A ventricular reservoir is a small, surgically placed neurosurgical device that provides reliable access to cerebrospinal fluid (CSF), the fluid surrounding the brain and spinal cord. Implanted under the scalp, it creates a port for repeated medical procedures, allowing medical professionals to bypass the need for multiple, less convenient interactions. This design enables a long-term solution for diagnostic testing and the delivery of therapy directly to the brain environment.
Defining the Reservoir and Its Location
A ventricular reservoir is a two-part system consisting of a small dome and a catheter. The dome is typically made of soft plastic, such as silicone, and is roughly the size of a quarter. This component is surgically secured beneath the patient’s scalp, where it often presents as a small, palpable bump. One widely recognized proprietary name for this type of device is the Ommaya reservoir.
The dome features a self-sealing membrane that allows for multiple punctures without leakage, serving as the main access point. Connected to the dome is the catheter, a flexible tube guided through a small opening in the skull. The catheter extends into one of the brain’s ventricles, the fluid-filled spaces where CSF is produced and circulates. This placement ensures direct communication between the external port and the internal fluid system.
Primary Medical Applications
The primary purpose of a ventricular reservoir is to enable long-term, direct interaction with the CSF for two main indications: diagnostic sampling and therapeutic drug delivery. The reservoir allows medical teams to safely and repeatedly draw CSF samples for testing. This testing is used to monitor pressure, detect infections, or search for cancerous cells.
The second major application is intrathecal drug delivery, administering medication directly into the CSF space. This method is particularly important for treating cancers that have spread to the meninges, a condition known as leptomeningeal carcinomatosis. Since the blood-brain barrier prevents most chemotherapy drugs from reaching the central nervous system effectively, injecting medication directly into the reservoir bypasses this barrier, ensuring the medication reaches the target area at a therapeutic concentration. The reservoir can also be used for the chronic drainage of CSF to manage conditions like hydrocephalus, especially in infants, by intermittently relieving excessive fluid pressure until a more permanent solution, like a ventriculoperitoneal shunt, can be placed.
The Implantation Procedure
Implanting a ventricular reservoir is a neurosurgical procedure typically performed under general anesthesia. The neurosurgeon prepares a small area of the scalp, makes an incision, and carefully drills a burr hole into the skull to access the brain’s interior.
Using specialized tools, the surgeon inserts the catheter through the burr hole until the tip rests accurately within a ventricle. Once positioned, the reservoir dome is secured beneath the scalp tissue and connected to the catheter. The scalp incision is then closed. The entire procedure is considered minimally invasive, generally lasts about one hour, and often requires a short hospital stay for post-operative monitoring.
Access and Potential Complications
Accessing the ventricular reservoir requires a procedure called a reservoir tap, performed under strict sterile conditions. A specialized needle is inserted through the skin and the dome’s self-sealing membrane into the reservoir chamber. The needle is used to either aspirate CSF for testing or to inject therapeutic agents like chemotherapy or antibiotics.
The frequency of access depends on the medical need, ranging from daily taps for temporary drainage to intermittent taps for drug administration. The most significant potential complication is infection of the reservoir or surrounding tissue, which can lead to meningitis. Other risks include catheter malfunction or obstruction, where the tube becomes blocked and prevents fluid flow. There is also a small risk of cerebrospinal fluid leakage at the puncture site or intracranial bleeding during or after the placement procedure.