Military Audiology Short Course

MASC 2002 Abstracts

Idiopathic Sudden Sensorineural Hearing Loss—On the Other Side of the Audiometer

Mr. F. Froman1, COL N. Vause2 , COL C. Byrne3 , CPT S. Packer1, LTC E. Helling1, LTC G. Vrentas4

1Brooke Army Medical Center. Audiology - ENT Section, Ft Sam Houston, TX
2 US Army Research Lab, Human Research & Engineering Directorate, AMEDD Field Office, Ft Sam Houston, TX
3AMEDD Center and School, Physician Extenders Branch. Ft. Sam Houston, Texas
4Special Troop Battalion, US Army Garrison, Fort Sam Houston, Texas

What is it?

Idiopathic Sudden sensorineural hearing loss (ISSHL) is a hearing loss that is greater than 30 dB in three contiguous frequencies and that occurs over a period of less than three days. The incidence is estimated at 20/100,000 persons per year, increasing with advancing age.

Definition of ISSHL
•Perceptive hearing loss
•Etiology remains unknown after clinical, laboratory and imaging studies
•Hearing loss occurred within 24 hours (some authors define over 3 days)
•Hearing loss is nonfluctuating
•Severity of the hearing loss averages at least 30 dB HL for three subsequent one octave steps in frequency as shown in the standard pure-tone audiogram
•Blank otological history in an otherwise healthy individual

The natural history of ISSHL is that about 65% of patients recover their hearing spontaneously. Negative prognostic factors are thought to be: age less than 15 years or older than 65 years, elevated ESR (>25), presence of vertigo or vestibular changes evident on ENG, and a hearing loss in the opposite ear. Positive prognostic factors are: seeking medical treatment within 10 days of onset, midfrequency or upsloping hearing loss. The severity of the hearing loss is inversely proportional to the rate of recovery. Note that 30% of the patients may present with URIs.

Etiology

ISSHL is probably a symptom of a wide variety of diseases or pathological processes.

The differential diagnosis of ISSHL is:
  1. Infections/inflammatory
    • Viral infections of cochlea/CN VIII
    • Syphilis
    • Meningitis
    • Encephalitis
  2. Neoplastic
    • Acoustic Neuroma
    • Cerebellopontine angle tumour
  3. Vascular
    • Sludging/occlusion due to hyperviscosity
      • Polycythemia vera
      • Macroglobulinemia
      • Leukemia
    • Accelerated coagulation
    • Arteriosclerosis related to
      • Aging
      • Diabetes
      • Hypertension
      • Hyperlipidemia
    • Aneurysm of Anterior Inferior Cerebellar Artery
  4. Trauma
    • Temporal bone fracture
    • Barotrauma (can cause fistula as in #8 below)
  5. Drug effects
    • Aminoglycosides
    • Furosemide
    • Antineoplastics
  6. Autoimmune
    • Cogan’s syndrome
    • Lupus
  7. Endocrine
    • Hypothyroidism
    • Diabetes
  8. Other
    • Multiple sclerosis
    • Round or oval window fistula
  9. Idiopathic (most common)

Signs and Symptoms

ISSHL is usually unilateral and accompanied by tinnitus (70%) and often vertigo (50%). Degree of hearing loss is variable. Patients often report that they awaken in the morning and notice a hearing loss. One of the patients in our case presentation initially noticed HL at lunch and observed a rapid deterioration of sensitivity over the afternoon and evening.

Initial Evaluation

A complete physical exam, looking especially at the ears. Rule out an effusion as the cause of hearing loss (pneumatoscopy is helpful). Perform tuning fork tests to differentiate a conductive from a sensorineural hearing loss. In cases where the exam is difficult or unclear, tuning fork testing can be helpful. A Weber test (512 Hz tuning fork placed on the top of the head) will lateralize toward an ear with a conductive hearing loss, but away from an ear with a sensorineural hearing loss. The Rhinne test, where loudness is compared on the mastoid bone (bone conduction) and beside the ear (air conduction). In a normal ear or with sensorineural loss the Rhinne will be negative (AC>BC), but a conductive loss showsBC>AC. Note in our case presentation the tuning fork test was misinterpreted by the ER PA.

