Object: The accurate placement of cerebral ventricular shunt catheters in hydrocephalus is an important clinical problem. Malfunction of shunts remains their most common complication and greatest liability, and the influence of catheter position on shunt function remains poorly defined. The objectives of this study were as follows: 1) determine the accuracy of intraventricular catheter placement with respect to a historically favored target, defined as a 1-cm radius sphere at the anterior lip of the ipsilateral foramen of Monro; 2) confirm that this target represents a satisfactory site for frontal and occipital catheter placement by examining whether inaccuracy is associated with more shunt failures; and 3) determine whether catheter trajectory, use of image confirmation, or other factors are associated with either the accuracy or the longevity of shunts.
Methods: A retrospective cohort analysis was conducted on 236 patients with 426 ventricular shunts placed or revised at the University of Minnesota over a 10-year period.
Results: Accuracy of shunt placement was optimal in 43.9% of patients and suboptimal or poor in 56.1% of patients. Time to failure was significantly affected by the accuracy of catheter placement with respect to the ipsilateral foramen of Monro, with a 57% higher risk of failure with suboptimal placement (hazard ratio [HR] 1.57, 95% CI 1.26-1.96; p < 0.001) and a 66% higher risk with poor placement (HR 1.66, 95% CI 1.45-1.89; p < 0.001) relative to optimal placement. The odds of highly suboptimal or unacceptable placement were significantly increased by lack of any intraoperative imaging (OR 5.89, 95% CI 2.36-14.65; p < 0.001). Use of a nonfrontal posterior trajectory also showed a trend toward poor placement (OR 1.64, p = 0.138).
Conclusions: The historical target for catheter tip placement within 1 cm of the foramen of Monro in the ipsilateral lateral ventricle was associated with significantly longer revision-free survival compared with other locations. This effect remained significant after adjusting for age and whether there was a prior history of shunting. The accuracy of catheter placement in both pediatric and adult patients was strongly associated with use of intraoperative fluoroscopic confirmation. In analyses comparing intraoperative fluoroscopy and no imaging, there was a non-statistically significant difference in the 3-year time to failure, but the worst-case scenario of catastrophic short-term failure was almost completely avoided with fluoroscopy. The authors conclude that accuracy of placement is critical for shunt survival, and that use of intraoperative imaging confirmation may optimize outcomes by avoiding the majority of unacceptable placements.