Author Of 1 Presentation
P0828 - Synaptic plasticity is reduced in patients with RRMS compared to healthy controls and associated with neuropsychological outcomes (ID 866)
Abstract
Background
The missing 1:1 relation of lesion to disability in patients with multiple sclerosis (MS) may be due to processes of functional and structural reorganization and plasticity, which can be summarized as the compensatory reserve. A sensitive and reproducible parameter to measure these mechanisms may be repetitive transcranial magnetic stimulation (rTMS) of the cortex. However, results of previous studies on rTMS-induced plasticity in MS patients are limited due to high variability of their rTMS protocols. Furthermore, the relationship between cortical plasticity and cognition has not been investigated so far.
Objectives
To reliably assess the compensatory mechanisms of motor cortex plasticity in patients with relapsing-remitting MS (RRMS) compared to healthy controls (HC) and to investigate the association of induced plasticity with information processing speed (IPS) and visuospatial memory.
Methods
25 patients with RRMS (mean disease duration=11.0[8.0], median Expanded Disability Status Scale=1.5[0.0-7.5]), and 25 age-, sex-, and education-matched HC entered the study. To assess cortical plasticity, the amplitudes of the motor evoked potentials at the extremities pre and post repetitive transcranial quadripulse stimulation (QPS), a protocol previously reported to show less variability, were recorded. Group comparisons were carried out with generalized linear mixed-effects models. IPS and visuospatial memory were assessed using the Symbol Digit Modalities Test (SDMT) and Brief Visuospatial Memory Test-Revised (BVMT-R), respectively. Associations of these measures with cortical plasticity were investigated with correlational analyses.
Results
Cortical plasticity was induced by QPS in both groups (p<.001). However, a significant interventionxgroup interaction (p=.032) indicated reduced plasticity in RRMS patients compared to controls. Patients also performed significantly worse on the SDMT (p=.008) and BVMT-R (p=.030) than HC. Correlational analyses revealed significant positive correlations between these parameters and QPS-induced plasticity (SDMT: rs=0.47, p=.018; BVMT-R: rs=0.50, p=.012) in the patient sample.
Conclusions
We provide evidence for reduced cortical plasticity in patients with RRMS compared to closely matched HC, emphasizing the promising role of transcranial magnetic QPS as a sensitive and reliable biomarker to measure compensatory reserve. Moreover, our data demonstrate, for the first time, that QPS-induced plasticity is positively associated with neuropsychological outcome measures of IPS and visuospatial memory in patients with RRMS.