Skull Base Anatomy

doi:10.1016/j.otc.2015.09.001

Otolaryngologic Clinics of North America

Volume 49, Issue 1, February 2016, Pages 9-20

https://doi.org/10.1016/j.otc.2015.09.001 Get rights and content

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Key points

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The sphenoid bone is at the center of the skull base and understanding its anatomy from multiple perspectives is important to understanding endonasal approaches.
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Within the sphenoid sinus, the lateral opticocarotid recess is a key landmark for identifying the locations of the parasellar carotid artery and optic nerve.
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The tuberculum sella is the anterior and superior limit of the sella. Limited removal of the tuberculum during pituitary surgery helps avoid CSF leak, while complete removal allows

Sphenoid bone

The sphenoid bone sits at the center of the skull base, and knowing its anatomy is central to understanding endonasal approaches. The sphenoid bone has been described as resembling a bat with its wings outstretched (Fig. 1). It consists of a central body, which is cuboidal in shape and houses the sphenoid sinus at its center. The sella turcica is located superiorly and the upper clivus posteriorly. The lesser wings extend from the superolateral aspect of the body and the greater wings from the

Sphenoid sinus

The sphenoid sinus varies considerably in size, shape, pneumatization, and septation. The degree of pneumatization varies with age, with most pneumatization occurring in adolescence. There are three types of pneumatization patterns in adults: conchal, presellar, and sellar. The conchal type has little to no pneumatization. The presellar type has some pneumatization but does not extend beyond the plane of the tuberculum sella. The sellar type is the most common and the cavity extends beyond the

Pituitary gland

The human pituitary gland is composed of two embryologically, anatomically, and functionally distinct parts. There is an anterior lobe or adenohypophysis, and a smaller posterior lobe or neurohypophysis. The anterior lobe develops from an invagination of oral ectoderm known as Rathke's pouch. It is a glandular structure that is responsible for the production and release of growth hormone, prolactin, adrenocorticotropic hormone, thyroid-stimulating hormone, luteinizing hormone, and

Cavernous sinus

The cavernous sinus is a venous lake that communicates with multiple venous tributaries and spaces: basilar plexus; superior and inferior petrosal sinuses; superior and inferior ophthalmic veins; veins of foramen rotundum, foramen spinosum, foramen ovale, and the foramen of Vesalius; deep middle cerebral vein; superficial sylvian vein; and the contralateral cavernous sinus via intercavernous connections. In addition to transmitting venous blood, it contains multiple neurovascular structures.⁴

Suprasellar space

The suprasellar space extends from the diaphragma inferiorly to the floor of the third ventricle superiorly. Access to the suprasellar space is obtained by removing the tuberculum sella, prechiasmatic sulcus, and posterior planum sphenoidale. The suprasellar space is divided into the infrachiasmatic, suprachiasmatic, and retrochiasmatic areas.

Within the infrachiasmatic space is found the inferior surface of the optic chiasm and the infundibulum in the midline (see Fig. 3A; Fig. 6A). The

Anterior cranial base

The anterior two-thirds of the anterior cranial base is composed of the ethmoid and frontal bones, and the posterior one-third is formed by the planum sphenoidale (Fig. 7A). The ethmoid bone consists of the cribriform plate and crista galli in the midline; the ethmoid roofs (fovea ethmoidalis) superiorly; and the lamina papyracea laterally, which separates the ethmoid sinuses from the orbit. The perpendicular plate of the ethmoid joins the vomer to become the bony septum.¹²

Once the ethmoid roof

Clivus

The clivus can be divided into thirds (Fig. 8A). The upper third or “sellar” clivus is made up of the dorsum sella and posterior clinoids down to approximately the level of the floor of the sella. Dorello's canal is located at the transition point between upper and middle clivus, just a few millimeters below the floor of the sella. The middle third or “sphenoidal” clivus extends from the floor of the sella to the choana. The lower third or “nasopharyngeal” clivus extends from there down to

Summary

Technologic advances have greatly improved the ability to access the ventral skull base. The endonasal route has been expanded to allow access to the anterior, middle, and posterior cranial fossas. Understanding of the complex anatomy of the skull base has also greatly expanded. A detailed understanding of the various anatomic relationships provides one with the ability to determine the safest and most effective approach to lesions of the ventral skull base. It allows one to minimize morbidity,

