The motor cortex shows adaptive functional changes to brain injury from multiple sclerosis

Abstract

Although multiple sclerosis (MS) is an inflammatory demyelinating disease, there can be substantial axonal injury and loss. We therefore hypothesized that adaptive cortical changes may contribute to limiting functional impairment, particularly in the early stages of the disease. To test our hypothesis, we used functional magnetic resonance imaging (MRI) to characterize the localization and volumes of activation in the motor cortex during simple flexion‐extension finger movements. There were differences in the patterns of cortical activation with movement between the 12 MS patients and the 12 normal controls. All patients showed greater relative supplementary motor area activation than did the normal controls. The relative hemispheric lateralization of sensorimotor cortex (SMC) activation decreased in direct proportion to the total cerebral T2‐weighted MRI hyperintense lesion load. This appeared to be due primarily to increases in ipsilateral SMC activation with increasing lesion load in white matter of the hemisphere contralateral to the limb moved. The center of activation in the contralateral SMC was shifted a mean of 8.8 mm posterior in patients relative to controls, providing additional evidence for cortical adaptive responses to injury. The magnitude of this posterior shift in the SMC activation increased with greater T2 lesion loads. These observations demonstrate that cortical recruitment for simple finger movements can change both quantitatively and qualitatively in the SMCs of MS patients, suggesting that cortical reorganization or “unmasking” of latent pathways can contribute to functional recovery. These adaptive changes are another factor potentially limiting the strength of the relationship between MRI measures of pathology and clinical measures of disability. Ann Neurol 2000;47:606–613

Clinical correlations of brain lesion distribution in multiple sclerosis

“…Aside from this influence of LL, cortical adaptive changes may also limit correlations between localized lesion probability and symptoms. Adaptive changes have been shown to contribute to functional recovery after axonal injury (32)(33)(34). These changes after axonal loss can involve local synaptic reorganization, reorganization at more distant sites, or recruitment of parallel existing pathways (33), hampering relations between the location of an original lesion and its remaining symptoms after the development of adaptation.…”

Impaired Object Manipulation in Mildly Involved Individuals with Multiple Sclerosis

“…We believe that a part of explanation could be found in adaptation within the CNS. For example, recent brain imaging studies conducted on mildly involved MS patients have suggested normal neurological functioning due to cortical reorganization (Lee et al, 2000;Pantano et al, 2005;Reddy, Narayanan, Arnoutelis et al, 2000;. In addition, no performance deficits in reaction time motor tasks was observed between mildly affected MS patients (with a mean EDSS score of 1.4) indicating an adaptive mechanism in the cortex (Cerasa et al, 2006).…”

Multiple sclerosis-related white matter microstructural change alters the BOLD hemodynamic response

“…8,[64][65][66] Thus, if RRMSPs showed restricted extent of activation compared to HCs, averaging across voxels in these ROIs might be expected to result in artificially attenuated BOLD-HRF peak amplitude. We tested for group differences in the percent of active voxels at each of the eight tent-derived time points (t 0 À t 7 ) in BA 4 and 17.…”