Neurosurgical decision-making in patients with traumatic brain injury (TBI) is often challenging for several reasons. First, no two TBI patients are identical—clinical and radiological findings may differ greatly [26]. Second, there is no high-quality evidence to support the range of possible neurosurgical procedures in TBI. Indications for surgical management are summarized in the Brain Trauma Foundation guidelines, [5] but are merely based on retrospective studies of small groups of selected patients. These guidelines provide general advice on surgical indications for evacuation of acute epidural (EDH), acute subdural (ASDH), and contusions/intracerebral hematomas (ICH) based on the size of the hematoma and midline shift. The guidance for decompressive surgery is even less clear. It is mostly performed to decrease raised intracranial pressure (ICP), either as a primary procedure in an acute setting, or as a secondary procedure to deal with diffuse edema or peri-contusional swelling. The guidelines state that this latter use of secondary decompression can reduce ICP, but does not necessarily improve outcome [6]. More fundamentally, the rationale for ICP monitoring has been challenged by the BEST TRIP randomized controlled trial (RCT), which found no benefit of a management protocol based on intracranial pressure monitoring, compared to one based on serial imaging and clinical examination. These results have generated doubts regarding ICP monitoring [1, 7, 15, 20, 28]. Overall, there is no clear consensus on the indications, extent, and timing of surgery [32].

This limited high-quality evidence for surgical management in TBI arises from a lack of RCTs, which may be difficult to conduct due to pragmatic, ethical, and methodological barriers [3]; however, observational studies to determine effectiveness are more prone for bias [2]. A promising alternative approach could be comparative effectiveness research (CER) [24, 33]. In this design, the heterogeneity and variability, that trouble RCTs in TBI, are accepted and exploited to study effectiveness of treatments as they occur in real-life practice. The current Collaborative European Neurotrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study aims to use CER methodology to study treatment effectiveness of several neurosurgical interventions [25].

The aim of this study was to explore differences in neurosurgical strategies for TBI across Europe to provide a context for CENTER-TBI, an up-to-date insight into European neurosurgical management of TBI, and to identify naturally occurring variation between trauma centers in order to identify substrates for neurosurgical research questions that might be answered using CER in the study.

Materials and methods

This study was conducted within the setting of the international observational study CENTER-TBI [25]. Between 2014 and 2015, all centers participating in the international multicenter observational study CENTER-TBI (www.CENTER-TBI.eu) were asked to complete a questionnaire on neurosurgical management of TBI (Supplementary file 1) [9]. The questionnaire was sent to 71 centers (Fig. 1), of which five centers dropped out and two joined in, resulting in 68 eligible centers from Austria (n = 2), Belgium (n = 4), Bosnia Herzegovina (n = 2), Denmark (n = 2), Finland (n = 2), France (n = 7), Germany (n = 4), Hungary (n = 3), Israel (n = 2), Italy (n = 10), Latvia (n = 3), Lithuania (n = 2), Norway (n = 3), Romania (n = 1), Serbia (n = 1), Spain (n = 4), Sweden (n = 2), Switzerland (n = 1), The Netherlands (n = 6), and The United Kingdom (n = 7).

Fig. 1
figure 1

Centers and countries included in the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study. Reprinted and updated from Cnossen et al. (2016) with permission from Dr. Cnossen and Maas et al. (2015). Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury: a prospective longitudinal observational study. Neurosurgery, 76:67–80, under a CC BY license, with permission from professor A.I. Maas

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Questionnaire development and administration

We developed a set of questionnaires based on available literature and experts to measure the structure and processes of TBI care in individual centers. Details regarding this process and the questionnaires used are described in a separate paper [9]. Pilot testing was undertaken in 16 of the participating centers and feedback was incorporated into the final design.

One of the questionnaires was on neurosurgical standard practice. This survey contained 21 questions which could broadly be divided into 3 categories: (1) center characteristics and internal structure; (2) general (neuro) surgical trauma care and processes; and (3) site specific neurosurgical management for treating ASDH, EDH, ICH, the use of DC, and policy with regard to orthopedic injuries in the context of patients who had suffered a TBI.

