Permission has been granted from Springer Nature Link regarding the use of some of the text in this introduction. Reproduced with permission from Kolias et al.1 © 2012 Springer Nature.
Scientific background
Head injury is common with approximately 900,000 people attending emergency departments per year in the UK,2 of which most patients sustain a mild traumatic brain injury (TBI). However, most fatal and unfavourable outcomes occur in patients with moderate or severe TBI, which account for approximately 10% of attenders. An estimated 1.2 million people live with some level of TBI-related disability in the UK, which has profound socioeconomic consequences, as the prevalence is particularly high among children and young to middle-aged adults.
By far, the most important early consequence of TBI is the development of an intracranial haematoma.3 Intracranial haematomas can be extradural, subdural, intraparenchymal or a combination thereof. Without effective surgical management, an intracranial haematoma may transform an otherwise benign clinical course with the expectation of recovery, to a situation where death or severe disability will occur.
Studies conducted after the introduction of computed tomography (CT) scanning report an incidence of acute subdural haematoma (ASDH) between 12% and 29% in patients admitted with severe TBI.4 Studies looking at patients with ASDH requiring surgery quote mortality rates between 40% and 60%. The decision to operate on an ASDH is usually based on the patient’s GCS score, pupillary exam, comorbidities, CT findings, age and, in delayed decisions, intracranial pressure (ICP). Neurological deterioration over time is also an important factor influencing the decision to operate. Different surgical techniques have been advocated for the evacuation of an ASDH. Patients with an ASDH that require an operation to remove the clot are currently treated either with a craniotomy or a decompressive craniectomy (DC). The choice of operative technique is influenced by the surgeon’s expertise, training and evaluation of the situation. Some centres treat all ASDH with DCs, whereas other centres used solely craniotomies.4
Head-injured patients with ASDHs that require an operation to remove the clot are currently treated either with a craniotomy or a DC.3 The steps of a craniotomy are: opening of the skin, removal of a piece of skull, removal of the clot, replacement of the piece of skull and closure of the skin. A DC is a similar procedure, but the piece of skull is left out prior to closing the skin. The advantage of a DC is that it is very effective in controlling brain swelling, which is often a problem in the days after the operation. When the swelling goes down, the patient has another operation to reconstruct their skull. The advantage of a craniotomy is that the patient will not need a later operation to rebuild the skull. However, this type of operation may fail to control the brain swelling in some patients.3 Both approaches are widely used among neurological surgeons (although the indications may differ); therefore, there is sufficient experience in the centres to set up a randomised trial.
Both procedures are carried out regularly in the NHS and worldwide. All neurosurgeons can perform both types of operation. With the objective of examining current practice patterns of surgical treatment for ASDH, we undertook a survey of members of the European Association of Neurosurgical Societies (EANS), Neurocritical Care Society, NeuroCritical Care Network, full members of the Society of British Neurological Surgeons (SBNS) and members of the British Neurosurgical Trainees Association during October and November 2011.5 The questionnaire survey was approved by the Academic Committee of the SBNS (project no. NE0026). From the survey,1 the question ‘When evacuating a traumatic ASDH, how often do you perform a primary DC (i.e. leave the bone flap out)?’ was answered by 283 neurosurgeons (201 board-certified consultants or equivalent; 82 trainees).
There were 138 from UK/Irish countries, 110 from other European countries, 13 North Americans and 22 respondents from various other countries. We decided to group together the responses of neurosurgeons working in countries with national representation to the EANS in order to have two similar-sized groups (UK/Irish and other European). We also think that these two groups have a degree of intrinsic homogeneity with respect to clinical neurosurgical practice. Although 41% of the respondents use primary DC < 25% of the time, almost one-third use DC in more than 50% of such cases. We found that a higher proportion of neurosurgeons from other European countries (48/110; 44%) as compared with UK/Irish neurosurgeons (29/138; 21%) use primary DC in more than half of ASDH cases (p < 0.001). Another interesting finding was that of the 23 UK/Irish neurosurgical units (NSUs) with at least 2 consultant respondents, only 6 units (26%) showed intradepartmental agreement regarding the use of primary DC for ASDH. We do not think that the observed variation in practice can be fully explained by regional/national differences in trauma care systems or the epidemiology of TBI within Europe. Rather, we believe that the variation in practice reflects the lack of high-quality evidence regarding the use of primary DC for ASDH evacuation.
