=====Closed system drainage=====
There is controversy among neurosurgeons regarding whether irrigation or [[drainage]] is necessary for achieving a lower revision rate for the treatment of [[chronic subdural hematoma]] (CSDH) using [[burr hole]] [[craniostomy]] (BHC). Therefore, Xu et al. performed a [[metaanalysis]] of all available published reports. Multiple [[electronic health database]]s were searched to identify all studies published between 1989 and June 2012 that compared irrigation and drainage. Data were processed by using [[Review Manager]] 5.1.6. Effect sizes are expressed as pooled odds ratio (OR) estimates. Due to heterogeneity between studies, we used the random effect of the inverse variance weighted method to perform the meta-analysis. Thirteen published reports were selected for this meta-analysis. The comprehensive results indicated that there were no statistically significant differences in mortality or complication rates between drainage and no drainage (P > 0.05). Additionally, there were no differences in recurrence between irrigation and no irrigation (P > 0.05). However, the difference between drainage and no drainage in recurrence rate reached statistical significance (P < 0.01). The results from this meta-analysis suggest that burr-hole surgery with closed-system drainage can reduce the recurrence of CSDH; however, irrigation is not necessary for every patient
((Xu C, Chen S, Yuan L, Jing Y. Burr-hole Irrigation with Closed-system Drainage
for the Treatment of Chronic Subdural Hematoma: A Meta-analysis. Neurol Med Chir 
(Tokyo). 2015 Sep 17. [Epub ahead of print] PubMed PMID: 26377830.
)).