Questions either sought quantitative estimates of key metrics (e.g., annual surgical volume, staff size, ASDH thickness, or ICP thresholds for surgery) or attempted to elicit the “general policy” of the center. To capture the latter, these questions were formulated in two ways: respondents were asked to estimate what the management strategy is in more than three quarters of patients in their center in a given context; or respondents were asked to indicate how often they used a particular surgical technique or how often specific factors influence their decision-making (never = 0–10%, rarely = 10–30%, sometimes = 30–70%, frequently = 70–90%, and always 90–100%). The options “frequently” and “always” were interpreted as “general policy”, in line with a previous report [17] and similar to previous publications on other questionnaires [8, 9].

The reliability of the surveys was tested by calculation of concordance in a previous publication [9]. Overall, the median concordance rates between duplicate questions were 0.81 (range 0.44–0.97) and specifically for the “Neurosurgery” survey 0.78 (range 0.68–0.86).

Analyses

The median and interquartile range (IQR) were calculated for continuous variables, and frequencies were reported along with percentages for categorical variables. Countries were divided into seven geographic regions: Northern Europe (Norway 3, Sweden 2, Finland 2 and Denmark 2 centers), Western Europe (Austria 2, Belgium 4, France 7, Germany 4, Switzerland 1 and The Netherlands 6 centers), The United Kingdom (7 centers), Southern Europe (Italy 10 and Spain 4 centers), Eastern Europe (Hungary 3, Romania 1, Serbia 1 and Bosnia Herzegovina 2 centers), Baltic States (Latvia 3 and Lithuania 2 centers), and Israel (2 centers).

For the following neurosurgical treatment strategies, we quantified regional differences: an absolute cutoff of hematoma thickness as an indication for surgery for ASDH, DC in the primary evacuation of an ASDH, early/pre-emptive surgical evacuation for ICH, and DC as a general policy in case of refractory raised ICP.

To assess the association of region with one of these treatment choices, a logistic regression was performed with treatment choice (general policy or “yes/no”) as a dependent variable and the region (categorical) as independent variable. Nagelkerke R2 indicated the variance explained by geographic region. Analyses were done in IBM SPSS Statistics version 20 (IBM, Chicago, IL, USA).

Results

Center characteristics

All 68 eligible centers completed the questionnaire on neurosurgery (response rate 100%). Questionnaires were mainly completed by neurosurgeons (n = 53, 78%), followed by local CENTER-TBI investigators (mainly research physicians or nurses: 19%). On average, 10 neurosurgeons (IQR 8–13) and four trauma surgeons (IQR 0–12) worked in each center. All centers reported that neurosurgical coverage was available 24 h a day/7 days a week, either by way of in-house availability of a qualified neurosurgeon (47%), or the availability of such an individual in less than 30 min (53%) (Table 1).

Table 1 Characteristics of centers participating in neurosurgery survey
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General (neuro) surgical care and processes

Treatment decisions regarding cranial surgical interventions in TBI patients within the critical care ER and ICU period are in most centers determined by the neurosurgeon (n = 65, 96%), followed by the orthopedic surgeons and neuro-intensivist in respectively 3% (n = 2) and 1% (n = 1). Urgent neurosurgical interventions (ICP monitor device insertion not included) for life-threatening traumatic intracranial lesions, are made by the neurosurgeon in 98.5% and trauma surgeons in 1.5% of the centers. Raised ICP will almost always be incorporated in decision-making, the time of day almost never (Fig. 2).

Fig. 2
figure 2

Factors of influence on neurosurgical decision-making. Shown are the percentages of centers that would be never/rarely, sometimes or frequently/always influenced by the described factors in the decision to perform neurosurgical procedures. Question was completed by all 68 centers. ICP: intracranial pressure; ED: Emergency Department B Other factors were not predetermined but were specified by responders

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With regard to extremity fractures, the general policy in 59 (87%) centers was so-called damage control with priority for TBI and delayed definitive treatment of the limb fractures (Table 2). This policy is protocolized in 21 centers (22%).

