In this nationwide registry-based study of patients undergoing surgery for intracranial meningioma, we benchmark the 30-day complication rate for clinically relevant complications. The risk of reoperation within 30 days of surgery due to complications was 5.2%, new focal neurological deficit occurred in 14.8%, new-onset seizures in 4.5%, VTE occurred in 3.0%, and the 30-day mortality was 1.5%. These real-world data on short-term outcomes may be useful in the decision-making process and prior to surgery.
Perioperative outcomes
We found that the most common postoperative complication to be new onset focal neurological deficit, which is in agreement with previous studies [
39]. In the literature, the proportion experiencing new or worsened deficit in unselected patients with meningioma is 8.3–9.3% [
9,
39]. A retrospective single-center study from 1984 reported postoperative deficits in 10.8% of patients during the first 30-day postoperative period, and thus, our data with 14.8% new deficits appears unfavorable [
9]. However, it is difficult to compare with retrospective assessment with standardized prospective registration due to detection bias [
12]. In selected materials, the range is wider and much affected by tumor location and preoperative symptomatology [
10,
27,
31]. In general, the literature reports improvement of neurological deficits in most patients during the initial follow-up time after surgery [
9,
40]. Additionally, the short-term neurological deficit may also predispose for other medical complications in the postoperative period [
39].
Onset of seizures after meningioma surgery is a renowned concern, explaining the interest in prophylactic treatment with antiepileptic drugs (AED) [
23], although the current evidence indicates no clear benefits in prevention of postoperative seizures with routine perioperative AED administration [
20,
38]. Routine perioperative administration of AED is not performed at any of the neurosurgical centers in Sweden. In this study, new onset seizures occurred in 4.5% and this is in line with the existing literature where new onset seizure postoperatively was reported in the range 1.9 to 19.4% [
23,
36,
38,
43]. In a recent systematic review and meta-analysis, among the 1085 patients with supratentorial meningiomas without seizures prior to surgery, new-onset seizures occurred in 12.3% [
13]. This large variability between the reported seizure frequency in the literature may be due to different lengths of follow-up, meningioma location, and pattern of evaluation because retrospective cross-sectional studies may capture different aspects than standardized and prospective reporting.
Postoperative hematoma following meningioma surgery was 9.4% and the percentage undergoing reoperation due to any cause within 30 days was 5.2%. The variable “postoperative hematoma” reported in to the SBTR is defined as symptomatic hematoma without additional information regarding what kind of symptoms. Reviewing the literature, postoperative hematomas in need of surgical evacuation were reported in the range of 2.1–7.1% [
14,
17,
22]. In a prospective study by Geßler et al. using postoperative imaging in 113 patients with meningioma, there were 30 patients (26.5%) who experienced symptoms postoperatively, including prolonged awakening, seizures, and neurological deficit [
15]. A total of 28 patients (24.7%) experienced postoperative symptoms and radiological verified hematoma. Two patients underwent reoperation due to a hematoma, which represents 1.8% of the cohort of 113 patients. The frequency of postoperative hematoma may seem high in our cohort, but since reoperations due to any cause occurred in 5.2% of patients, this seems comparable with previous reports. It is not reported to the registry the cause of operation within 30 days, but according to literature, the majority of the reoperations within 30 days after surgery of intracranial tumors were due to hematomas, leakage of cerebrospinal fluid, or infection [
22,
32,
41].
Venous thromboembolism occurred in 3.0% of our cohort, in accordance with previous results where numbers ranged from 3.6 to 7.2% [
17,
35]. In SBTR, we are unable to differentiate deep vein thrombosis from pulmonary embolism. The risk-benefit of routine anticoagulation prophylaxis should be carefully weighed given the ratio of hematoma/VTE seen in an unselected meningioma cohort [
35]. The timing of complications also indicates that prophylaxis may be safer to delay until > 24 h postoperatively [
41].
