Laboratory Studies
The following laboratory measurements are indicated in patients with craniopharyngiomas:
Serum electrolytes levels establish readiness for surgery. Importantly, the endocrine dysfunction frequently associated can cause abnormalities in several of these test findings.
Intracranial germ cell tumors can also primarily occur in the suprasellar region. Therefore, serum beta-HCG and alpha-fetoprotein (AFP) measurements should be considered to help narrow the differential diagnosis prior to definitive biopsy.
Growth hormone levels, including thyroid-stimulating hormone/thyroid hormone levels, steroid hormone levels (cortisol), follicle-stimulating hormone/luteinizing hormone levels should be obtained preoperatively as a baseline. Obtain tests to allow for perioperative hormone replacement as necessary.
Imaging Studies
Skull Radiography
Approximately 85% of craniopharyngiomas have calcifications above or within the pituitary fossa on plain radiographs of the skull.
Enlargement of the sella turcica can also be reliably identified.
If hydrocephalus is associated with a tumor in a young patient, split sutures may be observed.
Head CT
This may be the only preoperative radiographic study needed because craniopharyngiomas are observed with mixed solid and cystic components, and the solid component is enhanced following the administration of intravenous contrast.
CT scanning is better than MRI at revealing the common tumor-associated calcifications.
Peritumoral edema is rare.
Hydrocephalus is identified and readily characterized.
Non-contrast Head CT with peripheral calcifications around a bi-lobed craniopharyngioma.
Brain MRI
MRI is better than CT scan at determining the relationship of the tumor to adjacent normal structures.
As with CT scanning, mixed solid and cystic components are identifiable, and multiple cysts are common.
Craniopharyngiomas are usually sharply demarcated and smoothly marginated (see the image below).
This MRI sequence was obtained following the intravenous administration of gadolinium contrast. Observe the relatively homogeneous and cystic mass arising from the sella turcica and extending superiorly and posteriorly with compression of normal regional structures. Note that the lesion is sharply demarcated and smoothly contoured. This fluid-filled mass is consistent with a typical craniopharyngioma.
The solid component of the lesion frequently enhances following intravenous contrast administration, and a smooth ring of enhancement of the cyst wall can also be present (see the image below).
This axial CT scan image demonstrates a cystic lesion in the typical location of a craniopharyngioma. Although most of the lesion is fluid filled, a rim of enhancing soft tissue is observed following the administration of intravenous contrast.
Distortion or obliteration of the third ventricle is common.
Frequent involvement of the optic chiasm is found.
Obtaining postoperative imaging within 48 hours after surgery to best distinguish residual tumor from postsurgical changes is important.
Other Tests
Preoperative intellectual or psychological assessment may be useful as a baseline examination prior to undertaking curative therapies.
Procedures
Angiography: Cerebral angiography can be useful in planning the surgical approach, although it has been largely replaced by MRI/magnetic resonance angiography (MRA) in most centers. A vascular blush can be observed, although the tumor is not visible.
Histologic Findings
Craniopharyngiomas can be histologically classified into 3 types: adamantinomatous, papillary, and mixed. The adamantinomatous type is by far the most common in children (92-96%). Grossly, these tumors usually have both solid and cystic components. The fluid within the cysts has been historically described as "crankcase oil" because of its frequently dark and oily intraoperative appearance. Upon microscopic examination, the fluid contains abundant lipids with birefringent cholesterol crystals. Clinically, spillage of the cyst fluid into the subarachnoid space can cause severe chemical arachnoiditis.
Microscopic examination of the solid components reveals an epithelial tumor with angulated columnar cells resting on a collagen basement membrane. Papillary structures are common, and calcification is nearly universal. Large tumors may induce an intense glial reaction and intensely adhere to the underlying normal brain.
Staging
Preoperative and postoperative MRIs of the brain are adequate staging modalities for most children with craniopharyngioma. The postoperative scan is important in assessing residual disease. Neuraxis dissemination does not occur; thus, full spinal evaluation is unnecessary in an asymptomatic patient.
A large study out of China looked at 226 pediatric and adult cases of craniopharyngioma and subdivided them into 3 anatomical growth patterns: infradiaphragmatic (Id-CP) (referring to the diaphragm sellae), suprasellar subarachnoid extraventricular (Sa-CP), and suprasellar subpial ventricular (Sp-CP). The authors went on to demonstrate that the Id-CP tumors were much more common in children and tended to have more invasive growth patterns than the other 2 sub-types. In addition, the surgical approached differed for the different anatomic sub-types as well, suggesting that pre-operative MRI categorization of these tumors may help in surgical planning. [15]
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This MRI sequence was obtained following the intravenous administration of gadolinium contrast. Observe the relatively homogeneous and cystic mass arising from the sella turcica and extending superiorly and posteriorly with compression of normal regional structures. Note that the lesion is sharply demarcated and smoothly contoured. This fluid-filled mass is consistent with a typical craniopharyngioma.
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This axial CT scan image demonstrates a cystic lesion in the typical location of a craniopharyngioma. Although most of the lesion is fluid filled, a rim of enhancing soft tissue is observed following the administration of intravenous contrast.
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Non-contrast Head CT with peripheral calcifications around a bi-lobed craniopharyngioma.
