Sudden sensori-neural hearing loss Dr. Vishal Sharma

Defining triad (Wilson, 1980) Sensori-neural deafness of > 30 dB HL over > 3 contiguous frequencies occurring in < 3 days Within 12 hrs: Cummings

Synonyms & alternatives Sudden sensorineural hearing loss is also called acute cochlear dysfunction Sudden sensorineural hearing loss accompanied by acute vertigo is also called acute cochleo-vestibular dysfunction Deafness occuring over days or weeks is called rapidly progressive hearing loss

Epidemiology Annual incidence (USA) is 5 - 20 cases / 1 lakh 47-70 % resolve spontaneously (do not report) True incidence rate is higher Gender not a risk factor Unilateral cases: 96-99% Bilateral cases: 1-4% Left ears are affected more (55%)

Distribution in 1220 cases (Shaia & Sheehy, 1976) Age (years) Distribution in 1220 cases (Shaia & Sheehy, 1976) < 30 13 % 30 – 39 40 – 49 21 % 50 – 59 22 % 60 – 69 18 % > 70

Etiology Idiopathic (single largest group: 90 - 95%) Cochlear causes Retro-cochlear causes Miscellaneous Psychogenic Malingering

Criteria for idiopathic SSNHL SSNHL present No other cranial nerve involvement except eighth cranial nerve No other etiology is known

Idiopathic SSNHL Various hypotheses are: 1. Labyrinthine viral infection (viral cochleitis) 2. Labyrinthine vascular compromise 3. Membrane rupture 4. Immune-mediated inner ear damage 5. Activation of cochlear nuclear factor kappa B

1. Labyrinthine viral Infection (20 – 40 %) Herpes, mumps, measles, maternal rubella, cytomegalovirus, varicella zoster 2. Labyrinthine vascular compromise caused by thrombosis, embolus, reduced blood flow, vasospasm Western diet (rich in saturated fat), alcohol intake & tobacco smoking are predisposing factors

3. Membrane rupture (Simmons) Pts hear pop sound before sudden deafness Oval & round window perilymph fistulae leak perilymph into middle ear  low perilymph pressure & relative endolymphatic hydrops Rupture of intra-cochlear membranes  mixing of perilymph & endolymph  altering endo-cochlear potential

4. Immune-mediated inner ear damage Antigen-antibody complex mediated destruction of cochlea Cross-reacting circulating antibodies seen in 65 % pt of SSNHL. Associated conditions are:  Cogan syndrome  Relapsing polychondritis  Systemic lupus erythematosus  Polyarteritis nodosa  Temporal arteritis

5. Activation of cochlear nuclear factor kappa B Merchant et al (2005) proposed this new theory Nuclear factor kappa B (NFҚ B) functions by:  regulating inflammatory response + apoptosis  regulating intracellular Ca & neuronal excito-toxicity NFҚ B activation is associated with destruction of spiral ganglion neurons & cochlear hair cells causing ISSNHL

Cochlear causes 1. Infection: bacterial, viral, spirochaetal, mycoplasma 2. Trauma: temporal bone #, acoustic trauma, barotraumas, perilymph fistula, radiotherapy 3. Vascular: hyper-coagulable states, thrombo- embolism, hypertension, migraine 4. Hematological: polycythemia, leukemia, anemia

Cochlear causes 5. Oto-toxicity: aminoglycoside, aspirin, frusemide, antimalarials, cisplatin 6. Endolymphatic hydrops 7. Metabolic: diabetes mellitus, hypothyroidism, hyperlipidemia, renal failure 8. Auto-immune: Cogan syndrome, systemic lupus erythematosus, relapsing polychondritis

Retro-Cochlear causes Meningitis Encephalitis Tumor: Vestibular schwannoma, other tumors of cerebello-pontine angle Multiple sclerosis Metastasis

Clinical Features Medical Emergency Sensori-neural hearing loss Tinnitus: seen in 60 - 70% pt Vertigo: seen in 20 - 40% pt Aural fullness: seen in 15 - 30% pt Viral URTI: seen in 20 - 40% pt

Patient Evaluation

Early diagnosis & Tx improves prognosis Deafness: onset, duration, severity, previous HL Associated vertigo / tinnitus / aural fullness Exclude trauma (noise / baro / temporal bone #) Exclude ototoxicity / DM / hypothyroidism / blood dyscrasia / hyperlipidemia / renal failure Tuning fork tests & fistula test Perform careful neurological examination

Basic Laboratory Investigations

Complete Blood Count + ESR: for infection BT, CT, PT, aPTT & INR: for bleeding disorder VDRL, FTA-Abs, TPHA, TPI: for syphilis ANA, Rh factor, other auto-antibody titre T3, T4, TSH: for hypothyroidism FBS & PPBS: for diabetes mellitus Fasting lipid profile: for hyperlipidemia Urea & Creatinine: for renal failure

Imaging Studies 1. MRI with gadolinium contrast (gold standard):  1-2% pt with ISSNHL have IAC or CPA tumors  3-12% pt with acoustic neuroma have SSNHL 2. CT scan temporal bone + contrast Detect anatomic defects (Mondini dysplasia or enlarged vestibular aqueduct syndrome)

Contrast M.R.I.: acoustic neuroma

Mondini dysplasia sac-like cochlea (black arrow) amorphous vestibule without any defined semicircular canals (white arrow) enlarged vestibular aqueduct (red arrow)

Enlarged vestibular aqueduct

Audiometry Pure-tone Audiometry Speech Audiometry Tympanometry & acoustic reflex tests SISI & Tone Decay Test Oto-acoustic emission BERA

High-frequency hearing loss: PTA at 4 & 8 kHz High-frequency hearing loss: PTA at 4 & 8 kHz exceeds PTA at 250 & 500 Hz by > 30 dB Low-frequency hearing loss: PTA at 250 & 500 Hz exceeds PTA at 4 & 8 kHz by > 30 dB Flat-type hearing loss: equal hearing losses at each frequency Profound hearing loss: no response at maximum intensity for > 2 frequencies Reference : Nakashima T, et al. Laryngoscope 1993;103:1145-49.

