FIGURE 39–1. Illustration of the endoscopic endonasal approach to the sella and suprasellar region. The endonasal surgical corridor offers direct access to the skull base and associated structures while minimizing surgical morbidity. As illustrated here in this sagittal CT scan of the paramedian skull base, the endoscopic approach to the sellar and suprasellar regions can be achieved via a standard bimanual “two-surgeon, four-handed” technique. Note: TC = transcribriform; TP = transplanum; TT = transtuburcular; TS = transsellar.
• Of note, posterior ethmoid air cells can often pneumatize superiorly and laterally into the sphenoid sinus; such posterior ethmoid cells are termed Onodi cells or sphenoethmoid cells. These cells are surgically relevant, given their intimate relationship to the optic nerve and internal carotid artery; additionally, the skull base surgeon must recognize the presence of these cells to ensure appropriate exposure of the sella and/or suprasellar regions.
• The anatomy of the sphenoid sinus can be highly variable in size and shape, and it is often divided by an irregular bony septum. It should be noted that this variable anatomy can also be further effected by tumor expansion. The posterolateral wall of the sphenoid sinus is comprised of the cavernous sinus and the intracavernous/parasellar portion of the internal carotid artery. Additionally, the optic canal often creates a bony prominence in the superolateral aspect of the sphenoid sinus posterolateral wall, which is bound medially by a bony prominence that corresponds to the lateral tubercular crest and inferiorly by a bony depression that represents the pneumatized optic strut. These osseous landmarks are termed the medial opticocarotid recess and lateral opticocarotid recess, respectively (Figure 39–2).
Sellar and Suprasellar Surgical Anatomy
• The sellar face lies in the midline of the posterior wall of the sphenoid sinus and is continuous with the tuberculum sella and planum sphenoidale (see Figure 39–2).
• Superoanterior to the sellar face is the tuberculum sella, which is formed by the convergence of the planum sphenoidale with the cranial most aspect of the sellar face. It is important to control the superior intercavernous sinus in transtubercular approaches, which lies in an intradural position posterior to the region of the tuberculum sella. Adequate exposure often requires concurrent sellar and planar dissection.
FIGURE 39–2. Endoscopic view of the sellar and suprasellar regions. Cadaveric dissection of the endoscopic endonasal approach to the sellar and supra-sellar regions. Illustrated here is the endoscopic view attained after complete sphenoidotomy, posterior septectomy, and resection of the intersinus septum and mucosal lining of the sphenoid sinus. Note: S = sella; IS = intersphenoid sinus septum; ICA = internal carotid artery; Sr = sphenoid rostrum; C = clivus; TS = tuberculum sella.
• In order to achieve maximal exposure of the suprasellar region, the posterior aspect of the planum sphenoidale, the tuberculum sella, and sellar face need to be removed. Access to the intradural suprasellar region generally provides exposure to the optic chiasm, pituitary stalk, optic nerves, floor of the third ventricle, and the vertebrobasilar circulation.
PERTINENT SELLAR AND SUPRASELLAR PATHOLOGY
Pituitary Adenomas: 10% to 15% of All Intracranial Tumors
• A microadenoma is defined as an adenoma less than 10 mm, whereas a macroadenoma is greater than 10 mm.
• Can become symptomatic either by compressing nearby structures or by causing increases or decreases in pituitary hormones.
• Prolactin-secreting adenomas are the most common of all functioning pituitary tumors; patients can present with galactorrhea and oligo/amenorrhea.
• Functional pituitary adenomas can also secrete ACTH, thyroid-stimulating hormone, or growth hormone; presentation can include Cushing syndrome (abdominal obesity, round facies, high blood pressure, abdominal striae), hyperthyroidism, and acromegaly, respectively.
• When the pituitary adenoma is non-functional, presentation is secondary to the mass effect on nearby structures; symptoms can include headache, visual field loss, and/or diplopia.
Meningiomas: Approximately 15% to 25% of All Intracranial Tumors
• Arise from arachnoid cap cells
• Slow-growing tumors, more common in women
• Radiographic appearance may include a dural tail.
• Treatment can include observation if the patient is asymptomatic as these tumors are very slow growing; however, follow-up for neurologic change and tumor growth is essential.
• Surgical intervention is indicated when there is progressive growth or neurologic deficit.
Rathke’s Cleft Cyst
• A fluid-fill sac that develops from the remnant of Rathke’s pouch.
• Most commonly found between the pars anterior and the infundibulum.
• If small, they do not cause compressive symptoms and are more commonly incidentally noted on an MRI performed for other reasons.
• If cysts are large, however, they can present with various patterns of visual disturbances, similar to those found with craniopharyngiomas.
Craniopharyngiomas
• Slow-growing tumor arising from remnants of the craniopharyngeal duct or Rathke’s cleft
• Frequently arise in the pituitary stalk and project superiorly to the hypothalamus
• Can often involve the prechiasmatic cistern or extend posteriorly into the third ventricle
• May present with various patterns of visual disturbances, most commonly bitemporal hemianopsia.
Schwannomas
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