Neuroradiology Case of the Week

Case 16

Ramon de Guzman, MD, P-L Westesson, MD, PhD, DDS,
Larry Buadu, MD, PhD and Manoj Ketkar, MD

Clinical Presentation: The patient is a 7-year-old female with history of long-standing headaches attributed to migraine. Approximately 3 days prior to admission, the patient began having nausea, vomiting and headaches. Initial consultation revealed papilledema.

Radiographic Findings: The MR of the head shows a multi-lobulated suprasellar mass that extends upwards into the third ventricle, posteriorly into the pre-pontine cistern (Fig. 1) and into the cerebellopontine angle cisterns, mostly towards the left side (Fig. 2). The lesion extends laterally into the left parasellar area, displacing the left uncus laterally (Fig. 2). There is also posterior extension into the interpeduncular cistern. It is encasing the distal portion of the basilar trunk. The lesion is hyperintense in T1 weighted images and of intermediate signal intensity in T2 weighted images. There is heterogeneous enhancement of the lesion following injection of gadolinium. CT of the head shows a partially calcified hyperdense extra-axial lobulated mass filling the suprasellar cistern extending into the adjacent basilar cisterns (Fig. 3).

Figure 1: Large lobulated sellar/suprasellar mass extending upwards to the third ventricle and posteriorly into the pre-pontine cistern (arrow).
Figure 2: Extension into the cerebellopontine angles more to the left (arrows) with left parasellar extension (arrowhead) and encasement of the basilar artery (small arrow).	Figure 3: Eccentrically located calcification within a hyperdense lobulated mass at the suprasellar region (arrow).

Diagnosis: Craniopharyngioma

Discussion:
Clinical Discussion
   Craniopharyngiomas are benign neoplasms typically found in the suprasellar cistern, accounting for 3% of all intracranial neoplasms, and 6% to 9% of pediatric intracranial tumors [1]. Although these lesions may be found at any age, nearly half are in patients between 5 and 10 years old, with a smaller peak in the fifth and sixth decades of life [2]. Clinically, most children and adults with craniopharyngiomas present with visual symptoms as their chief complaint, including diplopia, visual field deficits and decreased visual acuity [3,4]. The most commonly found hormonal deficiencies are growth hormone in up to 75% of patients, luteinizing hormone-follicle stimulating hormone in approximately 40%, and corticotropin and thyroid-stimulating hormone in as many as 25% of patients [5].
   Craniopharyngiomas are believed to be derived from cell rests of the outpouching of the primitive oral stomodeum, called the pouch of Rathke. Approximately 90% are suprasellar [2], but may extend directly into the anterior, middle, or posterior cranial fossa [2,6,7]. As these cell rests may lie anywhere along the path of the craniopharyngeal duct, these tumors may arise anywhere from the posterior pharynx to within the third ventricle [7-14].
   These histologically benign tumors are composed of squamous epithelium with a loosely palisading basal layer that often undergoes keratinization and calcification [1]. This combination of squamous epithelium with loose fibrous stroma resembles the enamel origin of a tooth and is referred to as an adamantinomatous pattern [1,2}. This pattern is more often seen in those craniopharyngiomas with large cystic areas and is the type seen in nearly all children and half the adult patients [3]. Grossly visible cysts are present in 70% of cases. Contents of the cyst vary in appearance, from clear to yellow to cloudy-milky and to red-brown in those with hemorrhagic components [15]. This reflects the cellular breakdown products that constitute the cyst contents, including cholesterol, protein, and blood [1,2].
   Calcification is said to be the hallmark of a craniopharyngioma and occurs overall in more than 70% of tumors and in nearly all of the pediatric tumors [16]. These calcifications are commonly found in the adamantinomatous type, and uncommonly in the papillary type [3,17].
   Although these tumors are benign, they are often difficult to remove because they become densely adherent to adjacent neural and vascular structures [18,19]. Leakage of the cyst contents, either spontaneously or during resection, has been known to cause arachnoiditis and chemical meningitis.

Differential diagnosis includes Rathke cleft cyst, necrotic pituitary adenoma, thrombosed aneurysm, and cystic hypothalamic opticochiasmatic glioma.

Neuro Imaging Discussion
   Modern imaging of craniopharyngiomas relies on CT and MR studies for tumor identification and characterization. Plain radiographs may reveal suprasellar calcifications which are variable in appearance from thin “egg shell” plaques to dense solid “popcorn” calcifications [20,21]. Calcifications are rarely off the midline to any significant degree and almost always, at least in part, in a suprasellar location [22,23]
   The superior ability of CT to identify even minute calcifications aids greatly in the differentiation of craniopharyngioma from other suprasellar masses that uncommonly calcify. Vast majority of cysts are low-density areas no matter what constitutes the cyst contents [16, 24-26]. The solid portion is seen as an enhancing mass lesion or simply as peripheral ring enhancement surrounding a primarily cystic mass [16, 24-27].
   MRI has superior ability to identify the soft tissue mass [24,28] as well as greater sensitivity in identifying the intratumoral cystic areas. It is well suited for the preoperative evaluation of craniopharyngiomas, because of its multiplanar imaging ability and its superior delineation of surrounding vascular and neural structures. It is inferior to CT in identifying calcifications [27] and so MRI is thought to be more useful for surgical planning [26,29] and post-operative follow-up [29]. Appearance of the cysts in MRI is highly variable.

References:

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