SUDDEN SENSORINEURAL HEARING LOSS

By :-

Dr. Trilok GuleriaJR ENT-HNS

Hearing Loss Impairment in the ability to perceive sound stimulus

is termed as hearing loss.

3 types:1. Conductive : due to defect in the mechanical

transmission of sound to the sensory apparatus of

the ear.

2. Sensorineural : due to defect in the sensory

apparatus of the ear.

3. Mixed

Sensorineural Hearing Loss

Hearing loss due to defect in the sensory

apparatus - cochlea (sensory). Or in the pathways of conduction of nerve

impulses to the brain (neural). Neural causes can be Peripheral: 8th nerve. Central: auditory pathway or cortex.

Features of SNHL

Normal appearance of external ear and

tympanic membrane on examination. Positive Rinne’s test : AC>BC. Weber’s lateralized to better ear. Bone conduction decreased. Normal air bone gap on PTA. Hearing loss can exceed 60 dB.

Causes Of SNHL

Congenital: present at birth, due to

anomalies of inner ear or due to pre or

perinatal factors. Acquired: acquired later in life due to

trauma, drug intake or disorders affecting

the ear.

Causes Of Acquired SNHL

Presbycusis. Trauma to inner ear, 8th nerve or auditory

pathways. Infections of inner ear – labyrinthitis. Noise induced.

Causes of acquired SNHL Meniere’s disease. Acoustic neuroma. Secondary to systemic disorders: DM,

Hypothyroidism, CKD, Multiple sclerosis,

Autoimmune disorders. Idiopathic Sudden sensorineural hearing

loss.

SUDDEN SENSORINEURAL HEARING LOSS

First described by De Klevn in 1944. Definition : Sudden sensorineural hearing loss

is defined as 30 dB sensorineural hearing loss in

at least 3 contiguous frequencies over a period

of less than 3 days (72 hours). Can be unilateral or bilateral (1%). Usually accompanied by tinnitus (70%) or

vertigo (40%).

Incidence Overall incidence of 5-20 / 1,00,000

population. In 1976, Shaia and Sheehy studied the

average age of incidence of SSNHL in 1220 cases:

Under 30 - 13% 30-39 - 13% 40-49 - 21% 50-59 - 22% 60-69 - 18% 70+ 13%

Etiology

Multiple factors are implicated in the

etiopathogenesis of Sudden SNHL. 90 % idiopathic. 5 - 10 % specific causes.

Etiology Viral infections Bacterial infections Vascular causes Autoimmune Hypoxia Metabolic causes Ototoxicity

Etiology Traumatic Neural Neoplastic Meniere’s disease Psychogenic Idiopathic

Viral Causes Viral infection causes Sudden SNHL by

causing cochleitis. Mumps Measles CMV Human immunodeficiency virus Rubella Chicken pox Herpes zoster Infectious mononucleosis (EBV)

Viral labyrinthitis Viruses reach the inner ear by blood stream

affecting stria vascularis

endolymph

Organ of cortiEg :- Measels ,Mumps ,CMV

The direct proof of invasion of viruses like Herpes zoster , Herpes simplex ,Rubella ,Influenza ,HIV, EBV in the labyrinth is not known but they are clinically known to cause hearing loss.

Mumps

More severe in adolescent and adults. Causes encephalitis and meningitis. Inflammatory changes in the stria

vascularis of the cochlea. Leads to unilateral, variable degree of

SNHL.

Measles Common in children. Labyrinthine involvement causes abrupt

bilateral hearing loss along with the measles rash.

Tinnitus and vertigo are present in 70 %.

Rubella SNHL is the most common sequela of congenital

rubella infection (58%). Most often seen when maternal rubella infection

occurs within the first 16 weeks of pregnancy. Vestibular function is spared . Hearing loss typically manifests in the first 6 to

12 months of life, although it can present at birth .

Audiograms often show a flat, uniform mild to severe SNHL, but isolated high-frequency hearing loss has been reported

Bacterial Causes Due to bacterial labyrinthitis as a

complication of CSOM or iatrogenic or spread through hematological route.

