Imaging of Craniopharyngioma Erin O’Connor

Childs Nerv Syst (2005) 21: 635–639 DOI 10.1007/s00381-005-1245-y SPECIAL ANNUAL ISSUE

John G. Curran Imaging of craniopharyngioma Erin O’Connor

Abstract Background: Craniopha- Keywords Cerebral angiography . Received: 30 May 2005 . Published online: 3 August 2005 ryngiomas are present with a wide Child Craniopharyngioma/ # Springer-Verlag 2005 range of appearances, but the diagnosis . Craniopharyngioma/ existence of cysts, calcification, surgery . Image processing, computer- . J. G. Curran (*) . E. O’Connor and enhancement in a suprasellar assisted Magnetic resonance Department of Medical Imaging, tumor strongly favors the diagnosis. imaging . Pituitary neoplasms/ Children’s Memorial Hospital, Discussion: There is a significant diagnosis . Tomography, X-ray 2300 Children’s Plaza, differential diagnosis that must computed Chicago, IL, 60614, USA e-mail: [email protected] be considered. The pre- and post- Tel.: +1-773-8803541 operative imaging of cranio- Fax: +1-773-8803517 pharyngioma is reviewed.

General imaging features of craniopharyngioma proximately 70% in adults. The typical appearance of an adamantinomatous type craniopharyngioma is a mixed cys- The characteristic imaging finding of craniopharyngioma tic and solid mass on CT, usually with a solid focus in the in a child is an enhancing suprasellar mass that is calcified sella, and cystic components arising above it. The papillary and cystic on CT. When two out of these three features are type of tumor is more often solid with less common inci- present, craniopharyngioma is still the most likely diagno- dence of calcification [2]. sis [1]. The tumor usually demonstrates T1 high intensity By MRI examination, the tumor is of variable T1 signal, on MR, reflecting the protein or cholesterol content of the often hyperintense. The T1 hyperintensity is usually sec- “motor oil-like” fluid found in the tumor cysts [2]. Rarely ondary to high protein content in the cyst fluid. However, on plain skull film, craniopharyngioma may be suspected other causes of T1 hyperintensity in craniopharyngiomas by the presence of sellar or suprasellar calcifications. have been described—fat, cholesterol, hemorrhage, or even Usually from the initial imaging, a craniopharyngioma mild calcification [4]. The mixed solid and cystic nature of can be located in the sella, and/or if partially or entirely the tumor is clearer on MR than on CT. Occasionally with suprasellar, can be described as pre- or retrochiasmatic. small cysts, even on postcontrast study, the heterogeneous Determination of size is important at presentation, as tu- nature of the tumor may not be apparent on CT. This mors greater than 5 cm in diameter have a recurrence rate of problem does not occur with MR [3]. Even small cysts are more than 80%, whereas in tumors less than 5 cm, the identifiable and the smaller solid portion of the tumor is recurrence rate is 20% [2]. Rate of growth is slow, so a usually heterogeneous or even isointense with brain (Fig. 1). rapid interval change in size in the absence of tissue On MR T2-weighted sequences, including Fluid Atte- diagnosis may require a reassessment of the etiology of the nuated Inversion Recovery (FLAIR), the solid portion is tumor. again usually heterogeneous, whereas the cysts are in- By CT examination, approximately 90% of childhood variably hyperintense (Fig. 2). The calcifications, in the craniopharyngiomas calcify. The percentage drops to ap- solid portion of the tumor or in the peripheral rim, are 636

