Definition and time course of pericavity edema after minimally invasive endoscopic intracerebral hemorrhage evacuation

Background Perihematomal edema (PHE) volume correlates with intracerebral hemorrhage (ICH) volume and is associated with functional outcome. Minimally invasive surgery (MIS) for ICH decreases clot burden and PHE. MIS may therefore alter the time course of PHE, mitigating a critical source of secondary injury. Objective To describe a new method for the quantitative measurement of cerebral edema surrounding the evacuated hematoma cavity, termed pericavity edema (PCE), and obtain details of its time course following MIS for ICH. Methods The study included 48 consecutive patients presenting with ICH who underwent MIS evacuation. Preoperative and postoperative CT scans were assessed by two independent raters. Hematoma, edema, cavity, and pneumocephalus volumes were calculated using semi-automatic, threshold-guided volume segmentation software (AnalyzePro). Follow-up CT scans at variable delayed time points were available for 36 patients and were used to describe the time course of PCE. Results Mean preoperative, postoperative, and delayed PCE were 21.0 mL (SD 15.5), 18.6 mL (SD 11.4), and 18.4 mL (SD 15.5), respectively. The percentage of ICH evacuated correlated significantly with a decrease in postoperative PCE (r=-0.46, p<0.01). Linear regression analysis revealed a significant relation between preoperative hematoma volume and both postoperative PCE (p<0.001) and postoperative relative PCE (p<0.001). The mean peak PCE was 26.4 mL (SD 15.6) and occurred at 6.5 days (SD 4.8) post-ictus. The 2-week postoperative time course of relative PCE did not fluctuate, suggesting stability in edema during the perioperative period surrounding evacuation and up to 2 weeks after the initial bleed. Conclusions We present a detailed and accurate method for measuring PCE volume with semi-automatic, threshold-guided segmentation software in the postoperative patient with ICH. Decrease in PCE after MIS evacuation correlated with evacuation percentage, and relative PCE remained stable after minimally invasive endoscopic ICH evacuation.