Findings: There is a 3.8 x 2.8 x 3.5 cm. lesion identified in the craniocaudal, transverse, and AP dimension respectfully within the suprasellar region in an extraaxial location. This causes splaying of the cerebral peduncles. This lesion demonstrates increased signal on the T1 weighted images, Turbo SPIN T2 images, and STIR images. This is compatible with proteinaceous fluid. There is enlargement of the lateral ventricles compatible with hydrocephalus. The third ventricle is seen to be compressed. The fourth ventricle is of normal contour. Given the patient's age and location and signal intensity, this finding is most compatible with a suprasellar craniopharyngioma, this correlated with pathology from a biopsy specimen.
Diagnosis: Craniopharyngioma.
Discussion: Craniopharyngiomas arise from squamous epithelial rest along Rathke's cleft. This are typically well delineated cystic masses. The contents of the cyst can vary from fluid material to a proteinaceous material. This explains the variable signal that is seen on MRI.
Craniopharyngiomas account for 2 to 5% of all intracranial masses. These lesions occur most frequently in patients under the age of 20 with 40% of these tumors occurring in children between the ages of eight and 12 years of age. Craniopharyngiomas account for half of all suprasellar masses in this age group. There is no gender bias.
Craniopharyngioma are mainly confined to the sellar region. More than 75% of these tumors are completely suprasellar or have a large suprasellar mass with smaller intrasellar component. 20% of these lesions are found as a primary intrasellar process.
Headache is the most common symptom, although endocrine deficiency, visual disturbance, and interruption of CSF flow are often seen.
As mentioned previously, the MR findings are variable due to the variable nature of the contents of these cysts. Plain films may demonstrate eggshell calcification or heterogenous calcification in the suprasellar region. CT scan may demonstrate an isodense to cystic lesion in the suprasellar region with rim calcifications. Rim calcification is seen quite commonly (80 to 90%) when these lesions appear in childhood, as seen on the postoperative head CT. These lesions may show rim enhancement, or if the lesion is partially cystic, the sellar portion will demonstrate enhancement.
References:
Woodruff WW. Fundamentals of Neuroimaging. W.B. Saunders,
Co., Philadelphia; 1993:352-356.
Osborn AG. Diagnostic Neuroradiology. Mosby, St. Louis; 1994(15)654-657.
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