A sellar mass sits in a small bony space, next to the optic chiasm, the cavernous sinuses and the hypothalamus, so what it does to a patient depends on three things: the anatomic location of the mass, the direction in which the mass extends, and the size of the mass.
Direction of expansion
The most frequent direction of expansion of pituitary adenomas is the suprasellar direction, upward out of the sella. Bony invasion by pituitary tumors is also possible, mostly in the floor of the sella turcica, which leads to invasion of the tumor into the sphenoid sinus.
Aggressive tumors can rarely invade the roof of the palate and cause nasopharyngeal obstruction, infections, and leakage of cerebrospinal fluid (CSF).
Headache
Headaches are a common feature of pituitary tumors even when they are very small and have no suprasellar expansion. Because of the confined nature of the pituitary gland, small changes in pituitary pressure stretch the dura mater, which causes the headache.
Visual disturbance
Suprasellar expansion can cause visual disturbances in several different ways. The most common is compression of the optic chiasm, the point where the two optic nerves meet. A tumor can also invade the optic nerves directly, or compromise the flow of CSF, which has a secondary effect on the visual system through hydrocephalus.
Cranial nerve involvement
Expansion to the side can damage the nerves that run beside the gland. Depending on the extent of neural damage, patients with pituitary tumors can have neurological manifestations due to invasion of cranial nerves III, IV, and VI, which can lead to diplopia, ptosis, strabismus, loss of facial sensation and ophthalmoplegia.
Pituitary stalk compression
Compression of the pituitary stalk by a pituitary tumor can decrease the flow of the portal system and the passage of neurohormones and dopamine from the hypothalamus to the pituitary gland, which results in early hyperprolactinemia and later concurrent loss of other pituitary hormones.
Metabolic alterations
Pituitary tumors can also cause metabolic alterations: precocious puberty, hypogonadism, diabetes insipidus, sleep disturbance, dysthermia (disturbed temperature regulation) and appetite disorder.
Hypothalamic localising signs
The signs and symptoms seen in a patient can point to the location of hypothalamic involvement:
- lesions involving the anterior and preoptic regions of the hypothalamus: paradoxical vasoconstriction, hyperthermia, and tachycardia
- posterior hypothalamic involvement: central disorders of thermoregulation
- damage to the preoptic regions of the hypothalamus: polydipsia or hypodipsia
- lesions of the central hypothalamus: over-activation of the sympathetic system, which causes arrhythmia, hypertension, and gastric erosion
Pituitary apoplexy
Pituitary apoplexy differs from the effects above in being sudden: it is sudden bleeding or infarction into a pituitary tumor, and it complicates roughly 2-12% of pituitary tumors, most often a non-functioning macroadenoma. It presents with the sudden onset of severe headache, vomiting, visual loss and meningism, and it can reduce the level of consciousness. Because the rapid expansion and necrosis leave most patients with acute hypopituitarism, and loss of ACTH is the life-threatening part, pituitary apoplexy is an endocrine emergency. Treatment begins immediately with glucocorticoid replacement and correction of fluid and electrolyte balance, and transsphenoidal decompression is considered when visual acuity, visual fields or consciousness deteriorate.