J Transsphenoidal tumor resections
1. Introduction
Approximately 10% of intracranial neoplasms are found in the pituitary gland and are diagnosed because of their mass effects or the hypersecretion of pituitary hormones. These tumors are rarely metastatic and produce local symptoms via bone invasion, hydrocephalus, and compression of a cranial nerve (most often the optic nerve). Frontal-temporal headache and bitemporal hemianopsia are the most common nonendocrine symptoms of enlarging pituitary lesions. Nonsecreting pituitary tumors account for approximately 20% to 50% of lesions in this area and are classified as chromophobe adenomas.
Tumors that secrete excess growth hormone produce acromegaly. Increased growth hormone increases the size of the skeleton, particularly the bones and soft tissues of the hands, feet, and face. The enlarged facial structures may increase the likelihood of difficult intubation. Excess growth hormone may also contribute to the development of coronary artery disease, hypertension, and cardiomyopathy. Hyperglycemia is also a common finding, reflecting growth hormone–induced glucose intolerance.
a) Surgical approach: Medical and surgical therapies exist for both functional and nonfunctional pituitary tumors. Transsphenoidal surgery offers several advantages over the intracranial approach. Statistically, morbidity and mortality rates are reduced because of a decrease in blood loss and less manipulation of brain tissue. In addition, the risk of inducing panhypopituitarism and the incidence of permanent DI are both reduced. For patients with large tumors (>10 mm), tumors of uncertain type, and tumors that have substantial extrasellar extension, the transsphenoidal approach is inadequate and a bifrontal intracranial approach is required for successful removal. Current trends are moving toward endoscopic approaches to the pituitary tumor. Less invasive approaches, such as the transnasal approach combined with endoscopic resection of tumor, have been performed. The endoscopic technique has less morbidity and a shorter hospital stay than the traditional approach.
2. Preoperative assessment
a) Patients undergo transsphenoidal operations for the treatment of hypersecreting pituitary tumors or nonsecretory tumors that cause visual complications because of their size and location. Clinical symptoms of secretory pituitary tumors include amenorrhea, galactorrhea, Cushing disease, and acromegaly.
b) Each preoperative condition has its own constellation of systemic disorders and accompanying effects on intracranial dynamics that should be considered when an anesthetic technique is selected.
c) Pituitary tumors can damage decussating optic fibers, producing blindness in the temporal half of the visual field of both eyes (bitemporal heteronymous hemianopsia).
d) Occasionally, an aneurysm of one of the internal carotid arteries may produce nasal hemianopsia on the affected side.
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