A Rathke’s cleft cyst is a fluid-filled sac that forms in the pituitary gland, located at the base of the brain. It develops from tissue left over during early embryonic growth and is almost always benign. These cysts are surprisingly common, found in up to 22% of people in autopsy studies, though the vast majority never cause symptoms and are only discovered by accident on brain imaging done for other reasons.
How Rathke’s Cleft Cysts Form
During the third and fourth weeks of embryonic development, a small pocket of tissue called Rathke’s pouch pushes upward from the roof of the mouth toward the developing brain. This pouch eventually becomes the front part of the pituitary gland. As the pouch matures, cells along its front wall multiply and fill most of the interior space, forming the hormone-producing tissue of the pituitary.
Sometimes those cells don’t fully fill the pouch, leaving a small gap between two layers of pituitary tissue. That remnant space can persist into adulthood as a fluid-filled cyst lined with a thin layer of cells. The fluid inside is typically mucus-like. The cyst lining cannot produce hormones on its own, so the cyst itself is hormonally inactive. Problems only arise when it grows large enough to press on surrounding structures.
Who Gets Them
In one study of 1,000 unselected autopsy specimens, 11.3% contained an incidental Rathke’s cleft cyst. Other autopsy series have reported prevalence as high as 22%. The cysts are far more commonly identified in adults than in children, and when they do appear in children, they tend to be smaller. Most people who have one will never know it.
Symptoms of a Growing Cyst
When a Rathke’s cleft cyst does become symptomatic, it’s because it has expanded enough to compress the pituitary gland, the stalk connecting it to the brain, or the optic nerves that pass just above it. The most common complaints are frequent headaches, vision changes, nausea, and persistent fatigue or drowsiness. Some people notice personality or behavioral changes, including confusion.
Because the pituitary gland controls a wide range of hormones, compression from a growing cyst can disrupt several body systems at once. Possible hormonal symptoms include:
- Irregular or absent menstrual periods
- Breast milk production unrelated to pregnancy
- Low libido
- Extreme thirst and frequent urination (a sign of diabetes insipidus)
- Slowed growth or delayed puberty in children
- Unexplained weight gain
- Low blood pressure, unusually dry skin, or difficulty regulating body temperature
In one clinical series of symptomatic patients, 65% reported headaches, 61% had some form of hormone disruption, and 19% had visual problems. Cyst size closely correlated with the severity of hormone deficiencies, particularly for growth hormone and thyroid-stimulating hormone. About 20% of symptomatic patients in that study showed deficiency across all pituitary hormones.
How It’s Diagnosed
MRI is the primary tool for identifying a Rathke’s cleft cyst. On imaging, these cysts typically appear as small, oval-shaped, purely fluid-filled structures sitting within or just above the pituitary gland. They usually show no enhancement or only a thin rim of enhancement around the cyst wall after contrast dye is given, which helps distinguish them from other growths in the same area.
The signal on MRI varies depending on the protein and mucus content of the cyst fluid, so the cyst can appear bright, dark, or intermediate on different scan sequences. Nearly half of cases show a small nodule inside the cyst, often appearing dark on certain MRI sequences. This intracystic nodule is considered a hallmark feature and carries high diagnostic value. Occasionally, a layered appearance is visible, with the upper and lower portions of the cyst showing different signal intensities and a clear border between them.
Distinguishing It From Similar Growths
Several other growths can occur in the same region, so radiologists look for specific patterns. Pituitary adenomas tend to be solid rather than cystic, enhance uniformly with contrast, and often have a “snowman” shape when they extend upward. Craniopharyngiomas, another embryological remnant, are typically larger, have a lobulated shape, contain both solid and cystic components, and show a reticular (web-like) enhancement pattern. Rathke’s cleft cysts stand out by being smaller, purely cystic, and oval-shaped with minimal wall enhancement.
When Treatment Is Needed
For cysts found incidentally that aren’t causing symptoms, watchful waiting is the standard approach. These cysts tend to remain stable over years of follow-up and rarely progress to cause pituitary dysfunction. Monitoring involves periodic MRI scans and hormone blood tests to catch any changes early.
Surgery is recommended when the cyst causes significant symptoms: persistent headaches, visual field loss, or measurable hormone deficiencies. There are no firm size cutoffs that automatically trigger surgery. Instead, the decision is individualized, weighing how much the cyst is affecting quality of life and pituitary function against the risks of the procedure.
What Surgery Looks Like
The standard approach is an endoscopic endonasal transsphenoidal procedure. In plain terms, the surgeon reaches the pituitary through the nose and sinuses using a thin camera and instruments, avoiding any external incisions or the need to open the skull. This technique provides a clear, direct view of the cyst with minimal trauma and allows for a faster recovery compared to older microscopic methods.
The goal of surgery is not to remove the entire cyst wall. Instead, surgeons open the cyst, drain its contents, and flush the cavity clean. Partial removal of the cyst wall may be performed, but attempting to strip away the entire wall is generally avoided because it sits so close to functioning pituitary tissue. Aggressive removal has been associated with complication rates as high as 47%, including new hormone deficiencies such as cortisol decline or loss of reproductive hormone function. By leaving the portion of the wall that is attached to the pituitary intact, surgeons significantly reduce the risk of additional hormonal damage.
Draining the cyst contents serves two purposes. It relieves the physical pressure that causes headaches and vision problems, and it removes the mucoid material that can trigger intermittent inflammation within the cyst.
Recovery and Recurrence
Most patients recover quickly after endoscopic surgery, with minimal postoperative discomfort. Headaches caused by cyst pressure often improve substantially. Elevated prolactin levels, which can cause breast milk production and menstrual irregularities, typically resolve. Recovery of other hormone deficiencies is less predictable and depends on how long the pituitary was compressed before surgery.
Recurrence is the main long-term concern. Because the cyst wall is intentionally left partially in place, the cyst can refill over time. Overall recurrence rates in published studies have reached as high as 48%, though not all recurrences require a second operation. Endoscopic techniques appear to have a lower recurrence rate (around 26%) compared to older microscopic approaches (around 57%), likely because the endoscope allows more thorough drainage and better visualization of the cyst cavity. Long-term follow-up with repeat MRI scans and hormone testing is essential after surgery to catch regrowth early. If a cyst does recur, the decision about repeat surgery requires careful consideration rather than an automatic return to the operating room.