Craniopharyngioma overview

# Overview
Craniopharyngioma is a rare, benign tumor of the central nervous system. It is a partly cystic embryonic malformation that can occur in the sellar/parasellar region and can result in a wide array of symptoms such as headaches, nausea and vomiting, visual disturbances, and endocrine disturbances.It has an incidence of 0.5 to 2 cases per million persons per year. Half of these cases occur during the first two decades of life. It represents 1.2% to 4% of all childhood intracranial tumors. It has a classical bimodal distribution of incidence with increased incidence rates in patients aged five to 14 years and 50 to 74 years. Craniopharyngioma has a very high recurrence rate, with reported rates as high as 50%. There are two subtypes of craniopharyngioma: adamantinomatous and papillary. It most commonly presents with signs of increased intracranial pressure (ICP) including headache and nausea and vomiting along with visual and endocrine disturbances. In children, failure to thrive and decreased growth rate may be the initial presentation. Multiple modalities can be implemented in the management of craniopharyngioma, including neurological surgery, radiotherapy, and instillation of sclerosing substances.

# Historical perspective
Primitive concepts of the function of the pituitary gland were formulated in the 4th century BC by Hippocrates. Harvey Cushing (18691939), had a major impact in the understanding of pituitary function and surgery however he was not the first surgeon to attempt pituitary surgery; this honor went in 1889 to Sir Victor Horsley. Hermann Schloffer (18681937), an Austrian surgeon, guided by the works of Davide Giordano, performed the first transfacial transsphenoidal approach in 1907. In the 1960s, transphenoidal surgery underwent a revival and has been universally accepted to owing to the contributions of Guiot and Hardy.

# Classification
Craniopharyngiomas occur in two histological subtypes; an adamantinomatous form and Papillary. Adamantinomatous form is the most common pediatric variant and the papillary form is found almost exclusively in adults.The pediatric form is thought to arise from epithelial remnants of the craniophayngeal duct or Rathke's pouch, an embryologic structure that develops into the anterior pituitary. Both forms typically have solid and cystic components and are often calcified on imaging. Recent genetic analysis has also shown differences between these two subtypes. Mutations in B-catenin , a downstream effector of the Wnt pathway that is involved in cellular growth and development, has been described in 6096% of adamantinomatous craniopharyngiomas. Papillary craniopharyngiomas recently have been discovered to frequently harbor V600E mutations of the BRAF gene, which is a key player in the mitogen-activated protein kinase pathway.

# Pathophysiology
Craniopharyngiomas are epithelial tumors that usually arise in the pituitary stalk adjacent to the optic chiasm. On gross pathology, craniopharyngiomas are cystic or partially cystic with solid areas.The cyst is filled with a turbid, proteinaceous material of brownish-yellow color that glitters and sparkles because of a high content of floating cholesterol crystals On microscopic histopathology, it is categorized into two subtypes: adamantinomatous and papillary.

# Differentiating craniopharyngioma from other diseases
Craniopharyngioma must be differentiated from other pituitary masses such as sarcoid, pituitary adenoma, aneurysm, teratoma, tuberculosis, rathke cleft cyst, chordoma, hypothalamic glioma, hamartoma of tuber cinereum, histiocytosis, meningioma and optic nerve glioma.

# Epidemiology and demographics
The demographic patterns of craniopharyngioma are not well described because the tumor is rare. In addition, most cancer registries collect data only on malignant conditions and, therefore, they are not useful in the study of craniopharyngioma as it is considered to be a borderline histological malignancy. Incidence rates are similar in males and females and between caucasians and african americans. Tumors are more common among children of age 5 to 15 years and older adults of greater than 65 years while the lowest rates occur among those aged 15 to 34 years. Survival is highest for patients diagnosed at a younger age.

# Risk factors
No predisposing risk factors have been identified.

# Natural history, complications and prognosis
Common complications of craniopharyngioma are long-term hormonal problems, visual defects and nervous system deficits. The prognosis of craniopharyngioma is good with treatment. The 5-year and 10-year survival rates are higher than 90%.

# Diagnosis
Brain MRI with and without contrast is the diagnostic study of choice. Computed tomography (CT) scan is optional and may show some calcifications that can be seen in these tumors. Imaging studies such as MR Angiography (MRA) or CT Angiogram (CTA) is decided on a case-by-case basis typically for surgical planning or if a possible vascular malformation is suspected.

# History and symptoms
Craniopharyngiomas are slow growing, and symptoms often are present for a year or more before the diagnosis is established. A wide range of symptoms may be present, depending upon the precise location of the tumor and its relationship to adjacent normal structures. Most common symptoms of craniopharyngioma include headache, nausea, vomiting, ataxia, polyuria, polydipsia, stunted growth, decreased libido, amenorrhea, weight gain, myxedema, vision loss, behavioral and learning problems.

# Physical examination
The diagnosis of craniopharyngioma is often made late after the initial appearance of symptoms. Clinical picture at time of diagnosis often dominated by nonspecific manifestations of intracranial pressure like headache, nausea and vomiting. Primary manifestations are visual impairment and endocrine deficits.

# Laboratory findings
Patients with craniopharyngioma may have abnormal pituitary hormone levels, which is suggestive of disruption of hormone production due to pressure effects on the pituitary gland. The hypothalamic-pituitary axis hormones, namely growth hormone, thyroid hormone, luteinising and follicle stimulating hormone should be measured together with cortisol levels and an assessment of serum and urine osmolality. In addition, an estimate of bone age and, for young females, ovarian ultrasonography is useful. Ideally, any abnormalities should be corrected pre-operatively but, at the very least, low cortisol levels and diabetes insipidus should be treated prior to a surgical procedure.

# CT
The CT findings depend on the subtype of craniopharyngioma. On CT, the adamantinomatous type is characterized by large cysts, vivid enhancement and peripheral calcifications. Papillary type tend to be more spherical in outline and usually lack the prominent cystic component; most are solid. Calcification is rare.

# MRI
The diagnostic evaluation of craniopharyngioma includes high-definition brain imaging. Brain MRI with and without contrast is the gold standard. Computed tomography (CT) scan is optional and may show some calcifications that can be seen in these tumors. However CT is not specific enough as a stand alone diagnostic test. vascular imaging studies such as MR angiography (MRA) or CTA, is decided on a case-by-case basis typically for surgical planning or if a possible vascular malformation is suspected.

# Treatment
The predominant therapy for craniopharyngioma is surgical resection. Medical therapy, adjunctive chemotherapy and radiation may be required.

# Medical therapy
The predominant therapy for craniopharyngioma is surgical resection. Adjunctive chemotherapy and radiation may be required. Subcutaneous pegylated interferon alpha-2B has been used to treat cystic recurrences. It can also be treated with intracavitary instillation of radioactive P-32, bleomycin or interferon-alpha via stereotactic delivery or placement of an Ommaya catheter. Paclitaxel and carboplatin have shown to prevent recurrence of malignant craniopharyngiomas. Intracavitary bleomycin reduces cyst size and toughens and thickens the cyst wall, thereby facilitating surgical excision of a cyst membrane that otherwise might fragment at the time of open craniotomy. Reports of intracystic bleomycin use are limited. Other agents like interferon alpha are being tested in recent days.

# Surgery
Surgery is the mainstay of treatment for craniopharyngioma. Radical surgery is done either by transsphenoidal approach or by craniotomy. Recent studies propose subtotal resection with postoperative radiotherapy as the management of choice for craniopharyngiomas, especially in the pediatric population. More advanced radiotherapy modalities currently under investigation include Gamma Knife and cyberknife radiosurgery.