Sudden Sensorineural Hearing Loss

Sudden Sensorineural Hearing Loss (SSNHL)

Introduction. SSNHL was first described by De Kleyn in 1944. Sudden hearing loss is defined as the subjective hearing loss of rapid onset, occurring over 72 hours or less, usually in one or rarely in both ears (about 1% of cases). In the audiometry test, there is 30-35 dB or more of SNHL in at least three consecutive frequencies. Though it is rarely seen. It is an otological emergency. The severity of the hearing loss may vary from mild to total loss, which can be permanent. SSNHL may be accompanied by roaring type tinnitus, or there are incidences of mild transient vertigo, which may also be associated with nausea and vomiting.

Definition

• SSNHL: Sensorineural hearing loss of ≥30 dB in 3 consecutive frequencies, developing over ≤72 hours.
• Usually unilateral (99%), rarely bilateral (1%).

Key Symptoms

• Sudden onset of hearing loss (often noticed on waking).
• Tinnitus (roaring or buzzing).
• Aural fullness or ear blockage.
• Mild vertigo, nausea or imbalance may be present.

Natural History. Patients first notice their hearing loss with or without associated tinnitus on awakening in the morning and often present with a full or blocked ear. It can be unilateral or bilateral. As this is a common and non-specific symptom, it can be underestimated by both patients and clinicians, thus leading to a delay in evaluation and treatment.

Prognosis. The prognosis is not as bad as is generally supposed. Approximately 50% of patients spontaneously return to normal hearing without any treatment. Spontaneous recovery of normal hearing is more likely to occur if good prognosis factors are present.

Good prognosis factors:

1. Early treatment.
2. If the recovery phase starts within 2 weeks. The shorter the delay between the onset of SSNHL and the onset of recovery, the better the prognosis for complete recovery.
3. Young age patients below 40 years.
4. No history of vertigo.
5. An Audiogram showing mild hearing loss with the involvement of low and mid frequencies.

Poor prognosis factors:

1. Late treatment.
2. If the recovery phase starts after 2 weeks.
3. Old patients above 60 years.
4. History of vertigo.
5. An audiogram shows severe to profound hearing loss with the involvement of high frequencies. A downward-sloping audiogram is associated with a poorer prognosis.

Aetiology

Viral infections, vascular obstruction, breaks or rupture in the cochlear membranes have all been described as possible etiologic factors for idiopathic sudden deafness. Perilymph fistulae may occur in the oval or round window as a result of physical trauma such as a blow to the head or ear, barotrauma, acoustic trauma, surgical trauma, chronic ear disease or may occur spontaneously.

1. Infections. Viral infections are a well-documented cause. It may affect the cochlea (viral endolymphatic labyrinthitis) or the eighth cranial nerve (viral neuronitis). Meningococcal meningitis, Encephalitis, Herpes virus (simplex, zoster, varicella, cytomegalovirus), Mumps, Measles, Human immunodeficiency virus, Lyme disease, Rubella, Syphilis, Toxoplasmosis.
2. Vascular. Vasospasm, thrombosis, embolism of the labyrinthine or cochlear artery. Vasospasm (ie, arterial vasoconstriction) is often due to stress, fatigue, and the emotional state of the patient. Thrombosis and embolism are usually due to arteriosclerosis. Haemorrhage (leukaemia) into the inner ear. They may be associated with diabetes, hypertension, polycythaemia, macroglobinaemia or sickle cell trait.
3. Trauma. Noise trauma, barotrauma, head injury, ear operations (stapedectomy), spontaneous rupture of cochlear membranes (perilymph fistula).
4. Autoimmunity. Immune-mediated sensorineural hearing loss. Wegener’s granulomatosis, Rheumatoid arthritis, Sjogren’s syndrome, Polyarteritis nodosa, Relapsing polychondritis, Lupus erythematosus Ulcerative colitis, Autoimmune inner-ear disease (AIED), Cogan’s syndrome Antiphospholipid syndrome, Sarcoid.
5. Neoplastic. Acoustic neuroma. Metastases in the cerebellopontine angle, carcinomatous neuropathy, Leukaemia, Myeloma.
6. Ear (otologic). Meniere’s disease, Cogan’s syndrome, large vestibular aqueduct.
7. Toxic. Ototoxic drugs (Aminoglycoside antibiotics, Loop diuretics, NSAIDs, Salicylates), insecticides, platinum-based chemotherapeutic agents,  general anaesthesia
8. Miscellaneous. Multiple sclerosis, hypothyroidism, sarcoidosis.
9. Psychogenic.

