Pituitary stones, also known as pituitary lithiases or pituitary calculi, are very rare types of brain stones characterized by extensive calcification in the sella turcica.
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Terminology
Throughout the literature, there is contention and inconsistency regarding what pituitary stones actually are. While some authors suggest the term be used only for calcifications in the sella turcica that occur in the absence of any other pituitary pathology, other authors use the term to more liberally to describe excessive calcification in the sella turcica from any cause, such as an extensively calcified pituitary adenoma 1-6. This article encompasses both definitions, as they share identical radiographic features.
Epidemiology
Although the exact incidence is unknown, given that the literature regarding pituitary stones consists of only case report level evidence 1-6, this entity is generally considered to be very rare.
However, calcification (micro- and macroscopic) in the pituitary gland is considered more common. One study found that approximately 10% of patients with known pituitary adenomas had calcifications visible on plain radiograph, while pathologically it was found that up to 25% of patients had such calcifications 2.
Clinical presentation
Clinical presentation varies significantly. Patients may be entirely asymptomatic or may present with a myriad of possible endocrinopathies, such as hypopituitarism or hyperprolactinemia (either from an underlying pituitary pathology or from pituitary stalk compression) 1-6. Additionally, symptomatic patients may develop neurological symptoms, such as headaches, nausea and vomiting or visual disturbances from optic chiasm compression 1-6.
Pathology
The etiology of 'primary' de novo pituitary stones remains an enigma, but is thought to be secondary to an unknown inflammatory process, subclinical hemorrhage or cartilaginous metaplasia 1. In cases secondary to other pathologies, most commonly pituitary adenomas (especially in prolactinomas), the exact mechanism has also yet to be fully elucidated but is thought to be a sequelae of fibrosis secondary to hemorrhage 1-6. In addition to pituitary adenomas, other secondary causes include 1:
metabolic imbalances (e.g. hypercalcemia)
chronic sequelae of pituitary apoplexy
Radiographic features
Plain radiograph
Although uncommonly performed, pituitary stones are usually clearly visible on plain radiographs of the skull, as solitary, and often nodular, dense lesions in the sella turcica 1-6.
CT
CT is the modality of choice for identifying pituitary stones, where they appear as obviously hyperdense lesions in the sella turcica 3,4,6. This lesion may appear to have septations, corresponding with the nodular appearance appreciated on plain radiograph, and may exert local positive mass-effect (including an enlarged sella turcica) 3,4,6.
MRI
MRI shows a lesion with the same morphological and spatial characteristics as is appreciated with CT 6. Additionally, there may be features of an underlying pathology, such as a pituitary adenoma (see article for an in-depth discussion) 6.
Signal changes are consistent with calcification, and include 6:
T1: low signal
T2/FLAIR: low signal
T1 C+ (Gd): contrast enhancement may be appreciated in septations (if present)
GRE/SWI: low signal
Treatment and prognosis
Management may include neurosurgical intervention, but this should be considered on a patient-by-patient basis depending on their clinical phenotype 1.
Differential diagnosis
calcified Rathke cleft cyst
calcified meningioma
calcified aneurysm in pituitary region
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