Introduction
Background
Craniopharyngioma is a histologically benign, extra-axial, slow-growing tumor that predominantly involves the sella and suprasellar space. Despite its histologic appearance, craniopharyngiomas occasionally behave like malignant tumors. They can metastasize, and patients can have severe symptoms that usually require surgery and/or radiation therapy (with intracystic chemotherapy in some pediatric patients). Recurrences, both local and along surgical tracts, have been reported, as has meningeal seeding. Characteristic radiographic findings help in differentiating craniopharyngiomas from other tumors that can occur in the same anatomic region. Zenker first described craniopharyngioma in 1857.1,2,3,4,5
Digital radiograph in a 23-year-old woman (same patient as in Image 4 in Multimedia) demonstrates characteristic calcifications (arrow) in the suprasellar space. This appearance can easily be misinterpreted as that of an aneurysm.
Axial CT scan in a 39-year-old man (same patient as in Images 9-10 in Multimedia) obtained without contrast enhancement demonstrates a large, cystic mass (arrow) in the suprasellar space that has predominantly fluid attenuation.
Sagittal nonenhanced T1-weighted image demonstrates a heterogeneous, cystic mass (arrows) in the suprasellar space (same patient as in Image 14 in Multimedia).
Angiogram obtained at the same time as Image 12 (see Image 12 in Multimedia) in anteroposterior projection clearly shows elevations of the A1 segment of the anterior cerebral artery (arrows) and anterior communicating artery.
Pathophysiology
Craniopharyngiomas are dysodontogenic epithelial tumors derived from the Rathke cleft, which is the embryonal precursor to the adenohypophysis. The craniopharyngeal duct is the embryonal structure along which the eventual adenohypophysis and infundibulum migrate. Tumors can occur anywhere along the course of this duct from the pharynx to the sella turcica and third ventricle,1 which partially explains the location of the tumor (see Anatomy). The trigger for tumor growth is not clear. Three distinct subtypes have been distinguished on the basis of histologic appearance: adamantinomatous, papillary, and mixed.
Regarding adamantinomatous tumor (pediatric type), the classic and most common appearance is that of a cystic tumor, usually with a solid component. These tumors occur in a wide range of sizes. The cyst contains fluid that can vary in color, but it usually has a tan appearance similar to that of motor oil. The color is the result of suspended blood products, protein contents, and cholesterol crystals within the cyst fluid; the color may be the result of repeated hemorrhage within the cystic cavity. Histologically, the cyst has a multistratified squamous epithelium with nuclear palisade. The solid component demonstrates clumps of wet keratin, dystrophic calcifications, trabeculae, nests, and squamous or columnar epithelium.
Extensive fibrosis and inflammation (which is considerably more severe with recurrent tumors than with others) are also observed. These findings may result in dense adhesion to adjacent structures and vessels, which accounts for the difficulty in resecting craniopharyngiomas. Intimate interdigitation of the tumor tissue and encasement of the vasculature of the circle of Willis are often present. Gliosis can make the differentiation of these tumors from a primary glial tumor difficult. Tumoral interdigitation also accounts for the frequency of recurrence of tumor in cases in which the tumor appears to have been totally resected on intraoperative visual inspection and despite the fact that these tumors are histologically benign.
The classic appearance of the papillary variant (adult type) is different from that of the other forms and involves only a solid component, which is typically seen without calcifications. The papillary type is frequently located in the third ventricle. These tumors are usually more encapsulated than the others and are therefore more amenable to surgical resection. They demonstrate extensive squamous differentiation with the formation of pseudopapillae.6,7
Unless otherwise indicated, the more common adamantinomatous type is the subtype referred to in this article.
Frequency
United States
Craniopharyngioma represents approximately 3-5% of intracranial tumors and 6-10% of pediatric brain tumors. In pediatric patients, craniopharyngiomas represent the most common intracranial tumor of nonglial origin; they account for approximately 54% of all sellar and prechiasmatic tumors.4,8,9
International
The international frequency is identical to that reported in the United States.
Mortality/Morbidity
In children, the 5-year survival rate is more than 80% after treatment with surgery and radiation. The overall 10-year survival rate is 64-96%.8,9
- Many patients have permanent endocrinologic deficits after treatment, though visual disturbances are usually reversible.
- Craniopharyngiomas are slow-growing tumors in which morbidity results from the compression of nearby structures.
- In both children and adults, early intervention significantly reduces the recurrence rate.4 In adults, surgical morbidity is low (£ 12% with microsurgical techniques); the mortality rate has been reported to be 0-3%. The size of the tumor at presentation determines the recurrence rate, which is approximately 83% for tumors larger than 5 cm and 20% for tumors smaller than 5 cm. Rare cases of tumor recurrence along the surgical tract have been reported.10
Race
No racial predominance is recognized.
Sex
The male-to-female ratio is equal.
Age
A bimodal age distribution is seen, with the first peak occurring in childhood and early adolescence, predominately at age 5-10 years. The second peak (for papillary types) occurs at age 40-60 years. A nearly even distribution in incidences is observed between both age groups.4
Anatomy
With regard to surgery, craniopharyngiomas are classified into 3 groups: sellar, prechiasmatic, and retrochiasmatic.
