Neuroscience Research Notes

The phenomenon of misophonia was brought into the lime of light in 2002 by Pawel Jasterboff, which indicates the hatred towards the sound. The traditional definition for misophonia is “an abnormally strong reaction occurring to a sound with a specific pattern and/or meaning to an individual” (Jastreboff & Jastreboff, 2014). The disorder is classified both as an auditory disorder and tinnitus, hyperacusis, phonophobia and as a psychiatric disorder classified under the DSM V under a form of obsessive-compulsive disorder. However, it is proven not to be a hearing disorder as hearing loss does not lead to misophonia or effect. Instead, it results from the strength of the connection between the limbic and sympathetic nervous systems, which causes abnormal processing of sound stimuli. With tinnitus being the abnormal perception of a ringing or buzzing sound, hyperacusis being unusual tolerance to environmental noise and a broad range of noises, phonophobia being extreme fear towards specific trigger sounds, misophonia on the other hand, is a selective sound aversion syndrome where they tend to have negative reactions towards specific sounds such as eating/chewing, lip-smacking, pen clicking, clock ticking and scratching.

Misophonia occurred with comorbid conditions such as OCD, attention deficit hyperactivity disorder, asthma, Tourette, dysthymic disorder, eating disorders, posttraumatic stress disorder, social phobia, body dysmorphic disorder, and panic disorder. Individual cases were also reported with borderline personality disorder, tinnitus and hearing loss, specific phobia, agoraphobia, generalised anxiety disorder, Kawasaki disease, hypochondria, skin picking, and bipolar disorder. However, these conditions were present alongside Misophonia, and no association between them has been established yet (Potgieter et al., 2019).

The onset of this problem has been reportedly varied across the literature. Few studies quote the onset to be during adolescence (within 18 years), few studies quote the onset to be during adulthood (above 18 years), and some say it can occur at any age (Potgieter et al., 2019).

The multiple sounds that can trigger a misophonic condition include oral sounds, especially those made by people eating, such as chewing, lip-smacking, swallowing noises, and throat noises, nasal sounds, such as breathing, blowing nose, sniffling, sneezing, consonants and/or vowels and specific voices were also reported as triggers. A context that includes a family, friends, and occupational or educational setting, is more likely to cause a stronger misophonia reaction. Other common trigger sounds include repetitive clicking and tapping or sounds produced by using utensils, keys, or ice in a glass.  Individual cases also describe bird chirps, dog barking, rustling, and other movement-related triggers such as rubbing of hands, swinging arms/legs, and jiggling, which can be classified under misokinesia (Cavanna & Seri, 2015; Potgieter et al., 2019; Jastreboff & Jastreboff, 2014).

The reaction towards a misophonia can differ from individual to individual. Some can be combinations of discomfort, distress, anxiety, annoyance, disgust, panic, extreme irritation, anger, hate, or sometimes rage with aggressive outbursts or involuntary violence. A physical reaction to trigger sounds included contraction, tension, or sensation in specific muscles, heavy breathing, pressure in the chest, arms or head, muscle tension. Recent study documents post mental trauma to commit suicide or near defying death post misophonia (Cavanna & Seri, 2015; Edelstein et al., 2013; Kluckow et al., 2014; Bernstein et al., 2013).

The neurophysiology behind Misophonia has been documented extensively in the literature. Schroder et al. (2014) documented the event-related potential findings in individuals with Misophonia. Results indicated a reduced N2 response indicating auditory information processing deficits. The same authors commented on significantly higher mood disturbances when compared to the normals. Functional imaging studies have been documented, and an fMRI study of the blood oxygen level-dependent (BOLD) on individuals with misophonia reveals hyperactivation of the bilateral Auditory Cortex and hyperactivation of the left Amygdala (Eijsker et al., 2019). Schroder et al. (2020) found increased physiological arousal, increased activity of the right Anterior Insular Cortex, right anterior cingulate and right superior temporal cortex. Kumar et al. (2017) conducted similar fMRI studies of the blood oxygen level-dependent and found increased activity in all regions responsible for regulating emotions, including the amygdala, hippocampus and posteromedial cortex (PMC), and the ventromedial prefrontal cortex (vmPFC). They observed increased hyperactivity in the right and left anterior insular cortex. Giorgi (2015) found hyperactivation in the bilateral auditory cortex and the left amygdala in patients with misophonia only with a misophonia trigger stimulus but not a neutral stimulus. Concerning the neuropsychological basis of Misophonia, very little literature has discussed the complex neuropsychological task. According to Frank et al. (2020), individuals with Misophonia have a long-standing neuropsychological weakness as in their task involving attention, individuals with misophonia had difficulty maintaining alertness. Silva & Sanches (2019) administered the dichotic sentence test in individuals with misophonia, tinnitus, and controls and found out that individuals with misophonia possess poor selective attention with a misophonic trigger as noise compared to individuals with tinnitus and normal. Eijsker et al., (2018) performed a stop-signal task and found intact response inhibition favouring accuracy over speed and hyperactivity of superior medial frontal gyrus in inhibition and hypoactivity of the posterior cingulate cortex during the success in a BOLD technique of fMRI.

