Round And Oval Window Reinforcement

Hyperacusis is an audiological disorder characterized by persistent oversensitivity and intolerance to everyday environmental sounds that are normally well-tolerated by most people. Patients with hyperacusis experience varying degrees of discomfort and impairments in day-to-day activities, resulting in poor quality of life. Hyperacusis is neither phonophobia nor misophonia. Phonophobia is a temporary sensitivity to sound secondary to migrainous attacks and is associated with other sensory aversions, all of which abate when the migraine resolves. Misophonia is an acquired adverse reaction to specific sounds, such as chewing or breathing, and may have an emotional component. The prevalence of hyperacusis ranges from 5.9% to 17.2%. Hyperacusis and tinnitus are strongly associated; 86% of patients with hyperacusis endorse tinnitus, and 40% of patients with tinnitus endorse hyperacusis. Historically, the diagnosis of hyperacusis has relied heavily on self-reporting, the Hyperacusis Questionnaire, the Loudness Discomfort Level test, and the Tinnitus Retraining Therapy interview.  Hyperacusis is most commonly caused by cochlear damage and head trauma but is known to be associated with depression, anxiety, adverse medication reactions, hearing loss, and autoimmune disorders. The pathogenesis of hyperacusis is not fully understood but may be due to acoustic overexposure, resulting in increased central auditory pathway gain. So-called “third window” pathologies such as superior semicircular canal dehiscence, perilymphatic fistula, and stapes hypermobility have also been proposed as possible etiologies of hyperacusis. Regardless of etiology, multiple pathophysiologic theories for hyperacusis have been proposed.  The most widely accepted etiologic theory of hyperacusis is the cochlear theory; cochlear damage from a variety of processes, including but not limited to Ménière disease, perilymphatic fistula, and noise-induced hearing loss, results in cochlear dysfunction and hyperacusis. Other theories are based on possible central nervous system origins of hyperacusis. The 5-hydroxytryptamine (5-HT, serotonin) hypothesis speculates that some cases of hyperacusis may share a common origin with other serotonin-related symptoms like photophobia and tinnitus; hyperacusis is common in patients with depression and migraine headaches, both of which are likely related to serotonin disturbances. Another theory hypothesizes that increased endogenous opioids may cause hyperacusis. Experiments in chinchillas correlated increased endogenous opioids with increased auditory sensitivities, possibly indicative of a physiological mechanism to increase auditory gain in fight-or-flight situations. Lastly, the central plasticity hypothesis states that long-term noise exposure, such as in factory workers, changes the level of the central gain phenomenon such that individuals can wholly or partially lose their stapedial reflex and not have any sound-dampening response, resulting in hyperacusis.  Treatment for hyperacusis includes avoidance of noise stimuli, tinnitus retraining therapy, cognitive behavioral therapy, and gradual sound exposure therapy. However, insufficient evidence exists to identify these strategies as an effective treatment for hyperacusis. Newly observed stapes hypermobility in hyperacusis patients has led to a surgical treatment involving reinforcement of the oval and round windows to reduce transmission of mechanical energy to the inner ear. Autophony is defined as hearing one’s voice or other bodily functions such as pulse, eye movements, and limb movements as loud or distorted. Autophony is most often related to third window pathologies such as various semicircular canal dehiscence syndromes, perilymphatic fistula, or an enlarged vestibular aqueduct. The proposed mechanism of autophony is that energy of the offending bodily sounds is mechanically transmitted through a pathological third window directly into the cochlea, thus overriding sounds being transmitted by the outer and middle ear. It has been demonstrated that reinforcing the natural windows, usually only the round window, returns the labyrinthine system to 2 windows and may improve autophony. However, this approach has not been extensively studied, and results are varied. Systematic reviews have suggested that primary window reinforcement is best employed as a first-line, low-risk intervention in medically complex patients not suitable for more invasive management of third window pathologies, such as transmastoid or middle cranial fossa craniotomy approaches to superior semicircular canal dehiscence.