Sellar and Parasellar Lesions: over and above adenomas.

Transcription

1 Sellar and Parasellar Lesions: over and above adenomas. Poster No.: C-2052 Congress: ECR 2013 Type: Educational Exhibit Authors: S. Paz Maya, P. Lemercier, I. lópez blasco, D. Soriano Mena, J. P. Ruiz Gutierrez, S. Sánchez Rodríguez, G. Silla; Valencia/ES Keywords: Endocrine disorders, Diagnostic procedure, MR-Diffusion/ Perfusion, MR, CT, Neuroradiology brain, Head and neck, CNS DOI: /ecr2013/C-2052 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 51

2 Learning objectives Review sellar and parasellar complex anatomy. Review imaging characteristics of various common and some rare sellar and parasellar lesions appart from adenomas in order to approach to differential diagnosis. Images for this section: Page 2 of 51

3 Fig. 1: Sagittal schematic view of the pituitary. AS, anterior clinoid; DS, diaphragma sella; III, third ventricle; IS, infundibular stem; ME, median eminence; NL, neural lobe; OC, optic chiasm; PC, posterior clinoid; PD, pars distalis; PI, pars intermedia; PT, pars tuberalis. Page 3 of 51

4 Background The sella turcica and adjoining area is a small but complex component of the central nervous system, containing many vital structures. The wide spectrum of sellar and parasellar masses often present with similar symptoms demonstrating profound neuroendocrine manifestations treatable. Early diagnosis and accurate characterization are able to provide significant clinical benefit. While definitive diagnoses usually await histologic correlation, a systematic approach and knowledge of the key anatomy and imaging features can help in narrowing down the differential diagnosis and sometimes to reach a specific one. The diagnosis of a pathologic process suspected to be located within the sella turcica and adjoining area requires an intimate knowledge of the complex embriology and anatomy of the region. Magnetic resonance imaging has virtualy supplanted other imaging techniques as the modality of choice to study this region, it provides multiplanar images with superior tissue contrast differentiation. A systematic approach to differentiate and diagnose lesions such as pitiuitary adenomas, empty sella, Rathke's cleft cyst, lymphocytic hypophysitys, craniopharyngioma, optic pathway gliomas, meningioma, germinoma, aneurysm, epidermoid cyst, chordoma, hamartoma, infundibular sarcoidosis and histiocytosis will be described. Images for this section: Page 4 of 51

5 Fig. 3: Drawing illustrates normal anatomy of the sella turcica and juxtasellar region in the parasagittal plane. a = adenohypophysis, b = neurohypophysis, c = infundibulum, d = optic chiasm, e = tuber cinereum, f = anterior third ventricle, g = mamillary bodies, h = interpeduncular cistern, i = prepontine cistern, j = clivus, k = sphenoid sinus. Page 5 of 51

6 Imaging findings OR Procedure details Diagnostic imaging evaluation of a pathologic process suspected to be located within the sellar and parasellar region requires much more than performing a routine CT or MR imaging examination of the brain. An intimate knowledge of the anatomy of the sellar and parasellar region is an essential prerequisite for imaging evaluation of this region. All neural components essential for vision and function of the eye and orbital structures converge in this region and contribute to the anatomic complexity. Furthermore, familiarity with the type and appearance of the pathologic processes that can be present at this location allows for a more precise and narrow differential diagnosis. Major disease categories affecting this region include primary and secondary neoplastic processes, congenital lesions, infectious and inflammatory processes, and vascular abnormalities. ANATOMY The sella turcica is a midline depression in the posterior sphenoid bone bounded anteriorly by the tuberculum sella and anterior clinoid processes and posteriorly by the dorsum sella and posterior clinoid processes. Fig. 1 on page 21 The sellar floor is a thin segment of sphenoid bone typically measuring 1 mm or less in thickness, which forms the roof of the sphenoid sinus. The lateral margins of the sella turcica are bounded by cavernous sinus, which extends from the superior orbital fissure to the petrous apex. The cavernous sinus is an extradural space that has been described both as a trabeculated cavernous channel as well as an interconnected plexus of small-caliber veins. The sinus serves as a venous drainage pathway for the ophthalmic veins, middle and inferior cerebral veins, as well as the sphenoparietal sinus. Posteriorly, the sinus drains via the superior petrosal sinus to the transverse sinus and via the inferior petrosal sinus to the internal jugular vein. Cranial nerves III,IV, V1, and V2 pass through the middle cranial fossa enclosed in individual nerve sheaths that are incompletely adherent to the lateral wall of the cavernous sinus. The cavernous portion of the internal carotid artery travels along the inferomedial aspect of the cavernous sinus accompanied by sympathetic nerve fibers. Cranial nerve VI exits Dorello's canal adjacent to petrous apex to enter the cavernous sinus and travels adjacent to the inferolateral margin of the cavernous carotid artery. Fig. 2 on page 22 Meckel's cave, a dural reflection located at the posterior aspect of the cavernous sinus, contains the trigeminal sensory ganglion and trigeminal (gasserian) cistern. Meckel's cave is located at the Meckel's impression (cavity) of the petrous apex The hypothalamus and pituitary gland are anatomically contiguous structures. The hypothalamus is the most ventral portion of diencephalon that lays anteroinferiorly to the Page 6 of 51

