Hyperacusis: Loudness intolerance, fear, annoyance and pain.

Hyperacusis is a debilitating loudness intolerance disorder that can evoke annoyance, fear and aural facial pain. Although the auditory system seems to be the "central" player, hyperacusis is linked to more than twenty non-auditory medical disorders such as Williams syndrome, autism spectrum disorder, fibromyalgia, migraine, head trauma, lupus and acoustic shock syndrome. Neural models suggest that some forms of hyperacusis may result from enhanced central gain, a process by which neural signals from a damaged cochlea are progressively amplified as activity ascends rostrally through the classical auditory pathway as well as other non-auditory regions of the brain involved in emotions, memory and stress. Imaging studies have begun to reveal the extended neural networks and patterns of functional connectivity in the brain that enrich sounds with negative attributes that can make listening unbearable and even painful. The development of animal models of hyperacusis have enabled researcher to begin to critically evaluate the biological bases of hyperacusis, identify therapies to ameliorate the symptoms and gain a better understanding of the neural mechanisms involved in loudness coding in normal and hearing impaired subjects.