Surgery for Craniopharyngiomas 

The first description of a craniopharyngioma is credited to Zenker, who made this observation in 1857. Following this, Mott and Barrett, in 1899, documented the occurrence of these tumors and postulated that they arose from the hypophyseal duct or Rathke pouch. This was subsequently partially confirmed in 1904, when Erdheim described the tumors histologically and suggested that they arose from remnants of the Rathke duct. Finally, in 1932, Cushing introduced the term “craniopharyngioma,” which has been widely used thereafter.

Craniopharyngiomas are benign, extra-axial, slow-growing tumors that arise from the anterior margin of the sella turcica and predominantly involve the sella and suprasellar space.^{[1, 2, 3, 4]} They do not undergo malignant degeneration, but can metastasize, and the difficulty in curing them can lead to serious morbidity or death. As craniopharyngiomas grow, they can cause significant neurological complications, including visual loss, pituitary insufficiency, and hypothalamic damage. Further, recurrence, both along local and surgical planes as well as meningeal involvement, has been reported.

Frequency

The incidence of newly diagnosed craniopharyngiomas is 0.13-2 persons per 100,000 population per year. Distribution by age is bimodal, with the peak incidence in children at 5–14 years of age and in adults at 65–74 years of age. Craniopharyngiomas account for 2.5-4% of all brain tumors, and half of these tumors occur in childhood. Further, in children, approximately half of all suprasellar tumors are craniopharyngiomas (compared with only approximately 20% in adults), making them the most common nonglial brain tumor in pediatric patients. No sex predilection exists. No genetic relationship is currently known; however, a few familial cases have been reported in the literature.^{[5, 6]}

Although the histologic description of craniopharyngiomas was first described over a century ago, considerable debate still exists. Currently, 3 theories are widely accepted, and from these, 3 histologic variants have been derived. They are as follows:

• The embryogenetic theory suggests that the adamantinomatous type (“adamantinoma") arises from epithelial remnants of the Rathke pouch or the craniopharyngeal duct– (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, which partially explains the location of the tumor.
• The metaplastic theory suggests that the squamous papillary type results because of metaplasia of squamous epithelial cell rests that arise from squamous cell nests normally found at the junction of the pituitary stalk and pars distalis.
• Another theory postulates that this tumor is a midline congenital tumor not fundamentally different from an epidermoid cyst.

The onset of symptoms is generally insidious, with a delay of approximately 1-2 years between symptom onset and diagnosis. Headache is the most common presenting symptom, followed by endocrine deficiencies and visual disturbances.

Headache (occasionally with nausea and vomiting) is usually related to either the tumor’s mass effect or hydrocephalus (due to obstruction of the foramen of Monro, third ventricle, or aqueduct of Sylvius) that occurs in 15-30% of patients. This obstructive hydrocephalus may on rare occasion require emergent management.

Endocrine disturbances usually manifest more prominently in children. Ninety-three percent of children experience growth failure (short stature). Adults have more varied presentations and may develop sexual or menstrual dysfunction. Eighty-eight percent of men experience decreased sex drive, while 82% of women have amenorrhea. On the other hand, exaggeration of endocrine function may lead to precocious puberty in children and obesity in adults.

Large tumors in adults can cause psychiatric symptoms, memory loss, apathy, incontinence, depression, and hypersomnia. Long-standing mentation deficits and profound memory loss have been reported and suggest a worse prognosis. Visual deficits are caused by compression of the optic chiasm from suprasellar tumor growth. Classically, the tumor presents as a bitemporal hemianopsia, but it may also manifest as homonymous hemianopsia, scotoma, or optic atrophy with papilledema.

Other presenting symptoms can include chemical meningitis from rupture of cyst contents into the subarachnoid space and seizures.

The most common indication for surgery is neurologic compromise from tumor mass effect. In children, hypothalamic and endocrine dysfunction may develop before visual defects are noticed. Obesity and lethargy are common in children with craniopharyngiomas. In general, any mass lesion in the pituitary sella and suprasellar area should undergo a biopsy or resection, if feasible.

Craniopharyngiomas have been surgically divided into 3 groups: sellar, prechiasmatic, and retrochiasmatic. Sellar-located tumors may be suprasellar (75%), infrasellar (21%), or intrasellar (4%). These tumors occasionally grow into the third ventricle, causing hydrocephalus. The arterial supply is usually from the anterior cerebral and anterior communicating arteries or from the internal carotid and posterior communicating arteries.

Craniopharyngiomas are usually avascular on angiography but may encase or displace vessels that form the circle of Willis. Usually, the internal carotid artery (ICA) is displaced laterally, the anterior cerebral artery (ACA) is displaced anteriorly, and the basilar artery is displaced posteriorly.

A craniopharyngioma does not receive blood supply from the posterior circulation, unless it is parasitized from the floor of the third ventricle. As these tumors enlarge, they may elevate and infiltrate the optic chiasm as well as the hypothalamic region. Occasionally, they extend into the pituitary fossa or posteriorly to the ventral pons, and, rarely, they invade the basal ganglia or the brain parenchyma.

When predominantly in the sella, these tumors erode the bony floor and enlarge the sella.

Surgery is contraindicated in patients with cardiac or respiratory abnormalities that make the risk of general anesthesia unacceptably high. Moreover, patients who take chronic anticoagulation medication must cease medication and demonstrate normal coagulation studies prior to surgery. Asymptomatic patients or those with a small tumor may be monitored with serial MRI scans. A small tumor in the pituitary region without mass effect or endocrine dysfunction may also be monitored with serial MRIs.