Objective: To determine the influence of intracerebral hemorrhage (ICH) location, volume and hematoma surface on perihemorrhagic edema evolution.
Methods: ICH patients of the prospective UKER-ICH cohort study (NCT03183167) between 2010 and 2013 were analyzed. Hematoma and edema volume during hospital stay were volumetrically assessed, and time course of edema evolution and peak edema correlated to hematoma volume, location and surface to verify strength of parameters on edema evolution.
Results: Overall 300 patients with supratentorial ICH were analyzed. Peak edema showed high correlation with hematoma surface (R2=0.864,p<0.001) rather than with hematoma volumes, irrespective of hematoma location. Smaller hematomas with higher ratio of hematoma-surface-to-volume showed exponentially higher relative edema (R2=0.755,p<0.001). Multivariable logistic regression analysis revealed a cut-off ICH-volume 30ml beyond which an increase of total mass lesion volume (combined volume of hematoma and edema) was not associated with worse functional outcome; specifically, peak edema was associated with worse functional outcome in ICH<30ml (OR 2.59[1.55-4.31];p<0.001), contrary to ICH ≥30ml (OR 1.20[0.82-1.75];p=0.339). There were no significant differences between patients with lobar versus deep ICH after adjustment for hematoma volumes. 
Conclusions: Peak perihemorrhagic edema, though influencing mortality, is not associated with worse functional outcomes in ICH volumes above 30ml. Although hematoma volume correlates with peak edema extent, hematoma surface is the major parameter for edema evolution. The effect of edema on functional outcome is therefore more pronounced in smaller and irregularly shaped hematomas and these patients may benefit more significantly from edema-modifying therapies.

PERIHEMORRHAGIC EDEMA: REVISITING HEMATOMA VOLUME, LOCATION AND SURFACE