Single- and dual-task gait assessment before and after cerebrospinal fluid drainage in suspected idiopathic normal pressure hydrocephalus: Dual-task walking identifies additional responders

BACKGROUND: Gait change after cerebrospinal fluid drainage (CSFD) in idiopathic normal pressure hydrocephalus (iNPH) is usually assessed during single-task walking. Dual-task gait assessment may provide additional diagnostic value, as both gait and cognition are commonly impaired in iNPH. METHODS: We analyzed GAITRite gait data from 122 patients with suspected iNPH before and after CSFD and from 146 cognitively healthy controls assessed once. Normal walking, working memory dual-task walking, semantic memory dual-task walking, and fast walking were examined. Eight parameters were analyzed across single- and dual-task conditions; fast walking was used to derive gait speed reserve. Exploratory responder analyses defined response per parameter as improvement ≥ 75th percentile of within-sample change and an absolute change ≥ 10% of the baseline group mean. Two sensitivity analyses applied combinations of lower and higher thresholds. RESULTS: Compared with controls, patients showed gait impairment across most parameters and walking conditions. After CSFD, most parameters improved, and gait velocity showed the largest within-condition standardized effect size. Pre-post effects were generally largest during normal walking. Under the primary responder model, 84 patients responded during normal walking, 85 during the working memory dual-task, and 72 during the semantic memory dual-task; 43 responded in all three conditions and 9 in none. Importantly, 25.7% of responders were identified only through dual-task conditions, while under the stricter model, 45.3% of responders would have been missed by normal walking alone. CONCLUSION: Normal walking captured the largest average gait changes after CSFD, but dual-task assessment added individual-level diagnostic information by identifying responders missed by normal walking.