCCQE1

• Presbycusis is the most common cause of hearing loss in the elderly (SNHL, bilateral, high frequency).
• Sudden SNHL requires urgent steroids; do not delay for imaging or specialist referral before starting treatment if strongly suspected.
• Unilateral SNHL or Unilateral Tinnitus is an Acoustic Neuroma until proven otherwise → MRI.
• Otosclerosis typically presents in young females with a positive family history and conductive loss (Carhart’s notch at 2000 Hz).
• Weber Test: Lateralizes to the BAD ear in Conductive loss, and the GOOD ear in Sensorineural loss.
• Noise-induced loss: Characterized by a “notch” at 4000 Hz.

Sample Question

Clinical Scenario

A 45-year-old male presents to your family medicine clinic complaining of sudden hearing loss in his left ear that started 2 days ago upon waking up. He also reports a “ringing” sound in the same ear. He denies vertigo, ear pain, or discharge. He has no history of trauma or recent respiratory infection. His vital signs are stable.

Physical Examination:

• Otoscopy: Both tympanic membranes appear pearly grey and intact with normal light reflexes. No cerumen impaction.
• Weber Test: Lateralizes to the right ear.
• Rinne Test: Air conduction is greater than bone conduction (AC > BC) bilaterally.

Question

Which one of the following is the most appropriate next step in management?

• A. Reassure the patient that it is likely viral and will resolve spontaneously
• B. Prescribe oral amoxicillin for 7 days
• C. Perform an urgent MRI of the brain
• D. Initiate high-dose oral corticosteroids and refer for urgent audiometry
• E. Refer for tympanometry to rule out Eustachian tube dysfunction

Explanation

The correct answer is:

• D. Initiate high-dose oral corticosteroids and refer for urgent audiometry

Detailed Analysis: This patient presents with Sudden Sensorineural Hearing Loss (SSNHL).

1. Interpretation of Data:

   • History: Sudden onset (<72 hours), unilateral.
   • Weber: Lateralizes to the Right (the “good” ear). This indicates either Right Conductive loss or Left Sensorineural loss.
   • Rinne: AC > BC bilaterally (Positive Rinne). A positive Rinne in the affected ear (Left) rules out conductive loss.
   • Conclusion: The combination of Weber lateralizing to the right and a positive Rinne on the left confirms Left-sided Sensorineural Hearing Loss.

2. Clinical Reasoning:

   • SSNHL is an otologic emergency. The window for effective treatment is narrow.
   • Current Canadian and international guidelines recommend the immediate initiation of systemic corticosteroids (e.g., Prednisone) to reduce inflammation and improve the chance of hearing recovery.
   • Urgent audiometry is required to confirm the diagnosis and establish a baseline.

3. Why other options are incorrect:

   • A: Observation is inappropriate because untreated SSNHL can lead to permanent deafness.
   • B: Antibiotics are indicated for bacterial infections (like AOM). The normal otoscopy rules out AOM.
   • C: While an MRI is eventually indicated to rule out retrocochlear pathology (like a vestibular schwannoma), it is not the immediate next step before treatment initiation/audiometry, and waiting for an MRI should not delay steroid therapy.
   • E: Tympanometry assesses middle ear function. Since the Rinne was positive and otoscopy normal, middle ear pathology is unlikely.

References

1. Medical Council of Canada. Objectives for the Qualifying Examination. Available at: mcc.ca 
2. Canadian Society of Otolaryngology - Head and Neck Surgery. Clinical Practice Guidelines.
3. RxTx (formerly e-Therapeutics). Hearing Loss. Canadian Pharmacists Association.
4. Canadian Task Force on Preventive Health Care. Screening for Hearing Loss.
5. Toronto Notes 2024. Otolaryngology Chapter.