A Pineal Cyst is usually a small, benign (not malignant) cyst located in the Pineal Gland in the brain. Most are small (>5mm) and these small cysts are common, and often an incidental finding on MRI. Small cysts do not cause symptoms.
Larger Cysts (<10mm) are more rare, and may be symptomatic. The importance of Pineal Cysts is that they cannot be distinguished from Pineal Tumours on MRI alone. Larger cysts, or cysts with irregular features may actually be a Cystic Pineocytoma, a slow growing malignant pineal tumour. But a tumour cannot be definitively diagnosed without tissue samples, which involves invasive surgery. If it is a Cystic Pineocytoma, the prognosis is excellent, when the tumour is completely removed surgically. Treatment also sometimes requires radiation and chemotherapy in severe cases. The five year survival rate is 86%, so if you have to have a brain tumour, this is a good one to have.
Most masses are more harmless cysts, however. Accurate imaging with contrast can often distinguish a benign Pineal Cyst from a much more serious Pineal Tumour. In some cases there is no way to be certain without taking a sample of, or removing the mass.
What is the pineal gland
The pineal gland is a small, pine one shaped gland located behind the third ventricle of the brain, deep in the centre of the brain. The pineal gland produces Melatonin which is the hormone that regulates sleep that regulates sleep patterns in seasonal and daily circadian rhythms.
Studies on rodents suggest other potential functions of the pineal gland include regulating the pituitary’s release of sex hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH) and also protection against neurodegeneration.
Pineal Cyst Symptoms
When Pineal Cysts cause symptoms, it is generally because of the accumulation of cerebrospinal fluid, and the growth of the cyst putting pressure on and compressing adjacent brain structures.
The symptoms include:
Headaches are the most common presenting symptom. Most commonly chronic, intermittent headaches, short term sudden headaches, or painful, persistent headaches.
Blurred vision / double vision
Balance problems / dizziness
Hydrocephalus (the abnormal enlargement of the brain ventricles due to a build up of cerebrospinal fluid (CSF)
Paralysis in upward gaze (Parinaud’s syndrome)
In rare, more serious cases, there may be seizures and loss of consciousness, and bleeding into the cyst, which can lead to death.
Pineal Cyst Treatment
In the vast majority of cases, no treatment is required. If the cyst is small, and not causing symptoms, it is not addressed unless it does start to cause symptoms.
Some sources say a cyst smaller than 10mm will not cause symptoms. Other sources say 5mm is enough to cause symptoms. So treatment is contentious.
Because of the difficult to reach location of the pineal gland, the ‘wait and see’ approach is most often recommended.
Larger non symptomatic cysts, larger than 5mm (some sources say 10mm), should be followed up annually to check for growth. Again some say if the cyst is asymptomatic, yearly imaging is unnecessary, so this is again contentious.
Symptomatic, larger cysts require treatment and need to be examined more closely and positively differentiated from the more serious Pineal Tumour (pineocytoma). Some pineal tumours may be cystic in appearance on imaging, and cannot be distinguished from a pineal cyst without microscopic examination of the tissue. Therefore the finding of a larger pineal cyst can cause significant anxiety, because pineal cysts and tumours are located deep within the midbrain, and are not easily reached surgically to remove. And the only treatment for a symptomatic cyst or tumour is surgical removal.
Surgical techniques include craniotomy, which is open brain surgery, and it can be an aggressive and very intrusive procedure, with the risk of exposing the patient to brain hemorrage or brain injury. The recovery is long, up to a year.
A less invasive option is endoscopy, where a thin, flexible tube is surgically inserted into the brain and remove the cyst completely. Recover is much quicker, often only 3 nights in hospital and full recovery in several weeks.
A pineal tumour, such as a pineocytoma, may also require radiation treatment, or chemotherapy if it is a more malignant tumour. Treatment is highly individual and depends on the size of the pineal cyst, or tumour, where it is located, whether it is malignant, and the symptoms it is causing. Each case and treatment is highly unique.