Table 2 Neurosurgical treatment policy of traumatic brain injury
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Of all centers, 58 (85%) estimated the space-occupying effect of traumatic lesions on the surrounding tissue by calculation of the thickness of the hematoma and midline shift on CT. A quarter of centers used actual volume measurement to make surgical decisions (Table 2).

Neurosurgical management of ASDH, EDH, ICH, and the use of decompressive craniectomy

ASDH provided the highest volume of neurosurgical TBI cases, on average 25 cases per year. When performing a DC (for any indication), hemicraniectomy was the preferential technique, and bifrontal craniectomy was rarely performed (Table 1). Less than half of the centers (n = 27, 40%) reported an absolute threshold for evacuating an ASDH. Four out of 10 centers generally incorporate age in their decision for evacuating an ASDH (Table 2 and Fig. 2).

ICH were seldom operated upon pre-emptively, but 67% of centers reported undertaking delayed surgery in the event of deterioration. Almost a third of centers reported within-center variations between individual neurosurgeons in decisions regarding surgical evacuation of contusions or traumatic ICH.

Only a very low proportion of centers would routinely perform a DC at the time of evacuation of either ASDH or ICH (respectively 6% and 1.5% of the centers). For refractory raised ICP, most centers (n = 64, 91%) would consider a decompressive craniectomy, while 32 (47%) see this as a general policy in their center (Fig. 3, Table 2 and figure in supplementary file 2). Ninety-six percent (n = 65) reported to have a specific threshold for DC in refractory raised ICP. This was most commonly specified as 25 mmHg (n = 39, 58%), followed by 30 mmHg (n = 12, 18%) and 20 mmHg (n = 11, 17%).

Fig. 3
figure 3

Treatment indications for neurosurgical interventions. Shown are the proportions of centers that generally have these specific preferences with regard to operating or not in ASDH, ICH, and raised intracranial pressure, respectively. ASDH: acute subdural hematoma; DC: decompressive craniectomy; ICH: intracerebral hematoma; ICP: intracranial pressure

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Guidelines and practice variation

Overall, the reported adherence to the BTF guidelines was high (Fig. 4). The use of surgical interventions and specific indications for these interventions varied substantially within and between regions (Table 3). Surgical evacuation of ICH was only performed in the Baltic States and Southern Europe and geographic region explained 35% of the variance in use of the intervention. Having a specific threshold for ASDH surgery and employing a DC for refractory-raised ICP showed the largest within-region and also between-region variation. Lastly, when directly asked whether variation in specific management strategies exist, respectively 31% and 43% indicated to have a structural variation within their center staff with regard to ICP sensor insertion and mass lesion evacuation (Table 4).

Fig. 4
figure 4

BTF guideline adherence. Shown are the percentages of centers that reported to never/rarely, sometimes or frequently/always follow the Brain Trauma Foundation guidelines for the management of SDH, EDH, or contusions. Question was completed by 68 of the 68 centers. TBI: traumatic brain injury; SDH: subdural hematoma; EDH: epidural hematoma

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Table 3 Within- and between-region variation in surgical management
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Table 4 Neurosurgical decision making
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Discussion

The aim of this study was to explore differences in neurosurgical strategies for TBI across Europe. We found substantial variability in practice and thereby provide useful indications regarding potential substrates for CER in CENTER-TBI. The structures and processes of neurosurgical care are generally homogeneous across centers with a comparable number of neurosurgeons, similar organization of neurosurgical coverage and uniform organization of responsibility for most surgical decisions on the ER and ICU. The indications for surgery, however, differ substantially with high within-region and between-region practice variations.

Contemporary neurosurgical care

There are no recent comparable studies providing an overview of neurosurgical management on this scale. Two recent national surveys, in The United Kingdom and the Republic of Ireland and The Netherlands, have shown a comparable variability among neurosurgeons regarding the decision to evacuate an ASDH or to perform a primary DC [21, 34].

