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Review Article | DOI: https://doi.org/10.31579/2768-2757/076
Neurosurgery Service, Guemes Sanatorium, CABA, Argentina.
*Corresponding Author: Torres, Pilar, Neurosurgery Service, Guemes Sanatorium, CABA, Argentina.
Citation: Pilar T., Guido B., Martina A., Jeronimo M., Fedra S., Sebastian B., (2023), Factors Influencing the Degree of Resection and Proposed Preoperative Scale for the Management of Skull Base Meningiomas, Journal of Clinical Surgery and Research, 4(3); DOI:10.31579/2768-2757/076
Copyright: © 2023, Torres, Pilar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received: 09 May 2023 | Accepted: 18 May 2023 | Published: 26 May 2023
Keywords: meningioma; skull base; Simpson; scale; unicentric study; statistical analysis
Objectives: to identify factors involved in the degree of resection of skull base meningiomas and to propose a scale to calculate the probability of total resection.
Materials and methods: unicenter, observational, retrospective study of patients operated on in the period 06/2018 – 06/2022. The following variables were used: age, clinic, location, size, previous embolization, perilesional edema, intertumoral calcium, characteristics in T2 and T1 and bone invasion. The degree of resection was measured with the traditional Simpson classification and was also divided into total (Simpson I, II and III) and subtotal (Simpson IV and V) resection. With the results, a scale was proposed taking into account the variables with statistical significance (p < 0.05). A literature review of the topic was conducted.
Results: A total of 23 patients were operated. They were statistically significant associated with Simpson's grade, location (p 0.002) and size (p 0.001). Associated with total and subtotal resection, bone invasion (p 0.013). For the scale we use: location (anterior 1 point, posterior 2 points, medial 2 points and medial involving cavernous sinus 3 points), size (<5 cm 1 point, >5 cm 2 points) and bone invasion (not 1 point and if 2 points). We performed an inferential analysis and an association was observed between the scale performed and the degree of resection (p 0.005).
Conclusion: In our study, an association was observed between bone size, location and invasion with the degree of resection achieved. We proposed a scale to measure the probability of total resection.
Meningiomas are the most common primary CNS tumor. They originate from meningothelial cells found in the arachnoid layer of the meninges, may be associated with the dura mater or choroid plexus, and account for 36% of all CNS 1 tumors. They grow along the outer surface of the brain, spinal cord or, less commonly, within the ventricular system. There are 3 grades based on WHO criteria. 80% are grade [1], benign and slow growing; 20 - 25% are grade 2 with higher probability of recurrence; and 1-6% are grade 3, malignant with metastatic potential [2].
They occur at an average age of 65 years. 66% of cerebral meningiomas occur in women, rising to 90% when they are located in the spinal cord [3]. Cases may occasionally occur in the pediatric population, and are generally associated with genetic syndromes or infant radiation [4].
The base of the skull is a complex anatomical region that forms the floor of the cranial cavity. There are several neoplastic processes that can manifest in the skull base, with different distribution depending on their location is anterior, middle or posterior. Meningiomas can develop in any of their locations.Surgery is the first-line treatment for most benign and malignant skull base tumors [5].
Gross total resection is the therapeutic paradigm that is intended to be reached when we diagnose a meningioma. Based on tumor resection, its residual remnant and infiltrated dura mater, Simpson introduced in 1957 a prognostic classification for the extent of resection, which has been widely applied in neurosurgical practice [6]. Simpson Grades I, II, and III can be defined as gross total resection and were associated with lower recurrence compared to Grade IV and V, defined as subtotal resection [7,8].
The surgical challenge of this type of tumor, which as we have mentioned are usually benign lesions in its great majority, is due to the difficult accessibility given the anatomy and its proximity to critical neurovascular structures. To avoid Complications, it is often necessary to perform a subtotal resection and preserve the patient's functional status [9].
Therefore, presurgical planning and the establishment of the objectives of tumor resection are essential parts, and they must be individualized, to provide an adequate surgical result.
It is very useful to identify predictive factors obtained in the preoperative assessment that influence the degree of surgical resection. The objective of this study is to identify these factors taking into account characteristics, either patient or tumor, that intervene in the degree of resection of skull base meningiomas, and propose a scale to assess the probability of total resection.
An observational, retrospective study was conducted, collecting data from clinical histories of patients operated with transcranial approach of skull base meningiomas during the period 6/2018 to 6/2022 by our neurosurgical team of the Güemes Sanatorium, CABA, Argentina.
Patients older than 18 years, without previous operations and with preoperative contrast MRI and brain tomography were included.
Patients younger than 18 years of age, with previous surgical interventions and with incomplete presurgical studies were excluded.
Epidemiological and clinical characteristics of the patient were analyzed, as well as characteristics of the tumor, whether location, size, imaging and whether he has previous embolization or not. The degree of resection was measured with the traditional Simpson classification and was also divided into total (Simpson I, II and III) and subtotal (Simpson IV and V) resection (Figure 1).
