Preoperative Considerations
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Pituitary adenomas are the most prevalent intrasellar lesions and the third most prevalent primary intracranial tumors. These lesions can lead to significant neurologic and/or endocrine-related morbidity secondary to compression of neurovascular structures and hormonal dysfunction.
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Pituitary adenomas may be either nonfunctioning tumors or hormone-secreting lesions (including ACTH, GH, prolactin, FSH, LH, TSH-secreting tumors). These tumors can be classified, according to size, as microadenomas (smaller than 1 cm) or macroadenomas (>1 cm).
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Symptoms related to pituitary adenomas include:
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Large lesions might present suprasellar and parasellar extensions, associated with optic chiasm compression and visual field defects as well as dysfunction of the cranial nerves in the cavernous sinus (III, IV, VI, V1 and V2).
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Hormone-secreting lesions are associated with different clinical syndromes, such as acromegaly, Cushing’s disease and hyperprolactinemia
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The evaluation of pituitary adenomas must include:
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CT scan for evaluation of the bone anatomy, calcifications within the lesion and preoperative evaluation of the different subtypes of sphenoid sinus that might be encountered.
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Sellar MRI scan for analysis of the location of the lesion and its relation to surrounding structures such as the internal carotid artery, optic chiasm and cavernous sinus. Dedicated pituitary MRI scans, with thin coronal cuts and dynamic contrast evaluation, are recommended in cases of microadenomas.
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Endocrine evaluation to determine the presence of hormonal dysfunctions.
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Ophthalmological evaluation to study the patient’s preoperative visual field accuracy and acuity.
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Indications
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Treatment options include clinical follow-up, medical treatment, surgery and radiotherapy/radiosurgery.
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Clinical follow-up with periodic MRI scan is recommended for most nonfunctioning adenomas smaller than 1 cm (microadenomas), which usually are asymptomatic lesions incidentally found in MRI scans.
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Medical treatment is the gold standard treatment in cases of prolactinomas. Drug therapy with bromocriptine and/or cabergoline is effective to achieve tumor remission in most cases. In cases of large GH-secreting adenomas, neoadjuvant or adjuvant treatment with octreotide may be useful to improve the hormonal control rate after surgery. In some cases, after medical therapy with cabergoline and/or octreotide the tumor may present a fibrous consistency, which may increase the complexity of the resection. This may be considered before the introduction of neoadjuvant medications.
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Stereotactic fractionated radiotherapy and radiosurgery may be useful in the treatment of recurrent adenomas and residual lesions in the cavernous sinus.
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Indications for surgery include:
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Non-functioning adenomas that present with development of new visual or ocular movement deficit.
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Lesions with progressive enlargement during follow-up.
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GH- and ACTH-secreting pituitary adenomas.
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Prolactinomas that did not respond to drug therapy or in those cases presenting with major side effects secondary to the medical treatment.
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Surgical Procedure
Patient Positioning
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The patient is placed in a 3-point head fixation system (Mayfield skull clamp or similar) in a slightly extended position to angle the sphenoid sinus and sella rostrally. Additionally, the head is rotated 5–10° towards the right shoulder so the nasal cavity is parallel to the surgeon’s working angle.
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The perinasal skin and nasal cavity are prepared with use of povidone iodine.
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After adequate prepping and draping, the nasal cavity is packed for approximately 2 minutes with afrin-soaked pledgets to reduce the bleeding originated by nasal mucosa manipulation.
Nasal Phase
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A paraseptal approach decreases tissue damage and provides optimal visualization of the sella. In most of cases of pituitary adenomas, a single nostril approach is used in order to reduce potential nasal complications secondary to surgical manipulation.
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With a 0° endoscope the surgeon identifies the anatomic landmarks of the nasal cavity, including the inferior, middle and superior turbinates, nasal septum, coana and ostium sphenoidale.
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Lateralization of the middle turbinate is performed to enlarge the working field in the nasal cavity. Resection of the middle turbinates is avoided in order to preserve the olfactory and nasal function.
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The sphenoid ostium is identified 1 cm superior and medial to the middle turbinate.
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With use of a monopolar electrocautery a vertical cut in the mucosa is done at the posterior part of the nasal septum. The mucosa is then pushed laterally dissecting it from the nasal septum and exposing the bone structure of the posterior nasal septum and the rostrum sphenoidale ( Figure 24.1 ).
Figure 24.1
Exposure of the sphenoidal rostrum. Once the posterior part of the nasal septum is pushed laterally, the sphenoidal rostrum is exposed. The sphenoid ostia are superior and lateral to the rostrum.Related posts:
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