Craniopharyngeoma

Introduction:

These are rare extra axial epithelial (squamous) tumors arising along the path traversed by craniopharyngeal duct. These are really slow growing tumors.

Theories accounting for pathogenesis of craniopharyngeomas:

1. Embryogenetic theory
2. Metaplastic theory

Embryogenetic theory:

This theory is based on the premise that neoplastic transformation occurs in the embryonic squamous cell rests of the involuted craniopharyngeal duct.

Metaplastic theory:

This theory suggests that craniopharyngeoma could originate due to metaplasia involving adenohypophyseal cells in the pituitary stalk / gland.

Incidence:

Craniopharyngeoma constitutes roughly about 5% of all CNS tumors. WHO designates this tumor as Grade I tumor.

Histological types:

Histologically this tumor is composed of nests of squamous epithelial cells surrounded by radially arranged cells. Eventhough these tumors are histologically benign they behave like a malignant lesion due to their ability to infiltrate into critical parasellar structures like optic nerves, pituitary stalk, pituitary gland, floor of 3^rd ventricle and circle of willis. These tumors have a tendency to recur even after apparantly complete removal.

1. Adamantinomatous type
2. Papillary type

Adamantinomatous type:

This type commonly occurs during the first two decades of life, although theoretically speaking it can occur at any age. In this type calcification is rather common and can be identified by neuroimaging.

Papillary type:

This type is primarily seen in adults. This type rarely calcifies. Absence of tissue calcification is a diagnostic pointer.

Craniopharyngeomas could be cystic / solid. When cystic it is filled with turbid, protenaceous straw colored fluid that glitters and sparkles due to the presence of high amounts of cholesterol crystals. This appearance allows it to be compared with machine oil.

Common locations:

These tumors commonly occur in sellar and suprasellar regions. They can extend anteriorly to involve the prechiasmatic cistern and subfrontal spaces. Posterior extension of these tumors could involve the following areas:

1. Prepontine cistern
2. Interpeduncular cistern
3. CP angle
4. 3^rd ventricle
5. Posterior cranial fossa
6. Foramen magnum

Lateral extension can involve subtemporal spaces.

Blood supply to craniopharyngeomas usually occur from the anterior circulation, usually from perforators of anterior cerebral artery.

The unique adhesive factors of this tumor are attributed to the presence of local inflammation. The levels of inflammatory cytokines have been found to be elevated in the cystic fluid.

Clinical features:

These tumors are highly variable in their clinical presentation which is dependent on the size, location and growth potential of the tumor.

Neurologic symptoms:

Head aches

Nausea

Vomiting

Hydrocephalus (common in children)

Visual symptoms:

Bitemporal hemianopia because of the proximity of the tumor to optic chiasma

Pituitary symptoms:

1. Growth failure
2. Delayed puberty (In children)
3. Hypogonadism (adults)

Hormonal symptoms:

Growth hormone deficit (common)

Follicle stimulating hormone / Leutinizing hormone deficit

Corticotrophin hormone deficit – Features include orthostatic hypotension, hypoglycemia, hyperkalemia, cardiac arrythmias, lethargy, confusion, anorexia, nausea and vomiting.

Thyroid stimulating hormone deficit – Causing weight gain, fatigue, cold intolerance and constipation.

Antidiuretic hormone deficit – Causing polyuria and polydipsia.

Major clinical syndromes associated with the location of the lesion:

Three major clinical syndromes have been identified.

Prechiasmal syndrome: Symptoms associated with this syndrome is dependent on the prechiasmal location of the mass. Classically these patients demonstrate optic atrophy. Clinical features include progressive decline of visual acuity with constriction of visual fields.

Retrochiasmal syndrome: This syndrome is frequently associated with hydrocephalus with signs of increased intracranial tension. Increased intracranial tension is manifested by the presence of papilloedema and horizontal double vision.

Intrasellar syndrome: This syndrome usually manifests with headache and endocrinopathy.

Investigations:

Imaging which include plain and contrast CT, MRI. Cerebral angiography can be performed in order to ascertain the blood supply to the tumor.

Serum electrolytes

Thyroid profile

Neuro opthamological evaluation

Management:

Since it is a benign tumor surgical excision is preferable. Trans sphenoidal approaches and extended trans sphenoidal appoaches are perferred to excise the tumor. Craniotomy approaches (i.e. Bifrontal, petrional and interhemispherical) can be attempted depending on the location of the tumor.

Streotactic radiosurgery can be utilized to remove tumors from difficult areas.