Figure 1: Representative images of patients operated on for meningioma of the anterior skull base of olfactory groove. A: T1 sequence with magnetic resonance contrast, axial slice. B: Same lesion coronal cut C: coronal Cort of postoperative imaging. D: approach and craniotomy performed.
Then, with the results obtained, a scale was proposed to graduate the probability of total or subtotal respectability of meningioma, taking into account the variables that had statistical significance (p < 0>
Finally, a literature review was conducted in order to compare results with other series.
Protocols and definitions of the variables studied
Patients were analyzed according to age in three cohorts: <40> 60 years. For the clinic, patients were divided into those asymptomatic at the time of diagnosis and symptomatic. Meningiomas of anteromedial localization were defined as those of the olfactory sulcus, sphenoid planum and tuberculum sellae. The anterolaterals are those that arise from the sphenoid wing, including those of the inner segment or clinoidal, those of the medial segment or wings and those of the lateral segment or pterional 10. Those of medial location were those of the cavernous sinus. And those of posterior location the petroclival meningiomas and the cerebellar ponto angle. For the size, the highest value obtained in any of its diameters was taken into account and divided into <3> 5 cm. Among the characteristics we obtained from the imaging studies, we collected whether or not intratumoral calcium was observed, if they had perilesional edema, if they had bone invasion, and their characteristics in sequence T1 and T2.
Information was also obtained on whether or not preoperative embolization was performed. Thedegree of resection was categorized according to the Simpson scale based on the intraoperative observation of the surgeon and its description in the surgical part; also comparing the results with resonance with gadolinium postoperative control. Simpson being grade I total removal of meningioma and dura mater, grade II total tumor removal and dura mater coagulation, grade III total tumor removal without dura mater coagulation, grade IV partial resection and grade V decompression or biopsy. We speak of total resection when a Simpson I, II and III was achieved, and subtotal resection with Simpson IV and V.
Taking the results of the variables studied of categorical type and with the database obtained, an analysis was carried out using frequent descriptive statistics and inferential statistics with chi square. SPSS version 25 or JAMOVI was used.
Patient characteristics
A total of 23 patients with skull base meningiomas were operated on during the study period (Table 1). Of these, 95% (n 22) were female. With respect to age, 21.7% (n:5) were younger than 40 years, 39.1% (n:9) between 40 and 60 years old and 39.1% (n:9) were older than 60 years. 73.9% (n:17) had clinical manifestation and 26% were asymptomatic at the time of diagnosis.
Tumor characteristics
The most frequent location was anterolateral with 47.8% (n:11), then posterior with 30.4% (n:7), anteriomedial 17.4% (n:4) and finally medial 4.3% (n:1). 4.3% (n:1) of tumors were smaller than 3 cm, 78.3% (n:18) measured between 3 and 5 cm, and 17.4% (n:4) were smaller than 5 cm; being less than 5 cm 82.6% (n:19).73.9% (n:17) of tumors did not have embolization prior to surgery
Imaging features of the tumor
52.2% (n:12) of meningiomas had perilesional edema and 17.4% (n:4) had intratumoral calcium. Bone invasion was found in 8.7% (n:2). A 34.8% (n: 8) were hyperintense in T2, 43.5% (n: 10) isointense and characteristic heterogenies 21.7% (n:5). Regarding its behavior in sequence T1 30.4% (n: 7) was hypointense and 69.6% (n: 16) isointense.
Degree of exeresis
Simpson I resection was achieved in 4.3% (n:1) of patients, Simpson II in 47.8% (n:11) of patients, Simpson III and IV in 21.7% (n:5) respectively, and Simpson V in 4.3% (n:1).
| Frecuencia | Porcentaje | |
| CLINICA | ||
| Sintomático | 17 | 73,9 |
| Asintomático | 6 | 26,1 |
| EDAD | ||
| <40> | 5 | 21,7 |
| 40-60 | 9 | 39,1 |
| >60 | 9 | 39,1 |
| LOCALIZACION | ||
| Anteromedial | 4 | 17,4 |
| Anterolateral | 11 | 47,8 |
| Medial | 1 | 4,3 |
| Posterior | 7 | 30,4 |
| TAMAÑO | ||
| <3> | 1 | 4,3 |
| 3-5 cm | 18 | 78,3 |
| >5 cm | 4 | 17,4 |
| EMBOLIZACION | ||
| No | 17 | 73,9 |
| Si | 6 | 26,1 |
| EDEMA PERILESIONAL | ||
| No | 11 | 47,8 |
| Si | 12 | 52,2 |
| CALCIO | ||
| no | 19 | 82,6 |
| Si | 4 | 17,4 |
| INVASIONOSEA | ||
| No | 21 | 91,3 |
| Si | 2 | 8,7 |
| T2 | ||
| Hiper | 8 | 34,8 |
| Iso | 10 | 43,5 |
| heterogeneo | 5 | 21,7 |
| T1 | ||
| Iso | 16 | 69,6 |
| Hipo | 7 | 30,4 |
| GRADO DEEXERESIS | ||
| I | 1 | 4,3 |
| II | 11 | 47,8 |
| III | 5 | 21,7 |
| IV | 5 | 21,7 |
| V | 1 | 4,3 |
Table 1: Frequency and percentage of variables
Regarding inferential results, two types of analysis were performed using the Chi-square test. On the one hand, the study variables were associated with the degree of excision measured with the Simpson scale taking the different five levels I, II, III, IV and V (Table 2). Only associations with location and size were found, with moderate and high effect sizes (Crammer's V).
