Hemispheric CSF volume ratio quantifies progression and severity of cerebral edema after acute hemispheric stroke

Abstract

As swelling occurs, CSF is preferentially displaced from the ischemic hemisphere. The ratio of CSF volume in the stroke-affected hemisphere to that in the contralateral hemisphere may quantify the progression of cerebral edema. We automatically segmented CSF from 1,875 routine CTs performed within 96 hours of stroke onset in 924 participants of a stroke cohort study. In 737 subjects with follow-up imaging beyond 24-hours, edema severity was classified as affecting less than one-third of the hemisphere (CED-1), large hemispheric infarction (LHI, over one-third the hemisphere), without midline shift (CED-2) or with midline shift (CED-3). Malignant edema was LHI resulting in deterioration, requiring osmotic therapy, surgery, or resulting in death. Hemispheric CSF ratio was lower on baseline CT in those with LHI (0.91 vs. 0.97, p < 0.0001) and decreased more rapidly in those with LHI who developed midline shift (0.01 per hour for CED-3 vs. 0.004/hour CED-2). The ratio at 24-hours was lower in those with midline shift (0.41, IQR 0.30–0.57 vs. 0.66, 0.56–0.81 for CED-2). A ratio below 0.50 provided 90% sensitivity, 82% specificity for predicting malignant edema among those with LHI (AUC 0.91, 0.85–0.96). This suggests that the hemispheric CSF ratio may provide an accessible early biomarker of edema severity.

Automated Measurement of Net Water Uptake From Baseline and Follow-Up CTs in Patients With Large Vessel Occlusion Stroke

“…There were several CTs in our cohort where either no infarct was visible or it was too subtle for segmentation. We have recently demonstrated how volumetric CSF-based biomarkers of evolving edema can be measured and reflect edema formation within the first 12–24 h after stroke ( 23 ). It is possible that these two biomarkers capture different aspects of edema formation, one densitometric and other volumetric.…”

“…These CTP-defined core masks were registered to the NCCT using FLIRT from FSL (FMRIB, Oxford, UK) ( 22 ). The brain was divided into hemispheres, using the registered midline, as previously applied to measure the hemispheric CSF ratio ( 23 ). The infarct region was then flipped along the brain midline to generate a homologous region in the contralateral hemisphere (as shown in Supplementary Figure 2 ).…”

Navigating the Ocean of Big Data in Neurocritical Care

“…In a similar vein, an imaging platform has recently been initiated to bring together computed tomography and magnetic resonance imaging for stroke and other brain injuries. Its goal is to facilitate high-throughput processing of brain images by using AI algorithms to measure phenotypes such as edema and hemorrhage from large cohorts of patients [12][13][14]. Dissecting the observed variability at a scale sufficient to find key pathways and mechanisms might allow scientists to begin evaluating the genetic basis for brain injury phenotypes [15].…”

Commentary on “Midline Shift Greater than 3 mm Independently Predicts Outcome After Ischemic Stroke”

“…Those patients with stroke who develop midline shift and deterioration have less reserve and greater CSF displacement measurable by the 24-h mark, a time when midline shift is often still minimal [4]. Furthermore, given that the majority of edema and consequent CSF displacement occurs in the hemisphere ipsilateral to the stroke, the ratio of CSF remaining in that hemisphere relative to the volume in the contralateral hemisphere can be used as a dynamic early biomarker of edema that is significantly lower in those destined to develop midline shift [5].…”