Presence of OAE indicates preservation of some outer hair cell function ABR reflects function of neural pathways ABR & OAE results also assist in diagnosing psychogenic hearing loss & malingering Vestibular tests are obtained when indicated by history & physical examination

Treatment

Treatment options (a) Vasodilators (b) Rheologic agents (c) Anti-inflammatory agents (Steroids) (d) Anti-viral agents (e) Diuretics (f) Hyperbaric oxygen (g) Surgery

General Treatment Bed rest & avoid strenuous exercise Avoid following aggravators:  Alcohol  Smoking  Stress  Sleep deprivation  CNS stimulants  Fatty diet  Straining  Loud noise

Vasodilators: reverse hypoxia Betahistine: 16 mg TID, PO for 3 wk Xanthinol nicotinate: 300 mg slow IV Q12H  500 mg BD, PO for 3 wk Carbogen (5% CO2 + 95% O2) inhalation: for 30 min, 8 times / day at 1 hour intervals in O.T. Nimodipine: 30 mg BD-TID, PO for 3 wk

Rheologic Agents  blood viscosity to  blood flow & O2 delivery Low-molecular-weight dextran: 10 ml / kg / d X 7d Pentoxifylline: 400 mg TID, PO for 3-4 wk Diatrizoate meglumine infusion: 40 ml/d X 7d Hydroxy-ethyl starch: 500-1000 ml/d X 7d Anticoagulants (heparin & warfarin): obsolete

Cortico-Steroids Anti-inflammatory agents Prednisolone: 1mg / kg / d in single or divided doses for 10 d  taper over 3 weeks Intratympanic dexamethasone solution (8 mg/mL): 0.3–0.4 mL with hyaluronidase on alternate days after grommet insertion in PIQ

Grommet in P.I.Q.

Post-steroid recovery

Side-effects of Steroids Hyperglycemia Hypertension Gastric ulceration Osteoporosis Flaring of infection & delayed wound healing Psychiatric disturbance (insomnia, euphoria) Weight gain & trunk obesity

Anti-virals & Diuretics Acyclovir: 800 mg PO, 5 times / day for 7 days Famciclovir: 250 mg PO, TID for 7 days Diuretics Used in SSNHL due to endolymphatic hydrops Hydrochlorothiazide: 25 mg PO, BD for 3-4 wk

Hyperbaric oxygen Consists of exposure to 100% oxygen at pressure of 250 kPa for 60 minutes in a multi-place hyperbaric chamber along with high doses of gluco-corticoids Best results achieved if treatment started early

Surgery Repair of oval & round window perilymph fistulae has been used in cases of ISSNHL associated with positive fistula test or history of recent trauma or barotrauma No standard methods are detailed

Result evaluation (Wilson) Complete recovery: PTA or SRT: < 10 dB of pre-SSNHL value Partial recovery: PTA / SRT: > 50% recovery of pre-SSNHL value No recovery: PTA / SRT: < 50% recovery of pre-SSNHL value

Result evaluation Patient with pre-SSNHL value of: Pure Tone Average = 30 dB Speech Reception Threshold = 30 dB Complete recovery: PTA or SRT  30 - 40 dB Partial recovery: PTA or SRT  41 - 45 dB No recovery: PTA or SRT  > 45 dB

Spontaneous Recovery Spontaneous recovery rates for SSNHL range from 47 - 70%, combining categories of complete & partial recovery Most spontaneous recoveries occur within 2 weeks

Results No high-quality, randomized, controlled trial shows efficacy of any medical therapy Most studies don't show significant beneficial effect of vasodilators, acyclovir, rheological agents, hyperbaric oxygen over placebo Corticosteroid therapy is only accepted therapy for ISSNHL. Recovery rates = 40 - 60%

Favorable prognosis Tx starting <10 days after onset of SSHL Mild to moderate SNHL Low or mid frequency SNHL Presence of tinnitus (doubtful significance)

Unfavorable prognosis High frequency deafness (especially 8 kHz) Hearing loss > 90 dB HL Vertigo / vestibular changes evident on ENG Bilateral sensori-neural deafness Tx starting >15 days after onset of deafness Age < 15 years or > 65 years Elevated ESR (>25) Poor speech discrimination score

Further Study

Leong, A.C. et al. (2007). Sudden hearing loss - A 12 minute consultation. Clinical Otolaryngology. 32: 391–394 Xenellis J. et al. (2006). Idiopathic sudden sensorineural hearing loss: prognostic factors. J.L.O. 120, 718–724 Xenellis J. et al. (2006) Intra-tympanic steroid treatment in ISSNHL. Otolaryngol. Head Neck Surg. 134, 940–945 Aoki D. et al. (2006) Evaluation of superhigh-dose steroid for SSNHL. Otolaryngol. Head Neck Surg. 134, 783–787 Bennett M. et al. (2005) Hyperbaric oxygen therapy for ISSNHL & tinnitus: J. Laryngol. Otol. 119: 791-798, Wilson W. et al. (1980) The efficacy of steroids in the treatment of ISSNHL. Arch. Otolaryngol. 106, 772–776

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