title: Quantitative assessment of impaired postevacuation brain re-expansion in bilateral chronic subdural haematoma: possible mechanism of the higher recurrence rate.
abstract: BACKGROUND
  Recurrence of chronic subdural haematoma (CSDH) occurs in up to 30% of patients. The rate of recurrence is higher in bilateral versus unilateral CSDH and the reason for this has not been fully elucidated. There are few quantitative studies of temporal changes in brain re-expansion after haematoma evacuation. The aim of this study is to use a simple volumetric image analysis method to quantify temporal changes of postoperative brain re-expansion in unilateral and bilateral CSDH.
  
  
  METHODS
  We reviewed computed tomography (CT) scans of 20 consecutive patients (16 men, 4 women; median age, 73.5 years) with CSDH (unilateral, n=10; bilateral, n=10) who underwent surgery (burr hole drainage on one or both sides) at our institutions during the period from June 2006 to August 2008. Haematoma volume was quantified preoperatively and on postoperative days 14 and 30 by computer-based image analysis (PACS Web 1000 System) of CT scans. We then calculated the brain re-expansion rate (BRR) for postoperative days 14 and 30.
  
  
  RESULTS
  Haematoma volume remained significantly higher (p<0.001) in bilateral versus unilateral CSDHs at both postoperative time points, and the BRR was significantly greater (p<0.001) in unilateral versus bilateral CSDH at both time points.
  
  
  CONCLUSIONS
  Results of this quantitative analysis provide definitive evidence for a poor BRR in bilateral compared to unilateral CSDH. This impairment may result in shifting of the brain and shearing of blood vessels, resulting in a higher recurrence rate.
authors.affiliation: Department of Neurosurgery, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan.
authors.forename: Woon-Man
authors.initials: WM
authors.lastname: Kung
authors.forename: Kuo-Sheng
authors.initials: KS
authors.lastname: Hung
authors.forename: Wen-Ta
authors.initials: WT
authors.lastname: Chiu
authors.forename: Shin-Han
authors.initials: SH
authors.lastname: Tsai
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Lin
authors.forename: Yao-Chin
authors.initials: YC
authors.lastname: Wang
authors.forename: Muh-Shi
authors.initials: MS
authors.lastname: Lin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003399:Craniotomy / Q000379:methods*; D004322:Drainage / Q000379:methods*; D005069:Evaluation Studies as Topic; D005260:Female; D020200:Hematoma, Subdural, Chronic / Q000453:epidemiology / Q000473:pathology / Q000517:prevention & control* / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D055502:Secondary Prevention; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome