Adaptive method for assessment of cerebrospinal fluid outflow conductance.

Outflow conductance (C(out)) is important for predicting shunt responsiveness in patients with suspected idiopathic adult hydrocephalus syndrome (IAHS). C (out) is determined by performing an infusion test into the cerebrospinal fluid system, and the reliability of the test is dependent on the measurement time. The objective of this study was to develop an adaptive signal analysis method to reduce the investigation time, by taking the individual intracranial pressure variations of the patient into consideration. The method was evaluated on 28 patients with suspected IAHS. The results from full time investigations (60 min) were compared to the results of the new algorithm. Applying the new adaptive method resulted in a reduction of mean investigation time by 14.3 +/- 5.9 min (mean +/- SD), p<0.01. The reduction of reliability in the C(out) estimation was found clinically negligible. We thus recommend this adaptive method to be used when performing constant pressure infusion tests.