Tag Archives: acoustic trauma

Noise Induced Hearing Loss

A teenage girl visited ENT clinic with her mother with ringing in the ear and felt like cotton in the ear. Previous night,  Diwali Night she had spent several hours setting off the fire crackers.

Her ear were normal on video otoscopy and Audiogram showed  35 db at 4000 and 8000 hertz, Several days later, her hearing had returned to normal.

This patient is an example of a “temporary threshold shift.” Or Reversible Hearing Loss by exposure to an intense “impulse” sound such as fireworks or loud rock concert.

If sound is too loud or duration of exposure is long enough, such as noise generated in a woodworking shop it may lead to permanent threshold shift.  This condition is called Noise Induced Hearing Loss which has no cure.

Acoustic trauma occurs when excessive sound energy strikes inner ear. When we are exposed sounds that are too loud or loud sounds that last a long time—small sensitive structures in our inner ear, called hair cells, can be damaged, Hair cells convert sound energy into electrical signals that travel to the brain. The louder the sound, the shorter the time period before NIHL can occur.

Sound is measured in units called decibels. Continual exposure to more than 85 decibels (dB) is dangerous to the ears. Firecrackers emit sounds from 120 to 160 decibels. Sound with 140dB can cause ear ache. A very high intensity sound (above 160 dB) may also damage the ear drum and can cause dislocation of middle ear ossicles.

An even higher intensity may cause leakage of inner ear fluid leading to permanent hearing loss associated with dizziness.

Symptoms

  • Hearing loss
  • Sense of fullness  the ear
  • Noises, ringing in the ear
  • Earache
  • Bleeding from the are
  • Dizziness,

Signs and tests

Acoustic trauma is suspected if hearing loss occurs after noise exposure. Audiometry may determine how much hearing has been lost. Audiogram has typical “notch” at 4000 hz, with better hearing at both lower and higher frequencies. Otoacoustic Emisson (OAE) testing is very sensitive to noise induced hearing loss.

Treatment

The hearing loss may not be treatable. The goal of treatment is to protect the ear from further damage. Hearing aid is prescribed for communication needs. If ear Drum is ruptured, surgery to repair ear drum may be needed.

Ear protection using noise protector ear plugs or ear muffs may prevent the hearing loss from getting worse.

Noise exposure, whether occupational or recreational, is the leading preventable cause of hearing loss. It can be prevented by avoiding “too loud” or “too long” Noise exposure and use of hearing protection when necessary.

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It’s a Noisy Planet. Protect Their Hearing campaign, a program of the National Institute on Deafness and Other Communication Disorders (NIDCD).
NIDCD

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Management of sudden sensorineural Hearing Loss

Previous Post:- Causes and evaluation of sudden sensorineural hearing loss

Sudden sensorineural hearing loss is an otologic emergency and challenge to otolaryngologist.

Thorough history, physical examination, appropriate laboratory and radiologic investigations including gadolinium enhanced MRI, and Audiometry tests should be carried out to find out known cause such as: – Infection (bacterial-meningitis/viral-mumps, herpes), Tumor, Trauma, Acoustic trauma, Ototoxic drugs (amino glycoside antibiotics), and Systemic diseases (hypothyroidism, Diabetes mellitus).

If an etiology is apparent, appropriate treatment may be initiated such as antibiotics for infection, withdrawal of ototoxic drugs.

In most cases cause remains unknown (idiopathic) thus existent treatment aims at improving blood flow.

Optimal treatment is still under research and controversies exist but treatment versus non-treatment and early initiation of treatment is proved to give better result.

1. Antivirals– Because of common association with viral infection antiviral medication is prescribed by some clinicians.

2. Steroids- Most widely accepted treatment option studies shows improved recovery rate with use of steroid. It can be given orally, or by injection, or Trans tympanic by means of middle ear instillation or round window micro catheter which is more effective than oral administration.

3. Vasodilator to improve blood flow or oxygenation to inner ear. Clinical studies shows mixed results. Carbogen inhalation, Papaverin, Histamine, Nicotin and Niacin have been used.

4. Immunosuppressant- Wang et al etanercept in experimental animal study improves hearing result.

5. Ginkgo Biloba-

6. General measures-

  • Low salt diet,
  • Avoid caffeine, nicotine and alcohol,
  • Avoid noise exposure,
  • Avoid heavy physical activity,
  • Well balanced diet,
  • Alpha-lipoic Acid, Antioxidants, Co-enzyme Q10.
  • Zinc, Magnesium, Calcium,
  • Vitamin D, B -Complex, Vitamin C

Prognosis of sudden sensorineural hearing loss-

50-65% spontaneous recovery within first 4-6 weeks.

Symptoms of ear blockage or deceased hearing is often considered as wax or middle ear infection and person delays visit to an otolaryngologist. A delay in initiating treatment may decrease the chances of recovery.

Negative factors in prognosis-

  • Age more than 65 years or less than 15 years
  • Severe hearing loss specially affecting high frequency
  • Hearing loss in opposite ear
  • Associated vertigo
  • Elevated ESR

Treatment protocol should be carefully applied and potentially harmful treatment should be avoided. A thorough evaluation to be done on emergency basis and all efforts should be taken to find out known causes. Steroids are most widely accepted treatment options.

Sudden Sensorineural hearing loss

  • It should be regarded as an otologic emergency.
  • Patient should be evaluated by otolaryngologist.
  • A thorough history, physical examination, appropriate laboratory and radiologic investigations including gadolinium enhanced MRI, and Audiometry tests should be carried out to find out known cause.
  • A tapering course of prednisolone/methyle prednisone is prescribed.
  • Antiviral medication may be considered.

