Remodelling of sensorimotor maps in paraplegia: a functional magnetic resonance imaging study after a surgical nerve transfer (original) (raw)
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Assessment of reorganization in the sensorimotor cortex after upper limb amputation
Clinical Neurophysiology, 2001
Objective: We wanted to investigate plastic changes occurring in the motor and somatosensory cortex after upper limb amputation, and their possible relationship to phantom pain. Method: To assess these plastic changes, we used transcranial magnetic stimulation (TMS) and source localization of somatosensory evoked potentials (SEP). Eleven patients with upper limb amputation were investigated. The phantom pain intensity was assessed by visual analogue scaling (VAS). Results: Using TMS mapping, we found a signi®cant lateralization of the amplitude-weighted centre of gravity (P , 0:01) and an enlargement of the excitable area (P , 0:05) on the hemisphere contralateral to the amputation. SEP mapping showed a signi®cant medialization of the N20 dipole (P , 0:05) on this side. None of these changes correlated with the phantom pain intensity. Conclusions: We conclude that after limb amputation, the relationship between plastic changes occurring in the sensorimotor cortex and phantom pain seems to be more complex than previously believed.
Brain, 2002
Peripheral and central nervous system lesions can induce reorganization within central somatosensory and motor body representations. We report changes in brain activation patterns during movements of nonaffected body parts in paraplegic patients with spinal cord injury (SCI). Nine SCI patients and 12 healthy controls underwent blood oxygen level dependent signal functional MRI during sequential ®nger-to-thumb opposition,¯exion and extension of wrist and of elbow, and horizontal movements of the tongue. Single subject and group analyses were performed, and the activation volumes, maximum t values and centres of gravity were calculated. The somatotopical upper limb and tongue representations in the contralateral primary motor cortex (M1) in the SCI patients were preserved without any shift of activation towards the deefferented and deafferented M1 foot area. During ®nger movements, however, the SCI patients showed an increased volume in M1 activation. Increased activation was also found in non-primary motor and parietal areas, as well as in the cerebellum during movements of the ®ngers, wrist and elbow, whereas no changes were present during tongue movements. These results document that, in paraplegic patients, the representation of the non-impaired upper limb muscles is modi®ed, though without any topographical reorganization in M1. The extensive changes in primary and non-primary motor areas, and in subcortical regions demonstrate that even distant neuronal damage has impact upon the activation of the whole sensorimotor system.
Upper limb cortical maps in amputees with targeted muscle and sensory reinnervation
Brain, 2017
Neuroprosthetics research in amputee patients aims at developing new prostheses that move and feel like real limbs. Targeted muscle and sensory reinnervation (TMSR) is such an approach and consists of rerouting motor and sensory nerves from the residual limb towards intact muscles and skin regions. Movement of the myoelectric prosthesis is enabled via decoded electromyography activity from reinnervated muscles and touch sensation on the missing limb is enabled by stimulation of the reinnervated skin areas. Here we ask whether and how motor control and redirected somatosensory stimulation provided via TMSR affected the maps of the upper limb in primary motor (M1) and primary somatosensory (S1) cortex, as well as their functional connections. To this aim, we tested three TMSR patients and investigated the extent, strength, and topographical organization of the missing limb and several control body regions in M1 and S1 at ultra high-field (7 T) functional magnetic resonance imaging. Additionally, we analysed the functional connectivity between M1 and S1 and of both these regions with fronto-parietal regions, known to be important for multisensory upper limb processing. These data were compared with those of control amputee patients (n = 6) and healthy controls (n = 12). We found that M1 maps of the amputated limb in TMSR patients were similar in terms of extent, strength, and topography to healthy controls and different from non-TMSR patients. S1 maps of TMSR patients were also more similar to normal conditions in terms of topographical organization and extent, as compared to non-targeted muscle and sensory reinnervation patients, but weaker in activation strength compared to healthy controls. Functional connectivity in TMSR patients between upper limb maps in M1 and S1 was comparable with healthy controls, while being reduced in non-TMSR patients. However, connectivity was reduced between S1 and fronto-parietal regions, in both the TMSR and non-TMSR patients with respect to healthy controls. This was associated with the absence of a well-established multisensory effect (visual enhancement of touch) in TMSR patients. Collectively, these results show how M1 and S1 process signals related to movement and touch are enabled by targeted muscle and sensory reinnervation. Moreover, they suggest that TMSR may counteract maladaptive cortical plasticity typically found after limb loss, in M1, partially in S1, and in their mutual connectivity. The lack of multisensory interaction in the present data suggests that further engineering advances are necessary (e.g. the integration of somatosensory feedback into current prostheses) to enable prostheses that move and feel as real limbs.
