Excitability of the supplementary motor area in Parkinson's disease depends on subcortical damage.
BACKGROUND
Cortical dysfunctioning significantly contributes to the pathogenesis of motor symptoms in Parkinson's disease (PD).


OBJECTIVE
We aimed at testing whether an acute levodopa administration has measurable and specific cortical effects possibly related to striatal dopaminergic deficit.


METHODS
In thirteen PD patients, we measured the electroencephalographic responses to transcranial magnetic stimulation (TMS/EEG) of the supplementary motor area and superior parietal lobule (n = 8) before and after an acute intake of levodopa. We also performed a single-photon emission computed tomography and [123I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane to identify the more affected and the less affected brain side in each patient, according to the dopaminergic innervation loss of the putamen. Cortical excitability changes before and after an acute intake of levodopa were computed and compared between the more and the less affected brain side at the single-patient as well as at the group level.


RESULTS
We found that levodopa intake induces a significant increase (P < 0.01) of cortical excitability nearby the supplementary motor area in the more affected brain side, greater (P < 0.025) than in the less affected brain side. Notably, cortical excitability changes nearby the superior parietal lobule were not statistically significant.


CONCLUSIONS
These results strengthen the idea that dysfunction of specific cortico-subcortical circuits may contribute to pathophysiology of PD symptoms. Most important, they support the use of navigated TMS/EEG as a non-invasive tool to better understand the pathophysiology of PD.
['Casarotto|Silvia|S|', 'Turco|Francesco|F|', 'Comanducci|Angela|A|', 'Perretti|Alessio|A|', 'Marotta|Giorgio|G|', 'Pezzoli|Gianni|G|', 'Rosanova|Mario|M|', 'Isaias|Ioannis U|IU|']
D000368:Aged D000071080:Cortical Excitability D004569:Electroencephalography D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D009044:Motor Cortex D010300:Parkinson Disease D015899:Tomography, Emission-Computed, Single-Photon D050781:Transcranial Magnetic Stimulation
Levodopa Transcranial magnetic stimulation Putamen Dopamine Electroencephalography