Evaluación de terapias acústicas como tratamiento de tinnitus crónico y refractario

Acoustic therapies have gain relevance due to the sound effects on human body functioning. The ear does not only make humans hear, but it also provides them kinaesthetic sense and significantly modifies the limbic system. Furthermore, to receive and perceive sounds goes beyond to decode and identify auditory stimuli. Sound is the propagation of mechanical waves that cause vibrations in the matter, and which can vibrate at different frequencies. This means that sound may modulate the human oscillation frequencies. It is possible to consider that sound-based treatments could reverse neural synchrony abnormalities in the auditory cortex that are generating tinnitus. Acoustic therapies generally seek to relieve stress and tension caused by tinnitus (i.e., to have a direct effect on the limbic system, which activates the parasympathetic nervous system), reduce tinnitus perception, or redirect the attention, which has been entirely attracted by tinnitus. To date, a large number of acoustic therapies have been applied to treat tinnitus, with the exception of Binaural beats. The effect that produces those auditory stimuli is, however, not well understood yet. Furthermore, the conventional clinical protocol is based on a trial-error procedure, and there is not a formal and adequate treatment follow-up. At present, the widely used to evaluate acoustic therapies is by means of subjective methods such as Visual Analog Scale (VAS) and ad-hoc questionnaires. Electroencephalographic (EEG) has become a standard brain imaging tool to quantify and qualify neural oscillations, which are basically spatial, temporal, and spectral patterns associated with particular perceptual, cognitive, motor and emotional processes. Neural oscillations have been traditionally studied on the basis of eventrelated experiments, where time-locked and phase-locked responses (i.e., event-related potentials) along with time-locked but not necessary phase-locked responses (i.e., event-related (de) synchronization) have been essentially estimated. Both potentials and levels of synchronization related to auditory stimuli are herein proposed to assess the effect of acoustic therapies. In conclusion, it has been previously demonstrated that acoustic therapies have moderate beneficial effects as an alternative treatment of chronic and refractory tinnitus. However, an integral treatment program based on different acoustic therapy designed according to the patient clinical history could increase the sound effects. Moreover, this thesis pursues to establish an objective methodology to treat tinnitus with acoustic therapies based on EEG activity evaluation