The mnemonic SATCHMO (Fig.1) is used to help memorize the most important sellar and parasellar region lesions. 

Fig. 1: Mnemonic SATCHMO for remembering the differentials for sellar and parasellar region lesions.

Fig. 2: Sarcoidosis, sellar tumor.

SARCOIDOSIS

It is a multisystem chronic granulomatous condition of unknown origin characterized by the presence of noncaseating granuloma.

Imaging features

The most common patterns are parenchymal lesions, dural thickening or mass, leptomeningeal enhancement, cranial nerve enhancement, and mass lesions.

SELLAR TUMOR

Pituitary adenoma is the most common tumor of the sellar region and comprises up to 80% of all tumors in this location. Adenomas are World Health Organization grade I tumors.

Tumors larger than 10 mm are classified as macroadenomas, whereas lesions smaller than 10 mm are considered microadenomas.

They are also classified as either functioning (secreting hormones) or nonfunctioning tumors. 

Imaging features

Macroadenomas

Usually extend beyond the boundaries of the sella turcica (Fig. 3), thus infiltration of the cavernous sinus, the sphenoid sinus or the clivus, compression of the optic chiasm and encasement of the internal carotid artery (Fig. 4) can be present.

In about 94% of macroadenomas enlargement of the bony pituitary fossa occur.

Intratumoral hemorrhage occurs in up to 10–15% (Fig.5). 

Fig. 3: Sella turcica coronal reconstruction CT image (A) and brain MR images (B) post contrast coronal T1-WI and (C) sagittal post contrast T1-WI demonstrate an intra and suprasellar lobulated mass with strong enhancement representing a macroadenoma.

Fig. 4: Brain MR (A) Coronal T2-WI and (B) sagittal post contrast T1-WI show an intra and suprasellar mass with intense enhancement. Another case of pituitary macroadenoma.

Fig. 5: Macroadenoma. Brain sagittal MR images (A) T1-WI and (B) T2-WI show an intrasellar mass with suprasellar extension and heterogenous signal. Note area of hyperintense signal both on T1 and T2 representing hemorrhage.

Microadenomas 

They usually appear hypo- or isointense relative to normal pituitary tissue on T1-WI.
After contrast administration, due to an earlier and more intense enhancement of normal pituitary tissue, they usually remain hypointense (Fig.6). 

Secondary signs include a convex superior border of the gland and displacement of the infundibular stalk away from the side of the tumor.

Fig. 6: Sella turcica MR images. Post contrast sagittal T1-WI (A) and post contrast coronal T1-WI (B) demonstrate a small non enhancing lesion on the left side of the pituitary gland. Microadenoma.

Fig. 7: Aneurysm

ANEURYSM

Aneurysm in the sellar or suprasellar region may mimic a mass (Fig. 8). It may arise from the cavernous or from the supraclinoid internal carotid artery. 

Imaging features

Peripheral rim calcification may be present.

On MRI, they show a signal flow void with phase-encoding artifact present. Partially thrombosed aneurysms may show alteration of signal intensity on T1-WI and T2-WI because of the presence of clot.

Fig. 8: Sella turcica MRI. Coronal post contrast T1-WI shows a sellar/parasellar mass with suprasellar extension. Giant aneurysm of the distal portion of the left internal carotid artery.
References: Borges et al. Arq Bras Endocrinol Metab 2006; 50(3):558-563.

Fig. 9: Teratoma, tuberculosis

TERATOMA

Teratomas are the second most common type of germ cell tumor. They occur in children, with a greater frequency in boys. 

The most common site intracranially is the pineal region followed by the suprasellar region.

Imaging features

The majority demonstrate fat and calcification as well as cystic and solid components.

On MRI, they show heterogeneous signal intensity on T1-WI, T2-WI and post-contrast sequences, with suppression of signal on fat-saturated imaging. 

TUBERCULOSIS

Although pulmonary tuberculosis is the most common form of this disease, neurotuberculosis is more severe and presents higher morbidity and mortality. 

Imaging features

MRI findings include basal leptomeningeal enhancement secondary to multiple granulomas and pial tuberculomas. The granulomas are  hypointense on T1-WI and hyperintense on T2-WI. 

Tuberculomas demonstrate homogenous or ringlike enhancement  (Fig.10). 

Fig. 10: Brain MR images in a patient with tuberculosis. Post contrast coronal (A) and sagittal (B) T1-weighted images demonstrate a left parasellar enhancing nodule (arrows). Also note small ring-enhancing lesions in the cortical/subcortical region.

Fig. 11: Craniopharyngioma, cleft cyst (Rathke), chordoma

CRANIOPHARYNGIOMAS

Craniopharyngiomas are nonglial tumors that arise from the stratified squamous epithelium of the Rathke pouch remnant and are the most common nonglial tumors of childhood.

They are present in all ages, although, the first peak incidence is between 10 to 14 years of age and the second peak incidence is during the fourth and sixth decades. They are more commom in males. 

Adamantinomatous and papillary are histological subtypes.  In the first peak, these tumors are usually of the adamantinomatous subtype and 75% are purely suprasellar.

Clinical findings include headache, signs of intracranial hypertension, visual changes, hormonal disorders and behavioral change. 

