The Role of Endoscopic Endonasal Surgery in the Management of Skull Base Chondrosarcomas: Technical Nuances and Short-Term Outcome

Background Chondrosarcomas affecting the skull base are rare, slowly growing, locally aggressive tumors comprising 0.2% of all intracranial tumors and 6% of skull base tumors. Frequently, chondrosarcomas are clinically silent until it has reached a sizable dimension with significant displacement of neurovascular structures. Resection of chondrosarcomas through transcranial approaches remains challenging, and has some disadvantages including brain retraction, inevitable manipulation of critical neurovascular structures, and limited exposure and visualization. All these drawbacks have a significant impact on morbidity and mortality rates.

Objective The aim of this study is to highlight the technical nuances and short-term clinical outcome of a series of patients with skull base chondrosarcomas resected via a pure endoscopic endonasal approach (EEA).

Methods We retrospectively reviewed the medical records of patients with skull base chondrosarcomas, treated via EEA at our medical center from July 2010 through December 2016. Clinical data, radiographic evaluations, intraoperative findings, histopathological examinations, postoperative complications, and early clinical outcomes were recorded and analyzed. Volumetric analysis of pre- and postoperative MRI was performed for the objective assessment of the extent of resection.

Preliminary Results We identified 12 patients with skull base chondrosarcomas who underwent endoscopic endonasal resection. The average age of patients was 48.8 years; with a men:woman ratio of 1:3. Cranial nerves deficits were the most common clinical presentation (8 cases, 66.6%). Three cases were incidentally diagnosed, and one patient presented with manifestations of panhypopituitarism. Headache was part of the clinical presentation in four cases (33.3%). Abducens nerve was the most commonly affected nerve in our series (4 cases, 33.3%), followed by the oculomotor nerve (3 cases, 25%). Five cases had previous surgeries, while two cases had previous radiotherapy. Intraoperatively, a CSF leak was encountered in eight cases (66.6%); however, no patient had a postoperative CSF leak. In all cases, vascularized nasoseptal flap (NSF) was used as the cornerstone of the multilayer skull base reconstruction. NSF was used in combination with free fat grafts in eight cases, and solely in the other four cases. Histopathological examination confirmed the diagnosis of intermediate-grade chondrosarcoma in eight cases, and low-grade chondrosarcoma in four cases. We achieved gross total resection in five cases, while near-total resection (>95%) in seven cases. Two patients underwent further resection in a second-stage via transoral and retrosigmoid approaches, and gross total resection was achieved. Follow-up duration ranged from 20.3 to 68.3 months (mean = 37.8 months). No patient had a new neurological deficit postoperatively. Cranial nerves deficits improved in seven patients, and were stable in one patient. Ten patients received postoperative adjuvant radiotherapy.

Conclusion EEA is a safe and effective surgical alternative for the resection of skull base chondrosarcomas. Multidisciplinary treatment strategy is of utmost importance for achieving local control of chondrosarcoma and improving patient survival. Large multicentric prospective studies addressing the endoscopic endonasal management of chondrosarcomas would better delineate long-term outcomes.