Sellar and Parasellar pathologies: a comprehensive review on MRI

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1 Sellar and Parasellar pathologies: a comprehensive review on MRI Poster No.: C-1854 Congress: ECR 2016 Type: Educational Exhibit Authors: S. Sahni, K. Saggar, K. GUPTA, C. Kakkar, A. Banerjee ; Ludhiana, Punjab/IN, Ludhiana/IN, Manipal, Karnataka/IN Keywords: Cancer, Imaging sequences, MR, CNS DOI: /ecr2016/C-1854 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 31

2 Learning objectives To discuss various sellar and parasellar lesions with an emphasis on MR imaging To develop a comprehensive approach for driving to a differential diagnosis To emphasize the role of MR imaging in preoperative evaluation of sellar and parasellar lesion with focus on important parameters for surgical resection of these lesions. Page 2 of 31

3 Background The sellar and parasellar region is an anatomically complex area that represents a crucial crossroad of important adjacent structures, e.g. orbits, cavernous sinus and its content, circle of Willis, hypothalamus through the pituitary stalk and dural reflections forming the diaphragm sellae and the walls of the cavernous sinuses. Although the cavernous sinus represents the most relevant parasellar structure, from the practical and clinical point of view all the structures that surround the sella turcica can be included in the parasellar region. ANATOMY Sellar region The sellar region encompasses the sella turcica and the pituitary gland. The parasellar region includes the structures and spaces bordering the sella turcica, namely the cavernous sinuses, suprasellar cistern, hypothalamus, and ventral inferior third ventricle. The sella turcica is a depression in the sphenoid bone, ventrally bordered by the tuberculum sellae and anterior clinoid processes and its dorsally by the dorsum sellae and the posterior clinoid processes. The roof consists of a thin dural covering: the diaphragma sellae. Within the sella turcica, the pituitary gland consists of the ventral adenohypophysis and the dorsal neurohypophysis. The adenohypophysis is formed by ascending ectodermal cells of the Rathke pouch and consists of the pars distalis, pars intermedia, and pars tuberalis. The adenohypophysis primarily secretes regulatory hormoes. In contrast, the neurohypophysis is formed as an extension or evagination of neural ectoderm from the floor of the third ventricle (diencephalon).the neurohypophysis consists of par nervosa and infundibulum. The infundibulum extends from the hypothalamus through the diaphragma sellae to the pituitary gland. The neurohypophysis primarily consists of axon terminals that secrete hormones formed in the hypothalamus into the blood. Parasellar region The parasellar region is a general term that traditionally encompasses the cavernous sinuses and the suprasellar cistern structures. The basisphenoid and the sphenoid sinus are occasionally included as well. The cavernous sinuses are multilobulated, trabeculated, venous channels lateral to the sella turcica and sphenoid sinus. Cranial nerves III, IV, V1, and V2 lie within the lateral dural wall, whereas cranial nerve VI lies within the cavernous sinus. It also contains the cavernous segment of the internal carotid artery (ICA). Page 3 of 31

4 The suprasellar cistern contains the optic chiasm/nerves, anterior third ventricle, hypothalamus, and tuber cinereum. Located along the ventral lateral aspect of the third ventricle, the caudal extent is formed by the infundibular stalk, tuber cinereum, and mammillary bodies. Located in the tuberal region of the hypothalamus and ventral to the mammillary bodies, the tuber cinereum is a lamina of gray matter. Part of the limbic system, the mammillary bodies are paired globular structures along the floor of the hypothalamus that connect with the hippocampi via the fornices. Pituitary adenomas are the most common cause of sellar mass in an adult. The differential diagnosis of nonpituitary sellar masses is broad and includes germ cell tumors, gliomas, meningiomas, metastatic tumors, vascular lesions, and granulomatous, infectious, and inflammatory processes. Differentiating among these potential etiologies may not always be straightforward because many of these lesions, tumorous and nontumorous, may mimic the clinical, endocrinologic, and radiographic presentations of pituitary adenomas. When evaluating sellar diseases, it is important to first localize the process to the sellar, parasellar, or suprasellar compartment and have a systematic approach toward analysis. With knowledge of the common and uncommon processes in that region, the patient's age and presentation, and the imaging features of the process, one can provide a limited, expert differential. Page 4 of 31

