Gait measurements performed with Protokinetics’ Zeno Walkway and PKMAS software highlight the superiority of quantitative vs qualitative gait assessment in patients with NPH.

Gait impairment is typically the primary manifestation of idiopathic Normal Pressure Hydrocephalus (NPH) and is usually the earliest and predominant symptom. NPH occurs when the natural system for draining and absorbing cerebrospinal fluid (CSF) does not function properly and too much CSF builds up in the ventricles of the brain. NPH causes several symptoms, including memory loss, speech problems, moodiness, gait problems, unsteadiness, leg weakness, shuffling steps, sudden falls, difficulty taking the first step, “freezing” when walking, and urinary incontinence.

The symptoms of NPH closely mimic Dementia and Parkinson’s Disease and most patients exhibiting symptoms of NPH are adults over the age of 60. This overlap of symptoms leads to frequent misdiagnosis. But unlike Dementia and PD, NPH can be reversed with appropriate treatment, if it is diagnosed correctly.

A Prospective Study on Gait Dominant Normal Pressure Hydrocephalus, performed at Barrow Neurological Institute in Phoenix, AZ, systemically analyzed gait and balance in patients with a clinical diagnosis of NPH. The subjects chosen for the study were from a group of patients treated for NPH who had undergone Lumbar Puncture (LP) followed by shunt placement. The study authors proposed that in order to better diagnose NPH and improve the outcome of shunt surgeries for NPH patients, a standard diagnostic procedure with specific criteria was needed.

Gait and balance data were recorded using a Protokinetics 4’ x 20’ Zeno Walkway and PKMAS software to allow for the collection of quantitative data without the interpersonal biases that occur with physical therapist assessments alone. Pre-LP, post-LP, and post-shunt treatment data sets were then analyzed by physical therapists using one-way ANOVA and Tukey-Kramer HSD. The pre-LP data set contained the initial assessments of the NPH patients prior to any treatment for the disease. The post-LP data set contained assessments performed 3-4 hours following a spinal tap procedure. The post-shunt data set contained assessments performed during a 6-month follow-up after ventriculoperitoneal shunt placement.

Ten data points of gait magnitude, symmetry, and variability were collected by Zeno and PKMAS:

  • Toe in/Out angle (degrees)
  • Step length (cm)
  • Stride length (cm)
  • Stride width (cm)
  • Stance %
  • Swing %
  • Single support %
  • Velocity (cm/s)
  • Ambulation time (seconds)
  • Cadence (steps/min)

From the analyses of the ProtoKinetics Zeno Walkway data, 7 out of the 10 measurements were significantly different among pre-LP, post-LP, and post-shunt conditions. According to the authors of the study, “These characteristics could serve as indications of NPH following spinal tap procedures as well as prognostic features for future improvement after shunt placement“. The remaining three measurements performed by the Zeno Walkway were not found to be significantly altered among the three conditions and therefore may not be important for diagnosis.

The analyses support the increased positive effect of constant removal of CSF by shunt when compared to a one‐time LP procedure. Only velocity was considered significantly different when comparing the post-LP and post-shunt data sets, which indicates an increased effect of continuous drainage from shunt placement on walking speed.

The authors note a significant finding: Ambulation time recorded by the Zeno Walkway, essentially identical to the physical therapist’s measure of 25’ walkway time, was found to be significantly altered, whereas the physical therapist records indicated a lack of significance. This shows the unavoidable subjectivity of qualitative assessment performed by physical therapists vs objective quantitative assessments recorded by a gait analysis system. The authors conclude that objective assessments made by a pressure-sensitive walkway mat such as the Zeno may be preferable for an accurate diagnosis.

 “Our results indicate that 9 out of 15 physical therapy assessments are significantly distinguishable among pre-LP, post-LP, and post-shunt data sets. These tests were found to be capable of measuring symptoms of NPH patients that were treatable by either LP or shunt placement or both. “From the reports of the ProtoKinetics Zeno Walkway, 7 out of the 10 measurements were significantly different among pre-LP, post-LP, and post-shunt conditions. These seven characteristics recorded by the computerized walkway could be labeled as symptoms altered by the disease and amenable by treatment.”A Prospective Study on Gait Dominant Normal Pressure Hydrocephalus

The study focused on quantitative measures of gait instead of relying on the common qualitative measure which can be subject to bias. By placing emphasis on quantitative measures, it becomes feasible to standardize the NPH evaluation process across practices.

Read the study here.