A systematic review published by the Brain Trauma Foundation in 2006 concluded that research on the role of DC versus craniotomy is the top key issue for future investigation likely to improve the care of patients with ASDH.3
The Brain Trauma Foundation systematic review (literature search from 1975 to 2001) demonstrated the dearth of high-quality evidence addressing the effectiveness of the two main surgical procedures (craniotomy and DC) used for treating patients with ASDH.3 The available evidence consists of retrospective studies only, which do not usually address the effectiveness of the procedure.
We performed a systematic literature search from 2001 to April 2013 using the same search terms/methodology as the Brain Trauma Foundation investigators. We identified 16 published studies which present the outcome from ASDH. No prospective randomised studies comparing DC with craniotomy for patients with ASDH were found. Only five retrospective cohort comparison studies addressing the effect of the operative technique on outcome from ASDH were identified (3, 5–8). A finding that was universal across these five studies was that patients undergoing DC had significantly more severe injuries compared to patients treated with a craniotomy.
All these studies have methodological weaknesses because of their observational designs, with limited details regarding patient selection, outcome assessment and small sample sizes. It is not possible to draw meaningful conclusions from the available non-randomised studies, and the evidence base for the use of one approach over the other is weak. A well-designed and conducted randomised trial comparing the effectiveness and cost-effectiveness of craniotomy and DC is needed to inform current NHS practice, health policy and individual surgeon and patient clinical decision-making.
Following a DC, patients require reconstruction of their skull. However, a number of currently unknown parameters could render DC more cost-effectively than craniotomy. These parameters include: functional outcome, health-related quality of life (HRQoL), length of stay (LOS) in the intensive care unit (ICU) and length of rehabilitation. An economic analysis, embedded within a pragmatic randomised trial, is required to establish the relative cost-effectiveness of the different procedures when adopted into routine clinical practice.
Currently, there is only class III evidence with retrospective studies investigating the role of DC as a primary procedure for ASDH.
Explanation of rationale
There is currently no high-quality evidence guiding surgeons as to which operation they should be offering as first-line treatment to patients with ASDH. The results of a high-quality study will be used to inform future National Institute for Health and Care Excellence (NICE) head-injury guidelines and the practice of neurosurgeons in the NHS and worldwide.
Five-year pilot data from an NHS NSU (Cambridge) showed that 56% of patients with ASDH were treated with a DC.3 In this retrospective cohort comparison study, 91 patients had an operation for an ASDH. The standardised morbidity ratio was lower in individuals who received DC [0.75, 95% confidence interval (CI) 0.51 to 1.07] than in those treated with a craniotomy (0.90, 95% CI 0.57 to 1.35). Although the standardised morbidity ratio 95% CIs overlap, this study lends support to the hypothesis that DC may lead to better functional outcomes in comparison to craniotomy for adult head-injured patients with ASDH.
Health technologies being assessed
The two health technologies we wish to assess are the two most widely used surgical techniques for the evacuation of an ASDH: craniotomy and DC. When an ASDH is evacuated, the bone flap can be left out or replaced prior to closing the skin. The RESCUE (randomised evaluation of surgery with craniectomy for patients undergoing evacuation of acute subdural haematoma)-ASDH trial will compare these two specific components of the operation to remove an ASDH (i.e. bone flap left out prior to closing the skin vs. bone flap replaced prior to closing the skin). Both options are widely practised and accepted, but they have never been compared head-to-head in a randomised trial. When the bone flap is replaced prior to closing the skin, the operation is named craniotomy. On the other hand, when the bone flap is left out, the operation is named DC. The advantage of a DC is that it is effective in controlling brain swelling, which is often a problem in the days after the operation. When the swelling goes down, the patient has another operation to reconstruct the skull (cranioplasty). The advantage of a craniotomy is that the patient will not need a later operation to rebuild the skull. However, it may fail to control brain swelling in some patients.