Sensory deficits of the paretic and non-paretic upper limbs relate with the motor recovery of the poststroke subjects

BACKGROUND

Post stroke, motor paresis has usually been considered to be a crucial factor responsible for the disability; other impairments such as somatosensory deficits may also play a role.

OBJECTIVE

To determine the relation between the sensory deficits (paretic and non-paretic upper limbs) and the motor recovery of the paretic upper limb and to predict the potential of motor recovery based on the sensory deficits among stroke subjects.

METHODS

The study was a cross-sectional study conducted in a rehabilitation institute. Ninety-five poststroke hemiparetic subjects having sensory impairment in any of the modalities were considered for this study. Sensory deficits were assessed on both the upper limbs (paretic and non-paretic) primarily using Erasmus MC modification of the revised version of Nottingham Sensory Assessment (Em-NSA) and Nottingham Sensory Assessment (Stereognosis) (NSA-S). The motor recovery was assessed using the Fugl-Meyer assessment (FMA).

RESULTS

The measures of sensory deficits exhibited weak but significant correlation [the paretic (Em-NSA and NSA; r = .38 to .58; p < .001) and the non-paretic (Em-NSA and NSA; r = .24 to .38; p = .03 to .001)] with the motor recovery of the paretic upper limb as measured by FMA. The potential of favorable recovery of the paretic upper limb may be predicted using the cutoff scores of Em-NSA (30, 21, and 24) and NSA-S (5, 8, and 5) of the paretic side.

CONCLUSION

In stroke, sensory deficits relate weakly with the recovery of the paretic upper limb and can predict recovery potential of the paretic upper limb.

The Impact of Light Touch and Pin Prick on Functional Outcomes in Patients with Traumatic Spinal Cord Injury

A spinal cord injury (SCI) can cause severe lifelong functional disability and profoundly affect an individual's daily life. We investigated the prediction of patients' post-SCI functional outcomes by evaluating sensory scores rather than motor scores, as the latter's association with functional outcomes is well established. We examined patients' responses to a light touch (LT) and pin prick (PP) at admission and the response data's usefulness as predictors of functional outcomes (i.e., ability to perform activities of daily living) at discharge. This exploratory observational study used data from the Japanese National Spinal Cord Injury Database (SCI-J). Data from 3,676 patients who met the inclusion criteria and were admitted for an SCI between 1997 and 2020 were analyzed. The motor score of the Functional Independence Measure (mFIM) at discharge was used as an index of functional outcome. A multiple regression analysis revealed that the mFIM was associated with both the LT response (β=0.07 (0.01), p<0.001) and the PP response (β=0.07 (0.01), p<0.001) at admission. The false discovery rate log-worth values for LT and PP were 6.6 and 8.5, respectively. Our findings demonstrate that LT and PP scores at admission can help predict patients' functional outcomes after an SCI, although the magnitude of their contributions is not high.

Three-dimensional reconstructions of mechanosensory end organs suggest a unifying mechanism underlying dynamic, light touch

Across mammalian skin, structurally complex and diverse mechanosensory end organs respond to mechanical stimuli and enable our perception of dynamic, light touch. How forces act on morphologically dissimilar mechanosensory end organs of the skin to gate the requisite mechanotransduction channel Piezo2 and excite mechanosensory neurons is not understood. Here, we report high-resolution reconstructions of the hair follicle lanceolate complex, Meissner corpuscle, and Pacinian corpuscle and the subcellular distribution of Piezo2 within them. Across all three end organs, Piezo2 is restricted to the sensory axon membrane, including axon protrusions that extend from the axon body. These protrusions, which are numerous and elaborate extensively within the end organs, tether the axon to resident non-neuronal cells via adherens junctions. These findings support a unified model for dynamic touch in which mechanical stimuli stretch hundreds to thousands of axon protrusions across an end organ, opening proximal, axonal Piezo2 channels and exciting the neuron.

Touch may reduce cognitive load during assisted typing by individuals with developmental disabilities

Many techniques have attempted to provide physical support to ease the execution of a typing task by individuals with developmental disabilities (DD). These techniques have been controversial due to concerns that the support provider's touch can influence the typed content. The most common interpretation of assisted typing as an ideomotor phenomenon has been qualified recently by studies showing that users with DD make identifiable contributions to the process. This paper suggests a neurophysiological pathway by which touch could lower the cognitive load of seated typing by people with DD. The required sensorimotor processes (stabilizing posture and planning and executing manual reaching movements) and cognitive operations (generating and transcribing linguistic material) place concurrent demands on cognitive resources, particularly executive function (EF). A range of developmental disabilities are characterized by deficits in sensorimotor and EF capacity. As light touch has been shown to facilitate postural coordination, it is proposed that a facilitator's touch could assist the seated typist with sensorimotor and EF deficits by reducing their sensorimotor workload and thereby freeing up shared cognitive resources for the linguistic elements of the task. This is the first theoretical framework for understanding how a facilitator's touch may assist individuals with DD to contribute linguistic content during touch-assisted typing.

