Sudden Sensorineural Hearing Loss (SSNHL)

Dr. Deepa Shivnani

Agenda

• Introduction • Definition • Causes • ISSNHL • Investigations • Prognostic Factors • Treatment Modalities • Conclusion • Take home messages

Introduction

• First described by De klevn in 1944 • Definitive diagnosis and treatment is still

unknown • Statistics

– 15000 reported cases per year worldwide – Highest : 50 - 60 years – Lowest 20 - 30 years – Male = Female – 2% bilateral – 90% idiopathic

Definition

How certain is it that the loss is “New”

• Degree of certainty

– Very Certain : Patient has had a full and documented audiologic assessment recently and now has a SNHL

– Certain : Patient has no otological history and regarded his pre-morbid hearing as normal

– Fairly Certain : Patient has had long standing hearing problem, there is deterioration now in comparison to hearing demonstrated in previous audiogram

– Uncertain : Clearly some pre-existing loss but this has never been documented

Causes of SSNHL

What investigations should be undertaken before SSNHL is deemed

to be “idiopathic” ?

Idiopathic SSNHL

• Definition of ISSNHL is difficult

• The definition of Wilson et al is widely quoted

• Proposed in the context of a RCT of steroid therapy, it requires the patient to have suffered a loss of atleast 30 dB at a minimum of 3 contiguous frequencies over a period of less than 3 days

Etiology of ISSNHL

• Proposed causes include

– Viral infection

– Vascular Occlusion

– Membrane Breaks

– Immunological

– Activation of cochlear nuclear factor Kappa B

• But Schukanecht described 3 putative causes for ISSNHL

– Vascular Legions

– Membrane Breaks

– Viral Pathology

Of these he believed that the clinical and pathological evidence favored a viral etiology

Epidemiology

• Incidence – 8 per 1,00,000 per year

• Specific cause found in less than 5%

• Equal in both gender

• Bilateral less than 1%

• Equal incidence in right and left year

Diagnosis

• No gold standard

• A number of potential causes of SSNHL can be excluded on the basis of history

– Noise Trauma

– Barotrauma

– Direct Temporal bone trauma

– Medication

Screening Blood Tests

• CBC • ESR • Urea and electrolytes • Lipid Profile • Glucose • Thyroid Profile • Syphilitic Serology • Auto-antibodies • MRI

Pragmatic Diagnostic Categories of ISSNHL

Prognosis

• 47%-63% Spontaneously resolve.

• Four prognostic variables

1. Time since onset

2. Age

3. Tinnitus/vertigo

4. Audiogram type

Time

Age

Vertigo

Tinnitus

• 80% alarming,25%preceding

• Does not affect the outcome

• Favorable prognostic sign

Wilson (1980)

• Vertigo not statistically significant

• Age less than 40 years favorable for recovery

• Type of audiogram

o Midfrequency loss-best recovery

o Profound loss-less likely to have recovery

o Loss b/w 40dB-85dB –more likely to respond to steroid therapy

Outcomes

• Complete spontaneous recovery seen in 50-75%

• Wilson defined recovery in three categories

1. Complete: within 10 dB

2. Partial: within 50%

3. No recovery: less than 50%

Cinamon et al-75%sp recovery

Wilson et al -47% sp recovery

Treatment

• Therapy for ISSNHL is controversial

• Difficult to study due to high spontaneous recovery rate and low incidence make validation of empiric treatment modalities difficult

Agents used in management of ISSNHL

Treatment

• Increasing cochlear blood flow

• No proven value

• Betahistine-histamine like effect on H1 receptors in the cochlea vasculature leading to increase in cochlear blood flow

• Glycerol iv in rabbit

Pentoxifylline/Oxpentyfylline

• Phosphodiesterase inhibitor and haemorheological agent

• Increase oxygen delivery to tissues

• IV given in SSNHL of vascular origin

• Probst et al, 1992: no significant difference

Calcium Antagonists

• Increase cerebral blood flow

• Nifedipine, nimodipine

• No significant difference with other drugs

• Further trials needed

Diatizone Meglumine(Hypaque)

• 1 ml of IV hypaque prior to vertebral angiography – significant hearing improvement

• Huang et al 1989- not better than spontaneous recovery – 65%

Low molecular weight Dextran(Rheomacrodex)

• 10% solution either in 55 dextrose or in normal saline

• No significant benefit

• Allergic Reactions

Hydroxyethyl Starch – Hetastarch-Hespan

• Artificial Colloid derived from waxy starch-myelopectin

• 6% colloidal solution In 0.9% Sodium Chloride

• No difference in hearing

• Pruritis

5% Carbon dioxide with 95% Oxygen(Carbogen)

• Cerebral Vasodilator

• 10% CO2 dangerous

• After carbogen inhalation – perilymphatic oxygenation of 8.6mmHg rose to 14.8 mmHg

• 95% O2 and 5% Co2 for 30 minutes – 8 times per day at intervals of 1 hour (Fisch et al 1984)

• ¾ patient improved

Other Therapies

• Hyperbaric Oxygen

• Anticoagulants

• Difibrinogenation Therapy

• Interferons

• Iron Therapy

• Ginko Extract

• Diazepam

1987- Wilkins & Associates

• “Shotgun” Regimen – dextran, histamine, hypaque, diuretics, steroids, vasodilators and carbogens

• No difference between treated and non treated patients

Steroid Therapy

• Treatment of choice when loss is retrocochlear

• Wilson et al, 1980 : double blinded clinical trial – statistically significant effect on hearing recovery in patients with moderate hearing loss(HL).

Cinamon (2001)

• Overall improvement in PTA at follow-up (73%)

– Steroid 80%

– Placebo 81%

– Carbogen 55%

– Placebo inhalation 77%

– Not statistically significant

The Latest Treatment – Intra-Tympanic Steroid Injection

• IT Dexamethasone, methylpredisolone and hydrocortisone all results in higher perilymph concentration of steroid than systemic delivery of steroids

• Intra-tympanic steroid treatment improved hearing loss in 55%

Advantages of IT Steroid

• May be used when systemic steroids are contraindicated or refused

• Greater concentration achieved at target end organ

• May be performed in Out patient setting

• Possible use for salvage of hearing

• Relatively low complication rate

Challenges for IT Steroids

• Not well established as primary treatment strategy

• Dosing ?

• Best delivery technique ?

• Long term effects ?

• Why does it work ? Sometimes ?

• IT delivery via Microcatheter (Kopke 2001)

– Methylprednisolone (62.5mg/mL) delivered continuously for 14 days at the rate of 10uL/hour using pump

– Dexamethasone 4-24mg/mL with Microwick

Conclusion

• No statistically significant benefit of

– Steroids over placebo

– Anti-virals plus steroids over steroids alone

– Steroids over other active treatment

Take Home Message

• Sudden Sensory Neural Hearing Loss is Otologic emergency

• Systemic steroids are main stay of therapy • Prednisone 60mg per day for 3-5 days, tapered 5-

7 days

• Better prognosis if treatment started early

• IT Steroids may be an alternative when systemic steroids are contraindicated/fail to restore hearing

??

Thanks !