7 thalamus and comprises the floor and portions of the walls of the third ventricule. It is bounded anatomically by the optic chiasm anteriorly, the optic nerve tracts laterally, and by the mamillary bodies posteriorly. The infundibulum extends off of the hypothalamus between the optic chiasm and the tuber cinereum. The diaphragm sellae is a rectangular dural structure forming the roof of the sella turcica, which has a central opening that transmits the pituitary infundibulum Fig. 3 on page 24 The primordium of the pituitary gland arises embryologically from growth of the epithelium of Rathke's. It is believed that an evagination of tissue of the roof of the oropharyngeal membrane fuses with a neuroectodermal evagination of tissue growing down from the floor of the diencephalon to form the anterior and posterior lobes of the pituitary gland. Fig. 4 on page 24 The pituitary gland lies within the pituitary fossa and is composed of the anterior lobe (adenohypophysis); intermediate lobe; and posterior lobe (neurohypophysis) The anterior lobe (adenohypophysis) is derived embryologically from the anterior wall of Rathke's pouch. This is comprised of the pars tuberalis, the pars intermedia, and the pars distalis It is the pars distalis that comprises the bulk of the adenohypophysis. The pars tuberalis is a thin membranous extension of the pars distalis, which is closely adherent to the anterior pituitary stalk and median eminence. Fig. 1 on page 21 The histologic diversity of it accounts for its ability to secrete a variety of hormones including growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL). The median lobe produces melanocyte-stimulating hormone (MSH). The neurohypophysis is composed of the neural stalk (median eminence and infundibulum) and the neural lobe and functions as the primary storage site for antidiuretic hormone (ADH) and oxytocin (OX). These hormones as well as other biologically active substances are released into the adjacent capillaries in response to hypothalamic nerve impulses. Fig. 5 on page 25 The optic chiasm is located approximately 10 mm above the pituitary gland. The pituitary infundibulum is located immediately posterior to the chiasm. In 80% of individuals, the chiasm is directly above the gland. The nasal retinal fibers (including the macular fibers), which provide sight to the temporal fields, cross In the chiasm and continue in the contralateral optic tract. The temporal fibers, which provide sight to the nasal field, continue directly without crossing into the optic tracts. The central portion of the chiasm contains crossing fibers and the lateral portion of the chiasm contains uncrossed fibers. Macular fibers compose almost 90% of the optic nerves and cross in the posterior and central portions of the chiasm. Page 7 of 51

8 The size of tumor and the rate and direction of growth, influence the type of visual loss in patients with a pituitary tumor. Classically, pituitary macroadenomas growing through the diaphragm sellae into the suprasellar cistern compressing the chiasm produce bitemporal hemianopsia secondary to compression of the inferonasal fibers from below, which are usually affected first. Fig. 6 on page 26 NORMAL IMAGING SPECTRUM. The size and shape of the pituitary gland is dependent on age and gender,being the average height of the adult pituitary gland is 5.4 ± 9 mm. The pituitary gland of a neonate is larger than in later childhood. Similarly, the gland is generally larger in women than in men. In pubertal girls and peripartum women, the gland may appear enlarged with a convex upper border,but in general, it should not exceed 10 mm. Normally, the size of the pituitary gland decreases with age. In adults, the anterior lobe is relatively isointense to brain parenchyma on T1-weighted MR images and T2-weighted sequences and enhances intensely with contrast because of its highly vascular nature and lack of a blood-brain barrier. The intermediate lobe sometimes can be identified on postcontrast T1-weighted MR images and is hypointense to the anterior and posterior lobes related to its relatively avascular nature. The posterior lobe, on the other hand, is typically inherently T1 hyperintense in 90% of healthy patients and almost 100% of normal infants. This hyperintensity accounts for the socalled ''pituitary bright spot.'' Fig. 7 on page 27 The high signal is likely related to antidiuretic hormone neurosecretory granules and its presence implies a normal transport of antidiuretic hormone from the hypothalamus to the posterior gland by the pituitary infundibulum. At times, the posterior lobe may be ectopic. Fig. 8 on page 28 In neonates up to 2 months of age and in pregnant women, the anterior pituitary may be as or more hyperintense on T1 as the posterior pituitary. This finding is thought to reflect the marked metabolic and hormonal activity that is characteristic of this period. INDICATIONS FOR IMAGING Pituitary imaging is indicated in patients who present with signs and symptoms of either excess or deficiency of pituitary hormone. Imaging is also indicated if a patient presents with symptoms suggestive of a pituitary mass, such as a visual field deficit and/or headaches. Fig. 9 on page 29 IMAGING MODALITIES Page 8 of 51

