Activation of frontal premotor areas during suprathreshold transcranial magnetic stimulation of the left primary sensorimotor cortex: a glucose metabolic PET study.

We employed cerebral (18)Fluoro-deoxyglucose positron emission tomography ([(18)F]FDG-PET) to visualize neuronal activation of the frontal motor and premotor cortex during suprathreshold repetitive transcranial magnetic stimulation (rTMS) applied to the left primary sensorimotor hand area (SM1(HAND)). Twelve right-handed normal subjects underwent two [(18)F]FDG-PET measurements at baseline without rTMS and during suprathreshold 2 Hz rTMS of the left SM1(HAND). In the rTMS condition, 1,800 magnetic stimuli at an intensity of 140% of motor-resting threshold were delivered immediately after intravenous injection of [(18)F]FDG. Relative differences in the normalized regional cerebral metabolic rate for glucose (rCMRglc) between the rTMS condition and baseline were determined using a voxel-by-voxel Student's t-test and a volume-of-interest analysis. Data analysis was a priori restricted to primary motor and premotor areas in the frontal cortex, namely the SM1, the supplementary motor area (SMA), the lateral premotor cortex (PMC), and the caudal anterior cingulate cortex (ACC) of either hemisphere. In addition to a relative increase in normalized rCMRglc in the stimulated SM1(HAND), suprathreshold rTMS was associated with well-localized increases in normalized rCMRglc in the caudal SMA and ACC on the medial wall of the frontal cortex and in the right precentral gyrus in the lateral PMC rostrally to the SM1. These data demonstrate that a selective activation of the SM1(HAND) is paralleled by an activation of a distinct set of remote premotor areas, suggesting a functional interaction between the primary motor and premotor cortex in humans.

Short-term motor improvement after sub-threshold 5-Hz repetitive transcranial magnetic stimulation of the primary motor hand area in Parkinson's disease.

Ten unmedicated patients with Parkinson's disease received sub-threshold 5-Hz repetitive transcranial magnetic stimulation (rTMS) over the primary motor hand area (M1(HAND)) contralaterally to the more affected upper limb. Compared to a midfrontal sham-rTMS, real-rTMS over M1(HAND) was associated with a significant decrease in the global motor UPDRS score 1 h after the cessation of rTMS. This was mainly due to a clinical improvement in the arm contralaterally to the stimulated M1(HAND). These preliminary data suggest that focal rTMS of M1(HAND) may have a therapeutic potential in PD.