Rodney Taylor, Doctor of Audiology, Advanced Studies in Tinnitus and Hyperacusis, Certified by the American Institute of Balance for Concussion and Vestibular Rehabilitation.
Audiologic Implications for Post-Concussion/Post-Whiplash Syndrome
A concussion, or mild traumatic brain injury (mTBI) is caused by a bump, blow, or jolt to the head or body that results in rapid movement of the head and brain. This results in chemical changes in the brain and stretching and damaging of brain cells. Concussions can be direct impact, acceleration-deceleration, blast, linear or rotational, or focal or diffuse. Diffusion tensor imaging can reveal white matter abnormalities following a concussion, usually at the corpus callosum, fornix, hippocampus, thalamus, or the cingulum (Borich et al., 2013; Cubon et al., 2011; Hayes et al, 2015; Hulkower et al., 2013; Laksari et al, 2018; Virji-Babul et al., 2013).
Coup injuries occur when the head is in a moveable environment when impact occurs and the maximal injury is typically beneath the point of impact. Contrecoup injuries occur when the head is moving and hits an immovable object. Maximal injury is usually located opposite the impact location and damage is most common in the frontal and temporal lobes (Debacker et al., 2018; Wolff et al., 2018). Studies have shown tha the corpus callosum was the most frequently reported brain structure affected, resulting in deficits in at least one measure of central auditory processing function. Bergemalam and Lyxel, 2005, found that 58a% of participants with TBI had central auditory processing deficits 7 to 11 years post injury. Areas of central processing typically include temporal processing, temporal resolution, temporal patterning or sequencing, binaural integration, binaural separation, binaural interaction, auditory closure, and auditory figure ground. Typical tasks recommended for improvement include a number of tasks such as dichotic interaural intensity difference training, two-element ordering, music training/therapy, games that focus on auditory sequencing, computerized auditory training programs, assistive listening devices (or low gain amplification with effective noise reduction, sound generation, and adaptive directional microphone technology).
Much of the brain’s energy is used to filter out irrelevant or unnecessary information. After sustaining an injury such as a concussion, most of the brain’s energy is diverted to basic functioning, and little is left over for filtering and censoring. Trivial or insignificant thoughts may often have the same weight in an individual’s mind as important ones, making decisions very difficult. The inability of an individual to attend to an auditory task in the presence of competing noise and visual stimulation is referred to as Brain Fog. The brain can often get stuck on an idea or phrase that keeps replaying and this uses a great deal of brain energy. New sensitivities can be very challenging and baffling for the injured individual. Going into environments that are flooded with changing visual stimuli may cause the brain to shut down. A common symptom of brain injury is hypersensitivity to sound (Assi et al, 2018). The auditory system becomes hypersensitive to environmental noise and has a great deal of difficulty dealing with competing noises.
In addition to reports of difficulty with memory, deficits in attention and concentration are the most commonly reported complaints following head injury (McKinlay, 1981). Complaints may include problems with concentration, distractibility, forgetfulness and difficulty with multi-tasking skills (Sohlberg and Mateer, 2001). Attention deficits and reduced speed of information processing are also reported (Gronwall, 1989, Chan, 2001). Other areas affected include thought organization, word finding, self-monitoring, difficulties with initiation, problems with planning and organization (Bigler, 1990).
Debacker et al., 2018, have estimated that more than 50% of the brain’s circuits involve vision and eye control. There are several systems that should be investigated in individuals with brain injuries that result in balance issues. These include the evaluation of the vestibulo-ocular reflex, the integration of visual and vestibular inputs, oculomotor testing, the evaluation of convergence and divergence and measures that require a verbal response from the patient. Researchers have investigated cortical activation patters in response to visual motion stimulation such as optokinetic stimulation and normal functioning individuals show distinct patters of cortical activations and deactivations that are reciprocal and simultaneious (Becker-Bense et al., 2012; Brandt et al., 1998; Deutschlander et al., 2008; Dieterich et al., 2003; Kikuchi et al., 2009; Kleinschmidt et al., 2002; and Rommer et al.,, 2015). Areas of cortical activation include the bilateral medial parieto-occipital visual areas, intraparietal culcus and the striate and extrastriate visual cortex. Cortical deactivations include the posterior insula, parieto-insular multisensory vestibular cortices, posterior region of superior temporal gyrus, inferior parietal lobule, anterior cingulate gyrus, hippocampus, and the corpus callosum.
Often, the vestibular system is involved and outcomes for recovery are often prolonged when vestibular dysfunction is involved. It is common for head injuries to result in Benign Paroxsymal Postitional Vertigo and this is easily diagnosed through patient history. Provoking symptomology can be done by placing the patient in different positions with different head alignments and performing canalith repositioning. This procedure is routinely done in individuals who present with the symptomology associated with specific complaints and the treatment is done immediately with the Semont maneuver or the Gans Repositioning Maneuver.
Vestibular rehabilitation is a well-documented, exercise-based rehabilitation strategy designed to promote central compensation for vestibular dysfunction. These measures can be customized to accommodate the patients’ unique needs and goals and is implemented on and individual basis. The protocols include elements of both in-clinic and home-based exercise therapy. 20 to 50% of individuals that do not experience significant improvements with conventional vestibular rehabilitation may not improve due to a failure to adequately address symptoms of visual motion sensitivity (Rossi-Izquierdo et al., 2011, Pavlou et al., 2013). It is my protocol to address these issues initially with a neuro optometrist, who is part of my team. They are equipped with exercises to reduce susceptibility to disorientation and autonomic symptoms, use optokinetic stimulation, and serve to reduce visual over reliance, especially as it relates to perceptual and postural responses. Neuro optometrists deal with binocular vision (the ability to use two eyes together as a coordinated team to see a single three-dimensional image of surroundings), convergence (the eyes work together to create a single fused image of near objects by simultaneous adduction of both eyes) and convergence insufficiency. The prevalence in concussion is between 47 to 64% (brahm et al., 2009; Capo-Aponte et al., 2012; Debacker et al., 2018). If diplopia develops or one eye turns outward 7 cm from the patient’s nose, this is a sign of convergence issues (Debacker et al., 2018). Saccades are abnormal in 30% of patients and smooth pursuit is abnormal in 60% of patients that suffer from head injury.
There is a strong association between tinnitus and Post Concussion Syndrome. The American Speech-Language-Hearing Association reported that tinnitus is frequently a symptom of mild traumatic brain injury (TBI) or concussion, and can occur as a direct consequence of TBI or the medications prescribed to treat it. Folmer and Griest (2009) state that tinnitus is a significant symptom that commonly occurs as a result of head or neck trauma. Not only is the tinnitus more severe from such insults, it is often accompanied by a greater number of co-symptoms that tinnitus from other causes, and this should be taken into account by clinicians that treat these patients. While tinnitus is often seen with hearing loss, the auditory system in those with PCS can appear to be totally normal. Researchers have speculated that this is due to the process of damaged neurons in the brain that attach to healthy auditory neurons. Kreuzer et al (2014) reports that up to 53% of individuals suffering from brain injuries develop tinnitus.
Rodney Taylor, Doctor of Audiology, Post-Doctoral Specialty Certificate in Tinnitus and Hyperacusis, Certified by the American Institute of Balance for Concussion and Vestibular Rehabilitation
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