9 MR imaging is the imaging mainstay of the sellar and parasellar regions. MR imaging has better soft tissue resolution than computed tomography (CT) and is not subject to artifacts from surrounding bony structures. In addition, MR imaging allows for direct imaging in all 3 planes. A typical pituitary MR imaging protocol includes high-resolution imaging of the sella and parasellar regions at 3-mm thickness, before and after contrast with fat suppression. Dynamic T1-weighted imaging may be performed when a pituitary microadenoma is suspected based on clinical parameters. High-resolution T2-weighted sequences are also usually performed. CT is better than MR imaging for detecting calcifications, and can be complementary to MR imaging if a primary bony lesion is suspected (eg, chordoma, chondrosarcoma). Fig. 10: Fist image: Bone erosion of clivus, petrous apex and temporal bone in a patient with clivus chordoma. Second image: Rim calcifications in a craniopharyngioma. References: Radiodiagnostic, Hospital Clínico Universitario de Valencia - Valencia/ES PATHOLOGIC PROCESSES IN THE SELLAR AND PARASELLAR REGION. Major disease categories affecting this region include primary and secondary neoplastic processes, congenital lesions, infectious and inflammatory processes, and vascular abnormalities. Pituitary adenomas are the most common tumor in the sellar region. Many other entities may arise in the sellar and parasellar regions, apart from adenomas. This presentation Page 9 of 51

10 is focused on them. Adenomas arise from the gland, whereas other entities are centered elsewhere and may be discernible from the gland with careful examination. PRIMARY AND SECONDARY NEOPLASTIC PROCESSES: ADENOMA Pituitary adenomas comprise 10% to 15% of all intracranial neoplasms and are the most common tumor in the sellar region. These adenomas are considered benign and are typically classified based on their size: microadenomas are smaller than 10 mm and macroadenomas are larger than 10 mm. Adenomas can be classified clinically, based their endocrinological activity or lack thereof. In general, functioning adenomas are discovered at a smaller size as a result of endocrinopathy. Nonfunctioning adenomas may not be discovered until there is mass effect on the optic chiasm or other surrounding structures. Approximately 75% of clinically apparent adenomas are hormone-secreting, with approximately 50% of these being prolatin (PRL). The next most common hormonal disturbances are GH and ACTH hypersecretion. Fig. 11 on page 29 CRANIOPHARYNGIOMA: Craniopharyngioma is a neoplasm of epithelial origin (from squamous epithelial rests along remnants of Rathke's cleft) that most commonly arise in the suprasellar region (90%) and account for 1% to 3% of all intracranial neoplasms. They often extend beyond the sella, and up to 10% may be confined to the sella. There is no gender predominance. There is a bimodal age distribution, with the majority occurring in childhood and th adolescence, and a second peak in the 6 decade. Patients may present clinically with headaches, visual disturbances, and hypothalamic and pituitary dysfunction. Classical visual presentation is bitemporal hemianopsia or inferior quadrantanopia caused by chiasmal compression. There are two pathological subtypes: Adamantinous and squamous-papillary types. The adamantinous type is the classic mixed cystic and solid or predominately cystic, lobulated, partially calcified mass that often has large nonenhancing hyperintense cysts on T1WI. The signal characteristics are thought to be due to proteinacious or hemorrhagic cyst contents. This type is more likely to encase vessels, show calcification, and recur than the squamous-papillary type. The squamous-papillary type of craniopharyngioma is typically more solid or predominately solid or predominately solid with hypointense cysts on T1WI, rounded, Page 10 of 51

11 less likely to calcify, and tends to occur in an older population. The solid tumor parts have an inhomogeneous but intense enhancement, with small necrotic areas. There may be a mixture of the histological subtypes in the same tumor. There is a fair amount of overlap in the imaging appearance of the two varieties of this tumor. Fig. 13: Suprasellar craneopharyngioma in a 35 years woman. Solidocystic suprasellar mass with nodular calcifications and enhancement after contrast administration. There is presence of hyperintense in T1WI cysts. References: Radiodiagnostic, Hospital Clínico Universitario de Valencia - Valencia/ES The distinction between the two tumor types is not thought to be of major clinical significance, because the treatment strategies for both subtypes are identical with significantly lower recurrence rates after gross total resection, even if the initial tumor was locally invasive. The hallmark of a craniopharyngioma on imaging studies is a suprasellar cyst with calcification and enhancement. Rim or nodular calcifications are present in about 80% of cases. Fig. 12 on page 30 Fig. 14 on page 32 Despite benign histopathologic features, craniopharyngiomas are locally invasive, with projections of tumor extending into the adjacent brain. Hence, total resection of this tumor Page 11 of 51

12 is often difficult, and local recurrence at the primary site or in the contiguous brain may ensue, usually within 5 years. EPIDERMOID AND DERMOID CYSTS These slowly growing benign tumors are thought to represent rests of ectodermal cells trapped during neural tube closure, which subsequently form inclusion cysts and a mass. Both dermoid and epidermoid tumors are benign, slow-growing, congenital tumors. These tumors may cause mass effect in the sellar or suprasellar region resulting in visual disturbance, endocrine dysfunction, diabetes insipidus, or cranial nerve deficits. Epidermoids are five times more common than dermoids. Dermoid tumors usually present in childhood, are more common in boys, and are usually located in the midline. Rarely, dermoids occur in a parasellar or subfrontal location. These tumors contain cutaneous adnexa, hair, and sebaceous and sweat glands, in addition to benign keratinizing squamous epithelium. This complexity results in heterogeneous signal intensity on MR images. High signal intensity of fat within these tumors is usually present on T1-weighted images; occasionally, a fat-fluid level is present. Calcifications can be seen in these tumors as signal void on MR images or to better advantage as high density on CT images Rupture of a dermoid results in a chemical meningitis due to spillage of its contents into the subarachnoid spaces and ventricles. This is seen as multiple well-defined fat particles within the CSF, having characteristic low fat density on CT or high signal intensity on T1weighted images. Fig. 15 on page 33 Intracranial epidermoids are more common in the cerebellopontine angle; however, they may also be seen next most commonly in a parasellar location. Epidermoid tumors arise from inclusion of ectodermal squamous epithelial rests during neural tube closure. Desquamated debris consisting of cholesterolin and keratin accumulates within the epidermoid. These tumors occur off the midline, most commonly in the fourth to fifth decades of life with an equal prevalence in men and women. They can be intradural or extradural; however, an intradural location is more common. Epidermoid tumors are lobulated masses with scalloped borders, having a tendency to surround or insinuate between normal neural structures. Epidermoids are hypodense on CT, usually slightly hyperdense to CSF, occasionally containing a small amount of calcification along a margin. Epidermoid tumors do not enhance on either CT or MR imaging. They may be isointense or slightly hyperintense to CSF on T1- and T2- weighted images and usually slightly hyperintense to CSF on proton density-weighted images. They show restricted diffusion. Page 12 of 51

