Dr. Richard Mabry: Blast Injury Hearing Loss

It’s always a pleasure to host Dr. Richard Mabry. His expertise was of great value in a manuscript I critiqued on hearing loss related to being in a confined space during an explosion. His next novel, Fatal Trauma, releases May 2015. 
Welcome back, Richard!

One of the possible medical scenarios for fiction is a hearing loss after a blast injury. I’ve read my share of detective stories and mysteries where gunshots occur, but only rarely have I seen addressed the ringing in the ears (tinnitus) and occasional brief hearing loss that may follow. But gunshots aren’t the only source of hearing change from loud sounds.

Let’s take an example of a blast in a confined space—a bomb, for instance. The first type of hearing loss to be considered would be due to the physical trauma to ears. Compression waves of a blast often rupture an eardrum, typically producing a triangular tear in the tympanic membrane. These sometimes heal spontaneously while other cases require a specialist to apply something like a paper patch to speed healing. In some situations a surgical procedure (tympanoplasty) is necessary.

Blast injuries can also disrupt the continuity of the three bones that form the chain conducting sound waves through the middle ear. This type of injury always requires surgical correction. However, assuming there is no damage to the inner ear (actual organ of hearing), all the injuries listed thus far are “conductive” losses—a hearing loss due to interruption of the conduction of sound.

When hearing is tested, levels are checked using earphones (air audiometry) and then a conductor of sound placed against the mastoid bone (bone audiometry). If there is a conductive loss, the air levels are decreased, but the bone levels remain fairly normal (because the sound short circuits the middle ear and goes direct to the organ of hearing). If both air and bone levels are down, the loss is caused by problems in the inner ear and is called “nerve” loss.

Noise, however produced, can also damage the inner ear (the curious can look up “Organ of Corti”), producing either a temporary or permanent nerve-type hearing loss. A rock concert may make a person’s ears ring and produce a temporary hearing loss (temporary threshold shift, or TTS) for up to a day or two.

Gunfire can do the same thing, and the bigger the gun, the bigger the bang, and the bigger the chance for noise-induced hearing loss (NIHL). This is sometimes temporary, but with repeated exposure or one huge sound exposure, the loss may be permanent. Although experimental treatments exist, at present there is no recognized treatment for NIHL and the tinnitus that accompanies it. How can you tell if the loss is permanent? You retest, because, as the saying goes, “only time will tell.”

Let me make a final point. What happens in your story isn’t as important as what happens in your life. Use ear protectors when you mow the lawn or at the shooting range. Encourage your kids to keep their exposure to noise down. And, if a sound makes your ears ring, avoid it in the future.

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Richard Mabry is a retired physician, past Vice President of the American Christian Fiction Writers, and auth or of “medical suspense with heart.” His novels have been a semifinalist for International Thriller Writers’ debut novel, finalists for the Carol Award and Romantic Times’ Reader’s Choice Award, and winner of the Selah Award. His latest, Critical Condition, is his seventh published novel. You can follow Richard on his blog, on Twitter, and his Facebook fan page.

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