Definition
There are a variety of different types of cysts that may be
seen within the pituitary. Although some pituitary tumors can have cystic
components, most cysts are not true neoplasms (tumors) and instead are
developmental in origin. The most common cyst is a Rathke’s cleft cyst (RCC).
Other cysts seen in the pituitary include arachnoid cysts, Pars Intermedia
cysts and epidermoid cysts.
Rathke’s Cleft Cysts
Rathke’s cleft is a normal part of the developing pituitary
gland in the fetus. The cleft actually begins as a pouch (Rathke’s pouch),
which can be seen in the human fetus beginning in the 4th week of development.
Part of the pouch goes on to form the anterior pituitary gland and part becomes
the intermediate lobe of the pituitary (which sits between the anterior and
posterior pituitary). As the anterior and intermediate lobes of the pituitary
form, what was a pouch becomes a cleft and ultimately the cleft regresses.
However, in some people the cleft does not fully regress and the space becomes
filled with liquid. Those people are said to have Rathke’s cleft cysts.
Symptoms
Although the majority of cysts are small and asymptomatic,
some are noticed, either incidentally or because of specific symptoms,
including headaches, visual deficits and pituitary hormone deficiency.
The most common symptom is headache. Because there is no
headache that is specific to a cyst, it can be challenging to distinguish what
is a headache from the cyst and what is anther type of headache.
If the cyst is large and extends above the pituitary, it may
put pressure on the optic chiasm. Pressure on the optic chiasm from below
typically affects the peripheral vision in both eyes.
Pituitary hormone deficiency can cause a wide variety of
symptoms. The pituitary hormones that are most sensitive to the effects of a
mass lesion are those controlling gonadal function. In women of childbearing
years, this will affect menstrual cycles. Men more often will report a decrease
in libido, or sex drive.
Treatment
Because most people with Rathke’s cleft cysts do not have
symptoms, most do not need surgery. However, there is a wide variety of cyst
sizes and potential symptoms that contribute to the decision making for
specific treatments.
While a small Rathke’s cleft cyst in a well person who has no
problems (visual or endocrine) requires no therapy, those with large cysts who
have visual deficits should be treated with surgery.
The main treatment dilemmas are in people who are diagnosed with
a Rathke’s cleft cyst during an evaluation for headaches. When the only symptom
is headache and the cyst is limited to the pituitary (does not compress the
optic chiasm), a trial of medical therapy for the headaches is warranted.
Follow-up imaging is often performed to confirm that the cyst is not growing.
Surgery
Virtually all Rathke’s cleft cysts can be operated on through
the nasal passages without an external incision on the skin (transsphenoidal
surgery). The surgeon may either attempt to remove the entire cyst wall or
drain the cyst and remove only a portion of the wall. There are
advantages and disadvantages of each type of removal. Although complete removal
of the cyst wall is associated with the lowest chance of recurrence, this
technique places pituitary function at risk. Also, cyst drainage and
fenestration are associated with a higher chance of recurrence but a lower
chance of injuring the pituitary gland. Simple cyst drainage and fenestration
may be the best choice for most patients.
Medication
There is no medical therapy that has been shown to be effective
in the treatment of Rathke’s cleft cysts, pars intermedia cysts, arachnoid
cysts or epidermoid cysts.
Radiation Therapy
Radiation therapy is not considered to be effective in the
treatment of Rathke’s cleft, pars intermedia, arachnoid or epidermoid cysts.
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