The skull base (SB) is the osseous foundation of the cranial vault. It contains many openings that allow communication between the extracranial and intracranial structures. This communication is crucial in normal physiologic processes yet may also arrow spread of disease. This article provides a comprehensive review of SB anatomy including important landmarks and anatomic variants relevant to SB surgery. We also illustrate the diverse pathologies affecting the SB.

Radical resection of complex lesions occupying multiple compartments at the central skull base remains a significant challenge, since surgical outcomes may be compromised by insufficient exposure and inappropriate techniques. However, the efficiency of the maxillary swing approach for these lesions has not been sufficiently evaluated. Careful assessment of lesion characteristics must be performed when selecting the appropriate procedure.
Between May 2006 and February 2017, 17 patients underwent resection of extensive lesions in the central skull base using the maxillary swing approach. As shown in the representative cases, data regarding clinical findings and technical considerations were reviewed.
Complete resection was achieved in all patients. The pathological findings were diverse, and the majority were schwannomas (9 cases, 52.94%), followed by meningiomas (World Health Organization II) (3 cases, 17.65%). Complications were managed as described in the case illustrations, and symptoms improved with time. The follow-up duration ranged from 62 to 192 months (median, 114 months), while 2 patients were lost to the follow-up. No mortality was observed. Two patients who experienced malignancy relapse were still under observation due to their asymptomatic status.
Our preliminary results suggest that the maxillary swing approach can be an alternative option for managing extreme cases, such as large, extensive, hypervascularized masses with fibrous or calcified consistency, or for recurrent lesions in the central skull base. En bloc resection can be successfully obtained, resulting in long-term local control.

Initially developed as a minimally invasive technique to approach inflammatory conditions, transnasal endoscopic surgery has progressively expanded its anatomic targets and clinical indications. Consequently, numerous surgical approaches to the anterior and central skull base were developed, referred to as extended endonasal approaches (EEA). The intrinsic advantage of EEA is the exploitation of a natural corridor provided by sinonasal airspaces, with no need for skin incision and osteotomy and limited soft tissue damage. In this context, imaging plays essential role, demonstrating the relevant anatomic relationships of the lesion, the proper surgical corridor, the anatomic variants that may increase the surgical risk.

Local reconstruction of central skull base defects may be inadequate for large defects or reoperative cases; free tissue transfer may be necessary. Inset of the flap and management of the pedicle can be challenging. We report our experience and approaches.
Retrospective review identifying seven patients with central skull base defects who underwent free flap reconstruction from 2016 to 2020.
Four patients with recurrent nasopharyngeal carcinoma, one with recurrent craniopharyngioma, one with clival-cervical chordoma, and one with meningioma of the middle cranial fossa were analyzed. Six defects were closed with an anterolateral thigh free flap and one with a radial forearm free flap. In two patients, the flap was secured in an onlay fashion to the defect via a Caldwell-Luc transmaxillary approach. In one patient, the flap was passed transorally, and the pedicle was delivered into the neck via Penrose drain. In two patients, a parapharyngeal technique and in two others, a retropharyngeal was used for nasopharyngeal inset with endoscopic assistance. There were no flap failures, with an average follow-up time of 20.1 (range 3.2-47.1) months. One patient required flap repositioning on postoperative day three due to midline shift and intracranial contents compression. The transoral inset flap necessitated flap repositioning on postoperative day 13 to improve the nasopharyngeal airway.
Free flap reconstruction of the central skull base is challenging, but transmaxillary, transoral, parapharyngeal, and retropharyngeal approaches can be used with endoscopic assistance to ensure secure inset flap and avoid airway obstruction.

BACKGROUND: This article provides an overview of the natural history and management of adenoid cystic carcinoma infiltrating the skull base (SB ACC).
METHODS: A comprehensive review of the available literature and discussion regarding the current management of SB ACC.
RESULTS: This review describes the unique pathology, appropriate diagnostic work-up and contemporary management options in SB ACC. There is a specific focus on the role of surgical resection with post-operative radiotherapy, given the literature suggesting a superior locoregional control rate. The importance of surgical decision making and varying surgical approaches are detailed. In addition, the emerging role of biological agents is discussed.
CONCLUSIONS: The gold standard for SB ACC is surgical resection and post-operative radiation, given the superior locoregional control. In patients not amendable to surgery, palliative radiation should be considered. The role of biological agents is still evolving. The complexity of SB ACC management mandates experienced multi-speciality management.

