Comparison of Descending Motor Pathways Between Prenatal
and Perinatal Unilateral Brain Injuries
SP24
AACPDM
September 2014
Rachel L. Hawe1,2 and Julius P.A. Dewald1,2,3
1Department
of Physical Therapy & Human Movement Sciences, 2Department of Biomedical Engineering, and 3Department of Physical Medicine & Rehabilitation, Northwestern University, Chicago, IL
Introduction
•  With early unilateral brain injuries, significant reorganization of motor
pathways is possible due to ongoing neural development.
Corticopsinal Tract Volume
Results
450
CONTROL
PERINATAL
PRENATAL
Volume (voxels)
•  In typical development, there are direct ipsilateral corticospinal
projections that are normally withdrawn while contralateral
projections are strengthened.
•  Following an early unilateral lesion, it is hypothesized that the
ipsilateral projections from the contralesional hemisphere are
maintained due to an increased reliance on these non-lesioned
pathways.
•  The timing of the injury (prenatal vs. perinatal) can determine the type
of lesion, what structures are damaged, and availability of remaining
structures for neuroplasticity
•  Understanding how injury timing impacts motor pathways will lead to
more individualized treatments for children with pediatric hemiplegia
Purpose: Determine if there are differences in the descending motor
pathways between prenatal and perinatal unilateral brain injuries
Methods
Subjects:
- Pediatric hemiplegia:n=12 with unilateral brain injuries (age 12.8 ± 8.7 yrs)
- Pre-natal injuries: n=6
- Peri-natal injuries: n=6
- Pediatric control: n=10 typically-developing children (age 12.3 ± 3.9 yrs)
Imaging:
- All subjects underwent diffusion tensor imaging on 3 T
- Echo planar based diffusion sequence
- 60 diffusion directions with b=1000s/mm2 and 8 scans with b=0
Image Analysis:
- Images were processes using FMRIB Software Library (FSL)
- A diffusion tensor model was fit at every voxel and a color map indicating
primary diffusion direction was generated
- Masks were hand-drawn on the transverse slice of the posterior limb of
the internal capsule and the cerebral peduncles, guided by the color map
- Probabilistic tractography was completed from the cerebral peduncles to
the posterior limb of the internal capsule, requiring fibers to pass through
both masks. Pathways were thresholded at 10% to remove unlikely
projections.
- Analysis was completed on the section from the internal capsule to
cerebral peduncles to improve accuracy of results
- Average fractional anistropy (FA), mean diffusivity (MD), axial (AD), and
radial diffusivities (RD) were computed as well as volume.
Figure 1. Representative Anatomical MRIs. Peri-ventricular lesions are common in prenatal
injuries, while MCA lesions can be seen perinatally.
1
0.5
PRENATAL
PERINATAL
CONTROL
*
**
*
* *
1
MD
AD
*
200
150
100
50
LESIONED
PRENATAL
NONLESIONED
PERINATAL
CONTROL
Figure 4. Corticospinal tract volume.
• Both prenatal and perinatal unilateral injuries result in decreased white matter
integrity on both the lesioned and nonlesioned corticospinal tracts
RD
• Perinatal injuries present with greater damage compared to prenatal injuries
• Perinatal injuries have greater compensatory increases in volume on the
nonlesioned side
Nonlesioned Corticospinal Tract
*
250
Conclusion
Figure 2. DTI metrics for lesioned corticospinal tracts.
1.5
300
* *
0
FA
350
0
Lesioned Corticospinal Tract
2
1.5
*
400
*
PRENATAL
PERINATAL
CONTROL
*
*
0.5
*
• Differences in corticospinal tract changes between prenatal and perinatal injuries
may be due to the nature of the lesion, with MCA lesions in the perinatal period
being more damaging
• An improved understanding of how the pathways are impacted differently
depending on injury timing can help to explain differences in motor deficits and
lead to more tailored interventions
Acknowledgments
0
FA
MD
AD
Figure 3. DTI metrics for nonlesioned corticospinal tracts.
RD
NSF Graduate Research Fellowship, NIH Grant: RO1 NS058667, and NIH Grant: T32 EB009406
Todd Parrish, Dan Krainak, and Theresa Moulton for technical expertise and data collection.