13 MENINGIOMA Meningioma is the most common nonglial primary brain tumor and accounts for 15% of all intracranial neoplasms. 5% to 10% of all meningiomas occur in the sellar region, where they are the second most common lesion in adults exceeded only by the pituitary adenoma. Meningiomas may arise from the suprasellar, parasellar (cavernous sinus) or intrasellar regions (diaphragm sellae). Suprasellar meningioma arises close to the optic chiasm displacing it posteriorly and superiorly. This usually results in vision loss, the most common and earliest complaint, usually involving monocular vision loss that progress to binocular vision loss, specifically amaurosis of one eye with temporal hemianopsia of the other eye. Other common symptoms include headaches, seizures, and mental changes. Parasellar meningioma of the lesser sphenoid wing can expand medially and affect the ipsilateral optic nerve and the superior orbital fissure. Diplopia may be present because of paresis of the extrinsic ocular muscles. Papillary dysfunction is not uncommon. Exophthalmos can result either from direct invasion of the orbit through the superior orbital fissure or obstruction of the draining venous system of the orbit and the cavernous sinus. Cavernous sinus meningioma can involve the cavernous sinus, Meckel's cave, or the sella turcica resulting in the cavernous sinus syndrome. Intrasellar meningiomas are rare and probably originate from the diaphragm sellae causing the diaphragm to be depressed if arising from above and elevated if arising from below Fig. 17 on page 35 Meningiomas are generally homogeneous, T1 isointense, and T2 iso-hyperintense masses that enhance avidly, often having a broad base with a dural surface. Meningiomas in the sella/parasellar regions can usually be distinguished from macroadenomas by the normal size of the sella turcica and identification of normal pituitary tissue separate from the mass They can invade the cavernous sinus narrowing or occlusing the cavernous ICA. CT maybe helpful for identification of hyperostosis. Fig. 16 on page 34 GERM CELL TUMORS:GERMINOMA Page 13 of 51

14 Germinomas are the most common intracranial germ cell tumors comprising 0.5% of all intracranial tumors. Other less common germ cell tumors include embryonal carcinoma, yolk sac tumor, teratoma, and choriocarcinoma. Fig. 19 on page 37 Approximately 20% of intracranial germinomas occur within the suprasellar cistern as either a primary suprasellar tumor or as cerebrospinal fluid spread from another site, such as the pineal region. Rarely, they may be intrasellar. They affect primarily children and young adults. They are midline tumors and most frequently arise in the pineal and suprasellar regions. Unlike pineal germinomas, which have a male predilection, primary suprasellar germinomas have no sex prevalence. They commonly invade the hypothalamus and extend into the third ventricle. They may also involve the optic chiasm and optic nerves or extend into the sella to involve the pituitary gland. Classically, patients present with diabetes insipidus, hypopituitarism, and visual symptoms. The visual disturbances include visual field deficits, optic atrophy, diplopia, and decreased visual acuity. Noncontrast CT demonstrates a hyperdense suprasellar mass that enhances strongly with contrast administration. On MR imaging, a germinoma usually appears as a well-defined, homogeneous, and infiltrative mass. It is isointense to gray matter on T1- and T2-weighted MR images and enhances intensely with contrast. Marked enhancement is seen with contrast medium administration, a feature that aids the search for tumor spread. Germinomas are usually homogeneous in appearance; necrosis, cyst formation, calcification, and hemorrhage are usually not seen. Fig. 18 on page 36 GLIOMA Gliomas of the optic chiasm are tumors of childhood. The majority are considered benign and slow growing. There is an association with neurofibromatosis type 1. Hypothalamic gliomas tend to be more aggressive and present in adulthood. Typical symptoms include visual and /or endocrine disturbances and hydrocephalus. They are typically isointense to brain on T1WI, slightly hyperintense on T2WI, and approximately half will enhance to some degree. Calcification and hemorrhage are not common features. The tumors may be quite large and invade or compress adjacent structures and have a greater likelihood than most gliomas to exhibit cerebrospinal fluid spread SCHWANNOMA The most common nerve sheath tumors in the parasellar region arise from branches of the fifth cranial nerve (33%), although the third, fourth, and sixth cranial nerves also course through the cavernous sinus or within its lateral wall. They are slow-growing Page 14 of 51