5 Images for this section: Fig. 1: Anatomy. (A) Sagittal precontrast, fat-saturated T1WI image through the midline sella turcica shows the normal T1 shortening in the neurohypophysis. (B) Postcontrast T1WI image shows the normal enhancement of the pituitary gland, infundibulum, and tuber cinereum region caused by the lack of a blood-brain barrier Page 5 of 31

6 Findings and procedure details MRI SEQUENCES Cross sectional imaging has revolutionised the imaging of sella. Starting with high resolution computed tomography in 70s and 80s, now MRI is the cornerstone of sellar and parasellar imaging. Thin section acquisition in sagittal and coronal planes provide clear anatomic information on the relationship of the gland to adjacent structures and also provide the best views of the infundibular stalk. The important MR sequences in this setting include: T2-weighted (T2W) - T2-weighted imaging is one of the basic sequence of MRI. It is used to differentiate anatomical structures mainly on the basis of T2 values; i.e. the scanning parameters are set (long TR/long TE) to minimize T1 relaxation effects. Compartments filled with water (e.g. CSF compartments) appear bright and tissues with high fat content (e.g. white matter) appear dark. T1-weighted (T1W) - T1-weighted imaging is another basic MRI sequence. It is used to differentiate anatomical structures mainly on the basis of T1 values; i.e. the scanning parameters are set (short TR/short TE) to minimize T2 relaxation effects. Tissues with high fat content (e.g. white matter) appear bright and compartments filled with water (e.g. CSF) appears dark. T1 signal hyperintensity of various degrees is observed at MR imaging of the sellar region. Vasopressin storage, bone marrow, and adenohypophysial hyperactivity are the three main causes of high T1 signal intensity in normal conditions. Lesions that contain blood products, fat, high concentrations of protein, or calcifications account for the majority of pathologic entities that cause high T1 signal intensity in the sellar and parasellar regions. Fluid attenuated inversion recovery (FLAIR) - This imaging uses an inversion recovery pulse after an inversion time to nullify the high signal of cerebrospinal fluid (CSF). FLAIR is sensitive in detecting meningeal disease, as in cases of hypophysitis. Gradient recalled echo (GRE) - The gradient echo sequence is the simplest type of MRI sequence. It consists of a series of excitation pulses, each separated by a repetition time. This sequence is useful for determining hemorrhages and calcifications. Diffusion-weighted imaging (DWI) - This sequence is particularly useful in tumour characterisation and cerebral ischaemia. Another important use is to detect necrotic cavities, as in cases of pituitary apoplexy and abscess. Page 6 of 31

