*Johnson Articles - Distinguishing between Cochlear Hyperacusis and Vestibular Hyperacusis

by Dr. Marsha Johnson, Audiologist, Portland, Oregon

Hyperacusis is a term that implies that someone perceives an unusual auditory sensitivity to some environmental noises or tones. The psychopathological effects of hyperacusis can range from a mild sense of unease to a complete loss of balance or upright posture with severe ear pain. In serious cases, it can cause seizure-like activity in the brain. Hyperacusis can be associated with autoimmune disorders, traumatic brain injury, metabolic disorders, and other conditions. It has not been sufficiently studied in the adult population and is often ascribed to psychological conditions rather than being recognized as a physiologic symptom of cochlear or vestibular damage.

The particular symptoms of cochlear hyperacusis and vestibular hyperacusis can help physicians and audiologists distinguish between the two disorders.

Many people understand that the hearing and balance systems of the inner ear are interconnected. Both systems are filled with fluid, whose movement stimulates tiny sensory cells. Sound is detected as energy vibrations by the cochlea and the hair cells that lie on the springy basilar membrane. Vestibular clues are detected by crystal-laden sensory cells, which provide information on the body’s physical position with respect to gravity.

The hearing and balance systems respond to vibrations with differing frequencies that occur in our environment. The human cochlea can hear best the frequencies associated with human speech (500–4000 Hz), while the balance system uses lower-frequency sensations to help maintain posture in relation to gravity. The eyes perceive very high frequencies as color and form. Our skin and nerve endings sense very low frequency energy as vibration, rumbles, movement, and so on.

One could say, then, that the human body is a large transducer of vibratory energy. The brain associates particular vibration patterns with specific entities, such as the purring of a cat or the presence of sunshine. We react to these sensations and signals based on our previous experiences. Every sensation or experience, becomes an electrical signal to the brain: all external and internal perception passses from the vibratory-energy phase into complex electrical patterns.

Hyperacusis is an abnormal condition in which these signals are misinterpreted, confused or exaggerated. The signals coming in are identical to those that present to a normal ear, but the reaction in the abnormal system is markedly different: for example, the sounds in a quiet library may seem like a loud parade to a person with hyperacusis.

Cochlear versus vestibular hyperacusis

With cochlear hyperacusis, subjects feel ear pain, discomfort, annoyance, and irritation when certain sounds are heard, including those that are very soft or high-pitched. Most people react by covering their ears or leaving the room. Severe emotional reactions may also occur; crying or panic reactions are not uncommon.

Vestibular hyperacusis is a disturbance of the balance mechanism that occurs in response to sound exposure. These disturbances have been called various names, including Tullio’s syndrome and audiogenic seizure disorder. In vestibular hyperacusis exposure to sound often results in falling or a loss of balance or postural control and some of the same reactions as with cochlear hyperacusis can also occur. Other symptoms include sudden severe vertigo or nausea. In the clinic, presenting a tone at 500 Hz and gradually increasing the loudness can often induce vestibular hyperacusis, provoking a sudden inability to maintain posture as well as a wide variety of emotional and physical reactions. In some cases, vestibular hyperacusis can affect the autonomous system and cause other problems such as loss of consciousness, mental confusion, nausea, or extreme fatigue.

In both auditory and vestibular hyperacusis, headache is common. In addition, many subjects with hyperacusis feel distinct cognitive changes during these exposures and will describe themselves as being “out of myself” or disassociated from reality, unable to take in other stimuli, having an immediate feeling of something wrong or a sensation of being unwell, or experiencing severe confusion.

What causes hyperacusis?

The physiologic conditions underlying to these alarming symptoms cannot be identified with certainty because of difficulties involved with studying the very small inner ear structures without damaging them.

Other possible explanations of cochlear hyperacusis are related to brain-chemistry dysfunction involving poor uptake of certain chemicals; or head trauma that damages the chain of tiny bones in the middle ear that act as sound amplifiers and help transmit vibrations to the inner ear fluid. Changes in the transmission of electrical signals along complex neural pathways are also highly suspect in cases of head injury.

In vestibular hyperacusis, we suspect that the main pathology is most likely the result of damage to the nerve cells in the balance system. These cells may suffer damage from trauma such as head injury; metabolic disruptions due to chemical ingestions, such as medications or anesthesia; or circulatory changes due to heart disease or artery blockages that result in oxygen deprivation. In addition, autoimmune disease, which can be triggered by many different causes, can harm the balance organ. Head trauma in a motor vehicle accident can set off an autoimmune reaction in the inner ear that can destroy the nerve cells, often weeks or months after the initial injury.

In my clinic, I have evaluated several serious cases in the past seven years where simple soft auditory stimulations at a specific frequency of less than 30 decibels, comparable to a a mid pitch musical note played at a very soft level, elicited loss of consciousness and seizures. All of these patients had suffered head and/or neck injuries in motor vehicle accidents that affected the brain stem and higher areas of the central nervous system. None of these patients had significant hearing loss or previous balance problems. One person loses her balance and consciousness frequently and must use earplugs and earmuffs all of the time to avoid injury when falling.

Treatment and testing innovations

In the clinic, special audiologic tests can reveal the presence and severity of cochlear hyperacusis, which can often be treated with acoustic therapies such as tinnitus retraining therapy (TRT). Simple tests such as the Loudness Discomfort Level Test and a Balance Screening using an audiometer and observation take only a few moments and can yield significant information. The LDL test was promoted for use in hyperacusis assessment by Drs. Pawel Jastreboff and Jonathan Hazell. Since 1985, thousands of patients with cochlear hyperacusis have completed the a course of acoustic treatment using the Jastreboff TRT protocol and recovered to normal or near-normal dynamic ranges of sound tolerance. The Jastreboff method remains the treatment of choice for cohleaer hyperacusis and is available from clinics that specialize in tinnitus and hyperacusis, around the globe. However, vestibular hyperacusis continues to go untreated or unrecognized in many cases and the treatment protocol vary widely depending on the level of expertise and interest of the treating physician. It seems that a low salt diet combined with anti-nausea drugs still dominates medical approaches although there are some pioneers like Dr. John Epley who have attempted to introduce anti inflammatory medicines directly into the cochlear/vestibular system using catheters with promising results. Often patients with vestibular hyperacusis wander from doctor to doctor without finding significant relief from their symptoms, unfortunately.

However, for individuals who complain of loss of balance with exposure to sound, thorough diagnostic testing should be completed in otology, neurology and audiology offices. Innovative clinical testing protocols could be devised to provoke or produce the response in a clinical setting. It is important that the clinicians be prepared to present tests tailored to the needs of the patient, for example, if someone complains about falling when large vehicles pass by, it may be critical to change a test to include lower frequency tones at very low volume levels, or narrow band noise, or even white noise, to attempt to locate the specific problem area. A portable audiometer could be used in conjunction with a computerized dynamic posturography test so that various sounds can be presented to induce a balance response. Another possibility is to develop an in-house EEG with an audiometer to present sound stimulation so that shifts in brain wave patterns in response to sound can be observed. A recent difficult case in the clinic resulted in creating that very strategy which was completed with clear evidence of brainwave anomalies that provided for the first time to the patient proof that there was indeed organic pathology that was producing these troubling symptoms. Her constant falling and loss of consciousness was indeed a physiologic condition and not a psychological one. These results provided a sense of relief to the patient,, whose EEG results before, without sound stimulations, were normal.

Adapting clinical assessment tools with the use of various stimuli and then making careful observations may allow medical providers to identify patients with vestibular hyperacusis and to devise better therapeutic strategies.

Comments, questions? Contact Dr. Marsha Johnson.

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