15 tumors that may erode the walls of the cavernous sinus and displace the cavernous carotid artery medially. Erosion of the floor of the middle cranial fossa or petrous apex may be seen. They can follow the course of the trigeminal nerve divisions, expanding the foramen ovale, foramen rotundum, and superior orbital fissure. These lesions manifest with mastication problems, sensory deficit, pain in a cranial nerve distribution, or diplopia depending on the cranial nerve involved or compressed by the mass. Schwannomas tend to be isodense with brain parenchyma, isointense to brain on T1WI, hyperintense on T2WI, enhance strongly, and follow the course of the involved nerve. Occasionally, they may appear heterogeneous with variable contrast enhancement patterns depending on cystic, necrotic, and hemorrhagic components METASTATIC DISEASE Metastatic disease to the sella and parasellar region can be from distant of a primary central nervous system malignancy; leptomeningeal spread (carcinomatosis, melanomatosis); or from local extension of lesions of the central skull base, sinuses, and head and neck. Page 15 of 51

16 Fig. 20: 49y man with nasal epidermoid carcinoma. An hyperenhancing mass is seen in nasal cavity with associated central skull base bony erosion. References: Radiodiagnostic, Hospital Clínico Universitario de Valencia - Valencia/ES Metastatic lesions tend to affect the stalk and the posterior lobe (likely because of its direct systemic blood supply from the meningohypophyseal trunk) more than the anterior lobe; however, involvement of the entire gland is possible. Breast cancer is the most common malignancy to metastasize to the pituitary followed by lung cancer, being nasopharyngeal carcinomas, the most common tumors to invade the skull base. Fig. 21 on page 39 Clinical presentation is variable; however, many patients present with diabetes insipidus. The imaging appearance of pituitary metastases is nonspecific. Metastases are usually hypointense on T1- weighted images, vary from hypointense to hyperintense on T2-weighted images, and enhance after gadolinium administration. The rapid growth of these lesions, enlargement of the infundibulum, and a tendancy to destroy bone of the sella turcica rather than remodel are features that help to differentiate metastatic disease from a benign adenoma. CHORDOMAS Chordomas are tumors derived from notochordal remnants yet are tumors of adults. The most common site for chordoma is in the sacrum, although approximately 35% of these lesions arise from the clivus. The tumor is histologically benign but locally invasive. Patients with chordoma may present with cranial nerve palsies, visual or pituitary deficits, hydrocephalus, or evidence of brain stem compression. Diplopia is the most frequent initial complaint usually secondary to involvement of CN VI. CT and MR imaging are complementary. CT, providing superior bony anatomic detail, demonstrates the bony extent of this destructive lesion of the clivus and tumoral calcification. Chordomas are of moderate signal intensity on T1-weighted and high signal intensity on T2-weighted MR images with variable contrast enhancement.fig. 23 on page 41 LIPOMAS Lipomas are benign fatty tumors and are usually incidental; they cause symptoms only when they are large. Lipomas are homogeneously hypodense on CT and hyperintense on T1 images. Usually they are well defined and do not enhance. Fat-suppressed sequences confirm fat content and distinguish them from hemorrhagic or proteinaceous lesions.fig. 24 on page 42 Page 16 of 51

17 CONGENITAL LESIONS RATHKE'S CLEFT CYSTS (RCC's) Rathke's cleft cysts are congenital, non-neoplastic sellar and suprasellar cysts derived from remnants of Rathke's pouch of (precursor of the anterior and intermediate lobes of the pituitary gland). These cysts are found during routine autopsies in 13% to 22% of cases. They are twice as common in women as in men. They are usually asymptomatic because they are not large enough to cause compression on surrounding structures. Symptoms, when present, result from compression of optic chiasm, hypothalamus, or pituitary gland, and include headache, endocrine dysfunction, or visual impairment. They are well-defined cystic lesions, which often are hyperintense on T1 and high attenuation on CT because of their proteinaceous content (mucinous). Cysts containing serous fluid are typically low attenuation on CT and hypointense relative to pituitary on T1-weighted images. They may contain an intracystic nodule (#T1WI and #T2WI) better seen as low signal intensity relative to that of surrounding cystic fluid on T2 WI, especially in cases in which the cyst fluid was high in signal intensity on T1WI. There is no enhancement after contrast administration. Nonetheless, they are often surrounded by the enhancing normal pituitary gland, thus mimicking wall enhancement. Fig. 25 on page 44 Treatment is usually by transphenoidal drainage and partial resection of the wall. There is a low incidence of recurrence and good visual prognosis ARACHNOID CYST Most arachnoid cysts occur in the middle cranial fossa. Approximately 15%, however, are located in the suprasellar region. Unknown pathogenesis; one theory is that they result secondary to an inflammatory process, such as postinfectious arachnoiditis. Another theory is that they develop from the splitting of arachnoid membranes and progressively enlarge. Because of lack of communication with the subarachnoid space, the cyst is under pressure thereby causing mass effect on the parasellar structures, determining the clinical manifestations: visual disturbances or endrocrine dysfunction: Hydrocephalus can result from obstruction of the foramen of Monroe. Age at presentation ranges from childhood to the second or third decade with greater prevalence in males. Arachnoid cysts are smooth, well-defined lesions. The density and signal characteristics are identical to CSF on CT and all MR imaging sequences. Because of their slow growth, CT may demonstrate bone remodeling. Unlike craniopharyngioma and Rathke's cleft cyst, there is lack of calcification or enhancement. Page 17 of 51