7 T1-weighted post-gadolinium (GAD) - Paramagnetic contrast agents like gadolinium are a useful adjunct in defining sella and parasellar pathology. The contrast is critical to evaluate the enhancement characteristics of sellar and parasellar lesions. Meningeal enhancement demonstration is important in case of granulomatous involvement of the pituitary. Dynamic contrast enhanced T1-weighted (DCE) - This is a dedicated sequence for detection of pituitary microadenomas. Rapid sequential T1-weighted coronal images using small FOV and thin sections are acquired after contrast administration to look for the differential enhancement of the tumor as compared to the normal gland. SELLAR AND PARASELLAR LESIONS PITUITARY ADENOMA Pituitary adenomas account for approximately 10% of all intracranial neoplasms and between one third to one half of sellar and parasellar masses. The majority of pituitary tumours are asymptomatic, discovered as "incidentalomas" in the course of investigation for other conditions. Adenomas are often classified by size; microadenomas are 10 mm or less in diameter, and macroadenomas are greater than 10 mm in diameter. They are further classified according to functional activity. Among the secretory adenomas, visual loss is rarely the initial complaint. The most common pituitary adenomas are prolactinomas, comprising approximately 30% to 40% of all pituitary tumors. Prolactinomas are predominantly seen in women with a 5:1 female to male ratio. Nonfunctioning adenomas are the second most common tumors, comprising 25% of pituitary adenomas. These tumors often grow to a significant size and cause optic chiasmal compression or other mass effect before they are detected. Because of its exquisite soft-tissue contrast for evaluation of sellar tumors, their suprasellar extension, parasellar cavernous sinus invasion, and dural invasion, MR imaging is the primary technique for preoperative assessment of pituitary adenoma and guidance of resection. In many centers, CT is used as an adjunct for guidance because of its superior depiction of bony anatomy, but though it has recently been reported to add useful information to pituitary MR imaging in depicting erosion of the sellar floor and clivus, it is not generally regarded as providing significant diagnostic information. On MR imaging, they adenoma appears isointense to gray matter on T1and T2-weighted MR images, and usually demonstrates intense contrast enhancement unless there are areas of necrotic degeneration or small amounts of haemorrhage. A slow-growing macroadenoma expands the bony sella and extends into the suprasellar cistern. Often, these lesions have a Page 7 of 31

8 ''figure of eight'' or ''snowmanlike'' appearance because the rigid dura of the diaphragm sellae results in a waist to the mass(figure 2). On imaging, pituitary microadenomas usually show contour deformity and minor stalk deviation. Dynamic MRI helps to better delineate the lesion, discriminating between the slowly enhancing microdenoma and the rapidly enhancing normal gland(figure 3). Cavernous sinus involvement is depicted by the extent of encasement of cavernous ICA. Total encasement of the intracavernous ICA by the tumor is the most reliable MR imaging sign of cavernous sinus invasion, but this sign occurs very late(figure 4). Posterior-inferior invasion into the clivus is rare but presents a technical challenge to surgical resection and may raise the potential risks of cerebrospinal rhinorrhea and other complications(figure 5). Macroadenomas can also reach upto the paranasal sinuses and nasal cavity (Figure 6) Pituitary apoplexy is a well-described acute clinical syndrome with headache, visual defects, and variable endocrine deficiencies. It is caused by hemorrhage into-or ischemic necrosis of-the pituitary gland. Although incidences vary depending on the series, apoplexy most commonly occurs in a pre-existing macroadenoma. The T1WI and T2WI features depend on the subtype of apoplexy as well as the timing of imaging (ie, hemoglobin state of oxygenation). The lesion shows peripheral contrast enhancement, and can rarely involute without any surgical intervention(figure 7). NON-ADENOMATOUS SELLAR LESIONS Rathke's cleft cyst - Rathke's pouch is an evagination of stomodeum (primitive mouth) ectoderm, which loses connection with the oral cavity at about the second month of development. Rathke's pouch extends dorsally and is induced by a downward extension of the diencephalon, the infundibulum, to develop into the adenohypophysis. They are most often discovered incidentally during cranial imaging for other causes. Clinical symptoms arise from mass effect; headache and visual symptoms are more common than hypopituitarism. Histologically, a single layer of columnar or cuboidal epithelial cells envelops the fluid within the cyst. The MR appearance of RCC is highly variable and neuroimaging diagnosis of RCC is often difficult. However, a few key findings that may help to distinguish RCC from other cystic lesions have been reported. RCCs usually do not exhibit destruction or enlargement of the sella turcica. Intracystic nodules, i.e. waxy nodules, if present, show characteristic intensity on MRI. RCCs are almost always homogeneous in MR intensity (Figure 8), except for waxy nodules, whereas other lesions Page 8 of 31

