Magnetoencephalography in stroke: a 1‐year follow‐up study

Abstract

Recovery after stroke is closely linked to cerebral plasticity. Magnetoencephalography (MEG) is a non-invasive technique, which allows location of cerebral cells activities. In the present work, a cohort of patients has been studied with MEG. Twelve patients with a recent ischemic or hemorragic stroke were included as soon as possible after onset of stroke. Neurologic assessment, including standard neurologic examination, functional independence measure (FIM) and Orgogozo's scale was performed for 1 year in addition to a study of the somatosensory evoked field (SEF) using a 37-channel Biomagnetometer system. No response could be recorded in five patients at the first SEF exploration. In three cases, no response was ever recorded during the study. All these patients had a bad recovery. The location of the SEF sources was always in the normal non-infarcted cortex of the postcentral gyrus. Sensory recovery seemed to be linked to the reorganization of the persistent functional cortex, which was a limiting factor for recovery. These observations confirm the experimental results obtained in animal models. After stroke it can be assumed that in the case of incomplete lesion, an intensive sensory peripheral stimulation could maximize the use of residual sensory function and then contribute to improve the sensory deficit. In case of total sensory loss other techniques have to be used, such as visual monitoring of hand activity in order to improve hand function.

Activation in parietal operculum parallels motor recovery in stroke

“…The amplitude of the early SI response has been shown to correlate with tactile discrimination ability [Knecht et al, 1996;Wikstrom et al, 2000], whereas association of SI activation strength with other functional outcome measures has been more variable [Gallien et al, 2003;Tecchio et al, 2006]. In the present study, no correlation between SI strength and motor recovery was observed at acute phase or during recovery.…”

“…Changes in somatosensory activation have been less extensively studied, but previous reports have shown that interhemispheric differences in the locations and latencies of the primary somatosensory (SI) cortex activation are associated with functional recovery of stroke patients [Gallien et al, 2003;Rossini et al, 1998;Tecchio et al, 2006].…”

The sensory side of post-stroke motor rehabilitation

“…First, in the early post-stroke phase, the cortical activity in response to somatosensory input predicts late motor outcomes (Zeman & Yiannikas, 1989). Absence of cortical activation by sensory stimulation is associated with poorer outcome in stroke patients (Gallien et al, 2003), while the increased activation of MI and SI by somatosensory stimulation correlates with improvements in neurological scores between the acute and chronic stages of illness (Huang et al, 2004); moreover, the degree of improvement in hand function correlates with the activation peak changes within the ipsilesional SI (Laible et al, 2012). On the other hand, in patients with poorer recovery, movements of the paretic limb are associated with a compensatory recruitment of parallel sensorimotor networks, including the bilateral dorsolateral PM, SMA, cingulate motor areas, and parietal cortices (Ward & Cohen, 2004).…”

Modulation of event-related desynchronization in robot-assisted hand performance: brain oscillatory changes in active, passive and imagined movements

“…Changes in cortical activity during active and passive movements and motor imagery in both normal subjects and stroke patients have been variously investigated using such different techniques as functional magnetic resonance imaging (fMRI) [8-13], positron emission tomography (PET) [14,15], magnetoencephalography (MEG) [16,17], near-infrared spectroscopy (NIRS) [18] and electroencephalography (EEG) [19]. Studies exploring the therapeutic utility of EEG have reported modulation in cortical activations during motor execution and imagery practices.…”