Wearable Sensors May Better Diagnose Normal Pressure Hydrocephalus Gait

A woman initially ignored her slowly worsening cognitive, gait and balance problems, in denial that something was wrong. She would occasionally stumble over sidewalks and drag her feet when she walked. One day, her son noticed her erratic walking patterns and urged her to seek help.

That’s when she was diagnosed with normal pressure hydrocephalus (NPH).

While gait disorders are one of the most prominent symptoms of NPH, it can be difficult to identify patients’ natural walking characteristics because controlled testing environments may subject patients to psychological pressures and bias, making retrieving accurate data difficult. And yet most current testing methods rely on in-office gait assessments.

To help address this challenge in diagnosing NPH gait, Kuruvithadam et al. used a wearable assessment device to determine differences in patients’ gait in a controlled environment versus in their day-to-day life.

Identifying these differences, they suggest, could be critical for detecting and diagnosing neurological gait disorders in the future.

Testing Differences in Normal Pressure Hydrocephalus Gait Patterns Between Environments

The study, which Kuruvithadam et al. believe to be the first to use computational methods to identify high-risk NPH patients based on gait patterns in real-life settings, included three groups of participants:

• • 20 healthy, young controls with an average age of 25 years
  • 20 healthy, elderly controls with an average age of 75 years
  • 12 NPH patients with an average age of 76 years

Each patient’s gait patterns were monitored through five wearable sensors attached to both ankles, both wrists and chest.

They were instructed to walk five meters (or 16.4 feet) two times at different prescribed foot spacings, and then underwent gait evaluation in a controlled lab environment. This was followed by a 10-meter (or 32.8 feet) walk four times at the patient’s preferred speed. After this testing, the patients were asked to continue to wear the sensors for three days to record movement patterns in their real-world settings.

After gait analysis, the study authors found the following:

• • There were significant differences between environments for all three subject groups.
    Comparing the real-world environment to the controlled environment, all three groups showed an increase in outward rotation and higher variability in stride time.
  • The elderly and NPH groups displayed specific differences between environments.
    In the real-world environment, both the elderly and NPH groups showed a decrease in gait speed compared to the lab environment.

• • The NPH group showed specific and significant differences between environments.
    In the real-world environment, the NPH group had a decrease in stride length, lower sensor clearance, increased stance/swing ratio, increase in double support phase, longer stance phase and a shorter swing phase.

From these results, the study authors noted that while both elderly and NPH patients aimed to increase their walking speeds in controlled lab settings, the elderly patients did so through a faster cadence. Meanwhile the NPH patients aimed to walk with longer strides. NPH gait also showed a significantly lower foot clearance in the real-world environment, which is commonly associated with disorders such as Parkinson’s or stroke-related defects.

Given the highly significant difference in gait between environments for elderly and NPH patients compared to the younger groups, Kuruvithadam et al. believe that this confirms that NPH patients are influenced by controlled environments and apprehension from being observed in a lab setting.

Additionally, their data showed a consistent improvement in gait classification ability when using real-world measurements, which suggests that home-monitoring systems are a better diagnostic tool for identifying normal pressure hydrocephalus gait and other neurological gait disorders.

Comparing Gait Patterns in NPH Patients and Other Neurological Gait Disorders

But are we using gait as a diagnostic tool for NPH patients in the right way?

While NPH patients are known to have gait abnormalities classically described as frontal gait, the variety of NPH gait presentations can make diagnosis difficult, because many other neurodegenerative and vascular diseases mimic the characteristics of NPH gait.

In order to help improve the time to diagnosis in NPH patients and patients with mimic diseases, Morel et al. sought to determine the prevalence of gait abnormalities between both groups so that they could be more easily distinguishable for diagnosis.

In their study published in the Journal of the Neurological Sciences, the study authors analyzed gait profiles of 80 patients with NPH and 60 patients with mimic diseases such as neurodegenerative conditions and dementia. Two independent raters blind to the patients’ clinical diagnoses classified their gait phenotypes as either frontal, parkinsonian, other or normal.

Morel et al. found that while both the NPH and mimic patients had similar prevalence of frontal gait and normal gait, parkinsonian gait was significantly more common among mimic patients than NPH patients.

This, they concluded, highlights that frontal gait cannot discriminate NPH from its mimics and is not the most common gait abnormality within NPH patients. Likewise, the presence of parkinsonian gait, while previously reported in NPH, should be viewed as an indicator of an alternate disorder during diagnosis.