Functional Reorganisation in Sensorimotor Cortex Is a Compensatory Mechanism in Early Parkinson's Disease: A Six Months Follow-Up Study (IN6-2.002)

Abstract

Objective: To study changes in motor cortex plasticity and intracortical inhibition over the early stages of Parkinson9s disease(PD), using Transcranial Magnetic Stimulation. Background In advanced PD motor cortex plasticity and intracortical inhibition are reduced compared to normal if patients are tested off dopaminergic treatment. However, there are no studies investigating how these electrophysiological parameters change with disease progression. Design/Methods: 17 newly diagnosed, clinically asymmetric and drug naive PD patients were studied at baseline. Six months later, measurements were repeated in 13 of them. 6 of the 13 had started treatment with dopaminergic drugs (and were studied after overnight withdrawal), while 7 patients remained untreated. Clinical disease severity was assessed with the motor section of UPDRS scale. 17 healthy participants were included as a control group. EMG recordings were made from APB and ADM muscles. Plasticity was probed in both hemispheres using an excitatory paired associative stimulation (PAS25) protocol. Short-interval intracortical inhibition (SICI) was measured using a paired-pulse paradigm. Results: At baseline, the less affected hemisphere had an increased response to PAS25 with a loss of topographic specificity, both in comparison with the more affected side and with an age matched control group. On the more affected side the response to PAS25 was reduced compared with less affected side and controls. SICI was normal on the less affected side and reduced on the more affected side. Six months later there was no significant change in the UPDRS score in treated and untreated patients. The interhemispheric differences in motor cortex plasticity and the amount of SICI were still evident at 6 months follow-up, and were not different between treated and untreated patients. Conclusions: Increased motor cortical plasticity on the less affected side is consistent with a functional reorganisation of sensorimotor cortex in early PD and may represent a compensatory change that contributes to delaying symptom progression. Supported by: Parkinson9s UK (G-1009). Disclosure: Dr. Kojovic has nothing to disclose. Dr. Kassavetis has nothing to disclose. Dr. Bologna has nothing to disclose. Dr. Berardelli has nothing to disclose. Dr. Rothwell has nothing to disclose. Dr. Edwards has nothing to disclose. Dr. Bhatia has received personal compensation for activities with UCB Pharma, Novartis and Ipsen as a speaker.