6-Hz primed low-frequency rTMS to contralesional M1 in two cases with middle cerebral artery stroke

Abstract

This case study contrasted two subjects with stroke who received 6-Hz primed low-frequency repetitive transcranial magnetic stimulation (rTMS) to the contralesional primary motor area (M1) to disinhibit ipsilesional M1. Functional magnetic resonance imaging (fMRI) showed that the intervention disrupted cortical activation at contralesional M1. Subject 1 showed decreased intracortical inhibition and increased intracortical facilitation following intervention during paired-pulse TMS testing of ipsilesional M1. Subject 2, whose precentral knob was totally obliterated and who did not show an ipsilesional motor evoked potential at pretest, still did not show any at posttest; however, her fMRI did show a large increase in peri-infarct zone cortical activation. Behavioral results were mixed, indicating the need for accompanying behavioral training to capitalize on the brain organization changes induced with rTMS.

Figure 1

Activation for subject 1 before (pretest) and after (posttest) intervention. Maps show a reduction in active voxels in left (contralesional) sensorimotor cortex (green circles) from pretest to posttest and an increase in active voxels and intensity in right (ipsilesional) sensorimotor cortex (yellow circles).

Figure 2

Activation for subject 2 before (pretests 1 and 2) and after (posttest) intervention. Maps show a small increase in activation in the left (contralesional) sensorimotor cortex (green circles) from pretest 1 to pretest 2, followed by a reduction at posttest. In the ipsilesional hemisphere, an increase in peri-infarct zone activation is seen at posttest, including in the small amount of surviving sensorimotor cortex (yellow circles).

Figure 3

Excitability of ipsilesional primary motor area in patient 1 before (pretest) and after (posttest) intervention. Each bar represents mean ± standard deviation of 10 measurements. (MEP=motor evoked potential, *p=0.029, **p=0.017)