T46. Correlates of motor disability and fatigue with alterations of cortical excitability and quantitative MRI parameters in relapsing remitting multiple sclerosis and neuromyelitis optica

Abstract

Introduction Relapsing Remitting Multiple sclerosis(RRMS) and Neuromyelitis optica(NMO) are primary demyelinating disorders with almost similar clinical symptoms but have varied etiology and response to treatment. Methods To study and compare clinical (fatigue depression and disability scores), electrophysiological and imaging characteristics of RRMS and NMO including correlation of (Transcranial magnetic stimulation) TMS parameters with clinical scores and imaging;and improvement in TMS parameters pre and post steroids.23 RRMS and 14 NMO patients were recruited over a period of 5 years and all parameters were done pre and post steroid therapy. Results Mean age at presentation-RRMS-31.1 ± 12.2 years;NMO-34.8 ± 10.9 years. Mean duration of illness- RRMS-50.9 ± 58.1 months; NMO-42.9 ± 48.6 months. Age at onset of illness -RRMS-26.9 ± 10.7 years; NMO-31.9 ± 9.2 years. Frequency of episodes were high in NMO (predominantly myelopathy) as opposed to RRMS (Brainstem syndrome). Disability, fatigue scores and Cerebrospinal fluid pleocytosis were significantly high in NMO than RRMS. Somatosensory Evoked Potentials (EPs) showed significant prolongation in RRMS while Visual EPs showed no difference between both entities. Duration of illness correlated positively with total T1, T2 lesion load and disability scores with T1 lesion load in RRMS. No correlation was found in any clinical scores and lesion load in NMO. As compared to NMO right uncus, insula and anterior cingulate gyrus were relatively preserved in RRMS with atrophy of left pre cuneus,cuneus,occipital gyrus,cerebellum and bilateral pulvinar as identified by voxel based morphometric analysis. Both RRMS and NMO showed significant prolongation of Central motor conduction time (CMCT) whereas reduction in Motor Evoked Potential (MEP) amplitudes and prolongation of contralateral silent periods was significant only in RRMS. In paired stimulation studies, none of the patients in RRMS and NMO group had intracortical facilitation (ICF) and Short interval intracortical inhibition (SICI) was found to be elevated in both group of patients, with more inhibition compared to controls. Trend towards improvement was noted in both the groups post steroids, in Resting Motor Threshold, MEP amplitude and ICF. Disability was found to have negative correlation with SICI in RRMS patients. Conclusion Patients of NMO were of later age at onset with more disability and fatigue compared to RRMS. Duration of illness correlated with total MRI lesion load and disability with T1 lesion load in RRMS.TMS parameters were found to be significantly abnormal in RRMS than NMO with significant CMCT prolongation in both the groups which improved post steroid therapy.Lack of cortical excitability was noted in both the groups with increased cortical inhibition.Negative correlation of disability with SICI was also noted only in RRMS and not NMO with no correlation of TMS parameters with fatigue and depression.TMS thereby helps in evaluation and assessment of response to therapy in both RRMS and NMO.