18 TUBER CINEREUM HAMARTOMA Hamartomas of the tuber cinereum are masses of gray matter with a cell density similar to that of normal hypothalamus and are therefore considered non-neoplastic. These tumors do not grow and are usually discovered incidentally or at autopsy. Endocrine disturbances, such as precocious puberty or acromegaly, and periodic episodes of laughter, termed gelastic seizures, may occur. MR imaging reveals a nonenhancing, pedunculated mass between the hypothalamus and the mammillary bodies with signal intensity on T1-weighted images similar to gray matter, iso or slightly hyperintense on T2-weighted images. EMPTY SELLA An empty or partially empty sella turcica is usually an incidental discovery on CT or MR imaging studies. The diaphragma sella may be absent or incompetent allowing herniation of arachnoid space into the sella. The incidence increases with age and is more frequent in women. CSF pulsations result in a flattened appearance to the pituitary. When symptomatic, complaints include headache, dizziness, or memory loss and may be due to an elevated intracranial pressure or altered CSF dynamics INFECTIOUS AND INFLAMMATORY PROCESSES LYMPHOCYTIC HYPOPHYSITIS Lymphocytic hypophysitis is a rare inflammatory condition seen most often in women in the peripartum period. Histologically it is characterized by chronic inflammatory changes, hyaline fibrosis, and infiltration by plasma cells or lymphocytes. It is thought to be secondary to an autoimmune response to pituitary antigens and may coexist with other autoimmune disorders. Clinical symptoms usually include diabetes insipidus, failure of lactation, amenorrhea, hypopituitarism, headache, or visual impairment. MR imaging reveals an expanding sellar mass with thickening of the pituitary stalk and uniform, intense contrast enhancement. Hormone replacement and steroids have proved to be an effective treatment. SARCOIDOSIS AND TUBERCULOSIS In adults, the primary granulomatous disease that involves the infundibulum is sarcoidosis. Other entities include tuberculosis and Wegener disease. Sarcoidosis is a multisystem disease of unknown etiology that affects the central nervous system in 5% to 15% of cases. It is an infiltrative disease characterized by Page 18 of 51

19 noncaseating granulomas. It usually occurs in the third and fourth decades of life, affecting women more commonly than men. Neurosarcoidosis affects predominately the leptomeninges but may involve the hypothalamus, pituitary stalk, and optic chiasm. Patients may present with hypopituitarism, diabetes insipidus, and visual symptoms On MR imaging, sarcoidosis can appear as a pituitary mass simulating a pituitary adenoma or cause diffuse thickening of the pituitary stalk. Lesions are isointense on T1-weighted and variable on T2-weighted MR images and demonstrate uniform enhancement. There is usually associated leptomeningeal enhancement. Fig. 27 on page 45 Tuberculosis can spread to the central nervous system, most commonly causing basilar meningitis. Sellar tuberculomas are rare and may result from hematogenous spread or direct extension of disease from the skull base. Tuberculomas may result presenting as masslike lesions in the sellar, parasellar, and suprasellar regions producing endocrine dysfunction, cranial neuropathies, or diabetes insipid as sarcoidose. MR imaging reveals lesions that are isointense on T1-weighted and variable on T2-weighted with strong enhancement, often ring like. There may be thickening of the stalk and leptomeningeal enhancement. Fig. 28 on page 46 HISTIOCYTOSIS Langerhans cell histiocytosis (LCH), a disease disease of unknown etiology that affects children and young adults. It consists in part of a proliferation of Langerhans' histiocytes and is assumed to be inflammatory rather than neoplastic.. Although isolated Langerhans cell histiocytosis of the central nervous system is rare, central nervous system involvement as part of the systemic process is common. This usually takes the form of neuroendocrine disturbances involving the hypothalamic-neurohypophyseal axis. The absence of normal high signal intensity of the posterior lobe, associated with a thickened pituitary stalk, although nonspecific for Langerhans cell histiocytosis, should, because of frequent systemic involvement, prompt further studies such as chest radiography, bone scanning, and temporal bone CT. Fig. 29 on page 47 VASCULAR ABNORMALITIES ANEURYSM Aneurysms of the cavernous or supraclinoid portions of the internal carotid artery, posterior communicating artery, and ophthalmic artery can present as parasellar and suprasellar masses. Clinical manifestations include hypesthesia or hypalgesia of the face, diplopia, and ptosis caused by trigeminal nerve involvement and ocular motor nerve palsies. Because the Page 19 of 51

