Recognizing and evaluating head injury-associated hearing loss.
The Center for Disease Control has estimated that as many as 5.3 million Americans are living with a brain injury, and that a significant head injury occurs about every 21 seconds. In 2010, about 2.5 million emergency department visits, hospitalizations or deaths were associated with traumatic brain injury (TBI). The primary contributing factor for TBIs among adults aged 65 and older is falls. Other contributing events include concussive high pressure waves from explosions and sports-related injuries.
There are three severities of TBI: mild, moderate and severe, and a TBI can change how someone learns, thinks, performs and behaves. A concussion is a type of traumatic brain injury (TBI) caused by a blow or jolt to the head. Concussions can also occur from a fall or blow to the body that causes the head and brain to move quickly back and forth. Medical diagnosis may describe a concussion as a “mild” brain injury because concussions are usually not life-threatening. Even so, their effects can be serious and sometimes long-term.1
How Head Injuries Affect Hearing and Communication
Usually a concussion will present itself as a cognitive or balance problem. The primary injury is often a contusion (bruising) from the brain moving in the skull. This motion affects the temporal cortex related to feature specific auditory processing. In moderate TBI, the injury can lead to a hemorrhage affecting the frontal/pre-frontal cortex which effects attention and listening.
A moderate injury can affect the parietal lobe affecting spatial processing, involve the occipital lobe which affects visual processing, and impair the cerebellum, affecting balance. In severe cases, the injury can be a more diffuse axonal injury in the corpus callosum affecting inter-hemispheric transfer or injury to the thalamus affecting organization and updating of cortical and brainstem connections, both of which are involved in the processing of language. Often, the outer and inner ear is directly in the path of any trauma, and hearing-specific problems often follow a concussion or TBI. There could be peripheral damage to the pinna or to the eardrum in the form of a rupture, as well as to the ossicular chain primarily affecting the ability to hear “soft” and “moderate “sounds.
If damage has occurred to the inner ear hair cells in the cochlea, this will affect both the ability to hear as well as the ability to hear clearly. For example, an individual may hear “ool,” but not be sure if the word was “pool,” “tool” or “cool.” Finally, our bodies maintain balance through touch, vision and our inner ear balance system. Trauma can cause inner ear vestibular damage, affecting our balance.
Following a head injury, hearing problems can occur for several reasons, including mechanical and neurological complications. Specifically, when the inner ear or temporal lobes have been damaged, TBI can often lead to the following auditory symptoms:
- Hearing loss
- Difficulty filtering one set of sounds from background noise
- Auditory agnosia
- Difficulty following rapid speech
- Difficulty following long conversations or instructions
The Problem With The Problem
Often the condition goes undetected by the patient. They may be slightly dazed but get up, or move away from the event and go on. And in some cases, there are multiple events, such as military explosions and sports-related injuries. The long-term effects of multiple concussions are currently being studied by researchers. Not only can repeated traumatic incidents contribute to the development of mild cognitive impairments such aschronic traumatic encephalopathy and other adverse outcomes, but a concussion history can also result in “post-concussion syndrome.” Individuals with a history of concussion are at an increased risk of sustaining a subsequent concussion
Making the Right Diagnosis
It is recommended that anyone suffering from head trauma be evaluated medically. Since many hearing problems cannot be detected by the patient, diagnostic evaluations may include neuroimaging, neuropsychological tests, and comprehensive audiologic evaluation including vestibular balance assessment with videonystagmography and posturography.
NOTE: It is strongly recommended on all audiology case history assessments that each patient is asked, not only have they ever suffered a concussion, but have they ever hit their head or been in a concussive event.
Currently, the Balance Error Scoring System (BESS) is used to assess balance deficits indicating concussion. In addition to BESS, a paper test such as the Standardized Assessment of Concussion is commonly used. The Acute Concussion Evaluation (ACE) was developed to provide physicians with an evidence based protocol to conduct an initial evaluation and diagnosis of patients (bot children and adults with known or suspected MTBI.
With auditory processing evaluations following an injury, it is important for audiologists and speech language pathologists to determine if other symptoms exist such as memory or attention difficulties, which can also interfere with normal hearing and may accompany a TBI. In addition, Speech Language Pathologists are involved with the collection of baseline cognitive-linguistic data that can be used not only as a reference point for determining severity of injury, but also as a benchmark for recovery, providing an indicator of improvement in subtle yet broad deficits to attention and concentration, that may not be readily evident on more traditional imaging studies such as CT scan or MRI.
Ensuring patients are open to using the interventions is an important part of the process.
Rest and careful management of physical and cognitive exertion are also keys to recovery. To help with communication directly, improvements in the signal to noise ratio through Frequency Modulated (FM) listening systems help to reduce the background nose and improve listening.
Auditory Training programs combining FM are starting to be used more frequently to help with temporal processing, speech-in-noise understanding, reported cognitive processing difficulties and improving working memory.
Tinnitus management strategies through audiology evaluations which identify the pitch and loudness of the tinnitus are also available. By analyzing the subjective rating and classification by the patient of their tinnitus, it is possible to determining if they are “hyper monitoring” their tinnitus. Then by evaluating if a hearing loss exists, it is possible to tune a graphic equalizing hearing system to filter a similar pitch to the auditory cortex which in turn appears to “help” the patient “manage” their tinnitus. In cases of severe hyper monitoring, Cognitive Behavioral Therapy can also assist patients in managing their tinnitus.
In some cases following a brain MTBI injury, hearing problems resolve themselves within just a few weeks, but for others, hearing problems can last indefinitely. Because hearing loss directly affects the primary means with which we communicate, hearing loss has the potential to complicate and frustrate other effects of brain injury, particularly cognitive and social problems. Cognitive issues such as trouble finding words are only exacerbated if the patients cannot hear what is going on around them.
The Acute Concussion Evaluation (ACE) form can be used to serially track symptom recovery over time. It provides a systematic protocol for assessing the key components for diagnosing an MTBI and serves as the basis for management and referral recommendations provided by the ACE Care Plan.
Peter Marincovich of Audiology Associates in Santa Rosa, Calif. has spent his career revolutionizing the way audiology and hearing diagnostics are performed and is highly versed in the latest treatments for helping patients manage hearing loss associated with brain injury.
Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 29 May 2014. http://www.cdc.gov/concussion/.