Hyperacusis

# Overview
Hyperacusis is a condition characterized by an over-sensitivity to a specific frequency of sound or intolerance to reasonable environmental sounds. A person with hyperacusis has difficulty accepting everyday sounds; some sounds may seem offensively loud to that person but not to others. In hyperacusis, a person gives inappropriate or exaggerated responses to sounds that are neither uncomfortable nor threatening loud to an average person; even low-intensity sounds can elicit the reaction.

# Classification
Based on the symptoms, hyperacusis may be classified as cochlear and vestibular hyperacusis.

### Cochlear hyperacusis:
- The most common form of hyperacusis
- Presents with ear pain and general intolerance to any sounds that most people don't notice or consider unpleasant.
- Crying spells or panic attacks may result from cochlear hyperacusis.
- Most of the time cochlear hyperacusis is associated with tinnitus.

### Vestibular hyperacusis:
- Associated with dizziness, nausea, or a loss of balance triggered by certain pitch sounds.
- Anxiety, stress, and phonophobia may be present in both types of hyperacusis.
- High risk for developing avoidant behavior to avoid a stressful sound situation.

# Pathophysiology
- Hyperacusis can be developed because of damage to the inner ear or hearing apparatus, affecting efferent part of the auditory nerve, and fibers that come out from the brain that control sounds.
- In this process, tissues of the auditory nerve are damaged, though the hair cells that permit us to hear pure tones remain integral.
- It can be as a result of injury to the neurological system of the brain. In some cases, hyperacusis may be triggered by a vestibular disorder.
- Stapes hypermobility can also be one of the causes of peripheral hyperacusis.
- Situations that comprise paralysis of the facial nerve (i.e., Ramsay-Hunt syndrome, Bells palsy, and Lyme disease) are involved in the causes of the condition.
- Hyperacusis increases in extent during anxiety, tiredness, or stress.
- The mechanism involved during stress, include endogenous dynorphins release into the synaptic region underneath inner hair cells.
- It potentiates the neurotransmitter glutamate, triggering sound to be seeming with excessive noise.

# Causes
Common causes of hyperacusis include:
- Severe head trauma
- Facial nerve dysfunction (to Stapedius)
- Surgery
- Ear irrigation
- TMJ (Temporomandibular joint disorder)
- Adverse drug reaction
- Williams Syndrome
- Autism
- Bell's palsy
- Meniere's disease
- Asperger syndrome
- Superior Canal Dehiscence Syndrome
- Chronic ear infections
- Minor Head Injury
- A vestibular disorder

## Differentiating hyperacusis from other diseases
On the basis of signs and symptoms, hyperacusis must be differentiated from misophonia, phonophobia, tinnitus, William syndrome, Lyme disease, migraine..

# Epidemiology and Demographics
Incidence
- The incidence of hyperacusis is approximately 1 in 50,000 people.
Prevalence
- The overall prevalence of hyperacusis among children and adolescents is between 3.2% to 1.7%. In adults, prevalence rate is between 8% to 15.2%.
Age
- Hyperacusis is commonly seen in individuals with any age group.
Gender
- Hyperacusis affects men and women equally.
Race
- There is no racial predilection to hyperacusis.

# Natural History, Complications, and Prognosis
Natural History
- In the case of a hyperacusis, patients can present with.
- Ear pain
- Annoyance
- Fear
- General intolerance to many sounds
- Crying spells
- Panic attacks
- Tinnitus
- Anxiety
- Stress
- Phonophobia
- Avoidant behavior
- Dizziness
- Nausea
Complications
- Common complications of hyperacusis depend on the etiology.
Prognosis
- Depending on the extent of the disease progression at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good.
- Patients with hyperacusis have profound psychological influence, patients presenting with self-harm or suicidal ideation.

# Hyperausis Diagnosis

## Diagnostic study of choice
Pure tone audiometry is the gold standard test for the diagnosis of hyperacusis.
- Loudness discomfort level( LDL) measured in decibels (dB); LDL decreased by 1618 dB than the general population is diagnostic of hyperacusis.
- 95% of patients with hyperacusis have LDL  77 dB (average LDL in a normal person is 100 dB).

## History and Symptoms
- The hallmark of hyperacusis is sensitivity to sounds.
- A positive history of over-sensitivity or distress to particular sounds is suggestive of hyperacusis.
- The most common symptoms of hyperacusis include annoyance, ear pain, loudness, and tinnitus.

## Physical Examination
Physical examination of patients' hyperacusis is usually remarkable for fear, irritability, and avoidance behavior.

## Laboratory Findings
There are no diagnostic laboratory findings associated with hyperacusis.

## CT scan
There are no CT scan findings associated with hyperacusis.

## MRI
There are no MRI findings associated with hyperacusis.

## Other Diagnostic Studies
Health questionnaires may be helpful in the diagnosis of hyperacusis. Findings suggestive of hyperacusis include:
- HQ score of  22 is diagnostic of hyperacusis.
- Disability
- Functional impact
- Psychological factors
- Impacted quality of life

# Treatment
The most common treatment for hyperacusis is retraining therapy that includes:
- Tinnitus Retraining Therapy (TRT), a treatment originally used to treat tinnitus, uses broadband noise to treat hyperacusis. By listening to broadband noise at soft levels for a disciplined period of time each day, patients can rebuild (i.e., re-establish) their tolerances to sound.
- Pink noise can also be used to treat hyperacusis.
Another possible treatment include:

# People
- Stephen Merritt, of The Magnetic Fields, suffers from this condition.