20 pupillomotor fibers are located peripherally in the third nerve, an aneurysm impinging on the third nerve affects the pupil first Imaging features vary greatly depending on the amount of calcification and thrombosis present within the aneurysm. CT may reveal a hyperdense mass with curvilinear calcifications and enhancement of a patent lumen. There may be evidence of bone remodeling of the sella turcica Aneurysms have variable MR imaging characteristics depending on whether they are patent or thrombosed. Patent aneurysms will appear hypointense, due to flow on T2-weighted images. However, thrombosed aneurysms may be T1 hyperintense and be of mixed intensity on T2-weighted imaging. The exclusion of an aneurysm is essential in evaluating a sellar mass because of its high morbidity. CAROTID-CAVERNOUS FISTULA Carotid-cavernous fistulas can be classified into two types: traumatic and spontaneous. Because the cavernous sinus communicates with the ophthalmic veins, the veins become arterialized and develop increased pressure. At the same time, arterial blood flow to the cranial nerves in the cavernous sinus is diminished. Consequently, patients may develop ophthalmic signs including palsies of cranial nerves III, IV, V, and VI and decreased visual acuity. They may present with pulsatile exophthalmos, ocular bruit, and chemosis, and be misdiagnosed as conjunctivitis. Secondary glaucoma is noted frequently. In addition, diplopia and ophthalmoplegia can occur because of venous congestion of orbital muscles or compression of cranial nerves in the cavernous sinus from mass effect. CT reveals enlargement of the ipsilateral cavernous sinus, ophthalmic veins, and extraocular muscles. MR imaging and MR angiography demonstrate abnormal flow voids in the cavernous sinus, dilated cavernous sinus vessels and ophthalmic veins, a convex lateral wall of the cavernous sinus, and orbital edema. On angiography, shunting of blood from the carotid artery into the cavernous sinus may be seen. Fig. 30 on page 48 PITUITARY APOPLEXY AND SHEHAN'S SYNDROME Acute hemorrhagic infarction of a pituitary adenoma is referred to as pituitary apoplexy. It is characterized clinically with acute onset of headache, vomiting, ophthalmoplegia, and visual loss. Hypotension and shock may result from interruption of normal hormonal function; more often though, this is a subclinical event with findings discovered incidentally. Pituitary apoplexy occurs most commonly macroadenomas. Severe shock at or near the time of delivery may result in pituitary infarction in the postpartum state, termed Sheehan's syndrome. Occasionally, there is near total recovery over a short interval; however, more commonly, symptoms due to varying degrees of pituitary insufficiency usually persist over a 15- to 20-year time period. Page 20 of 51

21 Acute hemorrhage within the pituitary gland appears hyperdense on CT. On MR imaging, this appears isointense on T1-WI and hypointense on T2-WI. In the subacute phase, extracellular methemoglobin appears hyperintense on T1- and T2-weighted images. Blood products may be seen layering posteriorly within the hemorrhagic mass. Fig. 31 on page 49 Images for this section: Page 21 of 51

22 Fig. 1: Sagittal schematic view of the pituitary. AS, anterior clinoid; DS, diaphragma sella; III, third ventricle; IS, infundibular stem; ME, median eminence; NL, neural lobe; OC, optic chiasm; PC, posterior clinoid; PD, pars distalis; PI, pars intermedia; PT, pars tuberalis. Page 22 of 51

23 Page 23 of 51

24 Fig. 2: Anatomic diagrams of cavernous sinus. A and B, Drawings of coronal (A) and lateral (B) views show structure of cavernous sinus. 1 = carotid artery, 2 = oculomotor nerve, 3 = trochlear nerve, 4 = ophthalmic nerve, 5 = maxillary nerve, 6 = abducens nerve, 7 = pituitary gland, 8 = sympathetic nerve, 9 = mandibular nerve. Fig. 3: Drawing illustrates normal anatomy of the sella turcica and juxtasellar region in the parasagittal plane. a = adenohypophysis, b = neurohypophysis, c = infundibulum, d = optic chiasm, e = tuber cinereum, f = anterior third ventricle, g = mamillary bodies, h = interpeduncular cistern, i = prepontine cistern, j = clivus, k = sphenoid sinus. Page 24 of 51

25 Fig. 4: Drawing illustrating the embriollogically primordium of the pituitary gland arising from growth of the epithelium of Rathke's. Page 25 of 51

26 Fig. 5: Drawing illustrating the anterior, intermediate and posterior lobes of pituitary gland and its hormone secretion. Page 26 of 51

27 Fig. 6: Drawing illustrating the optic pathway and the different visual fields' defects depending on the level of the lesion. Page 27 of 51

28 Fig. 7: Parasagittal T1-weighted MR image shows the normal anatomic structures: adenohypophysis (thick white arrow), neurohypophysis (open arrow), infundibulum (thin white arrow), and optic chiasm (black arrow). Page 28 of 51

29 Fig. 8: Ectopic posterior pituitary lobe. Fig. 9: Common indications of pituitary images Page 29 of 51

30 Fig. 11: Pituitary non-functioning macroadenoma with left cavernous sinus invasion. Heterogeneous and enhancing mass, iso-hyperdense, isointense in T1 and T2WI with cystic components in a 59 years women. Page 30 of 51

31 Fig. 12: Suprasellar craniopharyngioma in a 29 years man. Predominantly cystic mass with rim calcifications and enhancement. Reduced perfusion compared with white substance. Page 31 of 51

32 Fig. 13: Suprasellar craneopharyngioma in a 35 years woman. Solidocystic suprasellar mass with nodular calcifications and enhancement after contrast administration. There is presence of hyperintense in T1WI cysts. Page 32 of 51

33 Fig. 14: Sellar craniopharyngioma in a 19 years man. Little cystic non enhancing mass with a tiny calcification visualized in TC. It was thought to be a Ratke`s cleft cyst, but pathology did the definite diagnose. Page 33 of 51

