The influence of one session of low frequency rTMS on pre-supplementary motor area metabolites in late stage Parkinson's disease

OBJECTIVE: To study the effect of Low Frequency repetitive Transcranial Magnetic Stimulation (LF rTMS) on brain metabolites in late stage Parkinson's disease (PD) patients (disease duration at least 4 years and Hoehn and Yahr (1969) score at least 2 in OFF). Several neuroimaging data support a role for pre-Supplementary Motor Area (pre-SMA) involvement in the pathogenesis of Parkinson's disease. Proton magnetic resonance spectroscopy (1H-MRS) measures in vivo metabolites, but results in PD brain remain conflicting and little is known of the effect of LF rTMS thereupon.

METHODS: We investigate the neurochemical profile of the right pre-SMA in 17 late stage PD patients (11 male and 6 female, mean age of 71 years) before and after one session of sham controlled 1 Hz rTMS (1000 pulses, 16 minutes), focusing on the tNAA/tCr and tCho/tCr ratios.

RESULTS: The tNAA/tCr ratio was unaffected by one session of LF rTMS. We did observe a significant effect of real LF rTMS on the tCho/tCr ratio, inversely correlated with disease duration, and not related to the presence of dyskinesias. As expected, one session of LF rTMS did not affect clinical outcome.

CONCLUSIONS: LF rTMS at the right pre-SMA in late stage Parkinson's disease patients does not alter tNAA/tCr, but influences tCho/tCr ratio, in particular in patients with shorter disease duration.

SIGNIFICANCE: Pre-SMA LF rTMS seems to influence membrane turnover, more importantly in patients with shorter disease duration. Larger LF rTMS treatment studies applying multiple sessions are needed.