Maladaptive plasticity in tinnitus — triggers, mechanisms and treatment

Abstract

Tinnitus is a phantom auditory sensation that reduces quality of life for millions worldwide and for which there is no medical cure. Most cases are associated with hearing loss caused by the aging process or noise exposure. Because exposure to loud recreational sound is common among youthful populations, young persons are at increasing risk. Head or neck injuries can also trigger the development of tinnitus, as altered somatosensory input can affect auditory pathways and lead to tinnitus or modulate its intensity. Emotional and attentional state may play a role in tinnitus development and maintenance via top-down mechanisms. Thus, military in combat are particularly at risk due to combined hearing loss, somatosensory system disturbances and emotional stress. Neuroscience research has identified neural changes related to tinnitus that commence at the cochlear nucleus and extend to the auditory cortex and brain regions beyond. Maladaptive neural plasticity appears to underlie these neural changes, as it results in increased spontaneous firing rates and synchrony among neurons in central auditory structures that may generate the phantom percept. This review highlights the links between animal and human studies, including several therapeutic approaches that have been developed, which aim to target the neuroplastic changes underlying tinnitus.

Somatic Tinnitus

“…This case demonstrates that tinnitus modulation can be found even when no somatic disorder is present; in fact, somatic modulation of tinnitus is a widespread condition that can be present with or without underlying somatic disorders 31,40 . Furthermore, as previously discussed, several authors reported a large capability of somatic tinnitus modulation in multiple patient series ranging between 65.3% and 83.3% 32,35,[41][42][43]45,47,61,65 . In this patient, the negative history for self-reported somatic disorder suggests caution while taking into account a somatic origin for his tinnitus.…”

“…Levine 42 described this phenomenon as a "fundamental characteristic of tinnitus", like its auditory and affective attributes. Somatic modulation has been reported in approximately two-thirds of tinnitus patients 35,43 ; other studies revealed tinnitus modulation in 85% 45 TMJ is the most common affected region in patients with somatic tinnitus. Rubinstein studied 102 individuals with tinnitus reporting that about one-third of the patients had influence on tinnitus by mandibular movements and/ or pressure applied to the temporomandibular joint [63][64][65] and found that subjects with tinnitus had a significantly higher prevalence of cranio-mandibular disorders.…”

“…These patients are considered to have otic tinnitus 2 ; extensive research has been done to identify protective drugs and management strategies for patients with tinnitus and hearing loss [26][27][28][29][30] . Tinnitus can be evoked or modulated by inputs from the somato-sensory, somato-motor and visualmotor systems in some individuals [31][32][33][34][35][36][37][38][39] . This means that the psychoacoustic attributes of tinnitus (loudness and pitch) might change-though often only temporarilyfollowing external stimuli, such as the forceful muscle contractions of head, neck and limbs 31,[40][41][42][43][44] , orofacial movements 45 , eye movements in the horizontal or vertical axis 46,47 , pressure on myofascial trigger points 48,49 , cutaneous stimulation of the hand/fingertip region 50 , and of the face 43 ; electrical stimulation of the median nerve and hand or finger movements 51 .…”

Radiological Evaluation of Inner Ear with Computed Tomography in Patients with Unilateral Non-Pulsatile Tinnitus

“…Numerous types of treatment modalities, such as oral medication, retraining therapy, or transtympanic laser therapy, have been attempted [3] . However, because of the unclear etiology of tinnitus in most cases, clinicians often fail to constitute a proper algorithm that can effectively treat it.…”

Somatic Modulation of Tinnitus: A Review and Some Open Questions

“…Data from animal studies indicates the relay of afferent somatosensory information by the trigeminal and dorsal root ganglia; somatosensory input causes changes in the firing rate and synchrony in dorsal cochlear nucleus neurons that may be at the base of somatic tinnitus. 16,17 The modulation of tinnitus by somatic movements is widely diffused among acute and chronic tinnitus sufferers and has been reported to involve one to two-thirds of them with different patient series ranging between 65% and 83%. [18][19][20][21][22] Several authors have developed sets of maneuvers to modulate tinnitus; a detailed description of these maneuvers has been published by Won in 2013 comparing the prevalence and characteristics of somatic modulation found in six previous studies.…”