Ultra-high-frequency acoustic stimulation and tinnitus control: a positron emission tomography study

Abstract

Ultra-high-frequency (UHF) external acoustic stimulation with the UltraQuiet device (UQ) has been reported to provide significant relief of severe disabling-type tinnitus. The nuclear medicine imaging technique of positron emission tomography (PET) was selected as a monitoring system to compare objectively metabolic alterations in brain function before and after UHF/UQ and to correlate the PET data with the subjective behavioral response of patients reporting tinnitus relief. PET of brain was completed on 6 patients randomly selected from a cohort of 15 patients included in a protocol to establish long-term tinnitus relief with UHF/UQ. Twelve specific regions of interest (ROI) were selected for PET of brain examination on the basis of results obtained with single-photon emission computed tomography (SPECT) of brain examinations recommended for patients with severe disabling-type tinnitus and demonstrating significant perfusion asymmetries in the right and left brain ROI of the primary auditory cortex; frontal, temporal, parietal, and medial temporal lobes; and cerebellum. PET of brain results included ratios of post- and pre-UHF/UQ stimulation that demonstrated no random response in the selected PET of brain ROI and ratios of post- and pre-UHF/UQ stimulation that demonstrated three categories of response in the selected PET brain ROI for all six patients: hypermetabolism in three patients; hypometabolism in two; and a mixed response in one. Correlation was established for each patient among PET and electrophysiological responses of alteration in minimal masking levels, the residual UHF neuronal response as reflected in the UHF audiogram, and the subjective reported behavioral responses of patients (obtained from outcome questionnaires for tinnitus relief, which focused on tinnitus intensity, annoyance, severity index, and a subjective scale of value of the UHF/UQ device for tinnitus relief. The subjective behavioral response for tinnitus relief with UHF/UQ was found to reflect a dual effect: acoustic stimulation of the residual neuronal function in the UHF range (10-14 kHz) and audiometric thresholds of 40-50 dB sound pressure level (SPL), and the metabolic activity at brain cortex for neuronal reprogramming. The PET of brain categories of response suggested that the UHF/UQ "masking" is predominantly reflective of neuronal reprogramming at the brain cortex. Nuclear medicine PET of brain imaging has provided an objective monitoring system for attempting to establish the efficacy of UHF/UQ for tinnitus relief. No complication of the tinnitus was reported secondary to the PET of brain examination. This limited PET of brain study supports the clinical recommendation of the efficacy of UHF/UQ external acoustic stimulation for a selected population of patients with tinnitus of the severe disabling type.