Endocrinology meet - Pituitary macroadenoma

Radiology meet

08-03-2014

R.Rengarajan

50 yr old male patient with

• Headaches on and off for 2 yrs

• Progressive loss of vision for 3 months

Pituitary macroadenoma

• Pituitary macroadenomas become clinically significant when they reach the size large enough to cause symptoms due to mass effect because most, but not all, macroadenomas are nonfunctioning tumors.

• Therefore, these lesions present late and can achieve quite remarkable volumes.

• Macroadenomas share some of the MR characteristics of their smaller counterparts.

• MR typically demonstrates a mass arising from the pituitary fossa, hypointense on T1-weighted images, compressing the higher-intensity normal pituitary tissue.

• Macroadenomas are more often hyperintense on T2-weighted images than are microadenomas. Hyperintensity on the T2-weighted images may be useful in predicting that a macroadenoma is soft or partially necrotic and thus easily removed by suction and curettage.

• A significant direct correlation has recently been shown between tumor consistency (hardness) and apparent diffusion coefficient (ADC) values.

• In most instances the macroadenoma completely fills the sella; the normal tissue is so compressed that it is virtually obliterated and cannot be identified.

• The posterior pituitary bright spot is seen in an ectopic location or not at all in the majority of cases.

• The essence of the diagnosis of macroadenomas is the definition of the lesion as intrinsic to the pituitary gland.

• The other feature to be sought is enlargement of the sella, because large pituitary adenomas virtually always enlarge the sella due to their slow growth and late presentation, whereas other intrinsic pituitary lesions, such as pituitary metastasis and inflammatory lesions, do not.

• The multiplanar capabilities, lack of bone and surgical clip artifact, and ability to demonstrate large arterial structures make MR a powerful tool in the pre- and postoperative assessment of pituitary macroadenomas

• Intratumoral hemorrhage occurs in 20% to 30% of pituitary adenomas, most often in macroadenomas.

• Although pituitary infarction and/or hemorrhage may result in the clinical syndrome of pituitary apoplexy, more frequently hemorrhage is subclinical and is discovered only incidentally on MR.

• In fact, only a small fraction of these patients has clinical findings of pituitary apoplexy.

• The incidence of bleeding is much higher in patients receiving bromocriptine.

• Larger pituitary adenomas may be accompanied by cystic degeneration with or without hemorrhage.

• Cystic degeneration in an adenoma is evident as sharply defined regions of very low signal intensity on T1-weighted images that are markedly hyperintense on the T2-weighted sequence.

• A fluid-debris level is a more specific sign of cystic degeneration but is infrequently present.

• Rarely, noncystic adenomas possess similar signal characteristics and mimic a cyst.

Criteria for non-invasion of cavernous sinus

(1) normal pituitary between the adenoma and cavernous sinus (positive predictive value 100%),

(2) intact medial venous compartment (positive predictive value 100%), and

(3) less than 25% ICA encasement (negative predictive value 100%).

Despite the fact that cavernous sinus involvement by pituitary adenomas is not uncommon, marked constriction or occlusion of the cavernous portion of the internal carotid artery is very rare.

• Surgical cavities packed with Gelfoam display variable MR signal intensities in the immediate postoperative period.

• The most common appearance of Gelfoam was isointensity to the pituitary gland with an irregular center of decreased signal intensity on T1-weighted images.

• It may be difficult to distinguish postoperative scarring or graft material from the normal gland or adenomatous tissue (especially in the first 6 months after surgery).

Thank you