The membranous labyrinth is totally destroyed causing the SNHL

Causative bacteria involved in labyrinthitis

Haemophilus influenza Neisseria meningitidis Streptococcus species Staphylococcus species Proteus species

Syphilitic Syphilis can cause Sudden SNHL and also

lead to fluctuating SNHL. Can be congenital or acquired. Congenital syphilis can cause profound

and usually bilateral loss. Sudden SNHL may be unilateral or

bilateral . Later is usually symmetrical in high frequencies.

Vascular Vertebrobasilar insufficiency Sickle cell disease Leukemia Polycythemia Macroglobulinemia Cardiopulmonary bypass

Etiologic Theories: Vascular

The arterial supply to the cochlea is such that the basal turn is fed first by the main cochlear artery with the cochlear apex fed last.

Based on this anatomy one would expect occlusion of the labyrinthine artery to cause both vestibular and auditory symptoms which is supported by histopathologic findings as describe above.

In addition, one would expect temporary occlusion in blood flow to affect low frequency areas of the cochlea first as these areas are the most distal in terms of blood supply.

Cochleovestibular blood supply may be affected by circulatory disorders such as embolic phenomenon, thrombosis, vasospasm, and hypercoagulable or high viscosity states resulting in SSNHL

The underlying pathophysiology can be explained by the occurrence of sudden anoxic injury to the cochlea.

The cochlea is extraordinarily intolerant of blood supply disruptions.

Suga and co-workers performed experimental embolizations of cochlear vessels and showed loss of cochlear action potentials within 60 seconds.

Autoimmune Autoimmune inner ear disease Ulcerative colitis Relapsing polychondritis Systemic Lupus erythematosus ( SLE ) Polyarteritis nodosa Cogan’s syndrome Wegener’s granulomatosis

The pathogenesis of immune-mediated sensorineural deafness and vestibular dysfunction are unclear, but are presumed to include: vasculitis of vessels supplying the inner ear, autoantibodies directed against inner ear antigenic epitopes, or cross-reacting antibodies.

Autoimmune hearing loss implies that inner ear proteins are recognized immunologically as foreign or non-self

Cogan Syndrome An autoimmune disease of the cornea

and vestibulo-auditory apparatus. Triad of autoimmune keratitis, vertigo

and SNHL. SNHL is progressive in nature after initial

symptoms. Hearing fluctuates with disease

exacerbations and remissions Majority develop bilateral deafness (67%)

Autoimmune inner ear disease (AIED)

McCabe first described autoimmune inner ear disease (AIED) in 1979.

The clinical picture of AIED usually consists of rapidly progressive bilateral sensorineural hearing loss usually in the absence of other systemic manifestations.

50% of patients may complain of dizziness. The symptoms often progress over weeks

or months but can also present as sudden hearing loss

Traumatic causes Breaks in the membranous labyrinth

Intracochlear Oval and/or round window

History – inciting event Blow to the head :Temporal bone fracture ,

Inner ear concussion Otologic surgery Sneezing Bending over Lifting a heavy object Exposure to sudden changes in barometric

pressure :Flying, SCUBA diving

Noise – induced It is seen in acoustic trauma. Due to sudden loud noise of over 140 dB. Rupture of Reissner’s membrane,

damage to organ of corti, hair cells and mixing of perilymph & endolymph occurs due to the loud noise leading to hearing loss.

May be accompanied by vertigo.

Hypoxia Induced Hypoxia to the brain causes direct cell

death of the cochlear or nerve cells leading to SNHL.

Hypercapnia also causes SNHL by deactivation of enzyme carbonic anhydrase which may participate in the generation of the endocochlear potential.

Metabolic Causes Acute and chronic renal failure. Alport syndrome: renal disease with

hearing loss. Diabetes mellitus: mainly due to

neuropathy. Insidious onset. Hyperlipidemia Hypothyroidism

Ototoxicity Drugs and chemicals which damage the inner ear

are called ototoxic. They cause sensorineural hearing loss,tinitis,

vertigo.1.AMINOGLYCOSIDES Streptomycin,Gentamycin,Tobramycin are primarily

VESTIBULOTOXIC. Destroy type1 hair cells of crista ampullaris. In large doses can damage cochlea. Neomycin, Kanamycin, Amikacin, Sisomycin and

Dihydrostreptomycin COCHLEOTOXIC. Destroy outer hair cells, starting at basal coil and

progressing up to apex of cochlea.

