H. Reddy et al., Evidence for adaptive functional changes in the cerebral cortex with axonal injury from multiple sclerosis, BRAIN, 123, 2000, pp. 2314-2320
Axonal injury occurs even in the earliest stages of multiple sclerosis, Mag
netic resonance spectroscopic imaging (MRSI) measurements of brain N-acetyl
aspartate (NAA), a marker of axonal integrity, show that this axonal injury
can occur even in the absence of clinically evident functional impairments
. To test whether cortical adaptive responses contribute to the maintenance
of normal motor function in patients with multiple sclerosis, we performed
MRSI and functional MRI (fMRI) examinations of nine multiple sclerosis pat
ients who had unimpaired hand function. We found that activation of the ips
ilateral sensorimotor cortex with simple hand movements was increased by a
mean of fivefold relative to normal controls (n = 8) and that the extent. o
f this increase was strongly correlated (sigma = -0.93, P = 0.001) with dec
reases in brain NAA, These results suggest that compensatory cortical adapt
ive responses may help to account for the limited relationship between conv
entional MRI measures of lesion burden and clinical measures of disability,
and that therapies directed towards promoting cortical reorganization in r
esponse to brain injury could enhance recovery from relapses of multiple sc
lerosis.