QuantitativeEvaluationof CerebrospinalFluidShunt Flow

We describea rigorousmethodfor measuringthe flow of cerebrosplnal fluid (CSF) InshuntcircuitsImplanted forthereliefofobstructive hydrocephalus. Clear anceof radioactivity for severalcalibratedflowrateswasdeterminedwitha Har yardInfusionpumpby Injectingthe Rickhamreservoirof a Rlckham-Holter valve systemwith100j@Cl ofTc-99maspertechnetate. Theellipticalandthe cylindrical Holtervalvesusedasadjunctvalveswiththe Rlckhamreservoiryieldedtwodiffer ent regression lineswhenthe clearanceswere plottedagainstflowrates.Thecx perimentalregressionlineswere usedto determinethe In vlvoflow rates from clearancescalculatedafter Injectingthe Rickhamreservoirsof the patients.The uniqueclearancecharacteristics oftheindividual shuntsystemsavailablerequires that calIbratIoncurvesbe derivedfor an entiresystemidenticalto oneImplanted in the patIentbeingevaluated,ratherthan justthe injectedchamber.Excellent correlationbetweenflow ratesandthe clinicalfindingssupports the reliabilftyof thismethodof quantification of CSFshuntflow,andthe resultsare fullyaccepted by ourneurosurgeons.