9 such as cystic craniopharyngioma and haemorrhagic adenomas are less frequently homogeneous. Meningioma - Approximately 15 to 25% of meningiomas occur in the parasellar region. Meningiomas may arise from the suprasellar (tuberculum sella, anterior clinoid processes, planum sphenoidale, upper clivus, diaphragm sellae); parasellar (cavernous sinus); or intrasellar regions (diaphragm sellae). They are generally isointense to gray matter on T1WI. On T2WI, the signal intensity is variable. Cerebrospinal fluid (CSF) cleft may be seen between the pituitary gland and the tumor. Sella turcica is only mildly enlarged as opposed to macroadenomas. Calcification may be seen as hypointense foci on both T1W and T2W sequences. Homogenous enhancement, suprasellar epicentre with broad dural base, and dural enhancement (dural tail) help in differentiating meningiomas from adenomas (Figure 9). Meningiomas can be locally aggressive, invading the adjacent cavernous sinus, impairing function of cranial nerves within the cavernous sinus. When invading into the cavernous sinus, meningiomas tend to constrict the carotid lumen, which is usually not a feature of adenomas. Craniopharyngioma - Craniopharyngiomas represent the most common suprasellar lesion. These benign, slow-growing, tumours are epithelial neoplasms arising from squamous epithelial remnants of Rathke's pouch. Although benign, craniopharyngiomas tend to recur and invade adjacent structures. Tumor adhesion to surrounding vascular structures represents the most common cause of incomplete resection. The age of presentation is bimodal: 5 to 14 years in children and 65 to 74 years in adults. There are 2 major histologic subtypes of craniopharyngioma (adamantinomatous and papillary) that vary in clinical and imaging presentation. The adamantinomatous subtype is the most common and predominantly presents in younger patients as a multiloculated, cystic, solid, calcified mass(figure 10). In contrast, the papillary subtype almost exclusively presents in adults as a predominantly solid, less commonly calcified mass. Calcification, present in 90% of cases and seen at the periphery of individual cystic components, can be challenging to identify on MRI. Low T1 and T2 signal that blooms on gradient-echo images is typical, although calcification may also be seen with high T1 or T2 signal or may be occult if present in low concentrations. CT obtained in equivocal cases can assist in distinguishing these from Rathke cleft cysts and macroadenomas, in which calcification is far less common. Hydrocephalus may be present when there is significant invasion of surrounding structures or extension into the third ventricle. Aneurysm - Aneurysms of the intracavernous segment of the internal carotid artery, as well as those originating in its supraclinoid segment or in the polygon of Willis, are the most common lesions that may occur in the cavernous sinus. Although the size of aneurysm is variable, parasellar location is the most common location for giant intracranial aneurysms. A patent aneurysm lumen with fast flow is seen as a welldelineated signal void, however if slow flow is present, then heterogenous T1 signal Page 9 of 31

