What Is the Best Technique for Removing a Chronic Subdural Hematoma?

By Roger Härtl, MD, Leonard and Fleur Harlan Clinical Scholar in Neurological Surgery, Associate Professor of Neurological Surgery, Department of Neurological Surgery, Weill Cornell Medical College. Dr. Härtl reports no financial relationships relevant to this field of study.

Synopsis: In a prospective randomized trial, use of a post-operative drain was associated with lower mortality and less recurrence in the treatment of chronic subdural hematoma (SDH)

Source: Santarius T, et al. Use of drains versus no drains after burr-hole evacuation of chronic subdural haematoma: A randomised controlled trial. Lancet 2009;374:1067-1073.

Chronic subdural hematoma (SDH) is one of the most frequently encountered lesions that neurosurgeons treat. It consists of liquefied blood and blood-breakdown products that accumulate in the potential space between the pia-arachnoid membrane and the dura mater. Only in a minority of cases can a previous significant traumatic event be clearly identified. Pathogenesis most likely involves the combination of a coagulation defect with some type of inflammatory process, both of which initiate and propagate the development of blood accumulation. Importantly, the inflammatory reaction frequently results in the development of a web of surrounding membranes with adhesions and septations. The presence of these adhesions can complicate surgical evacuation. Technically, the surgical treatment of SDH is straightforward and one of the most rewarding operations for neurosurgeons and their patients. The challenges result from the tendency of these lesions to recur.

Surgical options for treatment include twist drill trephination, burr holes, and open craniotomy with or without intraoperative irrigation and with or without a closed postoperative drainage system. More recently, a variation of the twist drill evacuation with a subdural evacuating port system has been described that can be placed at the bedside and permits drainage of fluid during a period of hours to days. The choice of operative technique is frequently dependent upon surgeon preference, training, and experience. A meta-analysis performed by Weigel and colleagues summarized 48 articles published between 1981 and 2001 and concluded that twist drill and burr hole evacuation were the safest procedures and that craniotomy was associated with the lowest recurrence rate but had a higher rate of perioperative complications.1 Intraoperative irrigation and postoperative drainage systems were not associated with an increased infection rate. The authors recommended twist drill and burr hole craniostomy with a drainage system, as first tier treatment, while craniotomy should be considered as second tier treatment and primarily for recurrent SDH evacuation.

In their well-performed, randomized, single-institution study, Santarius and colleagues from Addenbrooke's Hospital, Cambridge, UK, report a recurrence rate of 9% using a drain (n=108) and a 24% recurrence without a drain (n=107). The drains were not associated with an increased rate of complications. The mortality at six months was 9% with a drain compared to 18% mortality without a drain.


In our experience, the success of surgery for SDH depends largely on the imaging characteristics of the SDH on preoperative CT or MRI scans. Chronic, homogenous fluid collections will usually be evacuated via twist drill or burr hole trephination, while the presence of substantial loculated pockets of subdural fluid will lead us to perform a craniotomy. The advantage of a craniotomy is that it allows fenestration with coagulation and / or removal of membranes. We always use intraoperative irrigation and postoperative drainage systems. One concern with the present study is the poor definition of chronic SDH and treatment assignment. The authors state that patients with "symptomatic chronic subdural haematoma proven by CT scan for burr-hole drainage were eligible for inclusion" and that those "in whom surgery other than burr-hole evacuation was indicated" were excluded. In our experience this would exclude the large number of patients with mixed density hematomas with septations, who likely would benefit more from a formal craniotomy. However, this remains unclear in the present study.

The authors certainly have to be applauded for performing a rare and needed prospective, randomized clinical trial comparing different neurosurgical operative techniques. Their results provide solid class I evidence and support what was expected based on previous studies. The significance of this trial can be best gauged when one takes into consideration the almost complete absence of prospective, randomized clinical trials within neurosurgery. For example, the "Guidelines for the Surgical Management of Traumatic Brain Injury" published in 2006 reviewed > 700 articles but found no controlled clinical trials to support one form of surgical management over another, or surgical vs. conservative treatment.2 It is understandable that such trials cannot be easily performed in patients who are actively deteriorating. However, there is no reason why it should not be attempted to have evidence-based medicine guide us in situations where patients are relatively stable and the best surgical technique is unknown.


1. Weigel R, et al. Outcome of contemporary surgery for chronic subdural haematoma: Evidence-based review. J Neurol Neurosurg Psychiatry 2003;74:937-943.

2. Bratton SL, et al. Guidelines for the management of severe traumatic brain injury. J Neurotrauma 2007; 24:Suppl 1.