Objective: To test the intracortical plasticity of motor cortex in treatment-naïve (de novo) patients with Parkinson’s disease (PD), by means of transcranial static magnetic field stimulation (tSMS). 

Background: De novo PD patients are characterized by absent corticospinal plasticity and reduced short-interval intracortical inhibition (SICI), a GABAAR-mediated inhibition in human motor cortex. We recently introduced tSMS, a non-invasive brain stimulation technique that is able to induce a short-lasting reduction in corticospinal excitability and an increase in SICI in healthy controls.

Methods: We performed a single-blind study to assess cortical excitability before and immediately after 10-min of tSMS applied to the more affected motor cortex in patients with de novo PD and in a group of healthy controls. No patients were on dopaminergic treatment. Corticospinal excitability was evaluated by the amplitude of motor evoked potentials (MEPs) elicited by single-pulse transcranial magnetic stimulation (TMS) and SICI assessed by a paired- pulse TMS protocol. 

Results: In healthy controls, tSMS significantly reduced MEP amplitudes while increasing SICI. In de novo PD patients, tSMS did not modulate MEP amplitudes, but – similarly to the healthy controls – significantly increased SICI.

Conclusions: These results confirm that dopamine depletion leads to deficient corticospinal plasticity, but they show that intracortical plasticity – assessed by SICI – is preserved in de novo PD. 

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MDS Abstracts - https://www.mdsabstracts.org/abstract/intracortical-plasticity-is-preserved-in-de-novo-parkinsons-disease-a-tsms-study/