10 may be demonstrated. Peripheral concentric lamellae of increased to intermediate signal on T1 weighted correspond to mural thrombus. Signal misregistration artifact in the phase-encoding axis due to disordered or pulsatile flow within the aneurysm is also a characteristic finding(figure 11). It is not seen in other masses involving the sella. The adjacent cavernous arteries in these other masses may create the same artifact, but it can be localized to the normal artery rather than the mass. An eccentric sellar lesion should suggest the possibility of an aneurysm. MR angiography is useful for diagnosing large aneurysms, however conventional angiography will be required for treatment planning. Gliomas - Hypothalamic-chiasmatic astrocytomas are primarily masses seen in childhood and are rarely documented in adulthood. Astrocytomas arising from the hypothalamus, optic chiasm, optic nerve, and optic tract account for approximately 30% of neoplasms in childhood.chiasmatic/optic nerve gliomas have a strong association with neurofibromatosis I. These gliomas are usually low grade gliomas, histologically resembling pilocytic astrocytomas.these lesions are often difficult to delineate between locations in the hypothalamus versus the optic chiasm; depending mainly on the epicenter of the lesion. Hence, they are often referred to in the literature as hypothalamic-chiasmatic gliomas. These patients present with visual loss, hydrocephalus, or hypothalamic dysfunction. These tumors are often quite large on presentation and may have areas of cystic degeneration. Contrast enhancement is seen in 50% of these lesions and is usually homogenous or occasionally rim-like. These are seen as a hypo- to isointense mass on T1WI with moderate hyperintensity on proton density and T2WI. The tumors can spread along the optic tracts, anteriorly into the optic nerve and posteriorly through the optic tracts and optic radiations(figure 12). Hypophysitis - Hypophysitis is an inflammation of the pituitary gland with two main histologic forms: Lymphocytic hypophysitis and nonlymphocytic/ granulomatous hypophysitis. Lymphocytic hypophysitis is an uncommon autoimmune inflammatory disorder of the pituitary gland that most often occurs in women of child bearing age, usually late in pregnancy or shortly after childbirth. Approximately 25% of patients have coexistent systemic inflammatory/ autoimmune disease. Thyroiditis, polymyositis, type 1 diabetes, and psoriasis have all been associated with it. Imaging shows a thickened, nontapering infundibular stalk. A rounded, symmetrically enlarged pituitary gland is common. The sellar floor is intact, not expanded or eroded. The posterior pituitary "bright spot" is absent in 75% of cases. LH enhances intensely and uniformly. Granulomatous Hypophysitis can occur with fungal infections, tuberculosis, sarcoidosis, Langerhans' cell histiocytosis, and Wegener's granulomatosis and accounts for approximately 1% of sellar masses. Sarcoidosis, a systemic disease featuring multiple noncaseating granulomas, may involve the central nervous system in about 5% of cases. Predilection sites are the leptomeninges, especially the sellar and suprasellar region, Page 10 of 31

11 such as the pituitary stalk and chiasm. Tuberculosis has a predilection for the basal cisterns and can present with leptomeningeal enhancement in the suprasellar cistern. Enlargement and enhancement of the pituitary stalk and masslike suprasellar lesions may be seen(figure 13). Imaging findings are nonspecific, resembling those of lymphocytic hypophysitis or pituitary adenoma. Metastasis - Metastatic disease to the sella and parasellar region can be from distant sites; CSF dissemination 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 Breast cancer is the most common malignancy to metastasize to the pituitary followed by lung cancer. It has been hypothesized that the hormonal-rich environment of the anterior pituitary is the preferred environment for breast cancer cells and enhances their proliferation.[45] Imaging shows locally invasive and rapidly growing lesions within or separate from the pituitary. Erosion of the dorsum sella or the inferior sellar wall may help to distinguish metastases from other adenomas or craniopharyngiomas, which are more typically invasive than destructive (Figure 14). Pituitary abscess - Pituitary abscess can be primary or secondary due to an adenoma or surgical procedure. Spread of Gram positive bacteria from the sphenoid sinus is the usual source of infection, but rare infectious diseases have been described. Typical MRI-findings are those of a round sellar mass with ring enhancement and diffusion restriction (Figure 15). T1 shortening around the rim rather than the center of the mass is characteristic of abscess. Furthermore, meningeal enhancement due to concurrent meningitis may help distinguishing pituitary abscess from pituitary adenoma. Epidermoid Cyst - Epidermoids are lesions of adulthood, most commonly in the second to fourth decade. They cerebellopontine angle is the most frequent site of occurrence, followed by the parasellar region. Epidermoid cysts can present with visual disturbance, hypopituitarism, diabetes insipidus, and cranial nerve abnormalities. These cysts generally appear isointense to CSF on T1-weighted images and hypointense to hyperintense in signal on T2-weighted images and do not enhance with contrast. Diffusion-weighted images can be helpful, typically showing a markedly increased signal(figure 16). Arachnoid Cyst - Most arachnoid cysts occur in the middle cranial fossa. Approximately 15%, however, are located in the suprasellar region. Intrasellar arachnoid cysts are rare but have been reported. Occasionally, an intrasellar arachnoid cyst may be confused with an empty sella. An empty sella, however, does not demonstrate mass effect because of its free communication with the subarachnoid space. Arachnoid cysts are smooth, welldefined lesions. The density and signal characteristics are identical to CSF on CT and all Page 11 of 31