The 30-day mortality in Sweden after surgery for intracranial meningioma is currently at 1.5%. This corresponds to similar findings in a Norwegian study where the overall surgical mortality of intracranial tumor surgery within 30 days was reported at 2.3% and for only meningiomas 0.9% [
22]. As expected, case selection is a strong predictor of outcome because studies on small meningiomas (< 3 cm) and convexity meningiomas show no 30-day mortality [
27,
31], and similarly, we present 0.3% mortality within 30 days in asymptomatic patients while 2.4% for patients with higher-grade meningiomas. A study from 1984 showed a mortality rate of 4.0% during the first 30-day postoperative period for intracranial meningiomas [
9]; hence, surgical treatment appears safer in modern neurosurgery. This improvement may be due to better surgical and anesthesiologic techniques, but treatment at an earlier time-point with less burden of disease due to better access to imaging may also contribute [
37].
Asymptomatic patients
Due to the usually indolent natural course, some argue that surgery should be reserved for larger meningiomas, meningiomas that exhibit growth, or meningiomas that become symptomatic [
8,
16]. Nevertheless, in clinical practice, the treatment plan is often individualized and adjusted for each patient, including patient’s preference. In principle, the treatment should be better than the natural history and, in this regard, a short-term neurological morbidity of 8.3% must be considered. Unfortunately, surgical indications are not reported in this study (e.g., radiological growth, patients wish), and hence, we cannot make direct assumptions of the expected natural course. In the literature, new neurological deficits in the short-term following surgery of asymptomatic patients are reported in a wide range with respect to frequency and severity [
21,
29,
44]. Thus, identifying patients with higher risk is of importance and both tumor size and location are presumably important, but also factors such as longer lasting surgery, poor functional status, and high patient age may impact postoperative outcome [
5]. We also explored possible predictive factors for neurological deficits after surgery but we were unable to identify any maybe due to rather crude variables.
Registry-based meningioma studies
Studies relying on data from clinical registries and administrative databases are useful for evaluating treatment strategies and add a different dimension to the results of more selective randomized controlled trials. This kind of research is especially valuable in the field of neurosurgery, where large variations in clinical practice exist [
3,
19]. Moreover, clinical registries and administrative databases allow inclusion of large patient groups that are ineligible for inclusion in randomized trials due to age and comorbidity. Additionally, registry-based studies allow monitoring of trends, costs, and complications of surgical procedures in a real-world setting.
Still, registry-based studies must build upon what is reported to a registry, sometimes limiting chances to explore potential interesting associations. However, for variables included, it is possible to collect large amounts of data in a population-based setting. The SBTR collects data from all regions in Sweden and has a good coverage and established systems for quality control, which makes it a useful source of information concerning collected quality metrics. The baseline characteristics captured by SBTR is similar to previous large-scale and population-based reports [
1,
39]. Very few studies have been published with registry-based data regarding meningioma using data from the Surveillance, Epidemiology and End Results (SEER) registry [
1,
2]. In comparison, the SBTR data contain important information on symptoms and the functional level as shown in Table
1. In addition, the SEER national tumor database collects reports from 20 regional cancer registries, which includes approximately 28% of the population in USA, making this registry not entirely representative of the national meningioma population. Another large registry used for patients with meningioma is the National Cancer Data Base (NCDB) [
26]. Two large studies have been performed with data from this registry where the main aim of the studies have been gross total resection and predictors of improved survival as well as factors for survival in meningiomas [
25,
34]. These studies do, however, lack the postoperative short-term aspects with regard to complications and surgically acquired deficits, aspects that may be important in the decision-making process.
Strengths and limitations
Limitations of this study include those inherent to registry-based studies with limited details and without possibility to complete missing data. Specifically, there is a lack of detail for variables including radiological parameters, meningioma location, and radiosurgery. The lack of long-term data if neurological deficits were transient or permanent is another limitation. Also, surgeon-evaluated deficit may not be sensitive for all aspects compared to patient-reported deficit [
12]. Finally, some variables may be subject to considerable interpretation (e.g., postoperative hematoma) while others are more robust (e.g., VTE, reoperation due to complication). Strengths include a truly population-based inclusion of a large number of meningioma patients from a recent time period where data are reported prospectively in a continuous and standardized fashion. Due to the regionalized health care system, any major complication in the post-operative course is treated at the same department that performed the primary surgery. Consequently, we expect that most major complications are reported to the SBTR.