Exploring Sensorimotor Integration Abilities of Individuals With Neurological Impairments: Can Added Haptic Input Improve Balance Control?

Abstract

Background Balance impairments are common in people with incomplete spinal cord injury (pwiSCI) and people with multiple sclerosis (pwMS). Impaired balance control during standing and walking may lead to falls and fall-related injuries. Understating and improving balance control is important for reducing falls in both pwiSCI and pwMS. Balance can be improved by using walking aids such as a standard cane, four-wheeled walker (4WW), or walking poles and by adding haptic input during standing and walking. Walking aids can be used in multi-functional ways either conventionally (provides mechanical support and sensory input) or lightly (provides only sensory input). Purpose To examine the sensorimotor integration abilities, the studies in this thesis examined the effects of added haptic input when using different modalities such as a standard cane, a fixed railing, 4WW, walking poles, and haptic anchors on standing and walking balance in pwiSCI, pwMS, and neurotypical individuals. Methods and results Study one: Postural sway parameters were measured using force plates where pwiSCI and neurotypical individuals stood for 90 seconds with eyes open and closed. All participants received added haptic input under five different conditions: 1) Lightly holding two walking poles, 2) lightly holding a cane, 3) standing with haptic anchors (strings with small weights at the bottom), 4) lightly touching a railing, or 5) not touching any external modality (NT). Cutaneous and proprioceptive impairments were evaluated in the upper and lower extremities of pwiSCI. Lightly touching a railing, poles, and cane reduced sway velocity (SwVel) in the mediolateral (ML; SwVelML) direction, while a light touch on a railing also reduced ML sway variability (SwVarML) for both groups. All participants had greater path length, SwVelML, and SwVarAP&ML during the eyes-closed conditions compared to eyes open. Group effects showed that pwiSCI had larger path length, SwVelML, and SwVarML compared to neurotypical individuals. Sensory impairments of pwiSCI did not correlate with outcome measures that significantly changed with added haptic input. Study two: Walking balance was evaluated using a three-dimensional motion capture system as pwiSCI and neurotypical individuals walked with eyes open and eyes closed for 10 meters under five different conditions: 1) Lightly holding two walking poles, 2) lightly holding a cane, 3) dragging haptic anchors, 4) lightly touching a railing, and 5) NT. Cutaneous and proprioceptive impairments were evaluated in the upper and lower extremities of pwiSCI. Participant perceptions of the ease and usefulness of each modality as well as the perceived effect of each modality on their walking performance were evaluated using visual analog scale (VAS) scores. Lightly touching a railing reduced stride velocity, the AP margin of stability (MOSAP), and step length (SL) compared to the NT condition. PwiSCI had step width (SW) values similar to the control NT values when using the poles. All participants walked slower with increased MOSML and variability (SD) of SL (SLSD), SW (SWSD), and MOSML, and decreased SL and MOSAP during the eyes-closed conditions. Group effects showed that pwiSCI had reduced stride velocity and MOSAP, and increased MOSML compared to neurotypical individuals across all conditions. Sensory impairments of pwiSCI did not correlate with outcome measures that significantly changed with added haptic input. PwiSCI perceive that the cane and poles improved their walking balance more than the haptic anchors. Study three: Walking balance was evaluated using inertial-based sensors as pwMS and neurotypical individuals walked for 10 meters under four different conditions: 1) Dragging haptic anchors, 2) lightly touching the handles of a 4WW (4WW-LT), 3) putting weight through the handles of a 4WW (4WW-W), and 4) NT. Cutaneous and proprioceptive impairments were evaluated in the upper and lower extremities of pwMS. For pwMS, disease duration, fall history, and the Patient Determined Disease Step (PDDS) were collected by patient self-report. In addition, baseline assessment for upper extremity function was obtained using the Nine-Hole Peg Test (NHPT), and a baseline for cognitive processing speed was measured with the Symbol Digit Modality Test (SDMT) for pwMS only. Participant perceptions of the ease and usefulness of each modality as well as the perceived effect of each modality on their walking performance were evaluated using visual analog scale (VAS) scores. Using 4WW (LT&W) reduced gait velocity, stride length, cadence, and lateral step variability (LSV) compared to the NT condition for all participants. All participants had reduced mediolateral trunk range of motion (ML-tROM) for all modalities compared to the NT. All participants spent less time in the double support phase (DS) in the 4WW-W condition compared to 4WW-LT and haptic anchors conditions. Group effects showed pwMS spent significantly more time in DS compared to neurotypical individuals. Cutaneous sensations, SDMT, and PDDS were not correlated to changes in any of the outcome measures. PwMS perceived that walking balance was improved more using 4WW-LT compared to 4WW-W. Conclusion Overall standing and walking balance were significantly worse in pwiSCI and pwMS compared to neurotypical individuals. This thesis provides further evidence that added haptic input from modalities impacts both standing and walking balance. Lightly touching a railing, cane, and poles improved standing balance, while anchors had no impact on standing balance for pwiSCI and neurotypical individuals as seen in study one. For study two, lightly using poles improved walking, lightly touching a cane and using the anchors did not impact walking, while touching the railing impacted walking negatively for pwiSCI and neurotypical individuals. For study three, the anchors, 4WW-LT and 4WW-W improved walking for pwMS and neurotypical individuals. In most cases (12/20 outcome variables), added haptic input from the modalities either improved or did not impact balance control suggesting that modalities can be used differently and the multifunction (light touch & mechanical support) use of walking aids such as 4WWs, poles, and canes may enhance balance control through more than just mechanics. PwiSCI and pwMS perceive improvement in walking balance when using a cane, poles, and 4WW respectively.