12 MR imaging sequences (Figure 17). Unlike craniopharyngioma and Rathke's cleft cyst, there is lack of calcification or enhancement. Page 12 of 31

13 Images for this section: Fig. 4: 30 year old male with headache, vision loss and syncope. Sagittal T2 (left) and Coronal T1 post contrast (right) images show an intensely enhancing mass lesion with peripheral cystic component in sellar and suprasellar location with a parasellar component on right side completely encasing the cavernous ICA (arrow). DIAGNOSIS - PITUITARY MACROADENOMA Page 13 of 31

14 Fig. 5: 47 year old female with headache and vision loss. T2 Axial (A) and Sagittal (B); T1 post contrast Coronal (C) and Sagittal (D) images show a heterogenously enhancing sellar mass with inferior clival invasion and left parasellar extension DIAGNOSIS PITUITARY MACROADENOMA WITH CLIVAL INVASION Page 14 of 31

15 Fig. 6: 37 year old male with headache, vision loss and neuropathy Sagittal T2 (A), Coronal T2 (B), Sagittal T1 post gad (C), and Axial CT (D) images of a large intensely enhancing sellar and suprasellar mass with bilateral parasellar extensions and extension into paranasal sinuses and nasal cavity. DIAGNOSIS - GIANT PITUITARY MACROADENOMA WITH EXTENSION INTO PARANASAL SINUSES AND NASAL CAVITY Page 15 of 31

16 Fig. 7: 60 year old female with headache and vision loss. Sagittal T2 (A), T1 post contrast (B) and Axial GRE (C) images of initial scan show a heterogenous peripherally enhancing sellar mass with blooming on GRE- suggestive of cystic pituitary macroadenoma with hemorrhagic necrosis - pituitary apoplexy. Sagittal T2 (D), Sagittal T1 (E) and Axial contrast enhanced CT (F) images of the follow up imaging after 2 months of conservative management shows a partially empty sella with no enhancing mass. DIAGNOSIS- PITUITARY MACROADENOMA WITH APOPLEXY AND SPONTANEOUS RESOLUTION Page 16 of 31

17 Fig. 9: 32 year old female with vision loss. T2 Sagittal (A) Coronal (B)and T1 post contrast Sagittal (C) and Coronal (D) images show an intensely enhancing homogenous mass in suprasellar location with separately visualized pituitary gland (arrow). DIAGNOSIS PARASELLAR MENINGIOMA Page 17 of 31

18 Fig. 10: 15 year old male with headache and altered sensorium. Sagittal T2 (A), GRE (B), CT(C), T1 pre contrast (D) and T1 post contrast (E) images show a solid cystic mass in sellar and suprasellar location. The cystic portion is hyperintense on T2 and T1WI, with the small eccentric heterogenous solid component showing blooming on GRE, confirmed as calcification on CT (arrows). On post contrast images the solid component enhances intensely and the cystic component shows thin peripheral enhancement. Mass effect is seen over the brainstem, with dilated supratentorial ventricular system DIAGNOSIS CRANIOPHARYNGIOMA Page 18 of 31

19 Fig. 8: 46 year old female with headache. Axial T2 (A); FLAIR (B); T1 (C) and Sagittal T1 (D) images show a small cystic lesion appearing hyperintense to cortex on T2 and T1WI, showing incomplete suppression on FLAIR. DIAGNOSIS- RATHKE'S CLEFT CYST Page 19 of 31

