Gait impairments may predict falls risk in idiopathic Normal Pressure Hydrocephalus: Evidence from 3D motion analysis

Introduction:
Falls are a major source of injury and loss of independence in older adults, particularly in those with subtle or central gait control impairments. Idiopathic Normal Pressure Hydrocephalus (iNPH), a treatable cause of gait disturbance in later life, presents with balance and mobility deficits that often precede overt falls. Yet current diagnostic assessments rely on simple testing that may underestimate risk. This study used three-dimensional (3-D) motion analysis to identify gait features in iNPH that may signal heightened falls vulnerability.

Method:
Twenty-three individuals with clinically diagnosed iNPH and eighteen age-matched healthy controls underwent 3-D motion capture during overground walking (Qualisys AB, Sweden). Ground reaction forces were recorded via embedded force plates, and kinematics were processed in Visual3D using a full-body model. Spatiotemporal parameters (gait speed, stride length, cycle time, step width) were compared between groups (independent-samples t-tests;Mann–Whitney U tests). Continuous joint kinematic data (pelvis, hip, knee, ankle angles) were analysed using one-dimensional Statistical Parametric Mapping (SPM{t}) to identify significant waveform differences across the gait cycle (α = 0.05).

Results:
Compared with controls, the iNPH group walked more slowly (–60%), with shorter stride length (–52%) and wider step width (+64%) (p<.001). Kinematic analysis revealed reduced hip extension, delayed and diminished knee flexion during swing, and attenuated ankle dorsi/plantarflexion in the iNPH group, indicating impaired limb clearance and reduced propulsion. These deficits collectively suggest compromised supraspinal coordination and reduced foot–ground clearance, both of which substantially increase tripping risk.

Conclusions:
Three-dimensional motion capture reveals distinct gait alterations in iNPH that correspond to known falls mechanisms: reduced propulsion, impaired interlimb timing, and insufficient foot-ground clearance. These findings highlight an elevated falls risk due to central motor control deficits. Translation of these metrics to wearable or clinic-based systems could enhance early detection and post-shunt mobility monitoring in this vulnerable population.