Functional brain abnormalities localized in 55 chronic tinnitus patients: fusion of SPECT coincidence imaging and MRI

Abstract

Tinnitus is often defined as the perception of sounds or noise in the absence of any external auditory stimuli. The pathophysiology of subjective idiopathic tinnitus remains unclear. The aim of this study was to investigate the functional brain activities and possible involved cerebral areas in subjective idiopathic tinnitus patients by means of single photon emission computerized tomography (SPECT) coincidence imaging, which was fused with magnetic resonance imaging (MRI). In this cross-sectional study, 56 patients (1 subject excluded) with subjective tinnitus and 8 healthy controls were enrolled. After intravenous injection of 5 mCi F18-FDG (fluorodeoxyglucose), all subjects underwent a brain SPECT coincidence scan, which was then superimposed on their MRIs. In the eight regions of interest (middle temporal, inferotemporal, medial temporal, lateral temporal, temporoparietal, frontal, frontoparietal, and parietal areas), the more pronounced values were represented in medial temporal, inferotemporal, and temporoparietal areas, which showed more important proportion of associative auditory cortices in functional attributions of tinnitus than primary auditory cortex. Brain coincidence SPECT scan, when fused on MRI is a valuable technique in the assessment of patients with tinnitus and could show the significant role of different regions of central nervous system in functional attributions of tinnitus.

Figure 1

Fusion of single photon emission computerized tomography coincidence imaging coincidence imaging and magnetic resonance imaging in tinnitus-related brain abnormalities in one subject. regions of interests (ROIs) were used for semiquantitative analysis of hyperactivity. (A and B) Abnormalities in frontal and inferotemporal lobes. Hyperactivity of brain was defined visually and semiquantitatively analysis. Activity ratio was calculated as follows: for unilaterally involved subjects, after localized abnormal area visually, regions of interests (1pixel size) were drawn and the count per voxel were compared with the ROIs in the other side. In bilaterally involved subjects, counts per voxel of the abnormal areas were compared with similar ROIs on cerebellum (as reference). We also classify all activity ratios as below: 1=normal, 1 to 1.5=mild, 1.5 to 2=moderate, and >2 as sever hyperactivity.