The fate of the bone flap is a significant decision during surgical treatment of acute subdural hematoma (SDH). A general guideline revolves around the surgeon’s concern for brain edema. However, limited studies have focused on the factors that contribute to perioperative brain edema. We proposed that assessment of brain volume via CT imaging in patients without bone flaps is a reasonable model to study brain edema.
From 2012 to 2015, 38 patients who underwent decompressive craniectomy for acute SDH were reviewed. Clinical data were extracted (age, gender, initial GCS, sodium level, hematocrit, and intraoperative blood loss). CT imaging was loaded into OsiriX MD (Pixmeo, Switzerland). From the preoperative scan, SDH volume, midline shift (MLS), and volume within the skull (to estimate baseline brain volume) were measured. From the postoperative scan, brain volume (including any herniating regions) was measured. Volume was obtained by a semi-automated protocol to select the region of interest through axial CT images. The extent of brain swelling was defined as Δ%, the percentage change in postoperative brain volume compared to preoperative volume. Other parameters [presence of contralateral injury, contusions, or intraventricular hemorrhage (IVH)] were noted. Univariate analysis occurred to evaluate relationship between independent variables and Δ%. Then, a multiple linear regression was carried out to predict Δ%.
Fifteen patients (39%) demonstrated negative Δ%. Univariate analysis found significant correlations between Δ% and the following: preoperative MLS, initial GCS, presence of IVH, and presence of contralateral injury (all p < 0.05). A multiple linear regression for Δ% that combined preoperative MLS, initial GCS, and IVH elicited a significant model [F (3,34) = 17.387), p < 0.01) with R2 0.605, where Δ% = 16.197 -1.246*GCS -0.986*MLS + 3.292*IVH (with 0 = no IVH, 1 = presence of IVH).
A high proportion can exhibit negative Δ%, or relative brain compression, after decompression of SDH. For these patients, replacement of the bone flap may be reasonable to avoid obligatory interval cranioplasty. Preoperative MLS, initial GCS, and presence of IVH can help predict whether overall brain volume will swell or compress within the normal confines of the skull. This can guide the decision to retain or remove the bone flap.
Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.
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