Brain Injury, December 2012; 26(13–14): 1731–1736 ORIGINAL ARTICLE Cerebral atrophy is associated with development of chronic subdural haematoma ANDREW IL YANG1, DAVID S. BALSER1, ARTEM MIKHEEV2, SHANI OFFEN1, JASON H. HUANG3, JAMES BABB2, HENRY RUSINEK2, & UZMA SAMADANI1,4 1Department of Neurosurgery, 2Department of Radiology, New York University School of Medicine, New York, NY, USA, 3Department of Neurosurgery, University of Rochester School of Medicine, Rochester, NY, USA, and 4New York Harbor Health Care System Manhattan Veteran’s Administration, NY, USA (Received 17 December 2011; revised 30 April 2012; accepted 21 May 2012) Abstract Objective: To test that cerebral atrophy is associated with increased risk for development of chronic subdural haematoma (cSDH), this study performed volumetric analysis of computed tomography (CT) brain scans from patients who were diagnosed with cSDH on subsequent CT scans and their age-matched controls. Methods: Volumetric analysis was performed on CT scans acquired a mean of 209 days prior to cSDH diagnosis in 19 patients. Cerebral atrophy present on these scans was then compared to 76 age-matched control patients randomly selected from cSDH-free subjects. For personal use only. Results: There was a higher degree of atrophy in cSDH patients (n ¼ 19, 14.3% Æ 5.4%) than in age-matched control patients (n ¼ 76, 11.9% Æ 5.5%; p ¼ 0.044). Logistical regression demonstrated that atrophy was found to be a significant predictor of cSDH at all ages (OR ¼ 1.11, 95% CI ¼ [1.01, 1.23], p ¼ 0.05). For younger subjects 65 years of age (n ¼ 50), atrophy was an even stronger predictor of cSDH (OR ¼ 1.17, 95% CI ¼ [1.02, 1.34], p ¼ 0.026). Conclusions: Cerebral atrophy is associated with the development of cSDH and this association is greater in patients 65 years of age. Keywords: Cerebral atrophy, chronic subdural haematoma, volumetric analysis Brain Inj Downloaded from informahealthcare.com by Nyu Medical Center on 12/01/12 Introduction mortality after cSDH is 32% [10] and patient Chronic subdural haematoma (cSDH) is a common prognosis is worse when there is conversion to neurosurgical condition, with an incidence of 1–13 acute SDH [3, 4, 9, 11]. per 100 000 people per year [1–3]. One-third Unlike acute subdural haematoma, 29–38% of patients treated surgically for cSDH have no mem- of affected patients are older than 80 years of age orable precipitating trauma [11, 12]. The majority of [4]. The incidence of cSDH has increased by 36% patients with cSDH have sufficiently mild trauma between 1998 and 2007 [4]. Patients with cSDH are that there is no loss of consciousness [13]. Several at risk for intracerebral haemorrhage [5], seizures [5] potential pre-disposing factors have been identified, and exacerbation of comorbidities associated with including alcohol abuse and anticoagulant or anti- the interruption of anticoagulant therapy [6]. Up to platelet therapy [3, 11, 12, 14]. 20% of patients have poor neurologic outcomes, Patients with extensive cortical atrophy have been resulting in significant disability [4, 5,7–9]. One-year anecdotally noted to sustain a higher risk of cSDH. Correspondence: Uzma Samadani, MD, PhD, 423 E. 23rd St 4168N MC112, New York, NY 10010, USA. Tel: 212 686 7500 x3665. Fax: 212 951 6876. E- mail: [email protected] ISSN 0269–9052 print/ISSN 1362–301X online ß 2012 Informa UK Ltd. DOI: 10.3109/02699052.2012.698364 1732 A. I. Yang et al. It was hypothesized that cerebral atrophy would be (Æ2 years) at a ratio of four controls per cSDH associated with increased risk for cSDH formation. patient. To test this hypothesis, volumetric analysis of The CT scans analysed for the cSDH group were computed tomography (CT) brain scans were per- performed a mean of 209 days (range from 12–683 formed from patients who were diagnosed with days; median ¼ 80 days) prior to the scan resulting in cSDH on subsequent CT scans and their age- a diagnosis of cSDH. matched controls using an automated 3D segmen- tation algorithm [15]. CT images were used due to CT scanning their lower cost and greater availability in the outpatient setting relative to MRI. All patient scans were helical CT obtained on Toshiba Aquilion 16 or Aquilion 64 scanners (Toshiba, Tustin, CA). Data from three different Methods scanners was used for this study. Acquisition param- eters were as follows: peak tube voltage 120 kVp, Scan selection x-ray tube current 300 mA, radiation exposure time Institutional Review Board approval was obtained. 500–1000 ms, number of detectors 16 or 64, field of The institutional network was searched in the ICD view 20–25 cm, soft-tissue reconstruction kernel and purpose of visit (POV) narrative field for the FC64, acquisition matrix size 512 Â 512 Â 30–50, keywords ‘subdural’ and ‘haemorrhage’ or ICD-9 isotropic in-plane resolution 0.390–0.468 mm and code 432.1. 