Analysis of MEP parameters in patients with post stroke spasticity in relation with rTMS therapy

Spasticity is a common complication of stroke limiting patient's daily activities. Transcranial magnetic stimulation is a painless and non-invasive method that can potentially reduce post-stroke spasticity (PSS). Motor evoked potentials (MEP) parameters have been shown to be related with prognosis of stroke patients. In this study we analysed the changes in MEP parameters after 3 sessions of low Hz rTMS therapy among PSS patients.

Patients with upper limb spasticity after stroke of 3 months duration were randomised into active and sham groups. In the active group three sessions of 1000 pulses, 1 Hz rTMS at an intensity of 90% of resting motor threshold were applied to the primary motor area of the contra-lesional hemisphere over three consecutive days. Sham rTMS intensity was 0% with coil placed over scalp for same duration. MEP was measured pre and post therapy in each group.

106 patients were screened of which 50 patients were selected. 25 patients were allotted to active group and 25 to sham group. Mean amplitude of MEP on stimulation of normal side was 1.98±1.70 mV before versus 1.53±1.16 mV after therapy showing significant reduction p=0.001 (95% CI-.135 - -.630). Similarly, there was significant increase in latency after therapy [22.92±2.25 ms vs 24.26±2.62 ms, p=0.001 (95% CI-2.0 - -.96)]. There was no significant change in amplitude (1.05±.69 mV vs 1.17±1.01 mV) or latency (23.66±2.45 ms vs 24.05±2.58 ms) after therapy in sham group.

MEP parameters revealed even three sessions of therapy can be helpful in supressing normal hemisphere. We found reduction in amplitude and increase in latency of MEP after low Hz rTMS therapy in contra-lesional hemisphere suggesting its suppression after therapy.