5.18 Craniopharyngioma
It is a benign tumor that originates from epithelial cells trapped in fetal life along the pituitary stalk. It is an embryonic residual of the primitive pharyngeal pocket.
It constitutes 2-3% of intracranial tumors, 5-13% of pediatric intracranial tumors. 60% of craniopharyngiomas occur in adult age. These tumors grow in the sellar region and in the third ventricle. Although benign, they have strong adhesions to the surrounding nervous structures: chiasm, stalk, hypothalamus. They are frequently cystic and may be very large. Pituitary function is generally impaired; optic nerves and chiasm are severely compressed. In children, they may cause growth impairment. If very large, they may cause hydrocephalus and intracranial hypertension.
The diagnostic tools are, as usual, CT scan and MRI.
craniopharyngioma
Fig.5.42a: Typical craniopharyngioma at frontal and lateral MRI scan. The yellow arrows point to the cyst, the red to the solid part of the tumor and the blue to a dilated lateral ventricle (hydrocephalus).
Craniopharyngioma therapy is microneurosurgery. The operation is technically demanding as the tumor may have firm adhesions, mainly to the hypothalamus. The operation is done under the operating microscope. Modern operative technologies should always be used. The approaches may be different, depending on the direction of growth of the craniopharyngioma. Intrasellar tumors may be removed from below, like in the case of a pituitary adenoma.

Fig.5.42b: Same case as in Fig. 5.46 after complete removal with a mininvasive supraorbital approach. The green arrow points to the optic chiasm.
In patients with large cystic craniopharyngiomas and major visual deficit, a symptomatic alternative may be the endoscopic approach. The endoscope is inserted through a frontal hole, then into the lateral and third ventricle, the cyst is perforated, its wall partly removed and a biopsy is taken. This technique (suitable for older patients or while waiting to restore good hormonal function) provides a direct approach to the tumor. Patients with chronic panhypopituitarism are very fragile.


Fig.5.43a: MRI in lateral view. Large cystic craniopharyngioma in an adult with severe hormonal deficiency, drowsiness and visual deficit. The yellow arrow points to the small solid part, the red to the large cyst.

Fig.5.43b: From left to right: endoscopic images showing the cyst in the third ventricle and the perforated cyst. Bottom right: post-operative CT scan. The right arrow points to a microcatheter left in the cyst.
A lesion that is similar to craniopharyngioma is Rhatke's cleft cyst. This is constituted by a single epithelial layer and it presents with visual and hormonal deficits. Therapy with decompression via the transnasal-transphenoidal approach is generally effective.
MRI of a Rhatke's cleft cyst
Fig.5.44: On the left, pre-operative lateral MRI of a Rhatke's cleft cyst. The red arrow points to the cyst, the yellow to the compressed and displaced pituitary stalk. On the right, post-operative view where stalk and pituitary gland have regained their normal position.