Lateralization of functional magnetic resonance imaging (fMRI) activation in the auditory pathway of patients with lateralized tinnitus

Abstract

Introduction Tinnitus is hypothesized to be an auditory phantom phenomenon resulting from spontaneous neuronal activity somewhere along the auditory pathway. We performed fMRI of the entire auditory pathway, including the inferior colliculus (IC), the medial geniculate body (MGB) and the auditory cortex (AC), in 42 patients with tinnitus and 10 healthy volunteers to assess lateralization of fMRI activation. Methods Subjects were scanned on a 3T MRI scanner. A T2*-weighted EPI silent gap sequence was used during the stimulation paradigm, which consisted of a blocked design of 12 epochs in which music presented binaurally through headphones, which was switched on and off for periods of 50 s. Using SPM2 software, single subject and group statistical parametric maps were calculated. Lateralization of activation was assessed qualitatively and quantitatively. Results Tinnitus was lateralized in 35 patients (83%, 13 right-sided and 22 left-sided). Significant signal change (P corrected <0.05) was found bilaterally in the primary and secondary AC, the IC and the MGB. Signal change was symmetrical in patients with bilateral tinnitus. In patients with lateralized tinnitus, fMRI activation was lateralized towards the side of perceived tinnitus in the primary AC and IC in patients with right-sided tinnitus, and in the MGB in patients with left-sided tinnitus. In healthy volunteers, activation in the primary AC was left-lateralized. Conclusion Our paradigm adequately visualized the auditory pathways in tinnitus patients. In lateralized tinnitus fMRI activation was also lateralized, supporting the hypothesis that tinnitus is an auditory phantom phenomenon.

The impact of tinnitus on adult Nigerians: health related Quality of Life assessment of sufferers using the Hospital Anxiety and Depression Scale (HADS) and the RAND-36 item health survey 1.0 questionnaire

“…These same brain areas also are responsible for the perception of tinnitus and tinnitus related comorbid distress 7,38,39 i.e., the limbic system responsible for emotions processes the neural impulses it receives from the auditory system 40 .…”

“…The negative impact of tinnitus on the HRQoL of sufferers is clearly documented in several research studies 5,9,29,39 especially in patients presenting with decompensated tinnitus 11 because patients with compensated tinnitus easily get accustomed to the sound and are less bothered by it 40 . In this study however, we did not set out to classify our patients into these two major groups.…”

The mechanisms of tinnitus: Perspectives from human functional neuroimaging

“…However, one finding that appears inconsistent with either model was that the magnitude of the noise-evoked activity in patients with bilateral TI was similar to the controls. **** Figure 3 here**** A recent fMRI study has similarly examined the pattern of sound-evoked activity in 35 patients with lateralised TI and explained the results within the framework of the 'saturation' model (Smits et al, 2007). Notably, the response to the bilateral music was smaller on the side contralateral than ipsilateral to TI.…”

Residual Inhibition Functions Overlap Tinnitus Spectra and the Region of Auditory Threshold Shift

“…ence of thalamocortical and lateral synapses on auditory neurons by the masker or other mechanisms that subside with a time constant on the order of 30 s. Although this account of tinnitus and RI emphasizes the role of A1 as the site of functional changes, effects occurring here could modulate activity in other brain regions that have been implicated in tinnitus by functional imaging studies (Melcher et al 2000;Lockwood et al 2001;Leaver et al 2006;Wienbruch et al 2006;Smits et al 2007;Schlee et al 2007;Weisz et al 2007). …”