In this study, we investigated the relationship between the motor evoked potentials obtained from trunk muscles and the clinical function of trunk muscle. Twenty patients with unilateral hemispheric stroke and 11 healthy adults were examined. The responses of the bilateral external oblique muscles and the erector spinae muscles to the magnetic stimulation of multiple sites over both cortical hemispheres were recorded. Trunk muscle performance was assessed using the Trunk Control Test and Stroke Impairment Assessment Set. In the stroke group, stimulation of the affected hemisphere resulted in a motor evoked potential in only one patient, while the other 19 stroke patients produced no response to stimulation of the affected hemisphere. Stimulation of the unaffected hemisphere evoked bilateral responses in 19 patients. Further, stimulation of the unaffected hemisphere in the stroke group produced larger motor evoked potentials in the ipsilateral muscles than the motor evoked potentials recorded in the ipsilateral muscles of the control group. The clinical assessment scores of trunk function (i.e. Trunk Control Test and trunk items of Stroke Impairment Assessment Set) were correlated with the amplitudes of the motor evoked potentials of the ipsilateral external oblique muscle that were evoked by stimulation of the unaffected hemisphere. Our results suggest that the recovery of trunk function after stroke is associated with an increase in ipsilateral motor evoked potentials in the external oblique muscle upon stimulation of the unaffected hemisphere, suggesting a role for compensatory activation of uncrossed pathways in recovery of trunk function.

The pixel values in fat/water suppression magnetic resonance (MR) images were measured for the thigh muscles of 18 healthy volunteers to investigate age-related changes in muscle water and fat content. Prior to the human studies the reproducibility of the data was confirmed using phantoms. The standard deviations (SDs) of the pixel values for one of the phantoms examined five times were found to be within a relatively narrow range. Both the pixel values in the fat suppression images (PV1) and the pixel values in the water suppression images (PV2) of all muscles tended to be higher in the oldest group. The results indicate that the water and fat content of skeletal muscles is higher in aged persons. Moreover, the PV1 in the non-dominant limbs was found to be increased in the extensor muscles of the knee joints, while the PV2 in the non-dominant limbs did not show a significant difference, except for the rectus femoris.

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