Friday 7 August 2020
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Understanding the Auditory Trauma among the victims with blast related Polytrauma

Understanding the Auditory Trauma among the victims with blast related Polytrauma

Dr. C. S. Jamunanantha

Tamil civilian population had been exposed to massive explosive’s during 2008-2009 in Vanni. Consequently they are suffering from associated blast related poly trauma.

Blast injuries are divided into four categories.

  1. Primary
  2. Secondary
  3. Tertiary
  4. Quaternary

Primary blast injuries are caused by barotraumas.

Secondary blast injuries are caused by metal fragments and other projectile penetrating.

Tertiary blast injuries result from displacement of the entire body by combined pressure loads.

Quaternary blast injuries consist of inhalation of dust, smoke toxic fumes and preexisting illness provocations.

We have to go for traditional, primary, symptom based approach for evaluating and treating patients with blast related polytrauma in community level.

Injury approach for evaluating and treating with blast related polytrauma also vital.

Auditory Trauma has a long term complication including hearing loss and tinnitus. Most of the victims suffer from high frequency hearing loss. This has led the voice of the women and children as hard to hear. Eventually family dispute. Alcohol abuse is common among the victims with Auditory trauma.

Otologic injury is typically considered a primary blast injury. The over pressurization of air molecules and the resultant impulse noise (characterized by excessive peak pressure levels) can cause instantaneous sensorineural, conductive, or mixed hearing losses. The tympanic membrane (TM) ruptures in -50% of adult ears. Other middle ear damage, such as disarticulation of the ossicular chain or fracture of the ossicles, can also result from blast exposure.

Within the cochlea, the basilar membrane (BM) is the structure that is most vulnerable to the effects of acoustic trauma. Because of the extreme force exerted on the BM, blast waves can tear the inner and outer hair cells away from their support cells. This can rupture the reticular lamina that connects the hair cells to supporting structures, leading to toxicity and death of the hair cells. The hearing loss that ensues from the anatomic damage to the inner ear can be temporary or permanent and occurs most often in the 2000- to 8000-Hz region along the BM. Reported rates of permanent noise-induced hearing loss vary from 35% to 54% of blast injuries.

  1. Part of a full audiologic evaluation (otoscopy, immittance measures, speech recognition thresholds, word recognition testing and pure tone air and bone conduction threshold).
  1. A bedside audiogram (otoscopy, immittance measures, pure tone air conduction thresholds and best bone conduction threshold).
  1. A pure tone threshold test conducted as part of a medical physical, which included the following frequencies 500, 1000, 2000, 3000, 4000 and 6000HZ.

Amputation, traumatic injury patients have a greater risk for hearing loss.

Among the victims hearing loss range 40-60% who have exposed to blast and TM perforation range 10-30%. Otalgio range from 15-25% and dizziness range from 10-20%. Hearing loss is classified as follows:

Mild                     26-40 dB HL

Moderate              41-55 dB HL

Severe                  56-90 dB HL

Profound              > 90    dB HL

(Normal hearing : 0-25    dB HL)

The current scenario of TM perforation is either active perforation or healed perforation.

Ototoxic medications and/or combat-related stress could account for the exacerbation and/or cause of tinnitus. Tinnitus can be particularly problematic for patients who suffer from it secondary to blast injury to their ears, because of the sudden onset of tinnitus in the case of blast injury, instead of the gradual onset of tinnitus developing slowly with progressive hearing loss. Tinnitus can be exacerbated   by other medical treatments and conditions. The deleterious effect of tinnitus is highly variable and medical treatment facilities need to provide subject matter experts who can evaluate the significance of this problem for patients and provide treatment/management as necessary.

Otologic injury after the explosive blast in the community is concealed unless we look it for. So the collection of data as they relate to hearing , tinnitus and other otologic injuries is vital.

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