2.Diuretics Ethacrynic acid, furosemide and bumetanide

cause EDEMA and CYSTIC CHANGES in stria vascularis

3.Salicylates 4.Antimalarials(Quinine) It cause vasoconstriction in the small

vessels of the cochlea and stria vascularis.

5.Cytotoxic drugsCause cochlear damage. Mainly affect outer hair cells of cochlea. Drugs :-Cisplatin, Carboplatin, Vinca alkaloids.

6.Miscellaneuos Desferoxamine:- High freq hearing loss

due to outer hair cell damage Mercury and its compounds Gold Lead Arsenic Aniline dyes Alcohol Tobacco Marijuana

Neural Causes Meningitis Multiple sclerosis Sarcoidosis Friedreich's ataxia Amyotrophic lateral sclerosis Vogt-Koyanagi-Harada syndrome Xeroderma pigmentosum

Neoplastic Acoustic neuroma Leukemia Multiple Myeloma Metastasis to internal auditory canal Meningeal carcinomatosis

Vestibular Schwannoma Also known as acoustic neuroma or 8th nerve

tumour. Benign, encapsulated, slow growing tumour

of the cerebello pontine angle. Arises from the Schwann cells around the

vestibular nerve in the internal auditory

canal. Expands to erode the canal and involve the

other cranial nerves like 5th, 9th, 10th and

11th.

Vestibular Schwannoma Progressive Unilateral SNHL with tinnitus

– main symptoms. Poor speech perception more than the

audiometric loss. Late or absent vestibular symptoms. Involvement of other cranial nerves. Brainstem, cerebellar involvement and

features of raised ICT.

Vestibular Schwannoma High frequency SNHL. Poor speech discrimination. Roll over phenomenon. SISI : 0 -20 % suggestive of nerve

deafness. TDT : retrocochlear lesion. Absent or diminished responses in caloric

tests. MRI with contrast is gold standard for

diagnosis.

Meniere’s Disease Also called endolymphatic hydrops. Attacks of SNHL followed by periods of normal

hearing. Increased volume of endolymph. Due to – Increased production by stria vascularis. Decreased absorption by endolyphatic sac. Both. Characterized by – Vertigo. Fluctuating SNHL. Tinnitus. Aural fullness.

Diagnosis Possible: no definitive episode. Episodic vertigo without hearing loss Probable: One definitive episode of vertigo Hearing loss recorded in PTA at least once Tinnitus or aural fullness Definite: Two or more episodes of vertigo lasting 20 mins. Hearing loss recorded in PTA at least once Tinnitus or aural fullness Certain: definite plus HPE confirmation

Meniere’s Disease Pure tone audiometry Sensorineural type of graph. Initially, only lower freq affected rising graph. As higher freq are affected, flat graph

downward sloping graph. Speech audiometry Speech discrimination score is between 55 -85 %. Even lower during acute attacks. Other tests Recruitment test positive. SISI score of over 70%. Tone decay test shows decay of about 20 dB. These indicate a cochlear pathology.

Caloric tests Cold caloric test shows reduced or absent

response on the affected side. Signifies canal paresis of the affected side. Electrocochleography Measures the electrical activity of cochlea and

the auditory nerve. Measures : CM: cochlear microphonics, SP:

summating potential, AP: action potential. In Meniere's disease, basilar membrane becomes

taut causing increase in summating potential. SP:AP ratio increases. Meniere’s: > 30%. Best obtained in acute phase.

Glycerol dehydration test 10dB improvement in 2 or more adjecent

octaves or 10% improvement in SDS after 1-2 hours is considered test positive.

Tinnitus and aural fullness also improves. Test can be combined with transtympanic

electro – cochleography. Acetazolamide test Acetazolamide 500 mg in aqueous solution

is injected intravenously over one minute. Electrocochleogram monitored continuously

for 45 minutes. Improvement is seen within 10 -15 minutes.

Idiopathic SSNHL Idiopathic SSNHL is a diagnosis of

exclusion. SSNHL is termed as idiopathic after ruling

out all the known causes of SSNHL.

