Background While magnetic resonance imaging has revealed progressive c
hanges in the pyramidal tract in accordance with histopathologic stage
s of wallerian degeneration secondary to a supratentorial lesion, comp
uted tomography (CT) has only demonstrated a shrinkage of the pyramida
l tract in the midbrain or pens during the chronic stage. We present a
patient with frontoparietal subcortical hemorrhage in whom serial CT
scans clearly demonstrated wallerian degeneration along the axis of th
e pyramidal tract early in the acute stage. Case Description A 63-year
-old man with a history of hypertension suddenly developed a deteriora
tion of consciousness, transcortical mixed aphasia, and dense hemipleg
ia on the right side. CT scans revealed a massive intracerebral hemato
ma in the frontoparietal subcortices of the left hemisphere. Although
initial CT did not detect any hypodense areas along the left pyramidal
tract below the hematoma, ill-defined areas of decreased density appe
ared in the posterior limb of the internal capsule, cerebral peduncle
of the midbrain, and pontine base of the left side on day 13 after the
stroke. These areas became well demarcated on day 22 and persisted th
ereafter. Conclusions An extensive hematoma can interrupt the pyramida
l tract fibers that arise not only from the motor cortex and caudal pr
emotor cortex but also from the somatosensory and parietal cortices, a
llowing very early CT demonstration of wallerian degeneration of the p
yramidal tract.