Skull base meningiomas: neurological outcome after microsurgical resection
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- Scheitzach, J., Schebesch, KM., Brawanski, A. et al. J Neurooncol (2014) 116: 381. doi:10.1007/s11060-013-1309-x
Microsurgical resection is the primary treatment of skull base meningiomas. Maximal resection provides the best tumor control rates but can be associated with high surgical morbidity. To understand the relation between extent of resection (EOR) and functional outcome we have analyzed the neurological improvement and recurrence rate in a large consecutive series of skull base meningioma patients. In addition, we defined anatomical and biological factors predictive for recurrence and overall outcome. We investigated 226 skull base meningioma patients receiving tumor resection in our institution. The most frequent location was the medial sphenoid ridge (29.6 %). EOR was rated according to the Simpson scale. Overall performance was measured by the Karnofsky performance score (KPS); neurological deficits were quantified using the Medical Research Council Neurological Severity Score (MRC-NPS). Complete resection was achieved in 62.8 % and the EOR was significantly correlated to tumor location. The morbidity and mortality rate was 32.1 and 2.7 % respectively, new permanent neurological deficits occurred in 3.5 % of all patients. From all patients with focal neurological deficits, 60.1 % experienced significant improvement. Both the MRC-NPS and the KPS significantly improved from the preoperative status to discharge, however the improvement rate was dependent on the tumor location. Recurrence rate was 15.5 %; tumor size, bone- and venous sinus infiltration, WHO grade, poor EOR but not MIB-1 labeling index were independent factors predictive for recurrence. Microsurgical resection of skull base meningiomas improves neurological impairment in the majority of patients. Specific risk factors for recurrence require consideration for postoperative management.
KeywordsSkull base Meningioma Recurrence Prognosis Surgery Radiosurgery
Meningiomas are mostly benign tumors that originate from the arachnoidal coverings of the brain  and account for 13–26 % of all intracranial tumors . About 30 % of all meningiomas arise from the skull base , these tumors frequently lead to serious and potentially lethal consequences due to their intracranial location . The primary treatment modality for skull base meningiomas is surgical resection, with radiation being the only accepted form of adjuvant therapy [5, 6]. Several studies have demonstrated a strong correlation between the extent of resection and the frequency of recurrence in skull base meningiomas [7, 8, 9, 10]. However, complete surgical resection of skull base meningiomas is frequently limited due to their intimate relationship to the brain stem, neurovascular structures and cranial nerves [11, 12]. Radical surgical strategies can cause high morbidity and poor overall outcome in these patients [13, 14]. To understand the impact of surgical resection on the functional outcome, we have analyzed the neurological improvement and recurrence rate in a large consecutive series of skull base meningioma patients. In addition, we determined factors predicting early tumor recurrence in this patient population.
