title: Mild cerebello-thalamo-cortical impairment in patients with normal dopaminergic scans (SWEDD).
abstract: 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.
  
  
  
  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.
  
  
  
  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.
  
  
  
  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.
authors.affiliation: Neurology, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Schirinzi
authors.affiliation: Neurology, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy; IRCSS Santa Lucia, Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Lorenzo
authors.affiliation: IRCSS Santa Lucia, Rome, Italy.
authors.forename: Viviana
authors.initials: V
authors.lastname: Ponzo
authors.affiliation: Neurology, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Maria Giuseppina
authors.initials: MG
authors.lastname: Palmieri
authors.affiliation: Institute of Neurology, Università Cattolica del Sacro Cuore, Rome, Italy; Don Carlo Gnocchi Onlus Foundation, Milan, Italy.
authors.forename: Anna Rita
authors.initials: AR
authors.lastname: Bentivoglio
authors.affiliation: Department of Biopathology and Diagnostic Imaging, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Orazio
authors.initials: O
authors.lastname: Schillaci
authors.affiliation: Neurology, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy; IRCSS Santa Lucia, Rome, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pisani
authors.affiliation: IRCSS Santa Lucia, Rome, Italy; Stroke Unit, Policlinico Tor Vergata, Rome, Italy. Electronic address: g.koch@hsantalucia.it.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Koch
mesh_terms: D000368:Aged; D002531:Cerebellum / Q000503:physiopathology*; D020821:Dystonic Disorders / Q000503:physiopathology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009434:Neural Pathways / Q000503:physiopathology; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013788:Thalamus / Q000503:physiopathology; D013826:Theta Rhythm / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014202:Tremor / Q000503:physiopathology*
keywords: Cerebello thalamo cortical; Dystonia; Parkinson's disease; SWEDD; Tremor