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A pineal cyst is a fluid-filled growth inside the pineal gland in the brain. In most cases, a pineal cyst is a benign tumor which does not cause any symptoms. Occasionally a cyst may enlarge and press on surrounding structures causing symptoms such as headaches and blurred vision. If this occurs, the cyst can be removed using surgery. The study of the brain and nervous system and the conditions that affect them is known as neurology.
Pineal cysts are usually small in size, with the majority measuring less than 0.39 inches (1 cm), and they are more common in women and people in their 40s. It is thought that they may be associated with changes in hormone levels; the pineal gland is involved in the production and secretion of melatonin, which interacts with reproductive hormones. This type of cyst will usually remain the same size, but a few will shrink and, in rare cases, a cyst will grow large enough to cause symptoms. Head pain, dizziness and vomiting may occur, as well as sight problems such as blurred or double vision and loss of eye movement.
Sometimes a condition known as Parinaud syndrome may develop as a result of an enlarged pineal cyst. Parinaud syndrome has symptoms involving the eyes, with the pupils ceasing to respond to light, although they will still contract normally when an object moves nearer. There are difficulties with moving the eyes to look upward, and irregular, jerky eye movements can occur.
If a mass such as a pineal cyst causes pressure on what is called the cerebral aqueduct, a channel in the brain which connects two fluid-filled spaces known as ventricles, fluid is prevented from flowing freely. This obstruction leads to a condition called hydrocephalus, where fluid can build up and put pressure on the brain. Rarely, this may happen suddenly and prove fatal, but more often there is time to treat the problem surgically.
This kind of cyst can be seen using a magnetic resonance imaging, or MRI, scan where it appears as a well-defined, oval mass with smooth walls. As these cysts are so common, thought to be present in almost a quarter of adults, any small ones which are not causing symptoms do not generally need any treatment or follow-up scans. Where symptoms are experienced, total removal of a cyst using surgery is necessary. In cases where hydrocephalus persists after the cyst has been removed, a tube known as a shunt can be put in place to drain fluid away from the ventricles.