The diagnosis of Misophonic individuals comes up with a detailed case history in an interview mode, documenting the history of possible comorbid issues and administration of questionnaires. The most commonly used questionnaire is the Amsterdam Misophonia scale (Schröder et al., 2013) based on the Yale-Brown Obsessive-compulsive scale. Other scales include Misophonia Assessment Questionnaire (MAQ), Misophonia Coping Responses Survey (MCR), Misophonia Trigger Severity Scale (MTS), Misophonia Activation Scale. The Misophonia Physiological Scale (MPS), Misophonia Emotional Response, Misophonia Questionnaire, and Misophonia Severity Scale (MSS) (Potgieter et al., 2019).

A variety of treatment options have been explored in these individuals to reduce the symptoms of their behaviour as the cause of misophonia still is challenging to investigate. These individuals develop coping strategies through avoidance behaviour, like wearing earphones and avoiding situations during an incoming trigger sound. Some have also quit their work if their work environment has trigger stimulus. Some strategies included telling the offender or confronting the offender to stop producing the trigger sound. Some also mimic the offensive or trigger sound for adaptation. Some try to engage with positive internal dialogue, distracting their mindset by producing anti sounds to the incoming trigger sounds. or diverting their thoughts (Schröder et al., 2014). A few rare cases report muscle-relaxing exercises as a coping strategy for misophonia. The most widely used treatment option is cognitive behavioural therapy. The main goal of cognitive behavioural therapy is to incorporate psychoeducation that helps in achieving habituation. The therapy incorporates a cognitive task by asking the patient to; practice diverting their attention to neutral stimulus, counter condition to break the association between the trigger sounds and negative emotions, and stimulus manipulation to achieve habituation (Roushani & Mehrabizadeh Honarmand, 2021). Few pieces of literatures have used mindfulness and acceptance methods using dialectal behavioural therapy, which aids a patient with misophonia transition from predisposed anger to an alternate solution (Schneider & Arch, 2017).

Another discussed treatment is the usage of desensitisation therapy (DST) in misophonics. Desensitisation therapy is used in individuals with tinnitus and hyperacusis; however, the approach must be different for misophonics because their auditory system works within the norms. A DST must be incorporated with regular counselling. If possible cognitive behavioural therapy to remove the negative effects of the trigger sound, in misophonics the principle is to weaken the enhanced connection between the auditory system and the limbic system.  This can be done based on four different protocols. Protocol one involves the patient having complete access to the sound type and controlling the type and volume sound. Protocol two involving the patient having partial access to the type of sound with the family member setting the appropriate volume control. Protocol three involves the patient knowing the type of sound but the clinician manipulating the sound types to give the patient different sounds. Protocol four involves combining the unpleasant sound with a normal sound enabling the patient to adapt (Jastreboff & Jastreboff, 2014).

There has been literature attempting to prescribe pharmacotherapy drugs, including escitalopram and alprazolam, to reduce their obsessive-compulsive behaviours. The alprazolam belonging in a class of benzodiazepines does have antianxiety effects, thus reducing obsessive-compulsive behaviours. However, it can also have adverse effects such as memory loss, drowsiness, talkativeness, tremor, low blood pressure, blurred vision, weight gain, nausea, and difficulty in speech (O’Sullivan et al., 1994; Potgieter et al., 2019).

Although these treatment options have been discussed, vagus nerve stimulation has not been discussed in the literature and can also be used as an additional option. The vagus nerve stimulation improves symptoms of psychogenic related disorders like stress and depression, along with controlling the hyperactivity of the brain. Individuals with misophonics who have an intolerance to specific sounds due to the hyperactivation in the auditory cortex, limbic system, amygdala, hippocampus, posterior medial cortex, the insular cortex can be tried with vagal nerve stimulators as they have an auricular branch that inserts in the nucleus of the brainstem, hence reducing the hyperactivity (Yap et al., 2020).

Even though the VNS has shown progress in a variety of individuals from epileptic to tinnitus when it comes to its clinical utility, the possible side effects must be considered. The limitations of implanting a vagus nerve stimulator include the possible general side effects, which are hoarseness, coughing, dysphonia, pain, throat and neck pain, headache, insomnia, indigestion, muscle twitch, nausea or vomiting, impaired sense of touch, tingling sensation in the skin (Yap et al., 2020). Another possible limitation of vagus nerve stimulation in misophonia is that there have been no known articles published related to it, and hence the efficacy of misophonics cannot be hypothesised or assumed unless related articles are published.

4.0 CONCLUSIONS