Spinal Cord Tissue Bridges Validation Study: Predictive Relationships With Sensory Scores Following Cervical Spinal Cord Injury

Background

Using magnetic resonance imaging (MRI), widths of ventral tissue bridges demonstrated significant predictive relationships with future pinprick sensory scores, and widths of dorsal tissue bridges demonstrated significant predictive relationships with future light touch sensory scores, following spinal cord injury (SCI). These studies involved smaller participant numbers, and external validation of their findings is warranted.

Objectives

The purpose of this study was to validate these previous findings using a larger independent data set.

Methods

Widths of ventral and dorsal tissue bridges were quantified using MRI in persons post cervical level SCI (average 3.7 weeks post injury), and pinprick and light touch sensory scores were acquired at discharge from inpatient rehabilitation (average 14.3 weeks post injury). Pearson product-moments were calculated and linear regression models were created from these data.

Results

Wider ventral tissue bridges were significantly correlated with pinprick scores (r = 0.31, p < 0.001, N = 136) and wider dorsal tissue bridges were significantly correlated with light touch scores (r = 0.31, p < 0.001, N = 136) at discharge from inpatient rehabilitation.

Conclusion

This retrospective study's results provide external validation of previous findings, using a larger sample size. Following SCI, ventral tissue bridges hold significant predictive relationships with future pinprick sensory scores and dorsal tissue bridges hold significant predictive relationships with future light touch sensory scores.

Analysis of Light Grip Influence on Standing Posture

Upright posture control and gait are essential for achieving autonomous daily living activities. Postural control of upright posture relies, among others, on the integration of various sensory information. In this context, light touch (LT) and light grip (LG) of a stationary object provide an additional haptic sensory input that helps to reduce postural sway. When LG was studied through the grasp of a cane, the sensory role of this assistive tool was often limited to a mediation interface. Its role was restricted to transmit the interaction forces between its tip and the ground to the hand. While most studies involve participants standing in an unstable way, such as the tandem stance, in this paper we study LG from a different perspective. We attached a handle of a cane firmly to a stationary support. Thus, we can focus on the role of the hand receptors in the LG mechanism. LG condition was ensured through the tactile information gathered by FSR sensors placed on the handle surface. Moreover, participants involved in our study stood in a usual way. The study involved twelve participants in an experiment composed of two conditions: standing relaxed while lightly gripping an equipped handle attached to the ground, and standing in the same way without gripping the handle. Spatial and frequency analyses confirmed the results reported in the literature with other approaches.

Does the Level of Difficulty in Balancing Tasks Affect Haptic Sensitivity Via Light Touch?

The purpose of this study was to determine whether the contribution of bimanual light touch varies according to the difficulty level of postural tasks (e.g., vision occlusion, height of support surface). Fourteen healthy young adults each were asked to stand in a tandem position, on a 20-cm height balance beam. Postural tasks included light touch and no touch conditions in two vision conditions, nonvision and full vision. The root mean square of amplitude of oscillation (mediolateral), mean velocity, ellipse area, and path length of the center of pressure revealed that touch conditions reduced sway to a greater extent in the elevated support surface, nonvision condition. Highly unstable balance tasks increase the optimization of light touch and affect the attenuation of postural sway.

Disruption of right posterior parietal cortex by continuous Theta Burst Stimulation alters the control of body balance in quiet stance

Control of body balance relies on the integration of multiple sensory modalities. Lightly touching an earth-fixed reference augments the control of body sway. We aimed to advance the understanding of cortical integration of an afferent signal from light fingertip contact (LT) for the stabilisation of standing body balance. Assuming that right-hemisphere Posterior Parietal Cortex (rPPC) is involved in the integration and processing of touch for postural control, we expected that disrupting rPPC would attenuate any effects of light touch. Eleven healthy right-handed young adults received continuous Theta Burst Stimulation over the left- and right-hemisphere PPC with sham stimulation as an additional control. Before and after stimulation, sway of the blindfolded participants was assessed in Tandem-Romberg stance with and without haptic contact. We analysed sway in terms of the variability of Centre-of-Pressure (CoP) rate of change as well as Detrended Fluctuation Analysis of CoP position. Light touch decreased sway variability in both directions but showed direction-specific changes in its dynamic complexity: a positive increase in complexity in the mediolateral direction coincided with a reduction in the anteroposterior direction. rPPC disruption affected the control of body sway in two ways: first, it led to an overall decrease in sway variability irrespective of the presence of LT; second, it reduced the complexity of sway with LT at the contralateral, non-dominant hand. We speculate that rPPC is involved in the active exploration of the postural stability state, with utilisation of LT for this purpose if available, by normally inhibiting mechanisms of postural stiffness regulation.

