Cognitive Processing Speed Assessment Combined With Gait Performance Improves Prediction of Shunt Surgery Responsiveness in Idiopathic Normal Pressure Hydrocephalus.

BACKGROUND: Idiopathic normal pressure hydrocephalus (iNPH) is a reversible neurological disorder. Cerebrospinal fluid tap test (CSF TT) is widely used to predict shunt surgery responsiveness, but its predictive performance remains limited, partly because cognitive evaluation has received insufficient emphasis. METHODS: 72 patients diagnosed with possible iNPH were enrolled and underwent CSF TT. Gait performance was assessed using the 5-m timed up and go test (TUG) and the 10-m walking test. Cognitive processing speed was assessed using the trail making test Part A (TMT-A) and the Symbol Digit Modalities Test (SDMT). Improvement rates at different time points were analyzed, and a combined predictive model (Combo model) was constructed using firth logistic regression. RESULTS: Cognitive processing speed progressively declined with increasing disease severity and showed strong correlations with gait abnormalities. Improvement rates at 24 h showed the highest or near-highest discriminative performance for shunt responsiveness across most measures. Both TMT-A and SDMT showed significant improvement at 24 h after CSF release. Optimal improvement rate thresholds were 50% for TMT-A and SDMT and 10% for TUG and 10-m walking test. The Combo model yielded an apparent AUC of 0.935. CONCLUSION: Cognitive processing speed reflects disease severity in patients with iNPH. Short-term improvement in cognitive processing speed after CSF release suggests potential benefits from shunt surgery. A combined model integrating cognitive processing speed and gait performance measures can substantially enhance the prediction of shunt surgery outcomes.