Sensitivity of physiotherapy-based clinical tests in detecting change in gait and balance performance following a 50 mL CSF tap test in idiopathic normal pressure hydrocephalus

Cerebrospinal fluid tap test (CSF TT) is a key predictive method commonly used to identify candidates for shunt surgery in idiopathic Normal Pressure Hydrocephalus (iNPH), however, the sensitivity of this procedure is limited. The aim was to compare sensitivity of a broad set of physiotherapy-based clinical tests for assessing changes following CSF TT in a group of selected iNPH patients and to explore potential sex-based differences in the responses. Ninety-five selected iNPH patients (mean age 77, SD 6, 57% male), underwent CSF TT prior to shunt surgery. Clinical tests comprised different static balance tests in varying conditions including feet and heels apart and together; eyes open and closed; on floor and foam cushion, followed by gait and functional performance measures including 10-meter walk test (10MWT), 3-meter backward walking (3MBW), Timed-up and Go (TUG) and 6-minute walking test (6MWT). Duration in seconds (sec) and distance were noted. Assessments were conducted at set time points before and after the drainage procedure. Changes in performance were analyzed, and responses compared between sexes. Significant increase was observed across most static balance tests except tandem eyes closed (EC) and one-legged stance tests. The largest enhancements were seen in the Romberg test (4.9 s), followed by foam cushion-eyes open (EO) tests (feet together: 3.9 s and heels together: 3.8 s), heels together-EC (3.8 s) and tandem-EO (3.1 s). Gait and functional tests significantly improved (p < 0.001) and 3MBW showed the largest change, with a 32% reduction in sec and a 23% reduction in steps, followed by decrease in TUG sec (27%) and 10-MWT sec (21%), and 6MWT distance increase (25%). Males demonstrated significant increase in heels together-EO and feet together-EO duration which were not observed in females; after adjusting for baseline performances, no significant sex-related differences in responsiveness to CSF TT were found. Challenging comprehensive physiotherapy tests, including gait assessments in direction and capacity, such as 3MBW and 6MWT, together with postural control evaluations using foam cushion and tandem stance increases the sensitivity to change and are suggested to be used to detect functional changes after CSF TT in patients with iNPH. The project is registered in "FoU inSweden” (Research and Development in Sweden) ID: 285356.