Two signs indicative of successful access in nuclear medicine cerebrospinal fluid diversionary shunt studies

Successful shunt access is the first step in a properly performed nuclear medicine cerebrospinal fluid (CSF) shunt study.

To determine the significance of the radiotracer configuration at the injection site during initial nuclear medicine CSF shunt imaging and the lack of early systemic radiotracer activity as predictors of successful shunt access.

With Institutional Review Board approval, three nuclear medicine physicians performed a retrospective review of all consecutive CSF shunt studies performed in children at our institution in 2015. Antecedent nuclear medicine CSF shunt studies in these patients were also assessed and included in the review. The appearance of the reservoir site immediately after radiotracer injection was classified as either figure-of-eight or round/ovoid configuration. The presence or absence of early systemic distribution of the tracer on the 5-min static images was noted and separately evaluated.

A total of 98 nuclear medicine ventriculoperitoneal CSF shunt studies were evaluated. Figure-of-eight configuration was identified in 87% of studies and, when present, had 93% sensitivity, 78% specificity, 92% accuracy, 98% positive predictive value (PPV) and 54% negative predictive value (NPV) as a predictor of successful shunt access. Early systemic activity was absent in 89 of 98 studies. Lack of early systemic distribution of the radiotracer had 98% sensitivity, 78% specificity, 96% accuracy, 98% PPV and 78% NPV as a predictor of successful shunt access. Figure-of-eight configuration in conjunction with the absence of early systemic tracer activity had 99% PPV for successful shunt access.

Figure-of-eight configuration at the injection site or lack of early systemic radiotracer activity had moderate specificity for successful shunt access. Specificity and PPV significantly improved when both signs were combined in assessment.