Comparison of comfortable and maximum walking speed in the 10-meter walk test during the cerebrospinal fluid tap test in iNPH patients: A retrospective study

Abstract

BackgroundThe 10-meter walking test (10 MWT) is widely used during a cerebrospinal fluid tap test (CSFTT) for idiopathic normal-pressure hydrocephalus (iNPH). However, various previous studies and guidelines do not specify whether to adopt a comfortable walking speed or maximum walking speed when implementing the 10 MWT. In this study, we analyzed the values of comfortable and maximum walking speeds during the CSFTT in patients who underwent shunt surgery to determine which walking form is desirable for evaluation. MethodsThe patients were 29 consecutive cases in which a CSFTT was performed, followed by shunting, between October 2012 and April 2019. Data on the 10 MWT comfortable walking speed and maximum walking speed were collected, as were data on the timed up and go (TUG) test and Mini-Mental State Examination (MMSE). We analyzed the rate of change in comfortable walking speed and maximum walking speed before CSFTT and on the first day after CSFTT, and the amount of improvement compared to baseline ability. In addition, diagnostic performance was compared using a receiver operating characteristic (ROC) analysis. ResultsTwenty-eight patients who underwent shunt surgery improved their symptoms and were designated as shunt responders. The remaining patient who underwent surgery was considered a non-responder with no improvement in symptoms. The parameters of the shunt responders that changed were muscle strength, the 10 MWT, and the TUG test, and there was no significant change in cognitive function. The rate of change, amount of change, and sensitivity were large at a comfortable walking speed, but ROC analysis showed that the maximum walking speed had a large area under the curve and excellent specificity. The higher the preoperative gait function, the lower the improvement rate of gait function. DiscussionThe comfortable walking speed is easy to measure, but its specificity is inferior to the maximum walking speed. However, the maximum walking speed may be affected by the ceiling effect and measurement errors. Despite this, we concluded that the maximum walking speed had a better diagnostic performance. Because the causes of gait disturbance in iNPH include decreased muscle output, postural instability, and gait rhythm disorder, and maximum walking speed is strongly related to each of these factors, this accounts for the changes in maximum walking speed. ConclusionIn conclusion, although comfortable walking speed was easy to measure in terms of changes and had high sensitivity, the maximum walking speed had the highest specificity and comprehensive diagnostic performance. It is recommended that maximum walking speed be evaluated when making a definitive diagnosis of iNPH.