Rathke Cleft Cyst
A Rathke cleft cyst is a benign, fluid-filled cyst that develops in the pituitary gland region from remnants of the Rathke pouch, an embryonic structure that normally gives rise to the anterior pituitary gland during fetal development. These cysts are relatively common, found in approximately 13-22% of people on autopsy studies, though most are small and asymptomatic. They are typically discovered incidentally during brain imaging performed for other reasons, though larger cysts can occasionally cause symptoms by compressing the pituitary gland or nearby structures.
What is it?
During fetal development, the pituitary gland forms from an upward extension of the primitive oral cavity called Rathke’s pouch, which normally fuses with downward-growing brain tissue to form the complete pituitary gland. The pouch then involutes (disappears), but sometimes a small cleft or space persists between what becomes the anterior and posterior pituitary. A Rathke cleft cyst develops when this residual cleft fills with fluid and expands to form a cyst. The cyst is lined with epithelial cells that may secrete mucoid material, causing the cyst to gradually enlarge over time, though growth is typically very slow.
Rathke cleft cysts are located within or adjacent to the pituitary gland in the sella turcica, a small bony cavity at the base of the skull. They are classified as congenital (present from birth) but may not become apparent until adulthood. Most cysts are small (a few millimeters) and remain stable throughout life. The cysts can contain clear, yellow, or brown fluid with varying protein content, which affects their appearance on MRI. Rathke cleft cysts occur equally in men and women and are typically diagnosed in adults between ages 30-50, though they can be found at any age. Unlike pituitary adenomas (tumors), Rathke cleft cysts are developmental remnants and not true neoplasms—they have no malignant potential.
Important to Know
The vast majority of Rathke cleft cysts are asymptomatic and discovered incidentally on brain MRI performed for headaches, head trauma, or other unrelated reasons. Small, incidentally discovered cysts typically require no treatment or follow-up imaging. When symptoms do occur—usually only with larger cysts (greater than 1-2 cm)—they result from compression of surrounding structures. Potential symptoms include headaches (the most common symptom when present), visual disturbances if the cyst compresses the optic chiasm above the pituitary (causing peripheral vision loss or bitemporal hemianopsia), and pituitary hormone deficiencies if the cyst compresses normal pituitary tissue, leading to symptoms such as fatigue, decreased libido, menstrual irregularities, or difficulty coping with stress. Rarely, cysts can rupture, causing acute inflammation (aseptic meningitis) with severe headache, fever, and neck stiffness. Diagnosis is made through MRI, which typically shows a cyst in the midline of the pituitary gland with variable signal characteristics depending on protein content—some appear similar to cerebrospinal fluid, while others have different signal intensities. A characteristic imaging finding is a small nodule along the cyst wall. Hormonal evaluation is performed to assess pituitary function if the cyst is large or symptomatic. Treatment for asymptomatic cysts is observation only. For symptomatic cysts, transsphenoidal surgery (performed through the nose) can drain or remove the cyst, relieving mass effect. However, cyst recurrence after surgery is relatively common (10-30%), sometimes requiring repeat intervention. Hormone replacement may be needed if pituitary function doesn’t recover after treatment. The overall prognosis for Rathke cleft cysts is excellent, with most people experiencing no symptoms and requiring no treatment throughout their lives.