An Ommaya reservoir is a plastic, dome-shaped device inserted underneath the skin on your scalp. The dome is connected to a catheter placed in the ventricle of your brain where the cerebrospinal fluid (CSF) circulates.
Doctors can use an Ommaya reservoir to inject medicine into the fluid around your brain and spinal cord or aspirate the fluid for testing.
LMD occurs when cancer cells from primary tumors enter the CSF or leptomeninges, the inner lining of the brain and spinal cord. Cancer patients who develop LMD may receive intrathecal chemotherapy as part of their treatment.
“An Ommaya can be placed to allow the delivery of chemotherapy directly to the cerebrospinal space. Doing so allows us to bypass the blood-brain barrier,” says O’Brien. “It can be a more effective, direct way of delivering chemo to some patients with LMD.”
“After the patient is asleep, we can use a stereotactic navigation system to select the location to guide the catheter into the patient’s ventricle,” says Weinberg.
The surgeon makes a large, C-shaped incision in the scalp and drills a small hole in the skull.
“We intentionally make the incision big because we cut all the nerves that bring pain to the flap overlying the dome,” explains Weinberg.
This means the patient will feel no pain any time chemotherapy is injected into the dome.
“We make a small nick in the brain tissue and then use the navigation system to guide the catheter through the hole we drilled and into the ventricle,” explains Weinberg. “Once it’s in the ventricle, we test to make sure we’re getting CSF flowing freely from the catheter.”
The Ommaya reservoir is secured with sutures to ensure it stays in place. The procedure typically takes 20 to 40 minutes.
Doctors will take a CT scan after the procedure to make sure the tip of the catheter is in the correct location and there’s no bleeding. Patients stay in the hospital overnight. If there are no issues, you can go home the following morning.
How do you care for an Ommaya reservoir after placement?
The most important thing is to make sure the wound heals properly.
“We don’t want the wound to get infected, so you must allow it to heal. That can take anywhere from 10 to 14 days,” says Weinberg. “Even then, the wound is still delicate, so make sure not to scratch or pick at it. You can exercise, but swimming is not recommended. It’s best to avoid contact sports for about a month following surgery.”
Check with your doctor to see when you can resume normal activities.
Are there any risks associated with an Ommaya reservoir?
Risks can include:
If the Ommaya reservoir is placed or ends up in the wrong location, you must see a neurosurgeon to get it repositioned.
If there’s a small amount of blood visible on a scan, your doctors may monitor for additional bleeding and do another CT scan. If bleeding is significant, you’ll need surgery to have the blood clot removed. This is extremely rare.
If the wound gets infected, you will need surgery to have the Ommaya reservoir removed.
How is an Ommaya reservoir used in leptomeningeal disease treatment?
MD Anderson’s Brain and Spine Center offers an Ommaya clinic for patients on Mondays and Thursdays. LMD patients with Ommaya reservoirs usually begin receiving chemotherapy twice a week.
When a patient visits the clinic, a neuro-oncology advanced practice provider (APP) cleans and sterilizes the area on the head. Then the provider inserts a needle into the reservoir and removes a small amount of fluid. This is known as an Ommaya reservoir tap.
“The fluid is sent to the lab for testing, and some of the fluid is earmarked for research if the patient has consented to a research study,” says O’Brien. “After the fluid is withdrawn, the provider injects chemo into the Ommaya reservoir.”
CSF cytology identifies cancerous cells in the fluid and helps doctors assess how well patients are responding to treatment. Research testing helps doctors learn more about the underlying biology of LMD, in part by assessing the molecular profile of the tumor.
Some patients may experience headaches, neck pain or nausea after the procedure. Doctors work with patients to manage these symptoms by adjusting the amount of fluid taken or prescribing steroids to reduce inflammation that may occur from injecting chemo.
“Patients typically follow up with their neuro-oncologist every four weeks while on treatment, and we reassess with imaging of the brain and spine every eight weeks to make sure the treatment is effective,” says O’Brien. “At eight weeks, if the treatment is working and all parameters look good, we consider decreasing the frequency of the Ommaya reservoir taps. It may go from twice a week to once a week or from once a week to every other week.”
Is an Ommaya reservoir the same as a shunt?
No. A shunt is commonly used in patients who have a blockage in their CSF pathway, causing fluid to accumulate in the brain.
“We will surgically place a shunt in the brain to help drain excess cerebrospinal fluid from the brain and transport it to another part of the body, where it gets reabsorbed back into the bloodstream,” says Weinberg. “The Ommaya reservoir – while we can attach a shunt to it, if necessary – is specifically placed to be used only when needed. There’s no continuous draining of fluid.”
How do you determine who is a good candidate for an Ommaya reservoir?
An LMD patient may have an Ommaya reservoir placed if doctors determine intrathecal chemotherapy is the best way to treat the disease. But it isn’t right for everyone.
“For instance, intrathecal chemotherapy only penetrates a few millimeters, so this therapy is not expected to help patients who have bulky or nodular LMD,” says O’Brien.
She carefully reviews the imaging to determine if the type of LMD the patient has can be appropriately treated by intrathecal chemo.
“If a patient functions well, doesn’t have any significant neurologic symptoms and has options to treat any active cancer outside of their leptomeninges, then they may be a good candidate for intrathecal chemotherapy via an Ommaya reservoir,” she says.
The goal of intrathecal chemo is to keep LMD under control, not manage symptoms. It’s important to have honest, realistic conversations with your doctors about your goals. Some patients want doctors to do whatever’s possible to help them make it to a special milestone in their lives. Other patients place more importance on quality of life and do not want to travel back and forth to a clinic twice a week to receive chemo.
“LMD can be tough to treat, so we must consider our options carefully,” says O’Brien. “A nice thing about intrathecal chemotherapy is it only treats the leptomeningeal compartment, so patients can often continue receiving systemic therapy without concerns of their treatments interfering with one another.”