Neurorehabilitation and Neural Repair, 2007
Background. Although the consequences of spinal cord injury (SCI) within the spinal cord and peripheral nervous system have been studied extensively, the influence of SCI on supraspinal structures during recovery remains largely unexplored. Objective. To assess temporal changes in cortical sensorimotor representations beginning in the subacute phase following SCI and determine if an association exists between the plastic changes within cortical sensorimotor areas and recovery of movement postinjury. Methods. Functional magnetic resonance imaging (fMRI) was used to study 6 SCI patients for 1 year, beginning shortly postinjury, and 10 healthy control individuals. During fMRI, individuals performed a simple self-paced wrist extension motor task. Recovery of movement was assessed using the American Spinal Injury Association (ASIA) Standard Neurological Classification of SCI. Results. In the subacute period post-SCI, during impaired movement, little task-related activation within the pri...
Cortical motor reorganization after paraplegia
Neurology, 1999
Objective: To determine whether a previously identified posterior reorganization of the cortical motor network after spinal cord injury (SCI) is correlated with prognosis and outcome.Methods: We applied the techniques of high-resolution EEG and dipole source analysis to record and map the motor potentials (MPs) of the movement-related cortical potentials in 44 patients after SCI. Twenty normal controls were also tested. Results were analyzed using a distance metric to compare MP locations. EEG was coregistered with individual specific MR images and a boundary element model created for dipole source analysis.Results: MPs with finger movements were mapped to a posterior location in 20 of 24 tetraplegics compared with normal controls. Two patients, one studied 4 and one 6 weeks after injury, initially had posterior MPs that, on serial testing, moved to an anterior position with recovery. Dipole source localization of the MP generators confirmed these results. Nine of 20 paraplegics had...
… and neural repair, 2010
Background. It is well documented that cortical sensorimotor representations are altered following nervous system pathology. However, little is known about these representations over time and, more specifically, in paralyzed individuals. Objective. To investigate the temporal changes in sensorimotor cortical activation in paralyzed individuals following spinal cord injury (SCI). Methods. Functional MRI (fMRI) was used to study 4 tetraplegic individuals repeatedly over the first year following traumatic SCI as well as 7 healthy individuals, 3 repeatedly. During fMRI, controls performed ankle movements, and patients attempted them. Standard clinical measures of SCI were used to assess movement ability. Results. Shortly after SCI, activation within the primary motor cortex (M1) was present at levels similar to those in controls. Extensive associated cortical sensorimotor activation, not seen in controls, was present. Over time, as paralysis persisted, activation in M1 was significantly reduced and progressively decreased in associated cortical sensorimotor areas. No session-specific dependence in M1 or associated sensorimotor cortical activation was found in healthy individuals. Conclusions. These findings provide the first report of the temporal evolution of cortical sensorimotor fMRI activation following traumatic SCI in humans who do not recover movement. Coupled with findings in patients who recover post-SCI, our results suggest an association between motor task-related fMRI activation and degree of motor function postinjury. Understanding the time course of plasticity and the relationship between cortical sensorimotor activation and motor ability following SCI could allow assessment of rehabilitation potential, monitoring of therapeutic efficacy, and improvement in therapeutic intervention along the course of recovery.
