Abstract
Transcranial static magnetic field stimulation (tSMS) is a recent low-cost non-invasive brain stimulation technique that decreases cortical excitability in healthy subjects. The objective of the present study was to test the ability of tSMS to modulate cortical excitability in patients with Parkinson’s disease. We performed a randomized double-blind sham-controlled cross-over study to assess cortical excitability before and immediately after tSMS (or sham) applied for 10 min to the more affected motor cortex of patients with Parkinson’s disease. Cortical excitability was quantified by the amplitude of motor evoked potentials (MEPs) elicited by single-pulse transcranial magnetic stimulation (TMS). tSMS significantly decreased MEP amplitudes in patients OFF medication (after overnight withdrawal of dopaminergic drugs), but not ON medication (after an acute dose of levodopa). The between-patients variability of tSMS-induced changes was significantly greater ON medication. The variability ON medication could be partly explained by disease progression, i.e. the more advanced the patient, the more likely it was to observe a switch from inhibitory tSMS plasticity OFF medication to paradoxical facilitatory plasticity ON medication. These results suggest that tSMS induces dopamine-dependent changes of cortical excitability in patients with Parkinson’s disease.
Highlights
Non-invasive brain stimulation (NIBS) techniques offer a set of tools to investigate plasticity phenomena in the human motor cortex[1, 2]
In patients with Parkinson’s disease, a large number of studies reported profound alterations of cortical plasticity induced by excitatory NIBS techniques – with a complex phenomenology that depends on the technique employed, the clinical asymmetry of the patients, the stage of the disease and the administration of levodopa – whereas only few studies investigated cortical plasticity induced by inhibitory NIBS techniques[13,14,15]
motor evoked potentials (MEPs) amplitude significantly decreased compared to baseline after Transcranial static magnetic field stimulation (tSMS) at 0–2 min (Dunnett, p = 0.0010), 2–4 min (p = 0.0010) and 4–6 min (p = 0.0229), whereas it did not change after sham (F5,60 = 1.3, p = 0.27)
Summary
Non-invasive brain stimulation (NIBS) techniques offer a set of tools to investigate plasticity phenomena in the human motor cortex[1, 2]. In patients with Parkinson’s disease, a large number of studies reported profound alterations of cortical plasticity induced by excitatory NIBS techniques – with a complex phenomenology that depends on the technique employed, the clinical asymmetry of the patients, the stage of the disease and the administration of levodopa A key observation is that inhibitory cortical plasticity – induced by continuous theta-burst stimulation (cTBS) – can be observed in treated non-dyskinetic patients after overnight withdrawal of dopaminergic medication (OFF) but is disrupted by acute levodopa administration (ON)[15]. The aim of the present study was to investigate the ability of tSMS to modulate cortical excitability in patients with Parkinson’s disease
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