Sudden Sensorineural Hearing Loss: Causes and Evaluation

Sudden Sensorineural Hearing Loss (SSNHL) is defined as a hearing reduction greater than 30 db, over at least 3 consecutive frequencies (on pure tone audiogram), occurring over or less than 3 days. It usually affects one ear, there may be mild to sever reduction of hearing, and there may be tinnitus and dizziness.

Most People (30-65%) may have a spontaneous recovery; others may have permanent hearing difficulties.

Causes of sudden sensorineural hearing loss-

There is no conclusive evidence as why it happens but some theories are suggested-

1. Generally 90% cases are idiopathic where cause is not known. Viral diseases appears to be most common cause (about 60% cases) as shown by association with herpes.

2. There may be partial or complete blockage of circulation or vascular spasm to inner ear and nerves of hearing.

3. There may be rupture of delicate inner ear membrane after strong physical activity or sudden change in barometric pressure (flying/scuba diving).

4. Immune theory may ply a role, because of its association with Cogan syndrome, SLE, Lupus and AIDS.

In most cases reason remains unclear.

Diagnosis of SSNHL requires thorough investigation to determine any known causes of sudden hearing loss. Some of the causes are following-

* CONGENITAL –

  • Rubella Syndrome
  • Atresia of the External ear canal
  • Congenital Cytomegalovirus
  • Congenital Perilymphatic Fistula
  • Fetal Methyl Mercury Effects
  • Fetal Iodine Deficiency Effects

* MEDICATIONS (Ototoxic Drugs)-

  • Aminoglycoside Antibiotics-streptomycin, kanamyin, neomycin, amikacin, gentamicin, tobramicin and netilmicin
  • Loop diuretics, ethacrynic acid
  • Antimalarial (quinine, chloroquine),
  • Salicylates
  • NSAIDS
  • Vancomycin
  • Erythromycin
  • Cisplatinum

* INFECTIOUS DISEASES-

Bacterial infection:

  • Otitis media
  • Labyrinthitis
  • Encephalitis
  • Meningitis

Viral infections:

Evidence is circumstantial, with the possible exception of mumps parortitis and herpes zoster, the clinical diagnosis of viral infection is unreliable.

  • Common Colds
  • Adenovirus
  • Cytomegalovirus (Cmv)
  • Infectious Mononucleosis
  • Influenza
  • Parainfluenza
  • Ear Infection (Otitis Media)
  • Mumps
  • Measles
  • Rubella
  • Herpes Simplex Virus Type 1

Others:

Rocky Mountain spotted fever-tick borne infection

Lyme disease- tickborne especially in endemic areas (mostly causes facial palsy)

Syphilis and AIDS

* IMMUNOLOGIC DISEASES-

Immunologic activity within the cochlea may be the cause as suggested by finding of antibodies and response to steroid therapy in many patients. Hearing loss in certain autoimmune diseases is documented.

  • Cogan’s Syndrome
  • Systemic Lupus erythomatosus
  • Fibromyalgia
  • Temporal arteritis

* TRAUMATIC-

Direct trauma (temporal bone fracture) or blunt head injury (concussion to labyrinth) can cause SSNHL.

  • Traumatic ear drum Perforation
  • Head Injuries
  • Skull Fracture (Temporal Bone)

* ACOUSTIC TRAUMA

  • Explosions
  • Fireworks,
  • Gunfire
  • Rock Concerts/Mp3 Players
  • Jets
  • Occupational Work Noise

* BAROTRAUMA and perilymphatic fistula

Barotraumas is caused by unequalized pressure differentials in middle ear and external ear such as in scuba diving, air travellingor blow to ear. If the pressure is severe, eardrum can rupture.

Barotrauma can cause acquired perilymphatic fistula (communication between inner ear and middle ear) leading to SSNHL and vertigo. Other causes of acquired perilymphatic fistula are direct or indirect trauma to temporal bone, heavy lifting or straining and complication of stapes surgery.

* TUMORS-

  • Acoustic Neuroma or Vestibular Schwannoma – SSNHL may be initial manifestation
  • Temporal Bone Metastases
  • Neoplasm of CPA or IAC

* OTHER SYSTEMIC DISEASES-

  • Leukemia
  • Diabetes
  • Hypothyroidism
  • Multiple Sclerosis
  • Ménière’s Disease
  • Syphilis

Evaluation  of sudden sensorineural Hearing loss (searching for cause)-

A thorough and detailed history of associated symptoms, noise exposure, any trauma, fever, medication and family history of hearing loss is necessary to determine the diagnosis.

Ear examination by otoscopy and pneumotoscopy is critical step.

Hearing assessment by Tunning fork test, pure tone audiometry (PTA) and speech audiometry should be done. Tympanometry, Auditory Brainstem Response and Otoacoustic emission may be useful.

Electronystagmogram (ENG)

Radiologic study should be done especially for patients with unilateral sensorineural hearing loss, such as MRI with gadolinium/CT temporal bone to investigate IAC/CPA tumors.

Laboratory investigations-

FTA-antibodies for syphilis

ANA, RA Factor, ESR for autoimmune disease

Coagulation profile

CBC for infection

TH for thyroid function

RBS/PPBS for Diabetes

Cholesterol/triglycerides for hyperlipidemia

Sudden Sensorineural hearing loss-

  • It should be regarded as an otologic emergency.
  • Patient should be evaluated by otolaryngologist.
  • A thorough history, physical examination, appropriate laboratory and radiologic investigations including gadolinium enhanced MRI, and Audiometry tests should be carried out to find out known cause.

Next Post– Management of sudden sensorineural hearing loss