The gray-white matter ratio is used to estimate tissue edema on head computed tomography scans in cardiac arrest research. This rapid review aimed to determine whether gray-white matter ratio values differed between studies that included children and adults. We hypothesized that brain maturity affects myelination and, consequently, age would alter the range of the gray-white matter ratio. We searched PubMed from 2000-2025. Studies were selected if they included children or adult patients with cardiac arrest and reported gray-white matter ratio values relative to neurologic outcome groups or to normal controls. We summarized the studies and explored how gray-white matter values trended with age, gray-white matter ratio equations, timing of image acquisition during the post-resuscitation phase, and neurologic outcome groups. We retrieved five studies in children and 40 in adults. Regions of interest and equations used to measure gray-white matter ratio varied between studies, but most included the basal ganglia. The gray-white matter ratio was generally lower in poor-outcome groups than in good-outcome groups. In children with good outcomes, gray-white matter ratio values were similar to those of adults with poor outcomes. The gray-white matter ratio values were lower in younger children than in older children and adults. We did not find a consistent relationship between gray-white matter ratio values and the elapsed time from cardiac arrest to image acquisition. This review revealed varying gray-white matter ratios between children and adults in cardiac arrest studies, underscoring the importance of accounting for age when evaluating gray-white matter ratios in pediatric cardiac arrest populations. Gray-white matter ratio values were dependent on the regions of interest included in the equations. Readers should be aware of these sources of variation when comparing studies that use the gray-white matter ratio as a biomarker of hypoxic-ischemic injury in cardiac arrest. Future work is warranted to optimize the use of the gray-white matter ratio in pediatric cardiac arrest research. Question: Do gray-white matter ratio values in head computed tomography after cardiac arrest differ between pediatric and adult studies? Findings: Gray-white matter ratio values were lower in younger children compared to older children and adults. Age altered the gray-white matter ratio values. Meaning: Gray-white matter ratio ranges differ between young children, older children, and adults. Predicting outcomes in children using gray-white matter ratio cut-offs characterized in adult populations is not advisable; our review suggests that pediatric patients may be misclassified into poor-outcome groups if adult expected ranges are used.
Honjo et al. (Wed,) studied this question.