Cerebellar atrophy in childhood arterial ischemic stroke: acute diffusion MRI biomarkers.

BACKGROUND AND PURPOSE Crossed cerebellar atrophy is uncommon in childhood arterial ischemic stroke. Acute corticospinal tract diffusion-weighted imaging (CST-DWI) changes occur in stroke of all ages. Contralateral CST-DWI is unexplained but approximates corticopontocerebellar pathways. We hypothesized that cerebellar atrophy can be quantified on clinical neuroimaging in childhood arterial ischemic stroke and is predicted by contralesional CST-DWI. METHODS Consecutive children (>28 days-18 years) were included with the following features: (1) acute, unilateral, middle cerebral artery arterial ischemic stroke, (2) DWI <14 days from stroke onset, (3) anatomic T1 MRI >6 months, and (4) Pediatric Stroke Outcome Measure >12 months. Blinded scorers measured cerebellar volumes (left/right/hemisphere/vermis/total) using Osirix software. Cerebellar volumes ratios (nonstroke/stroke) were expressed as asymmetry indices (AI), with chronic/acute ratio <1.0 suggesting crossed atrophy. Acute brain stem and cerebellum (peduncle, hemisphere) DWI ratios were scored. Software measures were compared with visual inspection. Associations between AI, motor outcome (good/poor), and contralesional CST-DWI were sought. Rater reliabilities were assessed. RESULTS Twenty-three children were studied (median age, 6.3±4.4 years; 62% male). Baseline cerebellar volumes were comparable (right=56.9 cm(3), left=57.1 cm(3)). Cerebellar atrophy was suggested across the sample with overall AI <1.0 (0.973±0.05; P=0.009). Visual atrophy detection was specific (≈100%) but insensitive (54%). Children with poor motor outcome did not have lower AI (0.983±0.027 versus 0.965±0.068; P=0.40); however, children with acute contralesional CST-DWI did (0.928±0.078 versus 986±0.040; P=0.03). Acute cerebellar DWI did not predict atrophy. Rater reliabilities were excellent (>0.92). CONCLUSIONS Cerebellar atrophy can be demonstrated on MRI in childhood arterial ischemic stroke. Association with acute contralesional pontine DWI signal suggests early degeneration of corticopontocerebellar connections. The clinical significance of cerebellar atrophy in childhood stroke remains to be determined.