The Ommaya reservoir is a plastic, dome-shaped device, with a catheter (thin tubing) attached to the
underside used to deliver chemotherapy (anticancer drugs) to the central nervous system (CNS or brain and spinal cord).
Purpose
Chemotherapy may be administered to patients by various methods depending on the type of cancer being treated. Some cancer types respond well to chemotherapy given by intravenous (IV) injection, and some cancer types may be treated with oral medication. In both cases, the chemotherapy reaches its target site systemically (carried by the blood). Cancers that affect the CNS pose a special challenge. Systemically delivered drugs seldom reach the CNS because of a network of blood vessels that surround the brain. This protective shield is called the blood-brain barrier. It acts as a filtering device for the brain by blocking the passage of foreign substances from the blood to the CNS. To avoid the obstacle created by the blood-brain barrier, alternative delivery treatments must be used. These treatments are collectively called intrathecal chemotherapy treatments. These treatments require injecting the chemotherapy directly into the cerebrospinal fluid (CSF). The CSF is the clear fluid surrounding the CNS. An oncologist (a physician specializing in cancer study and treatment) will determine the frequency of the treatment schedule and will decide if it is better for the patient to receive intrathecal chemotherapy injections directly into the spinal column or through an Ommaya reservoir implanted in the brain. The Ommaya reservoir may be used in several ways. Its primary function is to facilitate the uniform delivery of the intrathecal chemotherapy. By implanting the Ommaya reservoir, multiple rounds of chemotherapy may be given through a single access site, thereby increasing patient comfort and reducing the stress and pain associated with repeated spinal injections. The Ommaya reservoir also serves as a sampling site for removal of CSF. Samples are withdrawn an analyzed for the presence of abnormal cells. Some physicians utilize the reservoir to deliver pain medication, and more recently, trials have been conducted to test the efficacy of using the Ommaya reservoir to deliver gene therapy (treating a disease caused by a malfuncting gene, by introducing a normal gene back into the diseased individual) to cancer patients.
Precautions
High-dose chemotherapy drugs such as methotrexate may produce toxic effects if the reservoir or catheter becomes compromised. For infants and children being considered as candidates for an Ommaya reservoir implant, the age of the patient should be considered. Some studies have suggested that infants may be at a higher risk for post-treatment neurologic and endocrinologic
problems, cognitive (learning) disabilities, and higher infant mortality when high-dose chemotherapy agents are administered via the Ommaya reservoir. These conditions are significantly reduced in adult patients. Any patient compromised by a pre-existing suppressed immune system should make the physician aware of this condition so the choice of chemotherapy and specific protocols for administering the drugs are employed.
Description
Placement of the Ommaya reservoir requires a minor surgical procedure with the patient placed under general anesthesia. The procedure is performed in the hospital by a neurosurgeon (a physician specially trained to perform surgery on the brain or spinal cord). The reservoir is placed under the scalp with the catheter positioned into the cavity of the brain where the CSF is formed. Once in place, chemotherapy treatments using the Ommaya reservoir may be conducted as outpatient visits either in the hospital, the home, or a satellite clinic staffed by specially trained healthcare professionals. To perform an Ommaya reservoir tap (CSF sampling and chemotherapy delivery) requires 15-20 minutes with little or no pain to the patient. Basic guidelines for the tap include:
Gently pump the reservoir to allow the reservoir to fill with CSF.
Clean the area with alcohol and iodine solution, maintaining a sterile field.
The healthcare professional will insert a small needle into the reservoir and slowly withdraw a sample of CSF.
The chemotherapy will be delivered by slowly injecting the prescribed medication into the reservoir.
The needle is removed and the site covered with sterile gauze.
Light pressure is applied, and the reservoir is gently pumped to enhance uniform distribution of the chemotherapy into the CSF.
The site is covered with a Band-Aid.
Preparation
Placement of the Ommaya reservoir will require a minimal stay in the hospital. The surgeon will provide detailed pre-operative instructions for the patient prior to the hospital visit. Post-operative recovery will monitor vital signs and watch for possible side effects from the anesthesia. Before the patient is discharged, an initial round of chemotherapy administered via the Ommaya reservoir will be performed to assure the device is working properly. No special preparations are required for routine scheduled chemotherapy treatments.
Aftercare
Following an Ommaya tap, the patient may participate in all normal activities. Hair may be washed. There are no special requirements for care of the reservoir site; however, a physician should be notified if symptoms appear such as a spike in fever, headaches with or without vomiting, neck stiffness, tenderness, redness, or drainage at the access site of the reservoir.
Risks
The most common risks associated with the use of the Ommaya reservoir primarily deal with complications due to malposition or malfunction of the device. Either condition may result in blockage or leakage of the catheter, leading to improper drug delivery. Lesions may develop along the catheter, infection may develop, and chemotherapy may reach toxic levels. In cancer patients scheduled for surgical intervention, who have previously received chemotherapy via an Ommaya reservoir, there is some evidence of increased perioperative (between admission and discharge from hospital) morbidity due to a diseased condition existing at the time of surgery.
Normal results
Patients may expect successful delivery of the intrathecal chemotherapy during each treatment session with minimal discomfort. It should be noted, however, that the chemotherapy delivered by the Ommaya reservoir works on cells that are actively growing and dividing. This means both cancer cells and certain normal cell types may be affected and may result in side effects. Depressed blood cell counts may lower resistance to infection and increase susceptibility to bruising and bleeding. There may be an overall decrease in energy levels. Hair loss (alopecia) may occur, and cells of the digestive tract may be damaged resulting in bouts of nausea and vomiting, and mouth sores. For female patients, symptoms of menopause may develop, and in males, sperm production may stop.
Abnormal results
Severe complications associated with drug delivery could occur. Due to improper function of the reservoir, toxic levels of chemotherapy could induce behavioral abnormalities, confusion, dementia, irritability, convulsions, sensory impairment, damage to pulmonary and renal function, and patient death.
Resources
BOOKS
Davson, Hugh, and Malcolm B. Segal. Physiology of the CSF and Blood-Brain Barriers Boca Raton: CRC Press Inc., 1996.
Meyer, Fredric B. Atlas of Neurosurgery, Basic Approaches to Cranial and Vascular Procedures. Philadelphia: Churchill Livingstone, 1999.
PERIODICALS
Hakim, A., et al. "Ommaya Catheter-Related Staphylococcus Epidermidis Cerebritis and Recurrent Bacteremia Documented by Molecular Typing." European Journal of Clini cal Microbiology and Infectious Disease 19 (2000): 875-877.
Stone, J.A., et al. "Leukoencephalopathy Complicating an Ommaya Reservoir and Chemotherapy." Neuroradiology 41 (1999): 134-136.
OTHER
Adult Brain Tumor Treatment Information for Physicians. 1999 CancerLinksUSA com, Inc. 01 April 2001 <http://cancerlinksusa.com>
