Functional MRI in normal subjects and sudden unilateral sensorineural hearing loss patients

Abstract

Brain activities in responses to amplitude modulation (AM) was evaluated using functional MRI (fMRI) in subjects with sudden unilateral sensorineural hearing loss (SSNHL) and those with normal hearing (NH). Totally 25 subjects with normal hearing and 30 with SSNHL were examined with fMRI in response to AM tones of 500, 2000 and 4000 Hz respectively with the modulation frequency at 8 Hz. The fMRI was examined within 12 days after the onset of SSNHL. The AM signals were presented at 96 dB SPL binaurally. An event-related design was combined with a sparse clustered volume acquisitioning paradigm in data collection in the attempt to reduce the influence of acoustic scanner noise. SPM2 software was used for offline data analyzing. Brain activation in fMRI image was found mainly in the primary auditory cortex (PAC) in both subjects with NH and SSNHL NH subjects showed a clear lateralization to left cerebral hemisphere(11/16) and SSNHL patients showed a lateralization ipsilateral to the impaired ear(16/22). The activation voxel and intensity shown in BOLD were found to be decreased with increasing signal frequency in both groups. The difference in the lateralization between the two groups suggests that an adaptive process occurs shortly after the onset of SSNHL