Test characteristics of quick brain MRI for shunt evaluation in children: an alternative modality to avoid radiation

Abstract

OBJECT Quick brain magnetic resonance imaging (QB-MRI) is a rapid, radiation-free technique to detect life-threatening CSF shunt malfunction. QB-MRI has not been widely studied or adopted. The primary objective of this study was to evaluate the test characteristics of QB-MRI for detecting shunt malfunction. Test characteristics of brain computed tomography (CT) and QB-MRI were then compared. Secondary objectives included comparison of time to study completion and use of sedatives for both modalities, as well as comparison of time to study completion for QB-MRI before and after implementation of a Pediatric Emergency Department (PED) shunt clinical pathway. METHODS A retrospective chart review was performed at 2 tertiary care hospital PEDs. The authors reviewed the charts of children who underwent QB-MRI or CT for suspected shunt malfunction between July 2008 and June 2012. They also reviewed the patients' neuroradiology reports and classified ventricular size as positive (enlarged) or negative (normal, smaller, or unchanged). Shunt malfunction was defined by surgical revision within 30 days. RESULTS Nine hundred ninety-seven PED visits (involving 724 QB-MRIs and 273 CTs) were included. Surgical revision was performed in 235 cases (23.6%). For QB-MRI, sensitivity was 58.5% (95% CI 51.1%–65.6%) and specificity was 93.3% (90.8%–95.3%). For CT, sensitivity was 53.2% (95% CI 38.1%–67.9%) and specificity was 95.6% (92%–97.9%). The mean time to completion of QB-MRI was 115 minutes versus 83 minutes for CT (difference 32 minutes, 95% CI, 22–42 minutes, p < 0.001). The mean time from presentation to completion of QB-MRI prior to application of the CSF shunt pathway was 132 minutes versus 112 minutes after application of the CSF shunt pathway (difference 20 minutes, 95% CI 5–35 minutes, p = 0.01). Anxiolytic medications were used in 3.7% of CT studies and 4.4% of QB-MRI studies (p = 0.74). CONCLUSIONS QB-MRI and CT have similar test characteristics for detecting CSF shunt malfunction in children and similar requirements for sedation. The longer interval from order placement to imaging completion for QB-MRI is arguably justified by reduction of radiation exposure in this population subject to frequent brain imaging.