Quantitative assessment of impaired postevacuation brain re-expansion in bilateral chronic subdural haematoma: Possible mechanism of the higher recurrence rate

Introduction 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. Conclusion 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.