Neurophysiological follow-up of motor cortical output in stroke patients

Abstract

Background and purpose: Transcranial magnetic stimulation (TMS) has been employed in following up a population of 20 stroke patients in a post-acute, apparently stabilized stage. Neurophysiological and clinical data were recorded in 5 different recording sessions, from the beginning of a neuro-rehabilitation treatment (T0, at about 5 weeks from the ictal event.), followed up for about 4 months (T4), with the purpose to study any modification of the cortical motor output in the course of a neuro-rehabilitation treatment. Methods: Motor evoked potentials (MEPs) were simultaneously recorded from 10 muscles of both upper limbs (affected and not-affected); meanwhile, clinical and functional scores were gathered. Spinal responsiveness was investigated via H-reflex and F-wave recordings. Results: We describe a pattern of improving changes still taking place four months after the stroke, even if the maximal amelioration burden was concentrated between T0 and T1 and T1 and T2 recording sessions (T0/admission to T2/42 days from T0=about 80 days from stroke occurrence). In particular, the excitability threshold (ETh) was progressively decreasing in the affected hemisphere (AH; P<0.001 between T0 and T4), while MEPs amplitude and latency tended toward normality, more in the resting state than during voluntary contraction. Slopes of neurophysiological and clinical data evolution were taken and trends of amelioration described. Conclusions: These findings suggest that rearrangements of motor cortical neural circuitries are still operating after several months from an acute vascular monohemispheric insult, coupled with a clinical improvement in disability and neurological scores. The steepest part of the slopes were evident in the first 80 days, suggesting that this period is the one in which plastic changes of cortical motor areas are mainly active.