Effect of low-frequency rTMS on motor neuron excitability after stroke

Abstract

The purpose of this study was to test the effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) over the non-lesional hemisphere on motor neuron excitability of the paretic upper limb in post-stroke patients by electrophysiological examination. Thirteen post-stroke patients with spastic upper limb hemiparesis were studied (age, 57.5 ± 11.1 years; time after stroke, 55.2 ± 51.4 months). Low-frequency rTMS of 1 Hz was applied for 20 min to the motor cortex of the non-lesional hemisphere. The M-response amplitude and F-wave parameters were recorded in the abductor pollicis brevis muscle following stimulation of the median nerve in both the affected and unaffected upper limbs. The F-wave frequency, F-max/M ratio (ratio of maximum F-wave amplitude to M-response amplitude), and F-mean/M ratio (the ratio of mean F-wave amplitude to the M-response amplitude) were measured before and after the 20-min rTMS, analyzed for both limbs. Application of low-frequency rTMS did not result in significant changes in the frequency of F-wave and F-max/M ratio in both upper limbs, but significantly decreased F-mean/M ratio in the affected upper limb (P < 0.005), but not in the unaffected limb. Low-frequency rTMS applied to the non-lesional hemisphere might be potentially useful therapeutically for post-stroke patients with spastic upper limb hemiparesis.