250 Is primary writing tremor a forme fruste of dystonia?

Abstract

ObjectiveTo investigate whether primary writing tremor (PWT) and dystonia share a common pathophysiology.BackgroundPWT is probably the most common form of task-specific tremor. Its pathophysiology is still debated and there is controversy about it being a type of focal dystonia, a variant of essential tremor or a separate entity.MethodsWe recruited 7 patients with PWT, who underwent the following neurophysiological tests: blink recovery cycle (BRC), eye-blink classical conditioning (EBCC), short and long-intracortical inhibition (SICI-LICI). Moreover, motor-evoked potentials (MEP), SICI and LICI were measured pre and post paired associative stimulation (PAS) plasticity paradigm. Data were compared with those obtained in 7 dystonic patients (DYT).ResultsData analysis for BRC showed a similar inhibition between DYT and PWT. There was no differ- ence between DYT and PWT in the number of conditioned response (CR) during. Baseline SICI and LICI were similar in the two patients’ group, but whereas they were unchanged in PWT after PAS, they were reduced in DYT.ConclusionsThe present results suggest that PWT and DYT have similar brainstem excitability and associa- tive learning. Cortical plasticity induced by PAS had a different effect on SICI and LICI in the two groups. Overall this data suggests that PWT and DYT share some pathophysiological mechanisms.a.latorre@ucl.ac.uk