Pituitary Tumors—Cinical Presentation Syndromes

Some clincal nuts and bolts of pituitary tumors.

Pituitary tumors present in two general ways:

Hormonal syndromes

are becoming better recognized clinically and more easily detected due to increasingly sensitive laboratory tests. Typical hormonal syndromes include:

Prolactinoma: galactorrhea/amenorrhea in a young woman, decreased libido and energy in an older man

Growth Hormone: acromegaly, including cardiomyopathy, diabetes mellitus, and peripheral neuropathy

ACTH: Cushing's Syndrome

TSH: hyperthyroidism

Local mass effect

occurs when the pituitary tumor either does not secrete active hormone, or when the effects of hormone hypersecretion are not recognized. The tumor simply grows, slowly but inexorably, until it impinges on surrounding structures, causing:

bitemporal hemianopia from pressure on the optic chiasm,
diplopia from pressure on the cranial nerves in the cavernous sinus, or
progressive panhypopituitarism from pressure on the pituitary gland itself.

Tumors which present this way are commonly nonsecreting tumors and prolactinomas in older men.

Pituitary Apoplexy

Pituitary apoplexy is a rare presentation of pituitary tumor (but like that Force 10 gale, it's the one that you remember...). People presenting with apoplexy are sick.

What happens?

A pre-existing (and usually undiagnosed) pituitary macroadenoma either infarcts and swells or bleeds acutely. The sudden doubling or tripling of the pituitary tumor's volume impinges on its surrounding structures and causes the characteristic findings of pituitary apoplexy. Sudden pressure on the optic nerves causes decreased vision, up to total blindness. Sudden pressure on the cranial nerves in the cavernous sinus cause diplopia. Sudden pressure on the pituitary gland cause pituitary shutdown and potentially lethal Addisonian crisis (lack of cortisol). Leakage of blood into the subarachnoid space causes unconsiousness and meningeal irritation.

History—Pituitary apoplexy typically begins with the INSTANTANEOUS onset
of severe headache, decreased consciousness, decreased vision, and
hypotension. The major differential diagnosis is SUBARACHNOID
HEMORRHAGE, which it resembles.

Physical examination—PE in pituitary apoplexy shows a hypotensive patient, often with impaired consciousness, who may have signs of nuchal rigidity, photophobia, nausea and vomiting. All this is also consistent with SUBARACHNOID HEMORRHAGE.
The KEY to differentiating these two disorders is the visual acuity: patients with pituitary apoplexy typically have significantly decreased vision in either one or both eyes. Diplopia is also usually present with pituitary apoplexy. Hypotension in pituitary apoplexy does NOT respond well to fluid challenge, but will respond dramatically to steroids (e.g. 300 mg of IV methylprednisolone).

Laboratory testing—Acutely is pretty inconclusive. Electrolytes are usually OK, WBC may be slightly elevated. Serum cortisols are low (but they usually can't be gotten stat).

Radiology—Is diagnostic. CT scanning usually reveals a lesion in the sellar area with or without subarachnoid blood. MR scanning can delineate this lesion exquisitely. If there is any question, get a stat MR of the sellar area looking for a large macroadenoma. If these studies are negative, consider lumbar puncture to diagnose subarachnoid hemorrhage and a cerebral angiogram to look for an aneurysm (cause of 90% of nontraumatic subarachnoid hemorrhage).

Treatment—THIS IS A NEUROSURGICAL EMERGENCY!
The visual defects, even blindness, can be reversed by rapid decompression of the tumor mass. Delay in surgical decompression may allow permanent blindness to occur. Get your neurosurgeon down there stat!

Nomenclature for discussing pituitary tumor size

There are a variety of proposed systems for naming pituitary tumors, based on size, location of invasion of surrounding structures, extent of invasion of surrounding structures, etc. We will ignore these systems for now.

The basic difference to identify is microadenoma vs macroadenoma:

Microadenoma: a pituitary tumor < 1 cm in maximal diameter (vide infra)
Microadenomas typically have a higher chance of being resected totally, because they may be totally contained within the pituitary gland itself.
Macroadenoma: a pituitary tumor > 1 cm in maximal diameter (vide infra)
Macroadenomas have broken out of the confines of the pituitary gland, and almost always have microscopic invasion of the dura lining the sella turcica. Probability of total cure by resection alone plummets when you have a macroadenoma.
"INCIDENTALOMA:" As MR scanning becomes more available in the USA (carpe diem...), many pituitary tumors are being discovered incidentally. The best treatment for these tumors is a matter of some controversy

MR imaging of pituitary tumors

Let's face it, technology works. MR imaging is the test of choice for diagnosing and planning treatment of pituitary tumors. The surrounding bone, which obscures CT scanning, disappears. The soft tissue of the pituitary gland, tumor, and surrounding structures is displayed with exquisite detail. Variations in MR imaging can elucidate even very small pituitary tumors. Examples of MR imaging in pituitary tumors follow:

Note the incompletely-enhancing (grey) area on the left side of the pituitary gland. Normal pituitary architecture persists.

Microadenoma

Here the normal architecture of the pituitary gland is completely obscured by the large tumor growing in the sella. The pituitary stalk is deviated to the left.