UNASSIGNED: The purpose of this three-dimensional (3D) study was to assess retrospectively the middle cranial fossa and central skull base of patients treated with the Herbst appliance (HA).
UNASSIGNED: 3D surface virtual models of 40 Class II, division 1 malocclusion patients were generated from cone-beam computed tomography (CBCT) acquired before treatment (T0) and after 8 months of HA treatment (T1). T0 and T1 3D models were superimposed volumetrically at the anterior cranial fossa. Twenty subjects who had been treated with the Herbst appliance (HAG) were compared to 20 subjects who were not treated orthopedically. The latter group served as a comparison control group (CG). Quantitative assessments of the location and directional changes were made with linear and angular measurements between anatomical landmarks. Qualitative assessments of the spatial behavior of the middle cranial fossa and central skull base relative to the anterior cranial fossa were displayed graphically for visualization with color maps and semitransparent overlays. Non-parametric tests were performed to compare the between the HAG and CG.
UNASSIGNED: Point-to-point linear measurements and skeletal rotation (pitch, roll, and yaw) changes were very small along the observational period and were not significantly different between HAG and CG. Visual analysis of color maps and overlays confirmed that no changes in the cranial base were associated with HA.
UNASSIGNED: HA therapy did not produce clinically significant changes in the middle cranial fossa and central skull base.

OBJECTIVE: Complete resection of a central skull base meningioma (CSM) is possible, but it is often associated with high morbidity. Stereotactic radiosurgery (SRS) plays an appreciable role in the management of skull base meningiomas. This study aims to apply volumetric methods to assess the CSM response after SRS and correlate it with clinical outcomes.
METHODS: The cohort consisted of 219 patients, of whom 73.9% were female (n = 162), with a median age of 55 years (19-88). SRS was the primary treatment for 45.7% (n = 100), while 37.9% (n = 83) underwent treatment for residual tumors, 14.2% (n = 31) for recurrence, and in 5 with others reasons. The median tumor volume was 4.9 cm3 (0.3-105 cm3) to a median margin dose of 14 Gy (5-35 Gy). Volumetric analysis of CSM was performed on the SRS scan and each available magnetic resonance image thereafter.
RESULTS: The median clinical and imaging follow-ups of the cohort were 72 (24-298) and 66 (18-298) months, respectively. The overall tumor control rate was 83.4% (n = 183) at last follow-up with tumor regression 72.1% (n = 158). Neurologic symptoms were improved after SRS in 6.8% (n = 15), stable in 72.6% (n = 159), and worsened in 20.5% (n = 45). The clinical deterioration usually occurred in the patients with tumor progression (P < 0.001). Following SRS, the volumetric analysis confirmed that tumor response at 3 years reliably projected volumetric change and tumor control at 5 years (R2 = 0.694) with P < 0.001 and 10 years (R2 = 0.571) with P = 0.001.
CONCLUSIONS: SRS affords effective tumor volumetric control and neurologic stability or improvement in the majority of patients with CSMs. The radiologic response of CSM as determined by volumetry at 3 years post-SRS is predictive of long-term tumor response at 5 and 10 years following SRS.

The skull base is a complex bony and soft tissue interface that is divided anatomically into compartments. This article will focus specifically on the central skull base, which has a complex embryologic development and anatomy. Multiple entities from notochord remnants, neoplasm, infection, and other abnormalities may occur, and imaging is critical for depicting skull base pathology.

Skull base imaging requires a thorough knowledge of the complex anatomy of this region, including the numerous fissures and foramina and the major neurovascular structures that traverse them. Computed tomography (CT) and magnetic resonance imaging (MRI) play complementary roles in imaging of the skull base. MR is the preferred modality for evaluation of the soft tissues, the cranial nerves, and the medullary spaces of bone, while CT is preferred for demonstrating thin cortical bone structure. The anatomic location and origin of a lesion as well as the specific CT and MR findings can often narrow the differential diagnosis to a short list of possibilities. However, the primary role of the imaging specialist in evaluating the skull base is usually to define the extent of the lesion and determine its relationship to vital neurovascular structures. Technologic advances in imaging and radiation therapy, as well as surgical technique, have allowed for more aggressive approaches and improved outcomes, further emphasizing the importance of precise preoperative mapping of skull base lesions via imaging. Tumors arising from and affecting the cranial nerves at the skull base are considered here.

The skull base is one of the most complex anatomical regions and forms the floor of the cranial cavity. Skull base surgery involves open, microscopic, and endoscopic approaches to the anterior, middle, or posterior cranial fossa. A multispecialty team approach is essential in treating patients with skull base lesions. Traditionally, rhinologists are involved in providing access to anterior skull base lesions while otologists are involved in the treatment of lesions of the posterior skull base. This is the case in most skull base centers today. In this article, we share a new perspective of an integrated skull base unit where a team of otolaryngologists and neurosurgeons treat anterior, middle, and posterior skull base pathologies. The rationale for this approach is that most technical skills required in skull base surgery are interchangeable and apply whether an endoscopic or microscopic approach is used. We show how the different skills apply to the different approaches and share our experience with an integrated skull base unit.