Tommaso Schirinzi1, Francesco Di Lorenzo2, Viviana Ponzo3, Maria Giuseppina Palmieri1, Anna Rita Bentivoglio4, Orazio Schillaci5, Antonio Pisani2, Giacomo Koch6. 1. Neurology, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy. 2. Neurology, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy; IRCSS Santa Lucia, Rome, Italy. 3. IRCSS Santa Lucia, Rome, Italy. 4. Institute of Neurology, Università Cattolica del Sacro Cuore, Rome, Italy; Don Carlo Gnocchi Onlus Foundation, Milan, Italy. 5. Department of Biopathology and Diagnostic Imaging, University of Rome Tor Vergata, Rome, Italy. 6. IRCSS Santa Lucia, Rome, Italy; Stroke Unit, Policlinico Tor Vergata, Rome, Italy. Electronic address: g.koch@hsantalucia.it.
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.
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 dystonicpatients. 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 dystonicpatients. 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 dystonicpatients, suggesting a distinct involvement of this pathway in the pathophysiology of these disorders.