248. Pediatric CSF Shunt Flow is Low – Protect the Natural CSF Absorption Pathways

Authors: Jeffrey R. Leonard, MD, FAANS (Columbus, OH)

Introduction:

CSF production in pediatric hydrocephalus patients is either absorbed through natural pathways or flows through CSF shunts.  Due to a lack of data on in vivo (non-EVD) shunt flow rates, the relative importance of each CSF path is unclear.  We analyzed shunt flow data from ShuntCheck, a non-invasive, thermal shunt flow test, to assess shunt vs natural absorption.

Methods:

A prospective, multi-center study tested 215 symptomatic pediatric hydrocephalus patients (age 3 to 29) and determined through 7 day outcome that 185 patients were “false alarms” and had patent shunts.  Thirty patients were determined to have a shunt malfunction and underwent surgery. Animal and bench model data submitted to the FDA demonstrated a linear correlation between shunt flow rates and the thermal responses reported by ShuntCheck.  It also established that ShuntCheck’s Flow Confirmed threshold of 0.2°C correlated with shunt flow of 4.0 ml/hr.  Using flow rates determined in animal models, the test’s thermal readings were correlated to cerebral spinal fluid flow rates. Flow rates were then calculated in the 185 patent shunt patients to determine average and range of CSF flow rates.

Results:

ShuntCheck thermal data indicates that the mean and median flow rate was 4.4 ml/hr with a range of 0 (due to intermittent shunt flow) and 19.4 ml/hr.  90% of patients had flow rates < 8 ml/hr.  This compares to CSF production of 20 ml/hr.

Conclusion:

This suggests a majority of CSF is absorbed through natural pathways, and  natural pathways are at least partially functional in a large number of shunted patients. This also suggests that the most effective strategies in hydrocephalus treatments  are to encourage the natural pathways to handle excess spinal fluid.