Pineal Tumors

Pineal region tumors come from the pineal gland which in humans doesn't do very much at all. The pineal gland is located at the posterior extent (back) of the third ventricle and extends over the tectal plate of the midbrain. This structure controls eye movements, particularly the ability to look upwards. In addition, the tectal plate sits over the Sylvian Aqueduct - a thin tube within the midbrain through which ventricular fluid flows. Pressure on the tectal plate results in obstruction of the aqueduct and a build up of ventricular fluid in the lateral and third ventricles. This is called obstructive hydrocephalus which can cause headaches, coma and eventually death if not treated.

There are a number of different cells in the pineal gland which can grow into a tumor. The pinealocyte, the cell with the greatest number in the gland, can transform into a pinealocytoma (pinealoma) or to the malignant pinealoblasoma. Primative cells within the pineal gland can give rise to germinomas or teratomas or so-called yolk sac tumors. Teratomas which are usually benign can turn into teratocarcinomas which can be highly malignant. Finally, the pineal has glial cells and these can develope into astrocytomas, oligodendrogliomas, mixed gliomas. Pilocytic astrocytomas can develope in this area also.

The symptoms of a pineal tumor are diplopia, loss of the ability to look upward and symptoms related to hydrocephalus and increased intracranial pressure. These lesions may be detected on CT scanning but are very well seen on MRI which defines the tumor and the surrounding anatomy very well. Germinomas are almost always found in male patients. A tissue diagnosis with tissue obtained at surgery is required for proper and effective treatment.

Pineal tumors are in contact with the spinal fluid and can seed the CSF. Malignant tumors such as pinealoblastomas, germinomas, yolk sac tumors and malignant teratomas can drop metastases in the CSF to the spine or elsewhere in the brain - to anywhere that CSF flows. This is why these lesions must be treated with chemothereapy or cranio-spinal irradiation therapy following surgery.

The best treatment for any pineal tumor is to take it out. There are two surgical routes : infratentorial (exposure above the cerebellum) and transtentorial (exposure between the two halves of the brain along the falx and though an incision made in the tentorium). Each has their advantages and disadvantages and the choice usually rests with the preference of the surgeon. In some cases stereotactic biopsy may be used to establish the tissue diagnosis in patients who may just receive radiation or chemotherapy. This may be the case in young males thought to have a germinoma or in elderly patients who may not tolerate an open surgical procedure. Some believe in stereotactic radiosurgery for these lesions.