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The history and evolution of transsphenoidal surgery
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Anatomy of the pituitary gland and sellar region
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Cited by (47)

Usefulness of Opening the Diaphragma Sellae Before Transecting Interclinoidal Ligament for Endoscopic Endonasal Transoculomotor Triangle Approach: Technical Nuances and Surgical Outcomes
2024, World Neurosurgery
Opening the oculomotor triangle (OT) and removing the posterior fossa lesion by endoscopic endonasal approach (EEA) is challenging for even an experienced endoscopic neurosurgeon. We summarize the treatment experience and technical nuances with EEA for resection of pituitary neuroendocrine tumors and cavernous sinus (CS) meningiomas invading through the OT.
Between 2018 and 2022, 8 patients, comprising 5 with pituitary neuroendocrine tumors (3 with nonfunctioning and 2 with somatotroph tumors with increased levels of growth hormone) and 3 CS meningiomas, were treated using an endoscopic endonasal transoculomotor triangle approach. The critical surgical technique is continuously opening the diaphragma sellae from medial to lateral toward the interclinoidal ligament and transecting it to enlarge the OT. We evaluated preoperative tumor size, previous surgical history, preoperative symptoms, extent of tumor resection, histopathology, and postoperative complications for all patients.
The gross total resection (defined as complete removal) in 3 patients (38%), near-total resection (defined as >95% removal) in 4 patients (50%), and subtotal resection (defined as ≤90% removal) in 1 patient (12%) and gross total resection of tumor invading through the OT was achieved in all patients through pure EEA. Two of 3 patients with visual deficits in nonfunctioning pituitary neuroendocrine tumors improved, and the other remained stable postoperatively. One patient showed transient oculomotor nerve palsy. The growth hormone level of the 2 patients with somatotroph tumors declined to normal. For 3 patients with CS meningiomas, cranial nerve palsy improved in 2 patients, whereas the other patient developed increased facial numbness after surgery.
The endoscopic endonasal transoculomotor triangle approach is an efficient surgical option for tumors with CS invasion and OT penetration.
Surgical anatomy of the anterior cranial fossa
2023, Cerebrospinal Fluid Rhinorrhea: Comprehensive Guide to Evaluation and Management
To adequately manage cerebrospinal fluid (CSF) leaks in the anterior ventral skull base region, it is paramount for otolaryngologists and neurosurgeons involved in the care of patients with these disorders to have a thorough understanding of the complex anatomy of the anterior ventral skull base. This knowledge allows surgeons to navigate the different intranasal surgical approaches that can be used to manage sinonasal and skull base pathology and to avoid surgical complications. CSFs leak in the anterior skull base can occur spontaneously or during extended endoscopic endonasal surgery in this region. CSF leak can also occur secondary to trauma or surgery during manipulation near the skull base. Thorough knowledge and understanding of the anatomy of this region allow proper preoperative planning, safer surgical procedures, and better outcomes.
Pathophysiology and clinical evaluation of blunt force and penetrating trauma of the anterior cranial base
2023, Cerebrospinal Fluid Rhinorrhea: Comprehensive Guide to Evaluation and Management
Traumatic cerebrospinal fluid leak of the anterior skull base can result in significant morbidity and mortality. A thorough understanding of these injuries and their clinical findings is necessary to promptly identify these injuries and initiate management in a timely manner to minimize sequelae. Advancements in imaging modalities have undoubtedly improved our ability to identify these injuries more accurately.
Imaging Review of the Endoscopic Operative Corridor for Clivus Lesions
2023, Current Problems in Diagnostic Radiology
Citation Excerpt :
Just lateral to the pituitary gland lies the carotid artery and cavernous sinus. Of note, the vidian nerve may run along the floor or within the sphenoid sinus and its canal can be identified on preoperative CT.11 (Fig 6) Once the sphenoid sinus is identified and opened to access the floor of the sella turcica, there are several important surface landmarks and the ventral surface of the clivus (Fig 7A-B).
