 British Journal of Neurosurgery, February 2014; 28(1): 93–97 © 2014 The Neurosurgical Foundation ISSN: 0268-8697 print / ISSN 1360-046X online DOI: 10.3109/02688697.2013.804488 Double-layer appearance after evacuation of a chronic subdural hematoma Hasan Kamil Sucu & Ömer Akar Department of Neurosurgery, I zmir Atatürk Research and Training Hospital, I zmir, Turkey Correspondence: Dr. Hasan Kamil Sucu, Department of Neurosurgery, I zmir Atatürk Research and Training Hospital, Pk: 53 Hatay 35361, I zmir, Turkey. Tel: +90-505-2118744. Fax: +90-232-8382341. E-mail: hsucu@yahoo.com Received for publication 11 October 2012; revised 17 March 2013; accepted 6 May 2013 Introduction After chronic subdural hematoma (CSDH) evacuation by burr-hole or twist-drill craniostomy, a double layer can sometimes be seen between the skull and the brain on con- trol computed tomographies (CTs). Tis structure could be thought of as the remaining part of a multilayer hematoma 1 and may lead to a second operation, especially when the patient shows little or no clinical improvement. Moreover, re-evacuation by an additional burr hole 2 or by craniotomy 3 can be considered to reach the inner layer. Generally, the inner layer is hypodense, while the outer layer is hyper- dense. To avoid unnecessary reoperations, it is important to know whether this fnding is related to intrahematomal septations/loculations that prevent the sufcient evacuation of the hematoma. We speculated that if the brain could not expand ade- quately when a CSDH is evacuated, the subarachnoid space could enlarge to fll the empty cavity. In this case, the inner hypodense layer represents subarachnoid fuid, while the outer hyperdense layer represents the remaining CSDH. Te purpose of this study is to investigate the cause and the out- come of the postoperative double-layer appearance and to determine whether it has any clinical importance. Materials and methods Both authors (ÖA, HKS) reviewed the fles, operation notes, follow-up records, and images of the CSDH cases that were operated upon during the last 3 years, between January 2008 and December 2010. Tis review was performed in May 2011. Pediatric patients (two patients, younger than 18 years) and patients operated on by craniotomy (one patient) were excluded from the study. Our database comprised the remaining 119 cases, who were operated on by burr-hole craniostomy. Operations were performed by any of the neu- rosurgeons working in our clinic (including the authors) and single or double burr-hole craniostomies were performed according to the surgeons’ preferences. We checked the preoperative, early postoperative (1–2 h after the operation), and late postoperative (after removal of the drains, usually on the second day after surgery) CTs of these patients. Early postoperative CTs were taken because our clinic’s policy is not to miss any complication such as the development of acute subdural hematoma or brain penetra- tion by the drain. We searched for a double-layer appearance as described by Tanikawa et al. 1 Tough Tanikawa grouped the CSDHs as monolayer and multilayer, we used the term of “double-layer” because there was no three or more level of hematoma. For the patients whose postoperative CTs showed a double-layer appearance, we measured the densi- ties of cerebrospinal fuid (CSF) in the lateral ventricles and preoperative CSDHs in the frontal and postparietal regions; ORIGINAL ARTICLE Abstract Objective. To investigate the reason for and the course of the double-layer appearance in the postoperative computed tomographies (CTs) of chronic subdural hematoma (CSDHs). Methods. We reviewed CSDH cases that were operated on during the last 3 years, between January 2008 and December 2010. We checked the preoperative, early postoperative, and late postoperative CTs of these patients. We investigated the relationship between the formation of a double- layer appearance and the prognoses and demographic characteristics of the patients. Results. Our database included 119 cases. A double-layer appearance was found in the postoperative CTs of 34 cases. The mean age of double-layer cases was older (72.5  12.1) than that of the remaining 85 cases (63.1  17.8). We did not fnd any relationship between the double-layer appearance and the reoperation/recurrence/ death rates. Conclusions. The double-layer appearance after evacuation of a CSDH might be caused by enlargement of the subarachnoid space and is not related to the presence of any residual hematoma. This appearance is not considered as a reason for reoperation. Keywords: chronic subdural hematoma; CT scan; subarachnoid space; surgical decompression