The tumors occur in suprasellar (75%), suprasellar and infrasellar (21%), or entirely intrasellar (4%) locations. Adamantinomatous-type tumors commonly occur entirely within the sella, the third ventricle, and the sphenoid sinus; they rarely occur within the nasal cavity. Craniopharyngiomas are usually avascular on angiography and may encase or displace vessels forming the circle of Willis. The internal carotid artery (ICA) is displaced laterally, the anterior cerebral artery (ACA) is displaced anteriorly, and the basilar artery is displaced posteriorly.
Three specific growth categories have been determined on the basis of the relationship of the tumor to the vascular structures and the optic chiasm: type A, type B, and type C.
In type A, the anterior communicating artery and the A1 segment of the anterior cerebral artery are not disturbed. Tumors of this type have little or no suprasellar bulge (ie, they are contained almost entirely within the sella). In type B tumors, the anterior communicating artery and the A1 segment of the anterior cerebral artery are elevated, but no posterior displacement of the basilar artery is observed. The tumor protrudes anteriorly between the optic nerves and pushes the optic chiasm posteriorly. In type C, the anterior communicating artery and the A1 segment of the anterior cerebral artery are elevated, with posterior displacement of the basilar artery and stretching of the posterior communicating arteries. The tumor protrudes posteriorly, pushing the chiasm forward and causing it to abut the tuberculum sellae. These tumors typically obstruct the third ventricle and cause hydrocephalus.
Presentation
The range of clinical presentations of patients with craniopharyngioma is broad; patients may be asymptomatic, or they may have endocrine, visual, or psychological disorders. Many patients remain asymptomatic; in others, however, the disease follows a progressively deteriorating clinical course. Because of the associated and frequent endocrine dysfunction, a complete endocrine pretreatment workup is frequently performed.
The most common presenting symptoms are headache, nausea, vomiting, and visual disturbances. The most common visual disturbances are bitemporal hemianopsia, homonomous hemianopsia, and amblyopia. Other common findings include oculomotor palsies, bizarre scotomas, blindness, asymmetric acuity deficiencies, and optic atrophy. Hydrocephalus may result from a tumor that obstructs the third ventricle. Papilledema frequently occurs. Visual disturbances usually improve after treatment, whereas most endocrine dysfunctions do not.
Growth failure and headaches are part of the most common presentation of pediatric patients with craniopharyngioma; for children, the median age at presentation is 5 years.
Other presenting symptoms are those of pituitary and adrenal hypofunction, diabetes insipidus, obesity, weakness, ataxia, coma, chemical meningitis (from rupture of cyst contents into subarachnoid space), and seizures. In particular, children can present with growth failure, obesity (one third to one half), and hypothyroidism (two thirds). Precocious puberty has been reported, as has diabetes insipidus (which affects up to one fifth of patients). Poor school performance is also common, as are psychological problems. In patients with tumors larger than 5 cm, postoperative recurrence and morbidity rates are higher than in patients with smaller tumors.11
Preferred Examination
CT and MRI are the complementary examinations of choice. Today, the best imaging tool is MRI, both with and without contrast enhancement.
CT can clearly demonstrate the characteristic calcifications and size of the tumor, whereas MRI exquisitely demonstrates the size and extent of the tumor and involvement of the third ventricle. MRI results can confirm cystic features of the tumor. Sequences such as fluid-attenuated inversion recovery (FLAIR), gradient-echo (GRE) imaging, and diffusion-weighted imaging, as well as MR spectroscopy, can be used to make a confident and correct diagnosis.
Plain radiography may show abnormalities; however, CT or MRI is still needed regardless of the plain radiographic findings. CT and MRI have supplanted angiography as the primary diagnostic modality; today, magnetic resonance angiography (MRA) or CT angiography (CTA) may be helpful in differentiating the tumor from an aneurysm of the anterior communicating artery.
In the later postoperative period, CT can be performed to establish the baseline for future follow-up scans and to determine the number and size of residual flecks of calcification. In the immediate postoperative period (first 48 h) and later, gadolinium-enhanced MRI may be performed to establish a baseline appearance and to determine whether residual tumor is present.8,12,13,14,15,16,17,18,19,20
Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.
NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.
Limitations of Techniques
Nonenhanced CT may be required to detect calcifications if typical MRI findings are absent. A papillary-type lesion can be missed on MRI or CT when no characteristic cystic component is present or when lesions are not enhanced after the administration of intravenous (IV) contrast material (as occurs in approximately 10% of patients).
MRI cannot be used in patients with pacemakers or implanted ferromagnetic metallic objects or in those with metallic foreign bodies in the brain, spinal cord, or soft tissues near important vascular structures. The use of MRI also is limited in patients with claustrophobia and in those who are unable to remain stationary for the required time. Both CT and MRI evaluations require IV contrast enhancement; therefore, IV access is needed.
Differential Diagnoses
Arachnoid Cyst
Astrocytoma, Brain
Epidermoid, Brain
Meningioma, Brain
Pituitary Adenoma
Rathke Cleft Cyst
Other Problems to Be Considered
Aneurysm
Germinoma
Teratoma
Dermoid/epidermoid
Ecchordosis
Choristoma
Eosinophilic granuloma
Inflammatory lesion
Sarcoidosis
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References
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Further Reading
Keywords
Rathke pouch tumor, craniopharyngeal duct tumor, hemangioblastoma, ameloblastoma, adamantinoma, dysodontogenic epithelial tumor, adamantinomatous tumor, papillary tumor, sellar craniopharyngioma, prechiasmatic craniopharyngioma, retrochiasmatic craniopharyngioma
