Hilbert-Huang transform analysis of somatosensory and motor evoked potential for intraoperative neurophysiologic monitoring

Abstract

Introduction: Motor surround inhibition (mSI) has been proposed in the selectively execute desired motor programs. The cerebellum play important role in motor control and co-ordination of movements. The aim of the study is to research the relationship with disrupted mSI and function of central nervous system during motor performance using functional MRI in patients with cerebellar ataxia. Methods and Patients: Seven healthy subjects (mean ages 34.7 9.1 years, all men) and seven patients with pure cerebellar ataxia (mean ages 60.7 11.9 years, 4 men and 3 women, six patients with SCA6, one SCA31 patient) were enrolled. Surrounding inhibition study: The experiment of surround inhibition was done according to S.Beck and M.Hallett. The EMG were recorded in both right FDI and APB. mSI was evaluated as the ratio of MEP size of APB to that of FDI. MEPs were measured by using single TMS which was given before signal and 100ms, 150ms and 1200ms after signal. Functional magnetic imaging for task and testing procedures: Each subject participated in two sessions during they performed righthand tapping. Results: In normal subjects, significant mSI was found within 150ms after finger tapping. However, FHD showed no SI during finger tapping. The finding of fMRI showed hyperactivity of motor area and excessive activation in prefrontal area. And also hyperactivity is observed in both cerebellar hemispheres. Discussion: In normal subjects, significant mSI was observed within 150ms. Functional MRI showed significant activation in cerebellum during tasks. In cerebellar ataxia patients, mSI study showed loss of surround inhibition of finger movement. Hypoactivation of cerebellum was observed in fMRI. These findings suggest that cerebellum may have some contribute to the generation of mSI.