457 patients were identified and the visit axial-slice thickness 3–5 mm. date from the first recorded POV entry including a Volumetric analysis diagnosis of a subdural haemorrhage was used as a date of diagnosis. Cortical atrophy A was defined as the ratio The search was then narrowed to those patients (expressed in %) of the cerebrospinal fluid (CSF) who had undergone a non-contrast head CT prior to volume to intracranial space (ICS) volume: the admission prompted by a cSDH. This reduced A ¼ 100 Â vol(CSF)/vol(ICS). Segmentation of the 457 patients to 185 patients. brain tissue was performed using Bridge Burner, a The control population was all patients who had fully-automated and validated 3D segmentation undergone a single non-contrast head CT for any algorithm [15]. Segmentation of the ICS was based reason and did not have a subdural haematoma. on soft-tissue intensity thresholding, connectivity For personal use only. There were 6757 control patients suitable for anal- and constrained growth [15]. The CSF volume was ysis. All of the patient scans for inclusion in this segmented by selecting all ICS voxels with attenu- study were performed between May 2005 and April ation values within the fluid range, i.e. from À4Hu 2011. to þ16 Hu (Figure 1). The ratio of the number of CSF voxels to the number of ICS voxels gives A. Randomization A representative image is included as Figure 1. To reduce the processing time while incurring Nineteen unique cSDH patients (including two minimal error in A (absolute difference <0.5%), the Brain Inj Downloaded from informahealthcare.com by Nyu Medical Center on 12/01/12 women) and 76 age-matched (Æ2 years) controls original image matrix was reduced from (four women) were randomly selected for analysis (512 Â 512 Â 30–50) to (256 Â 256 Â 30–50) by via the following algorithm to assure that the sample in-plane averaging. User interaction was limited to chosen was representative of the entire population excluding axial slices below the petrous portion of the and that the statistical conclusions are valid: temporal bone. This was done to focus the measure- ments on cerebral atrophy, which included the two (a) the identifying numbers of all suitable subjects lateral and third ventricles and all peripheral (sulcal) (i.e. those satisfying the age constraint) were atrophy. The atrophy in the cerebellum, 4th ventricle placed in the excel sheet, one per row, and the and spinal canal were not measured. rows were numbered; (b) a random number generator function (REF) in Statistics excel was used to determine a row number in the list; and Logistic regression was used to calculate the associ- (c) the corresponding ID was marked as selected ation between A, the continuous predictor variable, and removed from the list. The procedure was on cSDH, the dichotomous outcome variable. After iterated with age constraints appropriately establishing the significance of the logistic model, the adjusted until the entire sample of 19 patients odds ratio (OR) of A as a risk factor for cSDH was and 76 controls was selected. Patients and assessed. Univariate analysis was performed using random controls were individually age-matched the F-test, Student t-test, chi-square test and Wald Cerebral atrophy and cSDH 1733 test. All values are expressed as mean Æ SD and As suggested by the data and by prior studies [16, differences were considered statistically significant if 17], a quadratic regression model fit this relationship the associated p-value was less than 0.05. well (Figure 2): A ¼ 0.0012x2 þ 0.058x þ 1.7 (R2 ¼ 0.372, p < 0.0001, F-test). Thus, each year adds 0.2% additional CSF to the intracranial Results cavity. There was a higher degree of atrophy in cSDH In 76 control patients there was a significant asso- patients (n ¼ 19, 14.3 Æ 5.4%) than in age-matched ciation between age and atrophy (Figure 2). control patients (n ¼ 76, 11.8 Æ 5.5%). This differ- ence was statistically significant (p ¼ 0.044, Student t-test) (Figures 2 and 3). If the subjects are separated into two groups by age, patients 65 (n ¼ 50, 10 with cSDH) and patients >65 years old (n ¼ 45, nine with cSDH), the difference in cerebral atrophy between those who have cSDH and those who do not is significant in the younger age group, but not in patients older than 65 years (Figure 3). For patients 65 years old, controls had 9.0% Æ 4.7% atrophy vs 13.7% Æ 6.7% in the cSDH group (p ¼ 0.007, student t-test). Logistical regression demonstrated atrophy to be a significant predictor of cSDH (OR ¼ 1.11, 95% CI ¼ [1.01, 1.23], p ¼ 0.05, Wald test).