Imaging features

CT is superior in the detection of calcifications.

On MRI they are heterogeneous with solid and cystic elements. Cysts frequently contain high protein, cholesterol, or blood products, which are hyperintense on T1-WI. 

The solid component show intermediate signal intensity on T1-WI,  isointense to hyperintense signal on T2-WI and heterogeneous enhacement (Fig. 12). 

Calcific areas appear hypointense on GRE and SWI images.

Fig. 12: Brain MR post contrast images (A) axial and (B) sagittal show an heterogenous enhancing suprasellar mass. Craniopharyngioma.

CHORDOMA

Most chordomas are histologically low-grade but locally aggressive tumors derived from embryonic remnants of the notochord. One third occur in the skull base.

The peak incidence is between 50 and 60 years of age.

These tumors most frequently occur in the midline (Fig.13) at the spheno-occipital synchondrosis. 

Imaging features

On MRI, they are well circumscribed and markedly bright on T2-WI. 

Interlobular septa appear hypointense on T2-WI with variable degrees of contrast enhancement.

Fig. 13: Brain MRI. Sagittal post contrast T1-WI demonstrates a sellar/suprasellar mass with heterogenous enhancement and destruction of the clivus. Chordoma.
References: Souza et al. Arq Bras Neurocir. 2011;30(4): 190-3.

RATHKE CLEFT CYSTS

Rathke cleft cysts are benign cystic lesions derived from Rathke pouch remnants. They are typically located partially intrasellar with a suprasellar extension. 

Imaging features

On CT, they are typically hypoattenuating.

On MRI, the signal may be variable because of the presence of protein. They may be hypointense on T1-WI and hyperintense on T2-WI (Fig. 14) or hyperintense on T1-WI and show variable signal intensity on T2-WI. They usually do not enhance. 

Fig. 14: Sella turcica MR images. Coronal (A) and sagittal (B) T1 weighted images show a small non enhancing lesion on the left (arrows). Rathke cleft cyst.

Fig. 15: Hypothalamic glioma, hamartoma, histiocytosis

HAMARTOMA

Hamartomas originate from the tuber cinereum of the hypothalamus.  These lesions are diagnosed in the first or second decades of life.

Patients typically present with precocious puberty and gelastic seizures. 

Imaging features

On CT they are usually iso to slightly hypodense.

On MRI, they are isointense to gray matter on T1-WI and T2-WI and  typically do not enhance. 

HISTIOCYTOSIS

Langerhans cell histiocytosis is a multisystem disorder involving the skin, bones, orbits, lungs, and CNS. Involvement of the hypothalamus leads to clinical presentation with diabetes insipidus.

Imaging features

On sagittal MRI, thickening of the pituitary stalk and absence of a normal, bright posterior pituitary signal are seen. 

Fig. 16: Meningioma, metastasis

MENINGIOMA

Meningiomas constitute the most common primary CNS neoplasms. 

They occur in the suprasellar and parasellar regions in 5% to 10% of cases. 

Suprasellar meningiomas may arise from the tuberculum sella and clinoid process, or extend from planum sphenoidale, olfactory grove, or medially from the sphenoid wing.

They are more common in middle age with a female preponderance. 

Imaging features

Meningiomas are well-defined, extra-axial masses and sometimes show a characteristic peripheral CSF cleft (Fig. 17).

They are isointense with brain parenchyma on T1 and T2-WI. Forty percent are hyperintense on T2-WI. 

Enhancement is usually marked, homogeneous, and fast (Fig. 18).  There may be a linear, enhancing dural tail. 

They often may cause hyperostosis at the sites of bony attachment

Fig. 17: Brain MRI. Sagital T1-WI (A) and axial FLAIR image (B) shows an extra-axial suprasellar mass. representing a meningioma. Note CSF cleft in the sagittal image.

Fig. 18: Brain MRI. Coronal (A) and sagittal (B) post contrast T1 weighted images demonstrate a suprasellar mass with strong enhancement. Meningioma.

METASTASES

Pituitary metastases (Fig. 19) most commonly arise from breast, thyroid or bronchial carcinoma. Breast and lung cancer account for approximately two-thirds of all suprasellar metastasis.

Imaging features

Typical MRI findings include a relatively small enhancing pituitary lesion. 

Bony destruction may occur.

Fig. 19: Head MRI. Coronal post contrast T1-WI shows a sellar/suprasellar mass with enhancement (arrow). Metastatic lesion from colon adenocarcinoma.
References: Souza et al. Arq Bras Neurocir. 2011;30(4): 190-3.

Fig. 20: Optic glioma

OPTIC GLIOMA

Optic gliomas may occur anywhere along the optic pathway. Most are WHO grade I-II astrocytomas, often the pilocytic type.

Approximately half of patients with optic pathway gliomas have neurofibromatosis type 1. 

Imaging features

On MRI, there is fusiform and/or nodular enlargement of the optic chiasm and/or optic nerves with thickening of the third ventricular floor and hypothalamus.

They usually have low-intermediate signal on T1-WI, intermediate-high signal on T2-WI and variable contrast enhancement. 

Fig. 21: Take home message.