Traditional transcranial approaches for lesions involving the clivus, in particular skull base chordoma have several disadvantages for midline skull base lesions as compared to the endoscopic endonasal approach (EEA), such as higher morbidity and lesser extent of resection. These disadvantages led to the development of endoscopic skull-base approaches to access pathology that involves the anterior cranial fossa, central skull base, and lower skull base lesions. In particular, lesions of the clivus are well suited for EEA. Surgical access of the clivus falls into 2 stages: the endonasal approach for access, and the endonasal resection of tumor. The objective of this article is to review the anatomy along the operative corridor for the purpose of image interpretation in preoperative planning in the context of EEA. We provide an imaging review of the sinonasal anatomy used for access by otolaryngologists and the anatomy of the clivus used by neurosurgeons for preoperative planning and resection.
Linking death, the paranasal sinuses, and traumatic head trauma
2022, Diagnosis and Treatment of Traumatic Brain Injury: The Neuroscience of Traumatic Brain Injury
There is a debate about the importance of the paranasal sinuses. The frontal, maxillary, ethmoid, and sphenoid sinuses comprise the paranasal sinuses. The paranasal sinuses are generally affected by trauma to the anterior skull base. Paranasal sinus fractures increase mortality and morbidity rates of patients with cranial trauma. These traumas may also lead to some fatal complications such as CSF leakage. We aimed to review the relationship between traumatic injury of the paranasal sinuses and mortality.
The “STARS–CT-MADE” Study: Advanced Rehearsal and Intraoperative Navigation for Skull Base Tumors
2021, World Neurosurgery
Citation Excerpt :
Due to the complex anatomy of this region, even small lesions can result in significant visual symptoms (i.e., reduction of visual acuity or hemianopsia) because of the close relationship with the optic nerve and the possibility of tumor infiltration into the optic canal, which may further worsen any visual symptoms.4 Therefore the challenge lies in both the delicate relationships with different neurovascular structures (e.g., optic nerve with chiasma, internal carotid artery, anterior and middle cerebral artery), which require extreme care during surgical dissection,5,6 and the necessity of performing the unroofing of the optic canal to decompress the nerve in the case of possible tumor infiltration.7-10 For these reasons, the treatment of such lesions is often left in the hands of more experienced surgeons,11 restricting the training possibilities for residents.
Skull base meningiomas represent a challenge for neurosurgeons, and the procedures are typically performed by experienced neurosurgeons, thus limiting resident training. A new simulation and rehearsal device can be used as an aid for senior surgeons during these operations and serve as a training tool for junior surgeons.
Forty patients harboring an anterior/middle fossa meningioma were recruited. Surgical Theater, a rehearsal/simulation platform, was used for preoperative planning and intraoperative 3D navigation on 20 patients (CT-MADE group), while the remaining (control group) underwent a traditional navigation. Qualitative comparisons between the 2 groups were made with regard to surgical procedure and patient outcome. Satisfaction questionnaires were completed by expert neurosurgeons and residents to assess the overall usefulness of the platform. Furthermore, the surface of the simulated craniotomy performed during the planning was compared with the one actually performed during surgery in order to evaluate the reliability of the planning.
No differences between the 2 groups were found (surgery duration: P = 0.4; visual impairment: P = 0.56). Both residents and senior neurosurgeons enjoyed using the platform for intraoperative navigation and planning; simulated craniotomies were significantly smaller as compared with the real ones (P = 0.009), probably because it was not intuitive to depict the exact margins of the operculum with the platform.
Surgical Theater helped residents to improve their anatomic and procedural comprehension and was deemed as a useful aid to safely perform some demanding neurosurgical procedures, by both senior and junior surgeons.

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: Disclosure Statement: The authors have nothing to disclose.

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Skull Base Anatomy

Section snippets

Key points

Sphenoid bone

Sphenoid sinus

Pituitary gland

Cavernous sinus

Suprasellar space

Anterior cranial base

Clivus

Summary

First page preview

The history and evolution of transsphenoidal surgery

J Neurosurg

Brief history of endoscopic transsphenoidal surgery–from Philipp Bozzini to the First World Congress of Endoscopic Skull Base Surgery

Neurosurg Focus

Anatomy of the pituitary gland and sellar region

Microsurgical anatomy and approaches to the cavernous sinus

Neurosurgery

Endoscopic endonasal middle clinoidectomy: anatomic, radiological, and technical note

Neurosurgery

Microsurgical anatomy of the diaphragma sellae and its role in directing the pattern of growth of pituitary adenomas

Neurosurgery