Management:

In the majority of cases, there is no cause present (idiopathic). Nonetheless, examination and investigation are important to exclude treatable causes.

1. Careful history and examination. Rule out possibilities such as middle ear infection or disease, viral endolymphatic labyrinthitis, ototoxicity, Meniere’s disease, trauma, bacterial labyrinthitis, and perilymph fistula, and elicit neurological signs if present.
2. Vestibular tests. It is important if vertigo and accompanying nystagmus are present. Fistula test, Fitzgerald-Hallpike caloric test with electronystagmographic monitoring.
3. Imaging studies of temporal bones. Magnetic resonance imaging (MRI) scanning to rule out acoustic neuroma, multiple sclerosis and cerebrovascular accidents. Fine-cut contrast CT of the temporal bone is advised if MRI is contraindicated.
4. Audiometry must be performed to determine the degree and type of hearing loss. 30-35 dB or more of SNHL in at least three consecutive frequencies occurring over 72 hours or less strongly indicates SSNHL. BERA can also be done.
5. Blood tests for autoimmune disease, inflammatory markers and syphilis are required. Blood glucose level for diabetes.
6. Exploratory tympanotomy where perilymph fistula is strongly suspected.

Treatment of SSNHL:

First, treat the cause if any. Idiopathic sensorineural sudden hearing loss treatment is empirical and consists of:

1. Bed rest.
2. Steroid therapy. Prednisolone 40–60 mg (1 mg/kg/day, up to a maximum of 60 mg daily) in a single morning dose for 1 week and then tapered off in 3 weeks. Steroids are anti-inflammatory and relieve oedema. They have been found useful in idiopathic sudden hearing loss of moderate degree. The treatment is based on the maximum adrenal output of hydrocortisone (cortisol), which is 200–300 mg/day during stress.
3. Inhalation of carbogen (5% CO₂+ 95% O₂). It increases cochlear blood flow and improves oxygenation.
4. Vasodilator drugs.
5. Low molecular weight dextran. It decreases blood viscosity. It is contraindicated in cardiac failure and bleeding disorders.
6. Hyperbaric oxygen therapy. Hyperbaric oxygen therapy (HBOT) delivers 100% oxygen to a patient at a pressure greater than 1 atmosphere. This increases the concentration of oxygen in labyrinthine fluids and improves cochlear function. Therapy typically involves multiple sessions of 1–2 hours over days to weeks. HBOT is an expensive and time-consuming intervention that is available only in selected centres.
7. Low-salt diet and a diuretic. It is empirical and has the same benefit as in cases of Meniere’s disease.
8. Intratympanic (IT) steroid therapy. It raises the local concentration of steroids in cochlear fluids, thus the main advantage of IT treatment is the reduction in systemic corticosteroid side effects. Dexamethasone and solumedrol (methylprednisolone sodium succinate) are the most commonly used IT steroids. Most studies quote doses of 10–24 mg/mL dexamethasone and 30–40 mg/mL solumedrol. Higher concentrations may have better outcomes. Adverse effects with IT steroids are infrequent but include pain, transient dizziness, infection, persistent tympanic membrane perforation, a possible vasovagal episode during injection, and the need for repeat visits. The main risk appears to be a persistent tympanic membrane perforation at the injection site.

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Mnemonic for SSNHL Causes: “VITAMINS N P”

• Vascular
• Infectious
• Trauma
• Autoimmune
• Metabolic
• Idiopathic
• Neoplasm
• Syndromes (Meniere’s)
• Neurogenic
• Psychogenic

High-Yield Points for Quick Revision

• SSNHL = ≥30 dB SNHL over 3 contiguous frequencies within 72 hrs.
• Most cases are idiopathic.
• Early treatment improves outcomes.
• MRI is mandatory to rule out acoustic neuroma.
• Steroids are the mainstay of therapy.
• IT steroids and HBOT are useful second-line options.

NEET PG & University Exam MCQs (10)