Fig. 1 Eleven-year-old boy with several week history of vomiting, T2 image showing cysts mainly hyperintense, but of varying inten- weight loss, ataxia, and abnormal behavior. a Axial CT noncontrast sity. e Axial FLAIR image showing cysts more uniformly hyper- image demonstrating a sellar mass with an irregular calcified com- intense. f Sagittal postcontrast T1 image showing peripheral rim ponent. b Sagittal noncontrast T1 image demonstrating a large sellar enhancement of the cysts, and heterogeneous enhancement of the and suprasellar mass with cysts of varying intensity, mainly hyper- solid lower portion of the tumor. g Coronal postcontrast T1 image intense. c Coronal noncontrast T1 image demonstrating multiple showing mainly the peripheral rim enhancement of the cysts cysts of varying intensity. Hydrocephalus is also apparent. d Axial hypointense on T2. They stand out particularly on a sus- Recommended imaging technique ceptibility sequence such as Gradient Recalled Echo (GRE) [3]. MR is the imaging modality of choice [3]. An MR exam- Following contrast, there is almost invariable enhance- ination should include thin T1 sagittal and coronal sections ment of the solid portion and the peripheral rim of the both pre- and postcontrast through the sella and suprasellar cystic portion on both CT and MR (Fig. 3). Contrast is region. It is useful to include a precontrast fat saturation T1 essential for the diagnosis on CT. In one study, three of nine sequence as it will help to identify the posterior pituitary tumors were not identified on the noncontrast CT [3]. The “bright spot.” enhancement of the solid portion may be either uniform Additional sequences may be helpful in answering spe- or patchy and heterogeneous. Enhancement patterns in a cific questions: given tumor are similar on both CT and MR [3]. – FLAIR is useful in delineating cystic portions of tumor One CT and MR study of 26 patients sought to divide the (which will be hyperintense) vs loculated portions of appearance of craniopharyngioma into patterns, i.e., solid, the third ventricle or other CSF spaces (which will tend calcified, proteic-like, CSF-like, hematic-like, and fatty [5] to be isointense). (Table 1). – GRE is useful as a susceptibility sequence in dem- There were no correlations between patterns except that onstrating calcification more clearly, or possibly dem- in no case did the CSF-like and the proteic-like pattern onstrating blood products if there is a question of coexist. Calcified and proteic-like tumors tended to be large. hemorrhage. Hematic-like and CSF-like tumors tended to be small [5]. – Diffusion Weighted Imaging (DWI) (diffusion imag- The most useful radiological findings to describe cranio- ing) is useful in the differential diagnosis if an epi- pharyngiomas are lesion size, cyst characteristics, and ves- dermoid is suspected. sel encasement [5]. – MR spectroscopy demonstrating a significant lipid con- On angiography, the tumor is usually avascular with tent may be useful. displacement of the major vessels of the circle of Willis. 637

Fig. 2 Nine-year-old girl with acute visual loss in the left eye. tense, partly solid, partly cystic tumor with both sellar and Provisional diagnosis of optic neuritis. a Axial noncontrast CT suprasellar components. d Coronal T2 image showing a heteroge- image showing a sellar mass with faint peripheral calcification. neous hyperintense sellar and suprasellar mass. e Sagittal postcon- b Axial noncontrast CT image showing partially solid, partially cystic trast T1 image demonstrating fairly uniform enhancement of the tumor. c Sagittal noncontrast T1 image showing mainly hypoin- majority solid portion of the tumor

Imaging in the differential diagnosis of craniopharyngioma in bulk within the sella and has a tendency to expand the sella. Craniopharyngioma will on the other hand tend to The most commonly listed differential diagnoses are: show greater superior expansion, often with a small sellar component without expansion of the bony sella. A pituitary 1. Pituitary adenoma tumor with a cystic component and/or a degree of hemor- 2. Hypothalamic or optic pathway glioma rhage can be difficult to distinguish from a craniopha- 3. Rathke’s pouch cyst ryngioma. Factors supporting the diagnosis of pituitary 4. Epidermoid tumor adenoma in a giant intra- and suprasellar mass include Other considerations would include: infrasellar extension, absence of calcification, and presence of low-signal cysts on T1-weighted images [6]. 5. Thrombosed aneurysm Hypothalamic or optic pathway gliomas lack two com- 6. Simple arachnoid cyst mon features of craniopharyngiomas. They rarely have a 7. Masses of infectious or inflammatory origin sellar component (although when large may erode the 8. Pituicytoma sphenoid bone) and are rarely calcified. The tumors are 9. Colloid cyst of the third ventricle usually isointense on T1 and usually lack a cystic com- Pituitary adenoma is uncommon in children, whereas the ponent. If a cystic component or necrosis is present, it peak age group for craniopharyngioma is 5–15 years, but is usually dominated by the solid component of the tu- nonetheless, this tumor is occasionally seen. It is often mor, whereas the cystic component is usually dominant noncalcified, so a noncontrast CT is a helpful component of in craniopharyngioma. the diagnostic workup. Pituitary adenoma often is greater 638

Fig. 3 Two and a half-year-old boy with several month history of polyuria and polydipsia. Now with strange eye movements. a Sagittal noncontrast T1 image demonstrating cysts of mixed hyper- and hypointensity. b Axial noncontrast T1 image demonstrating mixed hyper- and hypointense cysts. c Coronal T2 image demonstrating cysts of varying intensity, mainly hyperintense. d Sagittal postcontrast T1 image demonstrating heterogeneous enhancement of the lower solid portion of the tumor, with peripheral rim enhancement in the cystic portion

