Pineal cysts are cysts of the pineal gland. The pineal gland is a small organ in the brain that produces the hormone melatonin, which helps regulate other hormones and maintains the body's circadian rhythm. Pineal cysts are relatively common and may be found by chance in up to 10% of people who have a head CT scan or MRI. Most people with a pineal cyst do not have any signs or symptoms. Rarely, a pineal cyst may cause headaches, hydrocephalus, obstruction of the vein of Galen (a vein at the base of the brain), Parinaud syndrome (eye problems related to difficulties with vertical eye movement), or other symptoms. The exact cause of pineal cysts is unknown. Treatment is usually only considered when a cyst causes symptoms. Treatment may involve open or stereotactic removal of the cyst, stereotactic aspiration, and/or CSF diversion (a procedure used to drain fluid from the brain).

When a pineal cyst does cause symptoms, they may include headaches (the most common symptom), hydrocephalus, disturbances in vision, and eye problems related to not being able to look upwards, and in some instances downwards as well (Parinaud syndrome). Although rare, people with symptomatic pineal cysts may have other symptoms such as difficulty moving (ataxia), mental and emotional disturbances, vertigo, seizures, sleep (circadian rhythm) troubles, vomiting, hormonal imbalances that may cause precocious puberty, or secondary parkinsonism.

The exact cause of pineal cysts currently remains unclear. It has been theorized that they may be developmental in origin, or may result from hormonal changes or influences.

Treatment may be recommended if the cyst causes symptoms. Depending on the size of the cyst and the symptoms present, treatment may involve open or stereotactic removal of the cyst, stereotactic aspiration, and/or CSF diversion or shunting (a procedure used to drain fluid from the brain). Radiation therapy may be considered for cysts that recur after treatment.

In some cases, pineal cysts may cause a variety of symptoms. In very rare cases, serious complications including sudden death have been reported. In some of these cases, a pineal cyst was first identified on autopsy.