When comparing our results to existing—much older—surveys, evacuation of a traumatic ICH seems to be less often considered than in the past [11, 30]. Our results are concordant with older surveys in reporting variable use of DC for refractory raised ICP, despite the DECRA trial (the RECUEicp was not published yet) [12, 19]. Interestingly, although the mostly applied cutoff for DC in refractory is reported to be 25 mmHg (60%), a lower value, 20 mmHg, and a higher value, 30 mmHg, are both reported to be used in almost 20% of centers.

More broadly, our results replicate past data that suggest poor guideline adherence and practice variability. Rayan et al. showed that in only 17% of a random sample of (brain) trauma patients care was delivered according to the BTF guidelines [31]. Of note, in the current study, surveys were sent to the centers between 2014 and 2015, so the more recent, updated BTF guidelines were not published yet, although the update was for medical management mainly (except DC in refractory IC) [6].

Comparable questionnaires on other aspects of TBI care have recently been published for ER and ICU management that, without exception, show practice variation [8, 9, 14, 18]. Practice variation has also been reported for other life-threatening or emergency disorders including ruptured abdominal aneurysm [4] and the spontaneous intracerebral hemorrhage [16].

Strengths and limitations

A strength of the current study is the methodology that we used to investigate practice variation. First, detailed questions were posed to shed light on specific clinical decisions with regard to neurosurgical interventions. Subsequently, (objective) answers on amounts (volume load, mostly from in-hospital registries) were combined with qualitative information (estimations of general policies, using two approaches). When integrated with the high response rate and low amount of missing data in 68 centers, this overview provides a complete picture of reported neurosurgical care across Europe.

This study also had weaknesses. First, responses to the questionnaire may have been biased by the abstract nature of the questions posed, which neglected to provide a more concrete clinical context for judgments about reported practice. Although the respondents were experienced neurosurgeons with a scientific background, the difficulty of weighing individual patient characteristics with potentially fatal consequences can never be fully captured by a theoretical survey. In particular, the rational decision-making can obviously be completely different due to the cognitive biases of neurosurgeons in the acute critical care period.

Second, there might be a concern as to how well the individual neurosurgeon respondent can represent the general center neurosurgical policy. Although we urged the respondent to report the general consensus on treatment at their center rather than individual management preferences (see Supplementary file 1), neurosurgical strategies may still be variable within centers between neurosurgeons; however, we did capture a qualitative assessment of this intra-center variability (Table 4). Third, we did not fully account for inherent regional variations such as evidence knowledge, caseload, and case-mix due to referral patterns or admission policies, as a potential explanation for differences in neurosurgery policies. Variations in evidence knowledge for some questions, such as those on guidelines, are important. Moreover, while we did asses the center’s caseload and casemix, the caseload and casemix of the (individual) respondent was not specifically asked. Fourth, the questions dealt with individual decisions in isolation, rather than the more complex real-life situation where several competing priorities need to be addressed. Fifth, the reports may have been biased (in varying extents) towards how centers would have been liked to be perceived, rather than a faithful report of actual clinical policy and practice. This issue will be addressed by a planned comparison of these Provider Profiling responses with actual treatment strategies employed in patient-level data from these centers in the CENTER-TBI Core study.

Finally, our study sample represents centers participating in TBI-research which are likely specialized neurotrauma centers with a tendency to have practice that is skewed towards up-to-date knowledge. An example is the fact that almost half of all centers stated to have a neurosurgeon in house 24 h a day. When studying all centers in Europe providing care to TBI patients, variability might be even larger.

