A Rathke’s Cleft Cyst (RCC) is a non-cancerous, fluid-filled growth found near the pituitary gland at the base of the brain. This lesion is benign and remains asymptomatic in the majority of cases. It is frequently discovered incidentally when a patient undergoes a Magnetic Resonance Imaging (MRI) scan for an unrelated health concern.
Understanding Rathke’s Cleft Cysts
The formation of a Rathke’s Cleft Cyst is rooted in embryonic development, specifically from Rathke’s pouch. This pouch is a temporary pocket of tissue that normally regresses as the pituitary gland forms. When remnants of this pouch persist, they develop into a cyst typically located between the anterior and posterior lobes of the pituitary gland. The cyst is lined with epithelial cells and gradually fills with a thick, often mucinous fluid.
The cyst is located within the sella turcica, a small, bony compartment at the base of the skull. This region is densely packed with crucial structures, including the pituitary gland, the optic chiasm, and the hypothalamus. Because the RCC develops in this confined space, its growth can mechanically interfere with the function of these adjacent tissues. Although present from birth, the cyst is most often detected in adults between the ages of 30 and 50.
The Natural Course: Stability, Growth, and Shrinkage
The natural history of an RCC is variable but generally favorable. Clinical studies tracking asymptomatic cysts show that the majority (around 70 to 75%) remain radiographically stable over many years. Stability means the cyst size does not change noticeably on successive MRI scans, alleviating the need for intervention.
Documented spontaneous shrinkage, or regression, of an RCC is relatively rare but possible. In one study, nearly 19% of conservatively managed cysts showed a measurable decrease in size over time. This reduction occurs due to changes in the cyst’s fluid dynamics, such as fluid absorption or a minor, temporary rupture that allows the fluid to dissipate.
While most cysts are stable or decrease, approximately 20 to 25% of RCCs may show some degree of growth during follow-up. This growth is usually slow and small, with only a very small percentage showing a significant increase in diameter. Growth is driven by the accumulation of more fluid or, in some cases, a small hemorrhage within the cyst. Ongoing radiological monitoring with periodic MRI scans is recommended for all asymptomatic RCCs.
When a Cyst Causes Symptoms
Rathke’s Cleft Cysts cause problems primarily when they grow large enough to compress the surrounding structures. Symptoms arise as a consequence of this mass effect. These cysts are usually asymptomatic until they reach a size that begins to exert pressure on the adjacent nerves and glands.
One major category of symptoms involves visual disturbances, which occur if the cyst expands upward and presses on the optic chiasm. Compression of the optic chiasm (where the optic nerves cross) often leads to a specific type of peripheral vision loss called bitemporal hemianopsia. Patients may not notice this loss until it becomes severe.
The other main group of symptoms relates to endocrine dysfunction, resulting from pressure on the pituitary gland. Interference with the pituitary gland, which regulates many hormones, can lead to hypopituitarism (a deficiency in one or more pituitary hormones). This may manifest as hypothyroidism, adrenal insufficiency (cortisol deficiency), or diabetes insipidus (extreme thirst and frequent urination).
Management Options and Surgical Intervention
Management is determined by the presence or absence of symptoms. For the majority of patients whose cysts are discovered incidentally and cause no symptoms, watchful waiting is the standard of care. This involves monitoring the cyst’s size and the patient’s hormonal status over time using periodic MRI scans and blood tests.
Surgical intervention is reserved for patients who develop symptoms, such as progressive vision loss or significant hormonal deficits. The primary goal of surgery is to relieve pressure on the surrounding structures. The standard procedure is Transsphenoidal Surgery (TSSA), which accesses the cyst through the nasal passages and the sphenoid sinus, avoiding the need for an open skull procedure.
During TSSA, the surgeon drains the fluid and removes only a portion of the cyst wall, a technique called marsupialization. Complete removal of the cyst wall is avoided because it carries a higher risk of damaging delicate pituitary tissue. This damage could worsen hormonal function and potentially lead to complications like diabetes insipidus. While surgery often improves visual symptoms and headaches, recovery of pre-existing hormonal deficiencies is less predictable.