FIGURE 6.1 Diagram of the exposure for the extended approach. The bone has been removed from the posterior planum to the sella.

HISTORY

Suprasellar tumors can present with a wide range of symptoms, from vision loss, to mental changes from secondary hydrocephalus, to pituitary hormonal abnormalities. For example, a typical adult patient with a craniopharyngioma may or may not have normal visual function but also may have headache, memory difficulties, fatigue, and mild sexual dysfunction. They will usually not have symptoms of diabetes insipidus.

PHYSICAL EXAMINATION

The physical examination in patients with suprasellar lesions concentrates on disorders of pituitary function and physiology and on abnormalities related to visual function. If the lesion has produced hypopituitarism from compression of the normal gland, physical signs may be those of pallor, generalized weakness, and changes in the texture of the skin. There may be associated cognitive deficits and occasional psychological disturbances.

The visual field examination may reveal a typical bitemporal hemianopsia, decreased visual acuity, enlargement of the physiologic blind spot, or scotomas. These findings may be quite subtle in the early stages of compression of the optic nerves and chiasm. Ocular computed tomography may be useful, as it can demonstrate the thinning of the retinal fiber layer that accompanies chiasmal compression.

INDICATIONS

Ordinarily, the major indication for surgery is progressive visual loss. Patients may also have intractable headache, pituitary hormonal failure (hypopituitarism), mental or memory changes from compression of the hypothalamus, or hydrocephalus, usually from obstruction of the foramina of Monro.

CONTRAINDICATIONS

The relative contraindications to the endoscopic endonasal transsphenoidal microsurgical approach to the suprasellar space are dependent upon the anatomy of the lesion and the anatomy of the skull base. If the sella turcica is small and the lesion is primarily suprasellar, the limiting factors of exposure are the distances between the cavernous carotid arteries and the optic canals. If these are narrow, and not expanded by the lesion, maneuverability may be compromised. More importantly, if the lesion engulfs arteries of the circle of Willis, or if it extends into the lateral optic canals intracranially, then a craniotomy approach may be a wiser strategy. These assessments depend upon neuroradiologic imaging with MRI and CT scans, which are essential to the preoperative planning. The position of the optic chiasm in relation to the sella and the lesion is often a major determinant of the surgical approach. The endoscopic transsphenoidal approach is best suited to the removal of retrochiasmatic lesions as the chiasm and optic nerves do not need to be displaced to expose the lesion.

PREOPERATIVE PLANNING

The majority of the preoperative planning should include a complete endocrine laboratory evaluation and extensive, sophisticated imaging studies. The endocrine evaluation includes measurement of serum levels of the primary hormones of the anterior pituitary and assessment of the patient for diabetes insipidus. It is imperative to normalize any preexisting hormonal deficits and to use perioperative corticosteroids to protect the patient and his/her vision when necessary. A high-resolution pituitary-centered MRI study should be performed to evaluate the lesion and the anatomic distortions produced by it. The position of the optic nerves, optic chiasm, and optic tracts should be carefully evaluated with imaging, as well as the relationship of the dorsal aspect of the tumor to the ventricular system. The sella itself can be enlarged, providing a natural pathway for the extended transsphenoidal approach. A CT scan should also be done to evaluate the presence of calcifications within a suprasellar tumor. An MRI may be adequate for the evaluation of the vessels of the circle of Willis and their tributaries. If not, image guidance using high-resolution CT angiography can be incorporated into the surgical planning and the operative procedure.

SURGICAL TECHNIQUE (VIDEO 6.1)

The image-guidance system is calibrated and used to determine the trajectory of approach and the important anatomic landmarks.

Ideally, a nasal septal flap (see Chapter 42) based posteriorly upon the sphenopalatine artery is raised and placed in the nasopharynx safely away from the operative pathway, without kinking its blood supply. This is an important step for craniopharyngiomas and other lesions where a large intraoperative cerebrospinal fluid (CSF) leak is created.

Through the right and left nostrils, using the operating endoscope, the ostia of the sphenoid sinus are identified by gently laterally displacing the middle and superior turbinates. In my experience, it is rarely necessary to resect a turbinate in order to achieve satisfactory exposure for midline lesions.

The mucosa around the ostia is cauterized, and the ostia are enlarged using bone punches. After a submucosal injection of Xylocaine and epinephrine, the mucous membrane over the posterior septum is incised and a submucosal flap can be raised to expose the vomer. Using a Cottle elevator, the posterior nasal septum is crossed and the mucosa over the anterior wall of the sphenoid sinus on the opposite side is elevated. Careful dissection will mobilize the mucosa away from the inferior aspect of the anterior wall of the sphenoid sinus, diligently protecting the sphenopalatine arteries. The mucosa posteriorly can be resected using a microdebrider.

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