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. 2016 Jul:28:23-8.
doi: 10.1016/j.parkreldis.2016.03.023. Epub 2016 Apr 1.

Mild cerebello-thalamo-cortical impairment in patients with normal dopaminergic scans (SWEDD)

Tommaso Schirinzi  1 , Francesco Di Lorenzo  2 , Viviana Ponzo  3 , Maria Giuseppina Palmieri  1 , Anna Rita Bentivoglio  4 , Orazio Schillaci  5 , Antonio Pisani  2 , Giacomo Koch  6
Affiliations

Mild cerebello-thalamo-cortical impairment in patients with normal dopaminergic scans (SWEDD)

Tommaso Schirinzi et al. Parkinsonism Relat Disord. 2016 Jul.

Abstract

Introduction: Patients with Scans-Without-Evidence-of-Dopaminergic-Deficit (SWEDD) often present asymmetric rest tremor not responsive to levodopa. Although a dystonic origin of this tremor has been proposed, the underlying pathophysiology of such condition is still unclear. An abnormal activity in the Cerebello-Thalamo-Cortical circuit is involved in the pathogenesis of tremor and other movement disorders. Here we used different paradigms of cerebellar transcranial magnetic stimulation to evaluate the Cerebello-Thalamo-Cortical functioning in patients with normal scans.

Methods: Cerebello-Thalamo-Cortical circuit was investigated in 12 patients with normal scans, 8 patients with Parkinson's Disease (PD), 8 patients with adult-onset isolated dystonia and 9 healthy controls. We studied the effects of a single cerebellar magnetic pulse over the excitability of the contralateral primary motor cortex tested with Motor-Evoked-Potentials (Cerebellar-Inhibition) both at rest and during arm extension. Furthermore, we also tested the effects of cerebellar continuous-Theta-Burst-Stimulation on Motor-Evoked-Potentials amplitude.

Results: patients with normal scans compared to controls show a deficient Cerebellar-Inhibition at rest but not in arm extension; in both conditions they differ from PD but not from dystonic patients. Cerebellar Continuous-Theta-Burst-Stimulation induced the expected long-lasting cortical inhibition of Motor-Evoked-Potentials amplitude in patients with normal scans differently from PD and dystonic patients.

Conclusions: patients with normal scans show a mild impairment in Cerebello-Thalamo-Cortical circuit that emerges only at rest. Such neurophysiological phenotype differs from the one observed in PD and dystonic patients, suggesting a distinct involvement of this pathway in the pathophysiology of these disorders.

Keywords: Cerebello thalamo cortical; Dystonia; Parkinson's disease; SWEDD; Tremor.

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