With over 3 million estimated incidents of traumatic brain injury (TBI) per year, it’s one of the most common injuries experienced by Americans today. It is the leading cause of death and disability in the U.S., and is most common among males aged 15-35.
What is Traumatic Brain Injury (TBI)?
TBI is any injury to the brain that is caused by physical force. This can be blunt trauma from a physical object or damage from vibration due to catastrophic sonic events. Common causes of TBI include sports injuries, car accidents, and gunshots. Because the brain is the seat of our personalities, sensory interpretation, and controls so many different functions in the body, TBI can have wide-ranging consequences for those who suffer from it. A mild concussion may or may not have lasting effects, but repeated minor traumas can lead to major cognitive issues and even death.
TBI & Hearing Loss
Our ears are so physically close to and functionally intertwined with our brains, it’s no wonder that TBI can often involve injury to our ears as well. Sometimes this damage comes from blunt force, causing conductive hearing loss due to damage to the ear canal, eardrum, or ossicles (bones of the middle ear). Other times, blast trauma that damages the brain through vibration rather than blunt force can also cause sensorineural hearing loss. TBI can also involve injury to the auditory cortex of the brain. In this case, patients may have problems with sound localization or distinguishing between sounds when more than one sound source is present, sometimes called “hidden” hearing loss.
TBI & “Hidden” Hearing Loss
Commonly seen in those who have suffered repeated, minor head injuries or concussion due to sonic blasts, hidden hearing loss is a type of hearing loss that causes problems understanding speech in the world, even though they test as “normal” in a hearing test.
In hidden hearing loss, our ears function normally, but there is a problem with our auditory nerves and/or auditory cortex due to tearing and shearing of the nerves’ or brain’s tissue. Vibration can cause damage to the myelin sheaths around the nerves, which are responsible for containing electrical impulses as they travel through nerve cells. This can make sending information through the nerve cells like running water through a leaky hose. The nerves still send information from the ears, but not all of it makes its way to the brain. In sonically simple environments hearing might be fine, but once the situation gets complicated enough speech information might leak out to make understanding it difficult or impossible.
Complicated Hearing Loss
TBI can cause damage anywhere from the outer ear up to the auditory cortex in the brain, and the damage won’t necessarily be limited to one part of the audio pathway or another. While some injuries may be treated with surgery or might heal with time, others may present permanent difficulties. Keeping in mind that these hearing issues are likely to be concurrent with other, non-hearing related problems due to the injury, and we can start to understand the complexity of the problems that TBI brings about.
Problems with Balance
TBI can also result in damage to the vestibular system, which is responsible for most of our sense of balance. The labyrinth, a fluid-filled organ responsible for maintaining our orientation to gravity, is often temporarily or permanently damaged in TBI. About 50% of people who experience concussions have dizziness amongst their symptoms, though in most cases this subsides. Tinnitus associated with TBI could also be the result of concussion to the labyrinth, and may subside after a short time or persist.
When To See a Hearing Professional
Most patients who seek treatment from a hearing healthcare professional following an incident of TBI will do so on a doctor’s recommendation. Because of the potentially complicated nature of a TBI patient’s hearing loss, it may take some time to determine whether hearing aids or cochlear implants would be of use to them, and in frequent cases the hearing provider will need to work with other medical professionals to determine the best treatments for TBI patients, who may need frequent adjustments in approach to treatment. It may be immediately clear whether surgery is necessary to restructure parts of the outer or middle ear, but some apparent damage may heal with time.