Work Up History Clinical examination Otological examination Audiometric evaluation Blood work up Radiological examination

History Detailed history to rule out possible

cause: Symptoms Unilateral/ bilateral Onset and progression Severity

History History of URTI History of acoustic / direct trauma History of ototoxicity History of systemic disorders History of surgery History of previous treatment History of similar complaints in family

Examination General examination: to rule out

systemic pathologies Neurological examination to rule out

cranial nerve involvement as in acoustic neuroma

Cardiovascular evaluation to rule out thromboembolism

Ear Examination Otoscopy to examine tympanic

membrane and EAC to look for lesions. To rule out any features of labyrinthitis

secondary to CSOM. Tuning fork tests to differentiate SNHL

and CHL. Rinne’s , Weber, ABC & Schwabach’s.

Cold caloric test and Dix- Hallpike test to examine vestibular function.

Audiometric Evaluation Pure tone audiometry: to diagnose and

quantify the degree of SNHL. Special tests for hearing to differentiate

cochlear from retro-cochlear pathology. Speech audiometry SDS TDT SISI

Audiometric Evaluation Objective tests: to evaluate the exact

hearing thresholds and to identify malingerers if any.

Oto-acoustic emissions Impedence audiometry. Brain stem evoked response audiometry.

Blood Investigations Complete blood counts with ESR: rule out

Leukemia, Infections. Blood sugar: to rule out DM. Renal function tests: to rule out renal

disorders. Lipid profile: to rule out hyperlipidemia

which is common in hypertensives.

Blood Investigations Thyroid function tests: to rule out

hypothyroidism. VDRL test: to rule out syphilis. HIV test. Coagulation profile: to rule out

hypercoaguable state. Auto-antibodies : to rule out Autoimmune

Diseases.

Radiological Investigations CT Imaging of temporal region – to rule

out labyrinthitis or other complications of CSOM.

MRI to rule out CP angle tumours or other intra cranial causes such as demyelination, typically seen in multiple sclerosis, and small vessel ischaemic changes.

Treatment Multimodal treatment. Most cases are idiopathic. Investigations to find any specific cause. Treatment should be started early for

better results. Patient should be admitted for treatment.

Combined therapy

Vasodilators

Diuretics

Plasma Expanders

Corticosteroids

Vitamins

Bed Rest Patient should be admitted and advised

bed rest. Especially in case membrane rupture is

suspected as the cause for SSNHL.

Oxygen Therapy Intermittent oxygen inhalation at 4-6 liters per

minute for 15 minutes every 6 hourly. Provide more oxygen to the nerve tissue by

increasing the perilymph oxygenation. Carbogen (5% CO2 + 95% O2) inhalation –

Increases the partial pressure of O2 in perilymph . CO2 is a known potent vasodilator of the vestibulocochlear vasculature, resulting in increased blood flow.

Improvement in hypoxia induced SSNHL. Oxygen therapy in the form of hyperbaric

oxygen has also shown good results.

Steroid Treatment Treatment of choice when the loss is retro-

cochlear, and are the only effective treatment.

Prednisolone in tapered doses over a period of 3 weeks.

Proton pump inhibitors given along with steroids.

Intratympanic injection of steroids is being tried alternative to oral steroids as it has shown to penetrate the inner ear effectively in animal studies.

Vasodilators Like xanthinol nicotinate, glycerol. Betahistine : 16mg three times a day Glyceryl Trinitrate / Nitroglycerine patch Helps to relieve vasospasm. Improves blood supply to the nerve

tissue. Glycerol increases the cochlear and

cerebral blood flow significantly after intravenous administration

Antiviral Course A course of antiviral drug – Valcivir,

Acyclovir, Famciclovir. Valcivir : 1 gm three times a day for a

week. Acyclovir : 800 mg four times a day for a

week. Famciclovir : 500 mg three times a day

for a week To treat viral infection if any.

Others Stellate ganglion block : blocks

sympathetic activity and results in vasodilatation of the vertebral artery. Effective within 2 weeks of onset of SSNHL.

Surgery

Exploration of the middle ear with repair of an inner ear fistula is recommended in patients with a clear history of sudden hearing loss associated with diving, straining, altitude change, or recent otologic surgery.

