Background and Purpose-Magnetic resonance spectroscopy (MRS) in ischemic st
roke has shown a correlation between N-acetylaspartate (NAA) loss from the
infarcted region and disability. We tested the hypothesis that NAA loss in
the descending motor pathways, measured at the level of the posterior limb
of the internal capsule, would determine motor deficit after a cortical, su
bcortical, or striatocapsular stroke.
Methods-Eighteen patients with first ischemic stroke causing a motor defici
t were examined between 1 month and 5 years after stroke. T2-weighted imagi
ng of the brain and localized proton (voxel, 1.5X2X2 cm(3)) MRS from the po
sterior limb of each internal capsule were performed and correlated to a mo
tor deficit score.
Results-Mean internal capsule NAA was significantly lower in the patient gr
oup as a whole compared with the control group (P<0.001). Reductions in int
ernal capsule NAA on the side of the lesion were seen in cases of cortical
stroke in which there was no extension of the stroke into the voxel as well
as in cases of striatocapsular stroke involving the voxel region. There wa
s a strong relationship between reduction in capsule NAA and contralateral
motor deficit (log curve, r(2)=0.9, P<0.001).
Conclusions-Axonal injury in the descending motor pathways at the level of
the internal capsule correlated with motor deficit in patients after stroke
, This was the case for strokes directly involving the internal capsule and
for strokes in the motor cortex and subcortex in which then was presumed a
nterograde axonal injury.