Movement Observation Activates Lower Limb Motor Networks in Chronic Complete Paraplegia
Neurorehabilitation and Neural Repair, 2011
Execution and imagination of movement activate distinct neural circuits, partially overlapping in premotor and parietal areas, basal ganglia and cerebellum. Can long-term deafferented/deefferented patients still differentiate attempted from imagined movements? The attempted execution and motor imagery network of foot movements have been investigated in nine chronic complete spinal cord-injured (SCI) patients using fMRI. Thorough behavioral assessment showed that these patients were able to differentiate between attempted execution and motor imagery. Supporting the outcome of the behavioral assessment, fMRI disclosed specific patterns of activation for movement attempt and for motor imagery. Compared with motor execution data of healthy controls, movement attempt in SCI patients revealed reduced primary motor cortex activation at the group level, although activation was found in all single subjects with a high variability. Further comparisons with healthy subjects revealed that during attempt and motor imagery, SCI patients show enhanced activation and recruitment of additional regions in the parietal lobe and cerebellum that are important in sensorimotor integration. These findings reflect central plastic changes due to altered input and output and suggest that SCI patients may require additional cognitive resources to perform these tasks that may be one and the same phenomenon, or two versions of the same phenomenon, with quantitative differences between the two. Nevertheless, the retained integrity of movement attempt and motor imagery networks in SCI patients demonstrates that chronic paraplegics can still dispose of the full motor programs for foot movements and that therefore, attempted and imagined movements should be integrated in rehabilitative strategies.
Increased Brain Sensorimotor Network Activation After Incomplete Spinal Cord Injury
Journal of Neurotrauma, 2016
After complete spinal cord injury (SCI), activation during attempted movement of paralyzed limbs is sharply reduced, but after incomplete SCI-the more common form of human injury-it is unknown how attempts to move voluntarily are accompanied by activation of brain motor and sensory networks. Here, we assessed brain activation during ankle movement in subjects with incomplete SCI, among whom voluntary motor function is partially preserved. Adults with incomplete SCI (n = 20) and healthy controls (n = 15) underwent functional magnetic resonance imaging that alternated rest with 0.3-Hz right ankle dorsiflexion. In both subject groups, ankle movement was associated with bilateral activation of primary and secondary sensory and motor areas, with significantly (p < 0.001) greater activation in subjects with SCI within right hemisphere areas, including primary sensorimotor cortex and pre-motor cortex. This result was further evaluated using linear regression analysis with respect to core clinical variables. Poorer locomotor function correlated with larger activation within several right hemisphere areas, including pre-and post-central gyri, possibly reflecting increased movement complexity and effort, whereas longer time post-SCI was associated with larger activation in left post-central gyrus and bilateral supplementary motor area, which may reflect behaviorally useful adaptations. The results indicate that brain adaptations after incomplete SCI differ sharply from complete SCI, are related to functional behavioral status, and evolve with increasing time post-SCI. The results suggest measures that might be useful for understanding and treating incomplete SCI in human subjects.
Reversible changes of motor cortical outputs following immobilization of the upper limb
Electroencephalography and Clinical Neurophysiology/Electromyography and Motor Control, 1997
We mapped the cortical representations of the abductor pollicis brevis, flexor carpi radialis, biceps and deltoid muscles in six subjects with unilateral wrist fractures, immediately after the removal of the splint. This was repeated 1 month later in three out of the six subjects. Duration of immobilization was 1 month. Muscle maps were obtained by delivering four focal magnetic pulses for each scalp position (1 cm apart with reference to Cz) over the contralateral hemisphere. Motor evoked potentials (MEPs) were averaged off-line and expressed as a percentage of the motor action potential evoked by supramaximal peripheral nerve stimulation. Volume, area and threshold of the motor maps showed no significant hemispheric differences within each muscle in 10 control subjects. In the first recording session the volume of each immobilized muscle was distinctly higher when compared to that of controls in terms of absolute value and side-to-side ratio. This finding disappeared 1 month later. Moreover, MEP amplitude difference recorded from hand muscle could be reversed during a small tonic voluntary contraction. Immobilization had no significant effect on the threshold for activation of the target muscles and on the area of the motor map. The increase in MEP amplitudes occurred without changes in spinal excitability as tested by the F wave. These findings suggest that immobilization of the upper limb induces a reversible enhancement of the excitability of structures along the corticomotoneuronal pathway. Sustained restriction of volitional movements and reduction in somatic sensory inputs might promote this functional modulation of the motor system.