Hearing loss after head injury can occur after you damage your temporal lobe or parietal lobe. It can also be a result of problems with the ear mechanism itself.
To help you navigate the various hearing problems that can occur after brain injury, this article will cover everything from diagnosing hearing loss to treating it.
Causes of Hearing Loss After Head Injury
There are two primary ways that hearing problems can arise after a head injury or concussion.
These causes are either neurological or mechanical.
If an injury affects the mechanical process of hearing, the ear will not transmit sound to the brain at all. This is the most common cause of hearing loss after head injury.
On the other hand, if the neurological side becomes damaged or disrupted, the brain can no longer process sound. Even if the ear itself works fine, you will still experience hearing problems.
How the Ear Processes Sound
To understand how hearing loss can occur after a head injury, it will help to understand how the ear works.
The ear itself comprises three sections: the outer ear, the middle ear, and the inner ear. Each section plays a part in the hearing process:
- The outer ear comprises the ear lobe and ear canal and protects the rest of the ear.
- The middle ear contains the tympanic membrane (eardrum), a thin layer of tissue that vibrates when sound hits it. This vibration transfers to three small bones (called the ossicle bones) in the middle ear which in turn transfer the vibration to the fluid in the inner ear.
- The inner ear contains fluid and a spiral structure called the cochlea. The cochlea senses the movement of the fluid and changes that movement into electrical impulses.
Finally, the cochlea sends electrical impulses to the auditory nerve, which transmits those signals to the brain.
If a head injury interrupts any part of this process, hearing loss will result.
For example, the blow from the impact can rupture the eardrum, dislocate the ossicle bones, or sever the auditory nerve. All of this will cause hearing problems.
5 Types of Hearing Loss After Head Injury
There are many types of hearing loss that can occur after a head injury, depending on which part of the ear or brain was damaged.
1. Conductive Hearing Loss
This type of hearing loss can occur when sound does not transmit to the inner ear.
Fracturing the temporal lobe will cause this type of hearing loss. This will make the vibrations in the eardrum unable to travel.
Another, less common cause of conductive hearing loss is otosclerosis. This is where the three small bones in the middle ear fuse until they are so stiff, they can no longer vibrate. Which again makes it hard for sound to travel.
For reasons researchers still don’t fully understand, brain injury can trigger abnormal bone growth throughout the body, including in the ear. Doctors call this heterotopic ossification. If bone growth happens inside the ear, this can lead to hearing loss.
Other factors that contribute to conductive hearing loss include wax build-up and ear infections.
Finally, if the head injury occurred directly over the ear, the force of the impact could tear the eardrum which will also cause conductive problems.
2. Labyrinthine “Concussion”
This occurs when the inner ear becomes damaged. What separates this type of hearing loss from others is this one occurs even if there are no visible bone fractures. Instead, the extreme force of the injury itself nearly destroys the cochlea.
Labyrinthine concussions also cause tinnitus (i.e. ringing in the ears). Dizziness is another possible side effect.
3. Meniere’s Syndrome
This disorder is caused by pressure in the inner ear chambers that contain fluid. The pressure causes the fluid to move too much, which can affect your hearing and your balance.
There is no cure for Meniere’s syndrome. However, steroids and other medications can ease symptoms.
4. Sensorineural Hearing Loss
This is the most common type of hearing loss after head injury. It occurs when there is damage to either the hair-like cells in the inner ear that transfer sound or to the auditory nerve itself.
This condition rarely causes complete hearing loss. It mainly affects the loudness or clarity of certain sounds.
It can also make a person extra-sensitive to sound, which may seem strange at first. Noises will seem so loud that it actually causes pain.
5. Auditory Verbal Agnosia (pure word deafness)
This is a rare type of hearing disorder that is similar to aphasia, except the person does not process speech at all.
It’s not that the person can’t understand words, they do not even hear any words at all. Yet they still retain their ability to recognize other sounds.
This condition is caused by damage to the regions of the brain that process language.
There is also another form of auditory agnosia which is essentially the complete opposite. Patients with this disorder have no trouble hearing or understanding speech, but they can’t recognize other sounds.
Diagnosing Hearing Loss After Head Injury
The best way to treat hearing loss after head injury is to first find out what type of hearing loss you have.
There are several ways your doctor might do that, including:
- Physical exam. This is where your doctor might look for any structural problems that are causing your hearing loss.
- Whisper test. With this test, your doctor will ask you to cover one ear at a time to see how well you respond to words at different volumes. Its accuracy is limited, but it can be a good first step.
- Tuning fork test. A tuning fork is a two-pronged, metal instrument that produces sound when struck. It can help your doctor find out where in your ear the damage lies.
- Audiometer test. This is the most thorough hearing test. Conducted by an audiologist, the test involves wearing earphones where sounds are directed to each ear. The audiologist repeats the tones at increasingly faint levels to find the quietest sound you can hear.
Treatment for Hearing Loss
Once you determine the cause and severity of your hearing loss, there are a variety of treatments available to you, such as:
- Surgical procedures to remove bone growth and repair your eardrum.
- Hearing aids to boost your hearing. For people with profound hearing loss, high power hearing aids or bone-anchored hearing devices can be especially helpful.
- Cochlear implants that bypass damaged parts of your inner ear and directly stimulate the auditory nerve. These are great for those who have seen only small improvements from a hearing aid.
For those with neurological hearing problems, some training programs such as auditory discrimination training and interhemispheric transfer training can activate your brain’s plasticity and teach you how to process sounds again.
Coping with Hearing Loss After Head Injury
Hearing loss is just one of the many complications of brain injury you can experience.
It’s common for there to sometimes be a delay between your head injury and hearing loss. During the first few chaotic weeks after a brain injury, you might not notice you have hearing problems until life quiets down.
Most hearing problems do go away as your head injury heals. If your hearing doesn’t improve on its own, talk to your doctor. You may have a more serious form of hearing loss that will require some of the treatment methods listed above.
Otherwise, it might be worthwhile to consult a speech-language pathologist to help you learn some compensation techniques. This will enable you to communicate and stay engaged with others despite hearing difficulties.