Neurophysiological evaluation of motor corticospinal pathways by TMS in idiopathic early-onset Parkinson's disease.

Objective: In a previous study we found altered motor corticospinal conduction in patients with early-onset Parkinson's disease (EOPD) and parkin gene mutations (PARK2). Aim of the present study was to evaluate central motor conduction in patients with EOPD, negative for parkin mutations to establish if prolonged CMCT is specific of PARK2 or it may be present in other EOPD patients.

Methods: Eleven patients with non-PARK2 EOPD underwent transcranial magnetic stimulation (TMS) to evaluate central motor conduction time (CMCT). Motor threshold (MT), motor evoked potential (MEP) amplitude, central silent period threshold (cSPT), and duration were also determined.

Results: All patients but one showed normal CMCT. CMCT and the other electrophysiological data did not differ significantly between patients and healthy controls, except for cSPT mean value which was higher in patients than in controls (p=0.008). No significant correlation was found between electrophysiological and clinical data in EOPD patients. CMCT was significantly prolonged in six PARK2 patients compared to non-PARK2 patients.

Conclusions: We conclude that CMCT is usually normal in idiopathic EOPD: we suggest that in presence of a prolonged CMCT the diagnosis of PARK2 should be considered.

Significance: CMCT may represent a simple electrophysiological test that could be utilized in an early phase of diagnosis to differentiate PARK2 patients from those with idiopathic EOPD.