Time-Dependent Discrepancies between Assessments of Sensory Function after Incomplete Cervical Spinal Cord Injury

We recently demonstrated that the electrical perceptual threshold (EPT) examination reveals spared sensory function at lower spinal segments compared with the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) examination in humans with chronic incomplete cervical spinal cord injury (SCI). Here, we investigated whether discrepancies in sensory function detected by both sensory examinations change over time after SCI. Forty-five participants with acute (<1 year), chronic (≥1-10 years), and extended-chronic (>10 years) incomplete cervical SCI and 30 control subjects were tested on dermatomes C2-T4 bilaterally. EPT values were higher in subjects with acute (2.5 ± 0.8 mA), chronic (2.2 ± 0.7 mA), or extended-chronic (2.8 ± 1.1 mA) SCI compared with controls (1.0 ± 0.1 mA). The EPT examination detected sensory impairments in spinal segments above (2.3 ± 0.9) and below (4.2 ± 2.6) the level detected by the ISNCSCI sensory examination in participants with acute and chronic SCI, respectively. Notably, both examinations detected similar levels of spared sensory function in the extended-chronic phase of SCI (0.8 ± 0.5). A negative correlation was found between differences in EPT and ISNCSCI sensory levels and time post-injury. These observations indicate that discrepancies between EPT and ISNCSCI sensory scores are time-dependent, with the EPT revealing impaired sensory function above, below, or at the same spinal segment as the ISNCSCI examination. We propose that the EPT is a sensitive tool to assess changes in sensory function over time after incomplete cervical SCI.

Plantar Cutaneous Sensitivity With and Without Cognitive Loading in People With Chronic Ankle Instability, Copers, and Uninjured Controls

STUDY DESIGN

Controlled laboratory study.

BACKGROUND

Deficits in light touch have recently been identified on the plantar surface of the foot in those with chronic ankle instability (CAI) but not in uninjured controls. It is unknown whether copers display similar deficits. Similarly, cognitive loading has been shown to impact postural control in different populations, but it is unclear how it may impact sensory perception.

OBJECTIVES

To evaluate the difference in cutaneous sensation thresholds at rest and under cognitive loading, using Semmes-Weinstein monofilaments (SWMs), among uninjured controls, copers, and those with CAI.

METHODS

A total of 45 participants (mean ± SD age, 20.2 ± 2.8 years; height, 167.6 ± 9.9 cm; mass, 66.3 ± 14.7 kg) were recruited and categorized to a CAI, coper, or control group, based on Ankle Instability Instrument scores. Participants were assessed with SWMs for cutaneous thresholds using a 4-2-1 stepping algorithm at the head of the first metatarsal, base of the fifth metatarsal, calcaneus, and sinus tarsi. Each participant was then retested while generating random digits to the beat of a metronome in order to simulate cognitive loading.

RESULTS

Participants with CAI displayed significantly higher SWM thresholds at the head of the first metatarsal, base of the fifth metatarsal, and sinus tarsi than those of the control participants, and significantly higher thresholds at the base of the fifth metatarsal and calcaneus than those of copers (all, P<.05). Copers showed higher thresholds than those of controls at the sinus tarsi only (P<.05). A main effect of cognitive loading was identified at all 4 sites (P<.05).

CONCLUSION

People with CAI have deficits in plantar sensation relative to controls and copers. Cognitive loading increases plantar cutaneous sensation thresholds irrespective of CAI status.

Interrater and intrarater reliability of the semmes-weinstein monofilament 4-2-1 stepping algorithm

INTRODUCTION

Semmes-Weinstein Monofilaments (SWM) are used to examine light touch sensation of the skin. Reliability of the 4-2-1 stepping algorithm approach for determining light touch detection thresholds has not been examined. The purpose of this study was to determine the interrater and intrarater reliability of the SWM 4-2-1 stepping algorithm on the plantar surface of the foot.

METHODS

Four raters with varying levels of SWM assessment experience tested light touch sensation over the plantar aspect of the first metatarsal head in 14 healthy adults. During the initial session, all raters performed the 4-2-1 stepping algorithm technique on each subject to determine interrater reliability. One week later, subjects were reassessed by 2 raters to determine intrarater reliability.

RESULTS

Interrater reliability ranged from moderate-to-good (ICC2,1  = 0.62-0.92). Intrarater reliability also ranged from moderate-to-good (ICC2,1  = 0.61-0.85).

