Estimation of Chronic Subdural Hematoma Size Using CT Imaging; a Comparison of In-Plane Thickness to 3D Volumetry

Backgrounds: Pre- and postoperative chronic subdural hematoma (CSDH) sizes have been used in clinical trials to predict the risk of postoperative recurrence. Commonly, dimensions of the pre- and postoperative lesions have been assessed by computerized tomography (CT) scans using maximum thickness as a linear measurement. Our goal was to characterize this common method for quantification of pre- and postoperative lesion sizes and to assess its estimation validity compared to estimation by hematoma volumetry. Methods: We prospectively investigated pre- and 1st postoperative day CT scans of 107 adult surgical patients with uni- or bilateral CSDH. Pre- and postoperative thickness of CSDH was determined and then compared to pre- and postoperative lesion volume measured with 3D hematoma volumetry. Results: Pearson correlation coefficients between mean pre- and postoperative lesion thickness and mean pre- and postoperative lesion volume in the unilateral subgroup were 0.491 and 0.498, respectively; in the bilateral subgroup 0.505 and 0.579, respectively; and in the whole series 0.653 and 0.472, respectively. Conclusions: Pre- and postoperative thickness of CSDH does not offer reasonable approximations of the pre- and postoperative lesion size when compared with results from 3D volumetry in the unilateral subgroup, bilateral subgroup or overall.