Diseases of the Sella and Parasellar Region: An Overview
Section snippets
Anatomy of the Pituitary, Parasellar Regions, and the Central Skull Base
The central skull base is formed by the posterior aspect of the presphenoid anteriorly, the basisphenoid centrally, the greater wings of sphenoid laterally, and the dorsum sella and petrous ridges posteriorly. The sella turcica is a saddle-shaped depression in the basisphenoid and houses the pituitary gland.1
The pituitary gland largely consists of 2 parts: the anterior pituitary or adenohypophysis, and posterior pituitary or neurohypophysis. The adenohypophysis starts as an evagination of the
Imaging Protocol
Sellar and parasellar imaging may be sought in patients with endocrinologic abnormality, cranial nerve III, IV, V, and VI deficits, and symptoms related to local suprasellar mass effect, such as visual field cuts.
Dynamic contrast-enhanced magnetic resonance imaging (MRI) is the preferred method of pituitary imaging at our institution. High-resolution coronal T1- and T2-weighted images (WIs) of the pituitary fossa from the orbital apex to the prepontine cistern are followed by dynamic
Age-Appropriate Imaging Appearance of the Normal Pituitary Gland
In the fetus and neonate, the entire pituitary gland is T1 hyperintense, and it demonstrates a convex superior border. At 2 months of age, the pituitary assumes its normal expected configuration and becomes concave superiorly. At about the same time, the anterior pituitary gland becomes isointense to brain on T1WI.6 The posterior pituitary remains hyperintense on T1WI owing to its neurosecretory granules.7 An absent posterior pituitary bright spot should be considered abnormal, only when
Pituitary Adenoma
Pituitary adenoma is the most common intrasellar mass. Depending on its size, it can be classified into microadenoma and macroadenoma.
Pituitary microadenoma is a benign tumor, measuring <1 cm in size. It may be symptomatic or completely asymptomatic and incidental.5 When symptomatic, which is often the case, it produces endocrine abnormalities. Prolactinoma is the most common type of pituitary microadenoma, and usually is seen with prolactin levels >150 ng/mL.5 This results in menstrual
Cystic-Appearing Lesions
Common suprasellar cystic-appearing lesions include RCCs, arachnoid cysts, epidermoid cysts, and dermoid cysts. All of these entities have a specific appearance on CT and MRI, and they do not demonstrate any enhancement after contrast administration. RCCs have been discussed earlier. Arachnoid cysts follow CSF signal on all pulse sequences, including DWI, and can exert mass effect, remodeling the adjacent calvarium from chronic CSF pulsation. Epidermoid cysts and dermoid cysts both result
Lipoma
Embryologically, intracranial lipomas are thought to arise from maldifferentiation of the primitive meninx, which forms the pachy- and leptomeninges. Lipomas are thus maldifferentiated cisternal spaces. Abnormal persistence of the primitive meninx can result in associated maldevelopment of adjacent structures, for example, suprasellar lipomas are often associated with hypoplastic mamillary bodies and tuber cinereum. Lipomas share similar imaging characteristics to dermoids, including presence
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- Gray H, Pickering P, Howden R: Gray's Anatomy: The Classic Collector's Edition, 15th ed. New York, Bounty...