The role of surgery in patients who do not improve with non-surgical therapy remains controversial.

Treatment Of Specific Causes

Anticoagulants like heparin in case thrombo-embolism is suspected.

Low molecular weight dextran: to treat hypercoaguable states. Increases capillary blood flow by hypervolaemic haemodilution and by decreasing factor VIII; this results in increased cardiac output and tissue blood flow. Contraindicated in patients with cardiac failure and bleeding disorders.

Treatment Of Specific Causes

Thyroxine supplementation: in case of SSNHL due to hypothyroid state.

Treatment or control of DM, HTN and hyperlipidemia.

Treatment of BACTERIAL LABYRINTHITIS Antibiotic is given based on cultural

sensitivity results. Should consist of broad-spectrum

antibiotic.

Treatment of Traumatic causesStrict bed restHOB elevated 30 degrees.Avoid straining or hard nose blowing+/- stool softeners

If the patient has improvement, 6 more weeks of

modified physical activity should be followed. If no improvement is seen after five days, surgical

therapy including middle ear exploration with

patching of the perilymphatic fistula should be

performed.

Bed Rest

Stool Softener

s

Stress

Alcohol

Elevate Head

Noise exposur

e

COGAN’S SYNDROME The cornerstone of therapy is

corticosteroids: topical for IK and oral for vestibulo-auditory involvement.

Most authors suggest using prednisolone 1mg/kg for 2-4 weeks with a subsequent rapid taper for cases of complete resolution and slow taper for those with incomplete response.

AIED Prednisone 1mg/kg/day for 4 weeks followed

by a slow taper if the patient responds. If the patient relapses on the taper, high

dose prednisone and if continued recurrence occurs with tapering, a cytotoxic agent such as methotrexate (MTX) dosage of 7.5-15 mg weekly with folic acid, or cyclophosphamide .

Vestibular SchwannomaTreatment depends upon size of tumour.Various modalities are surgery, steriotactic surgery.

Meniere’s Disease• General measures• Vestibular sedatives: Dimenhydramine , Promethazine ,

Prochlorperazine• Vasodilators: inhalation of carbogen, histamine drip.• Diuretics.Criteria for ablative procedures• Only in definite Meniere’s disease.• Ablative procedure done in long standing, unilateral

Meniere's disease with no evidence of disease in contralateral ear at time of procedure.• Advanced age is a relative contraindication.

Rehabilitation of hearing Recovery in case of SSNHL is very less

unless treated aggressively as early as possible.

There is usually residual hearing loss of varying level even after treament.

Rehabilitation of hearing Rehabilitation of hearing impairment can

be done using : Hearing aids – when residual loss is not

profound. Cochlear implant – when recovery is

minimal and profound hearing impairment is present. Results are better as the patient is post lingual.

Prognosis Published series report spontaneous recovery

rates for patients with SSNHL range from 47% to 63%.

Patients in whom there is no change within 2 weeks are unlikely to show much recovery.

Four variables have been shown to affect recovery from ISSNHL• Time since onset• Audiogram type• Vertigo• Age

Patients with ISSNHL have an overall better chance at hearing recovery if:

They receive treatment within the first 7 to 14 days of ISSNHL. Sooner the patient is seen and therapy initiated, the better the recovery.

Those under 15years and over 60 years have significantly poorer recovery rates

Patients with severe vertigo have significantly worse outcomes than patients with no symptoms of vertigo

Patients with profound hearing loss significantly decreased recovery rates as compared to mild to moderate degree of hearing loss

SUMMARY SSNHL is subjective sensation of hearing

impairment in one or both ears developing within 72 hours and a decrease in hearing of more than or equal to 30 decibels (dB), on 3 consecutive frequency in comparison to normal ear on audiometry

Most patients with SSNHL cannot be given a cause for their diagnosis.

Highest incidence in 50-60 yrs. old

Recovery usually begins within two weeks of onset

SSNHL is considered to be a true otologic emergency, given the observation that there is less recovery of hearing when treatment is delayed.

Thorough History, Examination & Investigations Rule out specific known causes. Corticosteroid therapy is the current standard

of care. Rehabilitate those whose hearing does not

improve.

Thank you