Clinical Outcomes and Decision-making Choice of Skull Base Approaches for Petroclival Meningiomas: a Single Center Report of 179 Cases

1. Study Design and Ethics Approval In this institutional study, 179 cases of PCM were retrospectively collected and analyzed from January 2011 to December 2020 in our neurosurgical department, Xiangya Hospital, Central South University. The studies involving human participants were reviewed and approved by the Ethics Committee of Xiangya Hospital, Central South University (approval no. 202103227) in accordance with the ethical standards of the 1964 Declaration of Helsinki and its later amendments. Patients provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.
2. Evaluative Criteria Clinical characteristics with manifestation, neurological function status, neuroimaging and surgical records, and follow-up data were reviewed and evaluated. The preoperative, postoperative and follow-up QOL were assessed and measured using the Karnofsky Performance Scale (KPS) score by two neurosurgeons, independently, on admission, discharge, and follow-up, correspondingly. The preoperative radiological data were obtained from routine examination of brain 3.0 T magnetic resonance imaging (MRI) with T1-weighted, T2-weighted and T1-contrast-enhanced sequences, computed tomography angiography (CTA) and skull base high-resolution computed tomography (HRCT) scans to evaluate tumor size, origin of dural attachment, growth pattern, involved circumjacent range, brainstem displacement, peritumoral edema, encasement of vital neurovascular structure and hydrocephalus to further identify tumor classification and treatment strategy. All of cases were re-examined with contrast MRI to identify the EOR within 72 hours post-operative. The EOR was divided into three levels of gross total resection (GTR) (Simpson Grades I/II), subtotal resection (STR) (Simpson Grades III/IV, with 90-99% excision of the lesion) and partial resection (PR) (Simpson III/IV, with below 90% excision of the lesion), depending on the intraoperative identification and postoperative MRI.

A combination of outpatient, telephone and Internet connections were used for follow-up. Follow-up data, including clinical and radiographic information, was collected 3 and 6 months after the surgical procedure and then every 1 or 2 years, in most cases via clinic visits. Questionnaires and phone calls were also carried out. The tumor recurrence or progress (R/P) meant lesion regrowth in situ in GTR cases or residual lesion regrowth with the increase of the maximal diameter more than 3 mm in STR/PR cases. Those who experienced tumor R/P were recommended for additional treatment. The latest follow-up deadline is March 1, 2021. 3. PCM Classification On the basis of the variation of PCM pathological alteration in anatomy and with the accumulating experience and incisive comprehension to PCM, we modified and improved our previous tumor classification into updated five types with two subtypes: clivus type (CV), petroclival type (PC), petroclivosphenoidal type (PC-S), sphenopetroclival type (S-PC) with two subtypes of S-PC I and S-PC II and central skull base type (CSB). 4. Skull Base Approach Choice The skull base approach choice was fundamentally followed by the modified classification. At the same time, the patient's age, request and physical condition cannot be ignored. In this study, the retrosigmoid approach (RSA), subtemporal transtentorial transpetrosal approach (STTA), extended pterional transtentorial approach (EPTA), pretemporal trancavernous anterior transpetrosal approach (PTCA) and presigmoid combined supra-infratentorial approach (PCA) were applied as the main surgical approaches. Moreover, the RSA included basic retrosigmoid approach (BRSA), retrosigmoid trantentorial approach (RTTA) and retrosigmoid intradural suprameatal approach (RISA). Intraoperative neurophysiological monitoring containing somatosensory evoked potentials (SSEP), motor evoked potentials (MEP) and brainstem auditory evoked potentials (BAEP) were essentially and routinely implemented. 5. Statistical Analysis Statistical analysis was performed using IBM SPSS Statistical Package 21.0. The t-test was performed to clinical data comparisons between the two groups and the ANOVA test was used to compare the difference between multiple groups. P < 0.05 was considered statistically significant.