Robot-Assisted Assessment of Chronic Stroke Adults’ Ankle Proprioception Deficits and Related Brain Injury

Academic Background

Stroke is a common neurological disorder, often resulting in hemiplegia, which affects the patient’s balance and gait control. Proprioception refers to the self-perception of body posture and movement, provided by mechanoreceptors located in muscles, joints, tendons, and skin. These senses are crucial for maintaining balance and controlling gait. Research has shown that stroke survivors often suffer from ankle proprioception impairment, particularly the loss of ankle position sense and movement sense. However, systematic studies on ankle position sense and movement sense are relatively scarce. [Cho et al., 2021] found that ankle proprioceptive impairment is a strong predictor of balance dysfunction in stroke patients; [Tuthill et al., 2018; Goble et al., 2011] pointed out that traditional clinical scoring scales can only detect the most severe proprioceptive deficits and are not sensitive enough for milder defects. Therefore, this study aims to quantify the deficits in proprioception after stroke by applying robotic technology and to determine the brain injury locations associated with it.

Source of the Paper

This paper was jointly authored by Qiyin Huang (University of Minnesota), Naveen Elangovan (University of Minnesota), Mingming Zhang (Southern University of Science and Technology), Ann Van de Winckel (University of Minnesota), and Jürgen Konczak (University of Minnesota). The paper was published in the Journal of NeuroEngineering and Rehabilitation (2024) and can be accessed through the following link: https://doi.org/10.1186/s12984-024-01396-9.

Research Process and Methods

Participants

The study included 12 chronic stroke adults (average age 54±10.9 years, average 6 years post-stroke), as well as 13 age and gender-matched neurologically normal control subjects (average age 54±15.3 years). All participants provided written informed consent before the experiment and passed the Mini-Mental State Examination (MMSE) to ensure normal cognitive function.

Robot-Assisted Proprioception Testing

The study used a robotic ankle proprioception assessment system for testing, consisting of a DC motor and built-in encoder, capable of rotating the footplate with high precision. Participants used the robot to passively extend their ankle to two different positions or speeds, then psychophysical just-noticeable difference (JND) thresholds and uncertainty intervals (IU) were obtained, which were used to measure the deviation and accuracy of proprioception, respectively.

Experimental Design

Each subject’s test protocol was divided into two parts: position sense and movement sense testing. In position sense testing, the robot passively flexed the foot from a neutral position to two different angles, holding for 2 seconds. The amplitude range for the comparison stimulus position (PC) was 8.3 to 14.6 degrees. In the movement sense testing, the speed range for the robot’s comparison stimulus was 5.2 to 9.4 degrees/second. In each test, the robot provided reference and comparison stimuli in a random order, and subjects had to answer which action was exceeded/faster, then the next comparison stimulus was selected by an adaptive Bayesian algorithm.

Data Analysis

The study included 30 trial data points, fitted with a logistic Weibull function to obtain psychophysical just-noticeable difference thresholds (JND) representing perceptual deviation and IU representing perceptual accuracy. Statistical analysis was done using Welch’s t-test and Wilcoxon-Mann-Whitney test to compare differences between groups, and Spearman or Pearson analysis for correlation.

Brain Injury Analysis

Standard brain imaging analysis software (MRIcron and SPM12) was used to perform manual lesion delineation and statistical parametric mapping (SPM) analysis on participants’ MRI scans. By spatially normalizing severe brain injury comparison MRI scans, the volume of brain lesions for each subject was obtained and analyzed in association with their proprioceptive deficits.

Research Findings

Characteristics of Proprioceptive Deficits

The study found that 83% of the stroke adults had abnormalities in either position sense or movement sense, or both. Compared to the control group, the stroke group’s psychophysical just-noticeable difference thresholds (JND) significantly increased, by 77% for position sense and 153% for movement sense. The accuracy of proprioception (IU) also significantly increased, by 148% for position sense and 78% for movement sense.

Brain Injury and Proprioceptive Deficit Correlation

The stroke group’s brain injury locations were concentrated in multiple areas of the cerebral cortex, including the primary somatosensory cortex, posterior parietal cortex, primary motor cortex, frontal lobe, insula, and temporo-parietal region. This suggests these brain regions are closely related to the processing of ankle proprioception.

Conclusion and Significance

This study systematically quantified for the first time the extent and frequency of deficits in ankle position sense and movement sense in chronic stroke adults, finding that most stroke patients have proprioceptive deficits. Moreover, these deficits are closely related to specific brain injury regions. By combining robotic technology with psychophysical methods, this study provides more precise and reliable methods and evidence for future clinical assessments and rehab.

Highlights of the Research

1. Systematic Assessment: The first systematic assessment of deficits in ankle position and movement sense in chronic stroke adults.
2. High-Precision Measurement: Quantification of proprioception deviation and accuracy using robotic technology and psychophysical methods.
3. Brain Injury Correlation: The first detailed revelation of the correlation between ankle proprioceptive deficits and specific brain injury regions.

Practical Value of the Research

The study demonstrated the potential application of robotic technology in detecting post-stroke proprioceptive deficits, providing direction and tools for future rehabilitation treatments. These findings help in designing more effective rehabilitation programs to improve balance and gait in stroke patients, thereby reducing the risk of falls and enhancing the quality of life.

This research on post-stroke ankle proprioceptive deficits and related brain injuries provides new perspectives and methods, paving new paths for future scientific research and clinical practice.