Audiological Management

We recommend patients should have a comprehensive audiometric workup (e.g., PT audiogram, Speech testing, UCL, MCL, Acoustic reflexes (with decay if possible), DPOAEs). Additionally, you should consider an ABR. The former documents the degree and pattern of hearing loss and cochlear hair cell loss while the latter describes the function of the auditory pathways up to the brainstem.

If vertigo is present they should have an ENG. Consider amplification and emotional effect of HL.

Otologic Management

If trauma or tumor is suspected, a temporal bone CT or MRI (with contrast) is indicated.

Since etiology is often unknown appropriate labwork to rule out systemic disease is usually indicated. Many authors suggest that all patients in whom idiopathic ISSHL is suspected should have the following blood tests:

Conservative therapy for ISSHL includes bedrest with the head of the bed elevated, stool softeners, avoidance of alcohol, stimulants, stress and loud noises.

Many medications have been used to treat ISSHL (for example vasodilators, anticoagulents, diuretics) but only steroids have been shown to be helpful. These are most helpful in patients who have moderate unilateral hearing loss (those with mild hearing loss are likely to recover spontaneously and those with severe hearing loss are unlikely to recover despite treatment). One dosage suggested is prednisone 20 mg qid for 10 days. What was used with these case studies was 60mg prednisone X2 wk (2 patients) X 3 wks (1 patient) in combination with an antiviral (famcyclovir or acyclovir) ) X1 0 days.

Middle ear exploration is indicated if a fistula is suspected. These patients typically have a history of ISSHL following diving, air travel, or even mild straining.

Conclusions

  1. ISSHL is a disabling disease. Patient considered the unilateral HL very disabling! Audiologists listen up!! Recognize the differences between gradual– vs–sudden onset from a patient's point of view—the other side of the audiometer!
  2. The incidence of ISSHL implies that many patients may be misdiagnosed or may spontaneously recover. More patients may suffer ISSHL than indicated by incidence.
  3. Use a diagnostic protocol when evaluating sudden sensorineural hearing loss. Does your clinic have a protocol preventing diagnostic omissions?
  4. This is an audiologic and neuro-otologic emergency. Additionally, ISSHL is a neuroradiological emergency as a labyrinthitis can probably only be visualized on gadolinium enhanced MRI during the very early phase of hearing loss. How does your facility handle these for after hours? Who is on–call for Audiology for a 24 hr consult? You only have 100 hours!
  5. Many patients may initially present to a variety of health care professionals. Conduct inservice training with ER, Troop Medical Clinic, Family Practice and Nursing staff to avoid misdiagnosis
  6. Misdiagnosis of sudden hearing loss makes a case for audiology to be an entry point for hearing loss related complaints. Can patients request an audiology appointment as the gateway to their hearing health care?
  7. Remember a synergistic therapeutical effect appears to exist from combined treatment with antiinflammatory (Corticosteroids - 60 mg X 2-3 wks) and antiviral medication on hearing recovery. (Many practitioners utilize the “shotgun” approach). Is your ENT aware that results from the “traditional” steroid alone treatment (201mg X I wk) are not as effective?
  8. Audiologists should recognize the emotional aspect of this hearing loss and be sensitive to the effect of HL on patient lifestyle. Don’t be just the data collector (highly paid technician) sending info to ENT! Talk with the patient and Listen—brush off those counseling skills as perception of disability was very individualized but in each case a disability!
  9. Consider using a 3 prong approach: medical, administrative and rehabilitative! ENT should initiate medical and administrative (profile) actions where audiologists now have disposable hearing aids in their tool bag. Ask what can you do to help this patient cope and function?
  10. Consider that the cost–benefit ratio is now affordable to fit disposable hearing aids on these patients. Audiologists are can now actively participate in the treatment (recruitment relief and improved hearing).
  11. Speech perception experiments simulating hearing loss experiments using filtering do not approximate speech perception of a damaged ear with distortion, tinnitus, and recruitment.

ISSHL References