Bilateral low frequency rTMS of the primary motor cortex may not be a suitable treatment for levodopa-induced dyskinesias in late stage Parkinson's disease.

Background: In late stage Parkinson patients there is an unmet need for new treatments to adequately control motor complications, especially dyskinesias. In several preliminary studies, it has been suggested that applying unilateral low-frequency repetitive transcranial magnetic stimulation (LF rTMS), delivered at the primary motor cortex (MC) or the supplementary motor area (SMA), may reduce levodopa-induced dyskinesias (LID), either in a single or a multiple session stimulation protocol. In our current clinical research, we examined whether single or multiple (accelerated) sham-controlled bilateral LF rTMS session(s) applied to the primary motor cortices are able to reduce levodopa-induced dyskinesias in patients with advanced Parkinson's disease.

Methods: During a levodopa challenge test, we first investigated the effect of a single sham-controlled session of LF rTMS (1 Hz) to both left and right primary motor cortical areas on dyskinesias and motor function in nine late-stage Parkinson patients. In a second study, patients were assigned to a five day sham-controlled bilateral motor cortex cross-over accelerated LF rTMS protocol and effects on dyskinesias, motor and executive function and emotional status were assessed.

Results: We found no significant clinical change in levodopa-induced dyskinesias and motor function with either stimulation protocol.

Conclusions: One or multiple bilateral LF rTMS session(s) applied to the primary motor cortex were unable to reduce levodopa-induced dyskinesias in late-stage Parkinson patients.