Materials and methods
Research council-neurological performance status scale (MRC-NPS)
No neurological deficit
Some neurological deficit but function adequate for useful work
Neurological deficit causing moderate functional impairment e.g. ability to move limbs only with difficulty, moderate dysphasia, moderate paresis, some visual disturbance
Neurological deficit causing major functional impairment e.g. inability
to use limbs, gross speech or visual disturbances
No useful function-inability to make conscious responses
Extent of resection expressed by Simpson grade and improvement rate of the MRC-NPS score of the analyzed skull base cases stratified by anatomical localization
Improvement rate (%)
Medial sphenoid ridge
Lateral sphenoid ridge
Histological classification of the analyzed skull base meningioma cases
Relation between extent of resection expressed by Simpson grading and recurrence rate
Extent of resection
Recurrence rate (%)
Complete resection including underlying bone and associated dura
Complete removal with coagulation of dural attachment
Complete removal without resection or coagulation of dural attachment
Uni- and multivariate analysis of factors predictive for tumor recurrence
5 % CI lower
95 % CI upper
MIB labeling index
Choosing the adequate treatment strategy for skull base meningiomas represents a formidable challenge. Compared to supratentorial meningiomas, these tumors grow slower and display a less aggressive biology with a significantly lower risk of malignant degeneration [15, 16, 17]. A subset of these lesions remains clinically silent , and can behave rather indolently with minimal symptoms even when left untreated . However, skull base meningiomas frequently cause severe neurological morbidity due to compression of neurovascular structures, which requires immediate and definite treatment . Surgery plays an indispensable role in the management of skull base meningioma, with a clear correlation between extent of resection and both recurrence rate and overall survival . This has caused increasingly aggressive attempts to remove skull base meningiomas  frequently leading to unacceptable high mortality and morbidity rates . Our results demonstrate that neurological impairment improved in the majority of the patients, with a new permanent postoperative deficit in only 3.5 % of all patients. Interestingly, we did not find a correlation between the extent of resection and the neurological improvement rate. Although several studies have not detected a correlation between extent of resection and neurological outcome [23, 24], Adachi et al.  have found a negative effect of extensive resection on neurological outcome in a subgroup of patients. Our results indicate that careful and complete decompression of eloquent structures is sufficient for the relief of clinical symptoms rather than attempting to radically resect the entire tumor shell [12, 25]. In addition, the postoperative improvement rate differed significantly between tumor locations, emphasizing the impact of location on the functional recovery rates in skull base meningiomas. The extent of resection differed significantly between tumor locations with the worst results in tumors of the petroclival region and the foramen magnum, which is in accordance to previous studies [26, 27]. In our patient cohort, extensive infiltration of neurovascular structures dictated a limited resection in those cases. The recurrence rate in our study population was 15.5 %, which is within the range reported in the literature . Factors correlating with recurrence in the univariate analysis were poor Simpson grade, tumor size, bone and venous sinus infiltration, WHO grade and a high MIB-1 labeling index. Surprisingly, in the multivariate model, MIB-1 labeling index was not found to be an independent factor predicting recurrence. Although a number of studies have found a significant correlation of high MIB-1 labeling indices with tumor recurrence [24, 28, 29], others have not [30, 31, 32]. Besides the definition of positive staining which varies between different institutions  a significant regional heterogeneity of cell proliferation in meningiomas has been demonstrated . The choice of representative tumor areas for MIB-1 index calculation therefore becomes an important source of interobserver variability. In our study, we have analyzed the MIB-index in a multivariate model with stratification for the WHO grade. Within the WHO grade I group, invariably showing low indices, it becomes difficult to distinguish tumors at risk for recurrence. This has led to the formulation of a threshold value of 3 % for grade I tumors with a higher risk of recurrence [24, 27], although a larger meta analysis has determined exactly 3 % as the average for all grade I tumors . Our results indicate that MIB-1 labeling undoubtedly has the potential to differentiate between benign and malignant meningiomas, but needs cautious interpretation in the individual tumor. Radiosurgery plays an increasing role in the multidisciplinary treatment of skull base meningiomas . In our study, all patients treated with radiotherapy only received conventional external beam radiation. Although conventional radiotherapy has been reported as an efficient and safe adjuvant treatment for skull base meningiomas , it is conceivable that radiosurgery will improve the tumor control rates and clinical outcome especially in patients of older age, poor overall performance stage or harboring tumors in unfavorable locations . Finally, we need to interpret our data concerning tumor recurrence carefully since the follow-up time has been relatively short for this tumor entity In conclusion, microsurgical resection of skull base meningiomas can lead to the improvement of neurological symptoms, however the functional recovery rate is depending on tumor location rather than the EOR. Bone and sinus infiltration as well as WHO grade and EOR are independent predictors for tumor recurrence. In order to define the optimal treatment strategy, a combination of microsurgical resection with radiation therapy and adequate follow up needs to be tailored to the individual patient in a multidisciplinary setting.
Conflict of interest
The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.