| (p) | |
| Localización | 0,002 |
| Edad | 0,238 |
| Clínica | 0,487 |
| Tamaño | 0,001 |
| Embolización | 0,724 |
| Edema | 0,172 |
| Calcio | 0,600 |
| Invasión ósea | 0,096 |
| T2 | 0,427 |
| T1 | 0,213 |
Table 2: Association of variables with Simpson's degree.
On the other hand, the variables were associated with the measures of the Simpson scale divided as total resection (I, II and III) partial resection (grade IV and V) (Table 3). Thus, associations were found between bone invasion and grade, with moderate and high effect sizes (Crammer's V). No associations were found between the rest of the variables with the Simpson scale (p > .05).
| (p) | |
| Edad | 0,814 |
| Clínica | 0,091 |
| Localización | 0,131 |
| Tamaño | 0,089 |
| Embolización | 0,638 |
| Edema | 0,408 |
| Calcio | 0,231 |
| Invasión ósea | 0,013 |
| T2 | 0,705 |
| T1 | 0,226 |
Table 3: association with total or subtotal resection.
Proposed scale
Given the results objectified and described above, three variables with statistical significance were found from the inferential analysis: tumor size, location and bone invasion.
For the scale we decided to use the three variables: location (anterior 1 point, posterior 2 points, medial 2 points and medial involving cavernous sinus 3 points), size (<5>5 cm cm 2 points) and bone invasion (not 1 point but 2 points) (Table 4).
| Localización | anterior | 1 |
| posterior | 2 | |
| medial | 2 | |
| medial(C) | 3 | |
| Tamaño | < 5 cm | 1 |
| > 5 cm | 2 | |
| Invasión ósea | No | 1 |
| Si | 2 |
Table 4: Presurgical scale
The minimum score is 3 and the maximum is 7. The probability of total resection with a score of 3, moderate with a score of 4 and low with a score of 5 or more was considered high (Table 5).
| Grado | Puntaje |
| Alto | 3 |
| Moderado | 4 |
| Bajo | >5 |
Table 5: scale score.
Of the total of our series (Table 6) 11 had a score of 3 points and all had total resection (Simpson I, II and III); 10 patients scored 4, 6 of them with total resection and 4 with subtotal resection. Finally, 2 patients had a score of 5 and both had subtotal resection (Figure 2).
| Total (n) | Resección total | Resección subtotal | |
| 3 puntos | 11 | 1 | 0 |
| 4 puntos | 10 | 6 | 4 |
| 5 puntos | 2 | 0 | 2 |
Table 6: Patient score from our study.
Figure 2: patients with different degrees of excision measured in Simpson and their relationship with the score obtained from our scale.
When performing an inferential analysis, an association was observed between the scale performed and the degree of resection (p: 0.005) (Table 7 and 8).
| Significación asintótica (bilateral) | |
| Chi- cuadrado de Pearson | 0,005 |
Table 7 and 8: association between proposed scale and degree of resection.
In our series, 23 patients were operated on in the period 06/2018 - 06/2022; Within the variables analyzed, we found that both the location, size and bone invasion of the meningioma were related to the degree of resection. Of the total number of patients studied, a complete exeresis (Simpson I, II and III) was achieved in 73.8%.
In different publications, a correlation was shown between the location of meningiomas and the degree of excision achieved, with the skull base being the site where less complete resection is achieved11. Meling. et al. in a study of 1148 patients, they found that in 68% of skull base meningiomas achieved total excision, compared to 89
Among the most complex procedures of the neurosurgical specialty, without a doubt, are the surgeries of the skull base meningiomas. Achieving the highest degree of resection with the lowest postoperative morbidity remain the objectives pursued in this type of surgery. Taking into account the different particularities of the tumor, as well as that of the patient and its comorbidities, it is often not only necessary but beneficial to perform a subtotal resection. To obtain good results by providing individualized planning, it is important to take into account the different characteristics that influence surgery and that allow us to predict the degree of excision, and thus anticipate surgical results and the requirement for adjuvant treatment.
Our study showed a statistically significant relationship between the location (0.002), size (0.001) and bone invasion (0.013) of the meningioma with the degree of excision achieved. We proposed a simple scale to measure the possibility of total resection taking into account these variables
Given the low number of patients (n23) because it is a rare pathology, the associations between variables may be biased, leading to a high probability of committing type II error (that there are differences, but cannot be detected by inferential analyses), and a low statistical power. Together, we understand its limitations as it is a retrospective observational study.
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