34 Fig. 15: Dermoid sphenoidal cyst seen in a 58 years woman. An oval non enhancing mass with fat attenuation and signal associated with punctiform calcifications is visualized. Page 34 of 51

35 Fig. 16: 59 years man with an avid enhancing mass, corresponding with a clival meningioma. Page 35 of 51

36 Fig. 17: Sellar meningioma with right cavernous sinus invasion is seen in a 49 years woman. Page 36 of 51

37 Fig. 18: Infundibullar germinoma in a 17 years man. Hyperenhancing infundibulum nodule in a patient with diabetes insipidus and germinoma cells in LCR. Page 37 of 51

38 Fig. 19: Mature teratoma in a 31 years woman with intracranial hypertension and visual disturbances. Solidocystic mass with calcifications, that compress third ventricule causing hydrocephalie. Page 38 of 51

39 Fig. 20: 49y man with nasal epidermoid carcinoma. An hyperenhancing mass is seen in nasal cavity with associated central skull base bony erosion. Page 39 of 51

40 Fig. 21: Cavum carcinoma in a 57 y man. A hyperenhancing mass centrated in cavum is seen with associated central skull base infiltration. Page 40 of 51

41 Fig. 22: A 59 y man with lung metastatic (left adrenal) carcinoma. An hyperdense and hyperenhancing infundibular mass is seen corresponding with pituitary metastasis. Page 41 of 51

42 Fig. 23: 52y with clival chordoma. An hyperenhancing with petrous bone extension and erosion is seen. Page 42 of 51

43 Fig. 24: Tuber cinereum lipoma in a 36 years woman. A nodule with fat signal is seen in tuber cinereum. Page 43 of 51

44 Fig. 26: Empty sella in 75 y woman. A flattened appearance of the pituitary is seen associated with herniation of arachnoid space into the sella. Page 44 of 51

45 Fig. 25: 23y man with sellar RCC. A cystic non enhancing sellar mass compressing normal pituitary gland is seen. Page 45 of 51

46 Fig. 27: An infundibular nodular enhancing thickness is seen in a 38 years woman with systemic sarcoidosis. Page 46 of 51

47 Fig. 28: A masslike lesions in the sella is seen with avid contrast enhancement in a 49 y man with pulmonary tuberculosis. A year after treatment, pituitary mass is resolved. Page 47 of 51

48 Fig. 29: An infundibular nodular thickness with no contrast enhancement is seen in a 13 years boy with systemic hystiocitosis Page 48 of 51

49 Fig. 30: An carotid cavernous fistula is seen in a 59 y woman who arrives with pulsatil exophtalmus. A dilated ophtalmic vein is seen. A fluid void in left cavernous sinus and ophtalmic vein are associated. Angiographic shunting of blood from the carotid artery into the cavernous sinus is seen. Endovascular treatment was done with morphologic and clinical resolution. Page 49 of 51

50 Fig. 31: Acute hemorrhage within the pituitary gland is seen in a 37 years woman in postpartum. Page 50 of 51

51 Conclusion Knowledge of the normal anatomy and pathologic imaging appearance of pituitary lesions is essential in the interpretation of MR imaging of brain and pituitary. Not every mass in sellar and parasellar region is an adenoma. Careful consideration of the anatomy and location of the lesion as well as correlation with the clinical situation and previous medical/ surgical treatment are essential in the imaging diagnosis of pituitary masses The wide spectrum of sellar and parasellar masses often present with similar symptoms. Accurate imaging characterization and early diagnosis are capable of providing significant clinical benefit. References 1. M. Pisaneschi, MD, G. Kapoor, MD et al. Imaging the Sella and Parasellar Region. Neuroimag Clin N Am 15 (2005) M. Fitzpatrick, md, l. M. Tartaglino, md et al. Imaging of sellar and parasellar pathology. Radiol Clin N Am 37 (1999) T. Ouyang, MD, W. E. Rothfus, MD et al. Imaging of the pituitary. Radiol Clin N Am 49 (2011) C. E. Swallow and A. G. Osborn. Imaging of Sella and Parasellar Disease. Seminars in Ultrasound, CT, and MRI 19 (1998) J. H. Lee, H. K. Lee et al. Cavernous Sinus Syndrome: Clinical Features and Differential Diagnosis with MR Imaging. AJR181 (2003) Woo Mok Byun, Oh Lyong Kim et al. MR Imaging Findings of Rathke's Cleft Cysts: Significance of Intracystic Nodules. AJNR Am J Neuroradiol 21 (2000) D. E.Jobnsen,, W. Woodruf et al. MR Imaging of the Sellar and Juxtasellar Regions. RadioGraphics 11 ( 1991) : F. Bonneville, MD, F. Cattin, MD et al. T1 Signal Hyperintensity in the Sellar Region: Spectrum of Findings. RadioGraphics 26(2006) B E. Hamilton, K. L. Salzman et A. G. Osborn. Anatomic and Pathologic Spectrum of Pituitary Infundibulum Lesions. AJR 188 (2007) W223-W J H Shin, MD1 H K Lee, MD et al. MR Imaging of Central Diabetes Insipidus: A Pictorial Essay. Korean J Radiol 2 (2001) Personal Information Page 51 of 51