Diffusion-weighted imaging of acute corticospinal tract injury preceding Wallerian degeneration in the maturing human brain.
OBJECTIVE
Wallerian degeneration, the secondary degeneration of axons from cortical and subcortical injury, is associated with poor neurologic outcome. Since diffusion-weighted (DW) imaging is sensitive to early changes of cytotoxic edema, DW imaging may depict the acute injury to descending white matter tracts that precedes Wallerian degeneration; this injury is not visible on conventional CT or MR images in the maturing human brain.


METHODS
Two neuroradiologists retrospectively analyzed clinical MR images in six children (aged 3 days to 5 months) with DW findings consistent with acute injury of the descending white matter tract due to territorial anterior or middle cerebral artery infarction. In five patients, images were obtained as a part of routine clinical evaluation. The remaining patient was a part of a prospective study of brain injury. Imaging findings were correlated with clinical outcomes.


RESULTS
In all six patients, DW imaging performed 2-8 days after the onset of ischemia depicted injury to the descending white matter tract ipsilateral to the territorial infarct. Conventional MR images of the ipsilateral descending white matter tracts were abnormal in three patients. In all five patients for which follow-up results were available, the presence of DW changes was correlated with persistent neurologic disability.


CONCLUSIONS
As shown in this retrospective analysis, DW imaging can depict acute injury to the descending white matter tract in neonates and infants, when conventional MR imaging may show normal findings. These DW findings likely precede the development of Wallerian degeneration, and they may portend a poor clinical outcome.
Mazumdar
Avi
A
Neuroradiology Section, Mallinckrodt Institute of Radiology, Campus Box 8131, Washington University Medical Center, 510 South Kingshighway Boulevard, St. Louis, MO 63110, USA.
Mukherjee
Pratik
P
Miller
Jeffrey H
JH
Malde
Hiten
H
McKinstry
Robert C
RC
D000208:Acute Disease; D001284:Atrophy; D001921:Brain / Q000473:pathology; D001929:Brain Edema / Q000175:diagnosis; D001930:Brain Injuries / Q000175:diagnosis*; D020208:Brain Injury, Chronic / Q000175:diagnosis; D002545:Brain Ischemia / Q000175:diagnosis*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D020243:Infarction, Anterior Cerebral Artery / Q000175:diagnosis*; D020244:Infarction, Middle Cerebral Artery / Q000175:diagnosis*; D008297:Male; D009460:Neurologic Examination; D011379:Prognosis; D011446:Prospective Studies; D011712:Pyramidal Tracts / Q000098:blood supply / Q000293:injuries* / Q000473:pathology; D012189:Retrospective Studies; D014855:Wallerian Degeneration / Q000175:diagnosis*