Craniopharyngiomas

Craniopharyngiomas are histologically benign yet locally aggressive tumors that develop near the pituitary gland at the base of the brain. Although malignant transformation of craniopharyngioma has occurred, this rarely happens. These tumors typically involve the pituitary stalk (connects the pituitary gland to the hypothalamus) and are sticky and adherent tumors. They vary in cystic and solid portions, with the majority having some cystic components.

They are very rare (about 2 per 1,000,000 people) and account for around 2-3% of all brain tumors with no gender or racial bias. They generally present during childhood (ages 5-14 years) or late adulthood (ages 50-74 years).

SYMPTOMS

Presenting symptoms depend on the tumor’s size and location. Certain tumors may be large before they cause symptoms, while others may present while very small. Symptoms include:

• Peripheral field vision loss
• Eye movement weakness/double vision
• Headache
• Vomiting
• Personality changes, confusion
• Hormonal insufficiency/hypothalamic dysfunction
  • Excessive thirst and urination (diabetes insipidus)
  • Fatigue
  • Hyperphagia and weight gain
  • Stunted growth or delayed puberty in children
  • Increased sleepiness, hot/cold intolerance
• Adrenal insufficiency
  • Fatigue
  • Low blood pressure

RISK FACTORS

They are sporadic tumors,so the cause of their development is not known, and no known risk factors exist.

DIAGNOSTIC IMAGING

Following a thorough history and physical examination by a doctor, additional tests may occur for patients showing craniopharyngioma signs (imaging studies like MRIs or CT scans).

This helps providers identify the location of important brain structures near the tumor (hypothalamus, pituitary stalk and gland, internal carotid arteries, optic nerve and optic chiasm.) Several classification systems for craniopharyngiomas are based on these imaging findings, helping to elucidate the most effective treatment option.

TYPES OF CRANIOPHARYNGIOMAS

1. Adamantinomatous Variant: Wet keratin, calcifications, stellate reticulum and palisading epithelium. Present mutations within exon 3 of CTNNB1
2. Papillary Variant: Lacks calcifications and almost exclusively found in adults with mutations within exon 15 of BRAF V600E identified. Encouraging research investigating the effectiveness of medical therapy with BRAF inhibitors for this subtype has already begun.

TREATMENT

Surgery

Surgical resection of a craniopharyngioma is usually the preferred initial treatment. It establishes and confirms the specific tumor and histological subtype diagnosis, provides opportunities to remove the pressure the craniopharyngioma may exert on normal brain structures such as the optic nerves and optic chiasm, and possibly improves vision. It also offers the best chance to remove the maximum amount of tumor. Portions of tumors adherent to the hypothalamus are typically not resected, due to the potential devastating effects of hypothalamic injury. There are some risks with surgery, so it is important to discuss them with a neurosurgeon.

There are two basic categories of surgical approaches, which each contain distinct advantages and disadvantages. The neurosurgeon’s experience, the patient’s age and overall health, along with the size and location of the craniopharyngioma influence the particular approach and surgical plan.

1. Open craniotomy: An incision on the scalp or eyebrow region to temporarily remove a window of bone. The lining of the brain is opened and the tumor is removed, typically with the aid of an operating microscope. The bone is then replaced with small plates and screws. The incision is sewn back together.
2. Endonasal (transsphenoidal): The neurosurgeon frequently works with an otolaryngologist to provide access to the skull base through the natural nasal passageway. Typically performed with an endoscope, The neurosurgeon removes the tumor, recreating the separation between the brain and nasal pathway with varying types of tissue (nasal mucosa, abdominal fat, thigh tissue, collagen grafts, and surgical glue)

Other Treatments

1. Radiotherapy: Damaging the DNA of the tumor. May be administered through different techniques (standard external beam, stereotactic radiosurgery, and proton beam). May be used following surgical resection to target residual or recurrent tumor or in treating tumors adherent to the hypothalamus. There are risks with radiotherapy that should be discussed with the provider.
2. Miscellaneous: There are less common, emerging treatments. This includes the use of chemotherapy (paclitaxel), carboplatin, and the administration of BRAF inhibitors for papillary craniopharyngioma, surgical placement of intracavitary phosphorus-32, yttrium, bleomycin, rhenium and the application of interstitial brachytherapy. There are risks with these that should be discussed with the provider.