1. Which of the following is NOT a known cause of SSNHL? A. CMV infection
   B. Acoustic neuroma
   C. Otosclerosis
   D. Perilymph fistula
   ✅ Answer: C. Otosclerosis
   Explanation: Otosclerosis causes progressive CHL, not SSNHL.
2. What is the most important first investigation in suspected SSNHL? A. CT scan
   B. Audiometry
   C. Tympanometry
   D. VDRL
   ✅ Answer: B. Audiometry
   Explanation: Confirms type and severity of hearing loss.
3. What is the standard steroid dose for idiopathic SSNHL? A. 5 mg/kg/day
   B. 1 mg/kg/day
   C. 60 mg once weekly
   D. 10 mg daily
   ✅ Answer: B. 1 mg/kg/day
4. A 65-year-old male presents with sudden hearing loss and vertigo. Which of the following predicts poor prognosis? A. Age <40 years
   B. No vertigo
   C. Mid-frequency loss
   D. Downward-sloping audiogram
   ✅ Answer: D. Downward-sloping audiogram
5. SSNHL is defined as loss of how many decibels in how many frequencies? A. 30 dB in 2 frequencies
   B. 40 dB in 3 frequencies
   C. 30 dB in 3 frequencies
   D. 20 dB in 3 frequencies
   ✅ Answer: C. 30 dB in 3 frequencies
6. Which test best helps in diagnosing retrocochlear causes of SSNHL? A. BERA
   B. Pure tone audiometry
   C. Tympanometry
   D. Rinne’s test
   ✅ Answer: A. BERA
7. Intratympanic injection in SSNHL is given to avoid: A. Delayed diagnosis
   B. MRI scan
   C. Systemic steroid side effects
   D. Vertigo
   ✅ Answer: C. Systemic steroid side effects
8. HBOT in SSNHL improves outcome by: A. Decreasing ICP
   B. Increasing oxygenation of inner ear
   C. Clearing infection
   D. Lowering BP
   ✅ Answer: B. Increasing oxygenation of inner ear
9. Commonest cause of idiopathic SSNHL: A. Acoustic neuroma
   B. CMV
   C. Vascular insult
   D. Unknown
   ✅ Answer: D. Unknown
10. MRI in SSNHL is done to exclude: A. Otitis media
    B. Meniere’s disease
    C. Vestibular schwannoma
    D. Otitis externa
    ✅ Answer: C. Vestibular schwannoma

Clinical Case Scenarios

Case 1: A young woman wakes up with left-sided hearing loss. She has no vertigo. Audiometry shows 35 dB SNHL in 3 frequencies.

• Diagnosis: SSNHL.
• Management: Start systemic steroids. MRI brain recommended.

Case 2: A 60-year-old diabetic male presents after 1 week of right-sided hearing loss and vertigo. Audiogram: severe loss with high-frequency dip.

• Poor Prognosis Factors: Age >60, vertigo, high-frequency involvement.
• Management: Systemic and IT steroids; consider HBOT.

Case 3: A scuba diver presents with sudden left ear hearing loss and tinnitus. No middle ear effusion.

• Suspected Diagnosis: Perilymph fistula.
• Management: Audiometry + MRI. Consider exploratory tympanotomy.

Case 4: Patient with Meniere’s disease has a sudden worsening of hearing.

• Diagnosis: Acute exacerbation of Meniere’s or overlapping SSNHL.
• Management: Low-salt diet, diuretic, steroids.

FAQs in Viva

• What is sudden sensorineural hearing loss (SSNHL)?
  Sudden SNHL is a rapid loss of hearing (≥30 dB in 3 frequencies) within 72 hours.
• Is SSNHL reversible?
  Yes, especially if treated early. Up to 50% recover spontaneously.
• What is the most common cause of SSNHL?
  Most cases are idiopathic; exact cause remains unknown.
• Why is MRI recommended in SSNHL?
  MRI is used to rule out vestibular schwannoma and other retrocochlear pathologies.
• How are steroids used in SSNHL treatment?
  Prednisolone 1 mg/kg/day for 7 days, tapered over 2–3 weeks.
• Can SSNHL affect both ears?
  Rarely. Only ~1% of cases are bilateral.
• Is hearing loss permanent in SSNHL?
  It can be, especially with delayed treatment or poor prognostic factors.

Download full PDF Link:
SSNHL Sudden Sensorineural Hearing Loss Best Lecture Notes Dr Rahul Bagla ENT Textbook

Reference Textbooks.

• Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
• Glasscock-Shambaugh, Textbook of Surgery of the Ear.
• P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
• Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
• Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck Surgery
• Hans Behrbohm, Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
• Salah Mansour, Middle Ear Diseases – Advances in Diagnosis and Management.
• Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head And Neck Surgery.
• Rob and smith, Textbook of Operative surgery.
• Anirban Biswas, Textbook of Clinical Audio-vestibulometry.
• Arnold, U. Ganzer, Textbook of  Otorhinolaryngology, Head and Neck Surgery.

Author:

Dr. Rahul Bagla
MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
Fellow Rhinoplasty & Facial Plastic Surgery.
Renowned Teaching Faculty
Mail: msrahulbagla@gmail.com
India

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