Perinatal hypoxic-ischemic brain injury: What's behind the "ribbon effect"?

Ribbon effect describes a perceived macroscopic color reversal of the gray and white matter, characterized by a pale cortex and diffusely dusky underlying white matter. This finding is thought to be unique to the perinatal period and indicative of hypoxic-ischemic injury. However, the clinical and microscopic correlates of this macroscopic finding have not been clearly defined. A 21-year retrospective study of autopsies was performed. Ribbon effect was seen in 190 subjects, ages 20 weeks gestation to 9.5 months adjusted age. Clinical associations and radiographic findings were similar in ribbon effect cases and controls. A variety of histologic findings were observed including acute neuronal injury, diffuse white matter gliosis, and white matter necrosis. Only white matter vascular congestion was significantly correlated to the macroscopic severity of ribbon effect; the severity of white matter injury and acute neuronal injury were not significantly correlated to ribbon effect. While hypoxic-ischemic changes were present in nearly all cases of ribbon effect, the location, severity, and chronicity of these changes varied considerably, and similar findings were observed in controls. The presence of ribbon effect therefore does not predict microscopic findings apart from vascular congestion, highlighting the importance of microscopic examination in perinatal brain autopsies.