Dr Emma Duncan, Staff Specialist in Endocrinology,
 Princess Alexandra Hospital

 

What is a Craniopharyngioma?
What is a Rathke’s cleft cyst?
What causes Craniopharyngiomas and Rathke’s cleft cysts?
What symptoms occur with craniopharyngiomas and Rathke’s cleft cysts?
How are they diagnosed?
How are they treated?
What is the likely outcome?

What is a Craniopharyngioma?

Craniopharyngiomas are benign (non-cancerous) tumours arising in the area of the pituitary gland – usually above and behind the gland.  They are extremely rare (around 1 person in a million present with this problem each year; giving around 20 cases each year Australia-wide).  Nearly half of these cases will present in children less than 16 years of age; the rest will present in adulthood.  6 to 13% of all intracranial (“brain”) tumours in children are due to craniopharyngiomas.  These tumours have a variable behaviour: they can be very slow growing but sometimes they can be more aggressive and grow quite quickly. 

Craniopharyngiomas can be very variable in their structure – from mainly solid tumour to a mix of solid and cystic (fluid-filled) parts to mainly cystic.  The fluid in the cysts can be oily, resembling engine oil, or can be shimmering with cholesterol crystals.  The tumour often shows areas of calcification, which can be detected even on a plain skull x-ray.

What is a Rathke’s cleft cyst?

Rathke’s cleft cysts are also benign and very uncommon and are a subset of the craniopharyngiomas.  They usually occur within the pituitary gland itself, and very uncommonly can cause symptoms.  Rathke’s cleft cysts contain oily fluid within the cyst wall and do not usually have much solid structure otherwise. 

What causes Craniopharyngiomas and Rathke’s cleft cysts?

The pituitary gland is made up of two parts – the anterior (front) and posterior (back).  These two parts arise from separate areas in the developing foetus – the anterior part grows upwards from the roof of the mouth (from Rathke’s pouch) and the posterior part grows downwards from parts of the brain.  These two parts then fuse together to form the pituitary gland in the developing foetus.  However, sometimes this developmental process is disturbed or imperfectly completed, and it is thought that craniopharyngiomas and Rathke’s cleft cysts may develop in these circumstances. 

What symptoms occur with craniopharyngiomas and Rathke’s cleft cysts?

These tumours cause symptoms mainly by pressure and disturbing the function on the surrounding structures, particularly the pituitary and hypothalamus.  Patients may notice headaches, nausea and vomiting from pressure on the brain and obstruction to the fluid system, causing build up of cerebrospinal fluid (CSF) within the brain (this is called hydrocephalus).  Pressure on the optic nerves may cause loss of vision.  Pressure on the pituitary gland (or alteration of the signals to the pituitary gland from the hypothalamus) may cause a loss of secretion of the hormones normally produced by the pituitary gland (Click here for further information on pituitary dysfunction).  As growth hormone and the gonadotrophins (LH and FSH) are important for normal growth and pubertal development, growth retardation and pubertal delay may occur in children.  In adults, partial or complete pituitary insufficiency may result (see Pituitary Conditions article - section on pituitary tumours for details of this). 

Craniopharyngiomas may also affect the hypothalamus (which lies above the pituitary gland).  As the hypothalamus controls secretion of the normal pituitary hormones from the pituitary gland, pituitary deficiency (hypopituitarism) may result (see Pituitary Conditions article - section on pituitary tumours regarding this also).  The hypothalamus also controls some behaviours, such as eating, drinking and sleeping, and influences memory and temperature control.  Patients may be excessively sleepy and forgetful, may have marked overeating (hyperphagia) and obesity, may not complain of thirst, even when they have large fluid losses, and may overheat in the summer months or after exercise.

How are they diagnosed?

Once a tumour is suspected (from visual loss, headache, and/or loss of pituitary function) a scan of the head with an MRI scan (magnetic resonance imaging) or a CT scan (computerised tomography) will show it.  Sometimes it can be difficult to differentiate these tumours from other pituitary tumours.  However, if a combination of cysts and solid elements is seen, it suggests a craniopharyngioma.  If a clearly cystic lesion is seen within the pituitary fossa, it might suggest a Rathke’s cleft cyst.

How are they treated?

These tumours usually require surgery. The type of surgery depends on many things, including the size of tumour, the site of the tumour, and the involvement of other structures that the tumour is invading or pressing on.  Hydrocephalus may require a shunt insertion, to drain CSF from the brain to the abdomen, thereby relieving the pressure.  Occasionally, some cysts can be drained without more extensive surgery; this procedure can be repeated if the fluid re-accumulates. However, craniopharyngiomas usually require removal, either a transphenoidal operation (through the nose) or a craniotomy (through the bone of the skull).

Before surgery, it is imperative that the pituitary function is carefully assessed, and that essential hormones are replaced before proceeding to surgery.

The surgeon often has to balance trying to remove a craniopharyngioma entirely with ensuring minimal damage to the underlying brain and other important structures.  This means that a complete removal is often not possible without unacceptable side-effects.  Therefore, in adults radiotherapy is almost always offered after surgery for a craniopharyngioma, to control the growth of any residual tumour.  In children, radiotherapy is often offered after surgery but this depends on the age of the child.   Although Rathke’s cleft cysts can reoccur, their surgical management may be more simple and radiotherapy is not always offered to these tumour types.

After surgery and/or radiotherapy, the function of the pituitary gland is reassessed carefully and deficient hormones replaced.

What is the likely outcome?

Unfortunately, it is not unusual for craniopharyngiomas to regrow, and patients may require further therapies, most commonly surgery and/or irradiation.  The exact number of patients who have recurrent disease is hard to quantify as it depends upon the type of initial therapy (for example, whether the surgeon tried to remove it completely or only partially; whether radiotherapy was given after the first operation, etc.).  Overall, around a third of patients with initial surgery and radiotherapy will need further management; more than half of those with partial removal will need further management.  Craniopharyngioma cysts that have undergone drainage only can re-accumulate and sometimes the cysts can be drained again without the need for more radical surgery.  Rathke’s cleft cysts usually do not re-accumulate or require radiotherapy.

As these tumours can grow back after many years, and as the long term results of radiotherapy can affect the function of the pituitary and the brain, it is imperative that patients with craniopharyngiomas are followed up lifelong, usually by an endocrinologist and a neurosurgeon.

 

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This article updated: July 2006