|Year : 2016 | Volume
| Issue : 6 | Page : 1202--1203
Ommaya reservoir placement: The focus on using neuronavigational guidance
Manish Singh Sharma
Department of Neurosurgery, Mayo Clinic School of Medicine, Department of Neurosurgery, Mayo Clinic Health System, Mankato, Minnesota, USA
Manish Singh Sharma
Department of Neurosurgery, Mayo Clinic School of Medicine, Department of Neurosurgery, Mayo Clinic Health System, Mankato, Minnesota
|How to cite this article:|
Sharma MS. Ommaya reservoir placement: The focus on using neuronavigational guidance.Neurol India 2016;64:1202-1203
|How to cite this URL:|
Sharma MS. Ommaya reservoir placement: The focus on using neuronavigational guidance. Neurol India [serial online] 2016 [cited 2019 Sep 20 ];64:1202-1203
Available from: http://www.neurologyindia.com/text.asp?2016/64/6/1202/193767
In the paper, “Elucidating the utility of neuro-navigation in reducing malposition rates in Ommaya reservoir placement: 23-year operative experience at the Louisiana State University,” the authors detail their extensive experience with the placement of Ommaya reservoirs, with and without the use of frameless stereotaxy. Of a total of 146 patients, 48 (33%) underwent reservoir placement via stealth-guided neuronavigation, while the remaining 98 patients (67%) had free-hand placement. Three patients (6.3%) in the neuronavigation group versus 8 (8.2%) in the nonstealth group had malpositioned catheters. One patient in either group (2.1% as opposed to 1.0% respectively) had an associated intracerebral hemorrhage. These data as well as the respective rates of infection did not reach statistical significance.
The authors attribute their higher rates of neuronavigation-related malposition, when compared to contemporary literature (0-1, 2%), to a learning curve when this technology was first introduced. Two of the three malpositions occurred in the first years of neuronavigation technology adaptation. They state that the use of frameless electromagnetic stereotaxy led to a decrease in malposition rates.
The authors are to be lauded for their meticulous data collection, intellectual honesty, and vast institutional experience. This is the single largest case series in world literature and very germane to the developing world where the use of the Ommaya reservoir has broader applications to include infectious meningitis and shunt failures. The cost of neuronavigational technology can be prohibitive in these settings and its acquisition may be deferred in favour of a microscopes, drills, bipolar electocautery, and intraoperative fluoroscopy. Moreover, the standard frameless infrared-based stereotaxy does not include the cost of electromagnetic tracking nor the cost of consumables., This data will be very reassuring to those without access to state-of-the-art technologies, especially when millimetric accuracy is not imperative. The computed tomographic images acquired for neuronavigational use also involve significantly more radiation during acquisition for three-dimensional modeling, which can be of concern in pediatric patients. In this subgroup, additional issues involve rigid pin fixation of the skull for infrared tracking.
Conversely, the merits of using neuronavigation cannot be debated if the technology is available. Intuitive reasoning would posit that malposition and hemorrhage rates would surely be higher in patients with slit ventricles, where my personal preference would be to use neuronavigation. A confounding factor that may have skewed the data in this paper towards statistical insignificance is that it does not account for the degree or, more importantly, lack of ventricular dilatation using, e.g., the Evan's ratio, as a predictor for using the neuronavigational tools. It would have been useful to know the average number of passes used to cannulate the ventricle in the free hand technique, and whether this correlated with the occurrence of hemorrhage and malposition.
In an ideal world, where resources flow freely and directly into the best possible patient care, intraoperative neuronavigation truly must be supplemented with real-time, post-reservoir placement imaging. This would immediately detect malposition and associated hemorrhage, allowing corrective steps to be instituted without the patient leaving the sterile operating room environment. Professionally, we are all too aware of the crushing disappointment of visualizing a catheter tip that is out of place and the blow to patient and surgeon morale that a return to the operating room involves.
Finally, in a resource-constrained environment, preoperative pneumoencephalography with intraoperative fluoroscopy may be an excellent tool for target acquisition and trajectory planning. Similarly, post Ommaya placement pneumoventriculography with intraoperative fluoroscopy may also assist in confirming a satisfactory catheter tip position.
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