20 Fig. 12: 7 year old female with headache and vision loss. T2 Axial (A,B), T2 Coronal (C) and T1 post contrast Coronal (D) images show large lobulated intensely enhancing lesion appearing heterogeneously hyperintense on T2WI in the suprasellar location involving hypothalamus and extending along the bilateral optic tracts. The sella is expanded with compressed pituitary gland visualized separately (arrow). DIAGNOSISHYPOTHALAMIC-CHIASMATIC GLIOMA Page 20 of 31

21 Fig. 13: 70 year old female with headache, vision loss, altered sensorium and fever. T2 Axial (A). Sagittal (B) and T1 post contrast Axial (C) and Coronal (D) images show and enlarged and heterogeneously enhancing pituitary gland with thickened pituitary stalk (arrow). DIAGNOSIS- GRANULOMATOUS HYPOPHYSITIS Page 21 of 31

22 Fig. 14: 46 year old female, known case of carcinoma breast, with headache and neuropathy. T2 Axial (A,B) and T1 post contrast Coronal (C) and Axial (D) images show an intensely enhancing left parasellar lesion completely encasing the cavernous ICA (arrow). DIAGNOSIS- METASTASIS Page 22 of 31

23 Fig. 11: 17 year old male with headache, altered sensorium and fever. Axial T2 (A); GRE (B); Coronal T2 (C) and Axial DW (D) images show a heterogeneously hypointense mass in right parasellar location, showing blooming on GRE, with diffusion restriction in right MCA territory. DIAGNOSIS- ANEURYSM Page 23 of 31

24 Fig. 15: 51 year old female with headache, altered sensorium and fever. Axial T2 (A); DW (B); and T1 post contrast Sagittal (C) and Axial (D) images show a heterogenous intrasellar peripherally enhancing lesion showing diffusion restriction. The pituitary gland is not separately visualized. DIAGNOSIS- PITUITARY ABSCESS Page 24 of 31

25 Fig. 16: 65 year male with altered sensorium and fever. Axial T2 (A), T1(B), FLAIR (C), DW (D), ADC (E) and Sagittal T2 (F) images show a right parasellar lesion, appearing hyperintense on T2, hypointense on T1, incomplete suppression on FLAIR, and diffusion restriction on DW/ADC. DIAGNOSIS- EPIDERMOID CYST Page 25 of 31

26 Fig. 17: 50 year old male with headache. Axial T2 (A), FLAIR (B), and Sagittal T2 (C) and T1 post contrast (D) images show a cystic sellar lesion following CSF signal intensity on T2, T1 and FLAIR with mild peripheral enhancement DIAGNOSIS- ARACHNOID CYST Page 26 of 31

27 Fig. 3: 22 year old female with amenenorrhea. Coronal T1 (A), Fat sat (B) images show infundibular stalk deviation to right (red arrows) and Dynamic post gad (C & D) images show true limits of the tumor (yellow arrows) as compared to the normally enhancing gland. DIAGNOSIS- PITUITARY MICROADENOMA Page 27 of 31

28 Fig. 2: 41 year old female with vision loss. Sagittal T2 (left) and Coronal T2 (right) images reveal a heterogenously hyperintense mass in sellar and suprasellar location, giving a "figure-of-8" appearance. DIAGNOSIS - PITUITARY MACROADENOMA Page 28 of 31

29 Conclusion Sellar region has a complex anatomy. It is a crucial crossroad of central and peripheral neural, meningeal, vascular, bone and soft tissue structures that predicts a wide diversity of primary or metastatic neoplasms arising from within any of these elements. As most of the lesions arising in relation to this region present with similar clinical picture, imaging remains the cornerstone of diagnosing these lesions. MRI is the investigation of choice for this purpose because of excellent anatomical tissue differentiation and the ability to perform multiplanar scanning, all without the use of any ionising radiations. The various MRI sequences performed for evaluation of sellar and parasellar region help in arriving to an intelligent diagnosis. The evaluation of the extent of the lesion is extremely helpful in deciding for a proper surgical approach. Page 29 of 31

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