Evaluation of the motor cortical excitability changes after ischemic stroke

Background: We evaluated progressive changes in excitability of motor cortex following ischemic stroke using Transcranial Magnetic Stimulation (TMS). Materials and Methods: Thirty-one patients (24 men, 7 women; age 37.3 +/- 8.2 years) were recruited and TMS was performed using Magstim 200 stimulator and a figure-of-eight coil. Resting motor threshold (RMT) was recorded from affected and unaffected hemispheres and motor evoked potential (MEP) was recorded from contralateral FDI muscle. Central motor conduction time (CMCT) was calculated using F wave method. All measurements were done at baseline (2nd), 4th, and 6th week of stroke. Results: Affected hemisphere: MEP was recordable in 3 patients at baseline (all had prolonged CMCT). At 4 weeks, MEP was recordable in one additional patient and CMCT remained prolonged. At 6 weeks, CMCT normalized in one patient. RMT was recordable (increased) in 3 patients at baseline, in one additional patient at 4 weeks, and reduced marginally in these patients at 6 weeks. Unaffected hemisphere: MEP was recordable in all patients at baseline, and reduced significantly over time (2nd week 43.52 +/- 9.60, 4th week 38.84 +/- 7.83, and 6th week 36.85 +/- 7.27; P < 0.001). The CMCT was normal and remained unchanged over time. Conclusion: The increase in excitability of the unaffected motor cortex suggests plasticity in the post-stroke phase.