Practical Anatomy of the Central Skull Base Region

Neurovascular structures in the lateral recess of the sphenoid sinus. A computed tomography evaluation

INTRODUCTION AND OBJECTIVES

Anatomical variations of the lateral recess of the sphenoid sinus and its relations with the adjacent neurovascular structures should be preoperatively evaluated to plan an adequate surgical approach and avoid iatrogenic injuries. This study aims to analyze the patterns of pneumatization of the lateral recess of the sphenoid sinus and their association with the presence of protrusion and dehiscence of the optic canal, carotid canal, vidian canal, and maxillary nerve.

MATERIALS AND METHODS

A retrospective evaluation of 320 sphenoid sinuses by computed tomography was performed. Studied variables included type of lateral recess, and protrusion, and dehiscence of the optic and carotid canal, and vidian and maxillary nerve.

RESULTS

The mean age was 45.67±17.43. A total of 55.6% (n=178) of the evaluated sphenoid sinuses corresponded to male subjects. Protrusion of the carotid canal, maxillary nerve, and vidian canal was associated with a type 3 lateral recess pneumatization, while dehiscence of these structures was most commonly observed in a type 2 lateral recess (p=<0.001).

CONCLUSIONS

Protrusion or dehiscence of neurovascular structures surrounding the sphenoid sinus has been associated with the extent of pneumatization of the lateral recess, increasing the risk of intraoperative injury. Preoperative identification of anatomical variations is mandatory to select the best approach for skull base lesions and avoid iatrogenic injuries.

Maxillary Swing Approach for Central Skull Base Lesions in Extreme Situations: A Single-Institutional Case Series

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Imaging in Endoscopic Cranial Skull Base and Pituitary Surgery

Endoscopic endonasal approaches have widely accepted techniques for managing benign and malignant processes along the entire ventral skull base with similar or better results compared with open procedures, but with lower rates of complication. Managing pathology affecting the skull base can be challenging because of complex anatomy and the proximity of critical neurovascular structures. Postoperative imaging can be challenging, because of surgical alterations of normal anatomy and the now common use of complex reconstruction techniques. Understanding the normal imaging appearance of skull base reconstruction is important for accurate postoperative interpretation and delineation between normal reconstructive tissue and recurrent neoplasm.

Transsphenoidal Approach in Endoscopic Endonasal Surgery for Skull Base Lesions: What Radiologists and Surgeons Need to Know

In the last 2 decades, endoscopic endonasal transsphenoidal surgery has become the most popular choice of neurosurgeons and otolaryngologists to treat lesions of the skull base, with minimal invasiveness, lower incidence of complications, and lower morbidity and mortality rates compared with traditional approaches. The transsphenoidal route is the surgical approach of choice for most sellar tumors because of the relationship of the sphenoid bone to the nasal cavity below and the pituitary gland above. More recently, extended approaches have expanded the indications for transsphenoidal surgery by using different corridors leading to specific target areas, from the crista galli to the spinomedullary junction. Computer-assisted surgery is an evolving technology that allows real-time anatomic navigation during endoscopic surgery by linking preoperative triplanar radiologic images and intraoperative endoscopic views, thus helping the surgeon avoid damage to vital structures. Preoperative computed tomography is the preferred modality to show bone landmarks and vascular structures. Radiologists play an important role in surgical planning by reporting extension of sphenoid pneumatization, recesses and septations of the sinus, and other relevant anatomic variants. Radiologists should understand the relationships of the sphenoid bone and skull base structures, anatomic variants, and image-guided neuronavigation techniques to prevent surgical complications and allow effective treatment of skull base lesions with the endoscopic endonasal transsphenoidal approach.