Implications

Our results should be interpreted in combination with the current evidence on the effectiveness of different surgical strategies. For the use of DC in refractory raised ICP due to diffuse swelling, two RCTs have provided useful guidance. The DECRA trial showed that early use of DC for modest rises in ICP was associated with worse outcomes [12]. More recently however, after the conduct of this survey, the RESCUEicp trial showed that, when used for refractory severe intracranial hypertension, DC can save lives, but results in an excess of severely disabled survivors [19]. It is clear that the intervention is not uniformly beneficial: while some functional improvements occur by 12 months, many survivors remain severely disabled. Rescue-ICP was not published yet at the conduct of this study. In our study, the majority of centers indicated that DC is often employed for both indications (pre-emptive and last resort).

With regard to focal lesions, a recent study suggested that in patients with an ASDH an aggressive approach towards evacuation is associated with better outcome compared to a conservative approach [35]. Similar trends were noted in the STITCH-trauma trial, which suggested better outcome with early surgical management of ICH [29]. In our study, a minority of centers considers an early strategy for ICH evacuation.

Lastly, DC in the primary evacuation of an ASDH seems to be associated with more favorable outcomes [22]. There is no class 1 evidence, although the research question is currently being challenged in an RCT (Rescue-ASDH; ISRCT87370545). In the current survey standard (in some cases preventive) DC in ASDH evacuation is rarely employed but mostly done in case of intraoperative swelling.

There may be several explanations for the practice variation that we observed. Although high practice variation rates can be a sign of poor implementation of evidence-based care, in this context it probably reflects the lack of strong evidence to underpin practice. In such a low evidence context, clinical decisions are not driven by careful consideration or penetration of the evidence, but by local customs and surgical training, handed down over the years from one surgeon to the other in a given center (or country). The professional cultural drivers that underpin such learned treatment preferences are resistant to change, and provide an important hurdle to the design and conduct of randomized studies for neurosurgical interventions in TBI [27].

Additionally, even where the results of RCTs are available, it is possible that many neurosurgeons do not think the RCT results applicable to their (individual) patients, or restrict their focus to short term clinical outcomes such as mortality and complication rates (instead of long-term clinical or patient reported outcomes). [13]

The results of the questionnaire point out burning clinical questions for neurosurgery in TBI. For ASDH and ICH, important questions include whether to operate or not, the timing of operative evacuation, and whether or not a primary DC should be undertaken. Future studies should address these questions. For DC, the variation should lead to studies exploring the lack of evidence penetration, in addition to studying effectiveness of DC in refractory raised ICP.

While RCTs may provide the security of randomization as a basis for examining answering these questions, RCTs have no successful history in TBI due to various reasons [24]. The CENTER-TBI Provider Profiling exercise has revealed large practice variation that can be related to variation in patient outcome [23]. Such a CER approach may be a pragmatic alternative to RCTs.

Therefore, different steps are required. Firstly, to specify, ideally a-priori, how and where treatment variation occurs. This was one of the goals of this provider profiling. Secondly, the CENTER-TBI Core Study will need to collect patient-level data from a large variety of centers, capturing the range of treatment variation and relate it to outcome. The main challenge is to disentangle the effect of specific surgical strategies in a center from other regional care variation that might affect outcome. To do so, we propose random-effect models in which the effect of “surgical strategy” on outcome is estimated with adjustment for other between-hospital differences in a random effect for hospital [10, 34, 35].

Conclusions

This survey study explored differences in neurosurgical strategies for TBI. Current neurosurgical care differs within Europe (and Israel), while the organization of trauma centers does not. This variation in practice likely reflects the lack of high-quality evidence for these important, potentially life-saving, emergency neurosurgical interventions. In addition, local professional culture may drive practice in ways that are not dependent on the availability or penetration of evidence. The resulting entrenched practice variation does not facilitate equipoise that makes RCTs easy to deliver. CER may provide a pragmatic approach to generate evidence on optimal neurosurgical strategies for TBI patients.

Funding/sponsors

This study was funded by the European Union Seventh Framework Program (grant 602150) for Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) and the Hersenstichting Nederland (Dutch Brain Foundation, grant PS2014-06) for The Dutch Neurotraumatology Quality Registry (Net-QuRe). There is no industry affiliation.