Since the invention of the Ommaya reservoir in 1963 [18], its use has evolved from the intra-CSF delivery of antifungal medications for which it was originally designed [19], to become the primary method of administering chemotherapeutic agents intraventricularly. Over the past two decades, as neuronavigation has gained prominence and become the standard of care for many neurosurgical procedures, its use in Ommaya placement has been frequently evaluated along with other surgical adjuncts such as endoscopy [11-14,16]. A meta-analysis by Lau et al. reviewed the operative complications of 43 pooled Ommaya studies, and reported an improvement in total surgical complication rate from 13.6% with conventional freehand placement to 6% with image navigation [14]. However, that study which is reportedly the largest observational analysis of operative Ommaya outcomes noted a higher risk of hemorrhage in image-guided surgical placements (3.4%) versus non image-guided placements (2.4%). Other complications such as catheter malfunction, malposition, early infection and mortality were shown to have a slight benefit with image guidance at rates of 2%, 2.3%, 0.7% and 0.6% respectively. Our results compare favorably with those of the meta-analysis as we had a 0% rate of catheter malfunction, infection, hemorrhage, CSF leak or pseudomeningocele. Of the 5 patients still alive at the time of data analysis, 3 (60%) were patients with carcinomatous meningitis from breast cancer, one had ALL and the other had Hodgkin lymphoma. Our longest surviving patient (2177 days post-placement) was the only one with a diagnosis of Hodgkin lymphoma which speaks to the curative nature of aggressive treatment in patients with this disease. Even though our long-term mortality rate for leptomeningeal breast cancer was 62.5% (5/8), the second longest surviving patient (1421 days post-placement) was a breast cancer patient. However, she had a favorable molecular profile; estrogen, progesterone and Her2 positive, thereby highlighting the heterogeneity of breast cancer and the importance of molecular and genetic factors as prognostic indicators.
Endoscopic placement
All the cases in our series utilized endoscopy assisted catheter placement and 90% of the cases used endoscopy alone without image navigation. We believe that direct visualization of the catheter tip within the ventricle using the endoscope provides a real-time visual confirmation of adequate placement which is not possible with other surgical adjuncts. There have only been a few publications that have mentioned the endoscopic-assisted Ommaya placement, and most of them have focused on placement into cystic craniopharyngiomas [11, 20-22]. Although a direct outcome-based comparison between image-guided placement and endoscopically placed Ommaya catheters have not been published, Wang et al. performed a retrospective cost-benefit analysis of placing Ommaya reservoirs with image guidance alone versus a combination of image guidance and neuroendoscopy [13]. This comparison revealed a cost benefit of $4784 savings per patient with the endoscope group due to the high complication-associated costs of two mispositioned catheters and one catheter-related hemorrhage in the image-guidance only group.
Timing of intraventricular administration
Very few published articles on Ommaya reservoirs have addressed the timing of intraventricular administration of chemotherapeutic agents after Ommaya placement. There is no consensus on the optimal or recommended time to start using Ommaya reservoirs after placement, and studies that have mentioned the time of use post-placement have varied from no earlier than 5 days postoperatively to as soon as 4 hours after implantation [15-17]. Classically, the recommendation to wait a few days prior to using an Ommaya reservoir post-placement was to allow for proper wound healing and to reduce the risk of backflow of the chemotherapeutic agent through the catheter tract [15]. However, there are no strong evidence for this stipulation although the rate of symptomatic leukoencephalopathy and neurotoxicity was reported to be 3% in a large series [17]. This compares to a 0% rate of neurotoxicity in our series and a 5% rate of asymptomatic leukoencephalopathy. With endoscopic placement of the catheter, the goal is to ensure that not only is the catheter within the ventricle, but all the holes of the catheter are intraventricular which would consequently limit the leakage of chemotherapy into the parenchyma.
Others have strongly recommended getting a postoperative head CT to confirm the location of the catheter tip prior to use [11]. In this review, we present the first report of intraoperative administration of chemotherapeutic agents immediately after Ommaya placement. Our 0% rate of wound dehiscence, infection, CSF leak, pseudomeningocele or symptomatic leukoencephalopathy provides evidence to counter the classic reasons and dogma to wait a few days prior to using Ommaya reservoirs post-placement. Patients with leptomeningeal disease and leukemic meningitis have a high risk of rapid disease progression and recent 12-month overall survival rates are as low as 10% with intra-CSF chemotherapy in patients with leptomeningeal breast cancer despite new molecular advances in therapeutic management [23]. It is therefore imperative to start intraventricular chemotherapy in these patients as soon as possible. In our experience, we have also seen delays in patients receiving their intraventricular drugs post-discharge from the hospital due to unforeseen insurance, administrative and logistical difficulties. By administering the intraventricular therapy intraoperatively, patients at least start getting therapeutic benefit immediately even if unforeseen situation arises postoperatively. Additionally, intra-operative delivery is comfortable for the patient under anesthesia and is not subject to availability of the oncologist to deliver the medicine in the next few days postoperatively. There are also increasing issues with oncologists who may not have hospital privileges of administering intraventricular chemotherapy as it is rare. Intraoperative delivery limits the risk of patients waiting for an oncologist to deliver chemotherapy at a later date when their schedule permits and allows same day surgery for Ommaya reservoir placement and intraventricular chemotherapy treatment.
The risk of encephalopathy and neurotoxicity particularly from intraventricular methotrexate has been shown to be reducible by avoiding simultaneous combination of systemic and intraventricular chemotherapy [24]. This is because high dose systemic methotrexate will result in cytotoxic CSF concentrations within 24 to 72 hours after administration [25]. Although, we defer chemotherapeutic regimen to the patients’ oncologist, it is advisable to avoid administering intraventricular methotrexate at the same time as systemic methotrexate.
Catheter Malpositioning
Our data revealed that endoscopic placement of Ommaya reservoir can be associated with a 100% rate of ventricular placement or a 95% rate of accurate positioning within the third ventricle, and a postoperative head CT is not necessarily mandatory prior to using Ommaya reservoir due to the visual confirmation afforded by endoscopy. However, we still obtained a postoperative head CT after the intraoperative drug infusion in order to establish an imaging baseline. It is important to note that regardless of the surgical adjunct employed for Ommaya catheter placement, there is always a small risk of catheter malpositioning, albeit, smaller than that observed with free-hand placement. As demonstrated by our single case with the catheter tip in the contralateral ventricle, endoscopic guidance is not fool proof. Sandberg et al. reported that of 5 patients who required Ommaya catheter repositioning, one had been placed with an endoscope, two catheters were placed under fluoroscopic guidance, one with the use of stereotactic techniques, and one without any intraoperative aids [11].