Rathke’s cleft cysts may at times be difficult to dif- ther calcification nor solid portion. They are typically ferentiate from small craniopharyngiomas. However, larger bounded posterior by the membrane of Lilliquist. Rathke’s cleft cysts are easier to differentiate as they typ- Inflammatory masses may occur in the suprasellar ically do not contain a solid component, do not enhance, region. and are not calcified [7]. Usually, these are infective in nature such as granulo- Epidermoid tumors may rarely occur in the suprasellar matous infections, but occasionally, other inflammations region. The substance of an epidermoid tumor may be such as sarcoid or histiocytosis may manifest as suprasellar identified by restricted diffusion; hence, the use of dif- disease. Typically, these lesions are infiltrative, layering fusion weighted imaging is recommended if that possibility along the pituitary stalk and the adjacent undersurface of is under consideration. Peripheral rim enhancement is less the brain, but occasionally, frank granulomas may occur in common in epidermoids [8]. Thrombosed aneurysms are a the suprasellar region giving rise to diagnostic difficulty. consideration in an older age group. They typically have an Granulomas are not usually calcified, are somewhat hete- eccentric pattern of concentric circles within the mass. rogeneous in signal, and often show diffuse enhancement. Identification of a residual lumen assists in confirming the Lymphocytic hypophysitis, an adult condition, is an in- diagnosis. Simple suprasellar arachnoid cysts contain nei- flammation of the anterior pituitary gland and usually presents with an infiltrative appearance including thick- ened pituitary stalk rather than a mass. Pituicytoma, or Table 1 Semiological patterns of craniopharyngioma on MRI and granular cell tumor, a rare adult tumor of the neurohypo- CT physis and infundibulum, gives rise to a suprasellar mass Solid pole 100% without significant compression of adjacent structures. The mass is noncystic and noncalcified and is closely asso- Cystic component 92.3% ciated with the pituitary stalk. Calcification 65.3% Colloid cyst of the third ventricle may cause confusion Proteic like 53.8% with a high third ventricular craniopharyngioma. The tumor CSF like 23% is of high signal on all sequences. However, the presence Hematic like 19.2% of a heterogenous suprasellar solid component and the non- Fatty component 15.3% collapse of the posterior third ventricle, despite a lesion 639 in the anterior, make the diagnosis of craniopharyngioma such as the chiasm or pituitary stalk, in the suprasellar much more likely [8]. region, if these are intact. The second postoperative scan may show reduction of residual tumor volume when compared to the first postop- Postsurgical evaluation of craniopharyngioma erative scan. Although this may be attributed to interval radiation therapy [10], such a volume reduction may be The main focus of postsurgical evaluation is the determi- seen in patients who have received no interval therapy [9]. nation of the presence and extent of residual tumor. How- As residual tumor volume reduction over months has also ever, in addition, the potential complications of surgery been seen in pituitary adenoma, presumably related to must be borne in mind. These include hypothalamic injury edema resolution, it has been suggested that an accurate with associated endocrine abnormalities, injury to the pi- estimation of residual tumor volume in craniopharyngioma tuitary gland, and vascular injury including pseudoaneu- may be obtained only at 2–3 months postsurgery [9]. The rysm formation of adjacent structures. period of tumor shrinkage after radiation therapy is often MR is essential in the immediate aftermath of cranio- long and varied (mean 29 months) [10]. pharyngioma surgery. Exact timing is not established, but Increase in size of residual tumor between the first and imaging within the first postoperative week is the usual second postoperative scan has been identified in certain standard. The normal appearance is of interval reduction in patients as attributable to interval radiation therapy, with tumor size. It is also common to identify residual tumor further follow-up scans demonstrating a regression of the (best delineated on the postcontrast T1 images), even when tumor [9]. there has been no residual tumor identified at the end of surgery [9]. There is usually no change in signal intensity of the cystic or of the solid portion of the tumor between the Conclusion preoperative and postoperative scans. A fluid collection, isointense to CSF, and usually resolved by the second The imaging modality of choice for craniopharyngioma postoperative scan, is typically seen on all immediate post- is MR. However, CT is very useful in determining the operative scans [9]. presence of calcification. The tumors present a wide variety With intraaxial lesions, luxury perfusion and disruption of appearances, but the presence of cysts, calcification, and of the blood brain barrier may give rise to new or more enhancement in a suprasellar tumor strongly favors the extensive contrast enhancement postoperatively. However, diagnosis. There is a significant differential diagnosis that in the case of craniopharyngioma as an extraaxial lesion, no must be considered. Postoperative follow-up with MR is new areas of enhancement are to be expected postsurgery. essential, but potential pitfalls such as the relatively fre- The emergence of such findings would therefore be a quent presence of residual tumor even in a gross total matter of concern [9]. resection, interval short-term increase in treated tumor, and Finally, the postoperative scan should usually demon- the potentially long period of tumor shrinkage must be strate a resolution of hydrocephalus if present preopera- borne in mind. tively and better visualization of the normal structures,

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