Introduction: Stroke is a leading cause of perinatal brain injury and cerebral palsy. Current therapeutic efforts focus on optimizing developmental curves but the biological processes dictating these outcomes are poorly understood. Alterations in myelination are recognized as a major determinant of outcome in preterm brain injury but are unexplored in perinatal stroke (PS).
Hypothesis: Ipsilesional delays in myelination occur in children with PS and are associated with poor developmental outcome.
Methods: Participants were identified through the Alberta Perinatal Stroke Project, a population-based research cohort. Inclusion criteria were: 1) MRI-confirmed, unilateral arterial PS, 2) T1-weighted MRI >6mo, 3) absence of other neurological disorders, 4) neurological outcome (Pediatric Stroke Outcome Measure, PSOM), and 5) motor assessments (Assisting Hand Assessment, AHA; Melbourne Assessment). FreeSurfer software measured hemispheric asymmetry in myelination intensity. A second method using ImageJ validated the detection of myelination asymmetry. Overall PSOM scores were classified as poor (>1) or not. Repeated measures ANOVA compared perilesional, ipsilesional remote, and contralesional homologous regions. Myelination ratios for stroke cases were compared to typically developing controls (t-test), PSOM scores (t-test), and motor assessments (Pearson’s correlation).
Results: Nineteen arterial stroke cases (mean age: 13.73±4.0yo) and 27 controls (mean age: 12.52±3.7yo) were studied. Stroke cases showed a greater degree of asymmetry with lower myelination in the lesioned hemisphere, compared to controls (p<0.001). Myelination in perilesional regions was decreased compared to ipsilesional remote (p<0.001) and contralesional homologous areas (p<0.001). Ipsilesional remote regions were decreased compared to homologous regions on the contralesional hemisphere (p=0.009). Contralesional myelination was also less than controls (p<0.001). Myelination ratios were not associated with PSOM, AHA, or Melbourne scores (p=0.144, 0.218, 0.366 respectively).
Conclusion: Myelination of uninjured brain in the lesioned hemisphere is altered in children with PS. Further study is required to determine clinical significance.