CONCLUSIONS

The 4-2-1 stepping algorithm demonstrated acceptable interrater and intrarater reliability when measured in healthy adults. Muscle Nerve 53: 918-924, 2016.

Children with developmental coordination disorder benefit from using vision in combination with touch information for quiet standing

In two experiments, the ability to use multisensory information (haptic information, provided by lightly touching a stationary surface, and vision) for quiet standing was examined in typically developing (TD) children, adults, and in seven-year-old children with Developmental Coordination Disorder (DCD). Four sensory conditions (no touch/no vision, with touch/no vision, no touch/with vision, and with touch/with vision) were employed. In experiment 1, we tested four-, six- and eight-year-old TD children and adults to provide a developmental landscape for performance on this task. In experiment 2, we tested a group of seven-year-old children with DCD and their age-matched TD peers. For all groups, touch robustly attenuated standing sway suggesting that children as young as four years old use touch information similarly to adults. Touch was less effective in children with DCD compared to their TD peers, especially in attenuating their sway velocity. Children with DCD, unlike their TD peers, also benefited from using vision to reduce sway. The present results suggest that children with DCD benefit from using vision in combination with touch information for standing control possibly due to their less well developed internal models of body orientation and self-motion. Internal model deficits, combined with other known deficits such as postural muscles activation timing deficits, may exacerbate the balance impairment in children with DCD.

Description of sensory preservation in children and adolescents with incomplete spinal cord injury

BACKGROUND/OBJECTIVE

This cross-sectional, multicenter cohort study describes patterns of preserved sensation in persons with American Spinal Injury Association (ASIA) Impairment Scale (AIS) B (sensory incomplete, or SI) and AIS C/D (motor incomplete, or MI).

METHODS

A total of 93 subjects with incomplete spinal injuries (58 with tetraplegia and 35 with paraplegia) were included for analysis. Sensation was based on the International Standards for Neurological Classification of SCI (ISNCSCI).

RESULTS

In the 44 subjects with AIS B (SI), some light touch (LT) was present in 35% of dermatomes below the neurological level and pin prick (PP) in 8%. In contrast, in the 49 subjects with AIS C/D (MI), LT was present in 77% of dermatomes and PP in 27%. AIS C/D (MI) subjects with tetraplegia had more dermatomes with preserved sensation than those with paraplegia. When reviewing areas at highest risk for pressure sores, only 4 of 22 (19%) of subjects with AIS B (SI)/tetraplegia had any preserved LT or PP sensation in the periscapular region (dermatomes T1-T6). In the buttocks region (S3 and S4-S5), sensation was preserved in fewer than 50% of patients with either tetraplegia or paraplegia.

CONCLUSIONS

(1) Sensory sparing below the neurologic injury was found to be surprisingly sparse in patients classified as AIS B (SI) (35% LT and 8% PP). Sparing was considerably better in patients who were AIS C/D (MI) (77% LT and 27% PP). (2) Preserved sensation in the periscapular region was very low in subjects with tetraplegia (19%) and was also low in the buttocks, with fewer than half of those classified as AIS B (SI) with either tetraplegia or paraplegia reporting sensation.

The role of vestibular and somatosensory systems in intersegmental control of upright stance

Upright stance was perturbed using sinusoidal platform rotations to see how vestibular and somatosensory information are used to control segment and intersegmental dynamics in subjects with bilateral vestibular loss (BVL) and healthy controls (C). Subjects stood with eyes closed on a rotating platform (+/-1.2 degrees) for frequencies ranging from 0.01-0.4 Hz in the presence and absence of light fingertip touch. Trunk movement relative to the platform of BVLs was higher than Cs at higher platform frequencies whereas leg movement relative to the platform was similar for both groups. With the addition of light touch, both groups showed similar trunk and leg segment movement relative to the platform. Trunk-leg coordination was in-phase for frequencies below 1 Hz and anti-phase above 1 Hz. Interestingly, BVLs showed evidence of a "legs-leading-trunk" relationship in the shift from in-phase to anti-phase around 1 Hz. Controls showed no preference for either segment to lead the coordinative shift from in- to anti-phase. The results suggest that the balance instability of BVL subjects stems from high variability of the trunk, rather than the legs. The high trunk variability may emerge from the "legs-leading" intersegmental relationship upon which BVLs rely. Because BVLs derive information about self-orientation primarily from the support surface when their eyes are closed, the legs initiate the shift to anti-phase trunk-leg coordination that is necessary for stable upright stance control. Higher trunk variability suggests that this strategy results in lower overall postural stability. Light touch substitutes for vestibular information, leading to lower trunk variability along with a trunk-leg phase shift similar to controls, without a preference for either segment to lead the shift. The results suggest that vestibulospinal control acts primarily to stabilize the trunk in space and to facilitate intersegmental dynamics.