Effects of Sensory Deficit on Phalanx Force Deviation During Power Grip Post Stroke

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.

Which sites better represent the sensory function of hands in convalescent stroke patients? A study based on electrophysiological examination

Background

Assessing hand sensation in stroke patients is necessary; however, current clinical assessments are time-consuming and inaccurate.

Objective

This study aimed to explore the nature of light touch sensation and two-point discrimination (2-PD) of different hand sites in convalescent stroke patients based on somatosensory evoked potentials (SEP).

Methods

Light touch sensation and 2-PD of the thumb, the index finger, the little finger, thenar, and hypothenar were measured (n = 112) using sensory measurement tools. Sensory differences among the hand sites were then compared. The correlation analysis between SEP and the hemiplegic hand function was made. Sensory functions were divided into three levels: sensory intactness, sensory impairment, and sensory loss.

Results

Light touch sensations were mainly associated with sensory impairment in the finger and palm region. The 2-PD of the finger region was mainly sensory loss and that of the palm region was mainly sensory impairment. There was no statistical difference in the light touch sensation among the sites of the hand. The correlation coefficients between the 2-PD and SEP N20 amplitudes differed. The correlation coefficients of the thenar and hypothenar were the smallest, and that of the finger was the largest. Light touch sensation and 2-PD in patients with stroke were related to the hemiplegic hand function.

Conclusion

Any site on the hand could be selected as the measurement site for light touch sensation. The little finger and hypothenar may be appropriate sites when screening for 2-PD. To improve the patient's recovery they could receive more sensory stimulation of the hand.

Cutaneous information processing differs with load type during isometric finger abduction

During submaximal isometric contraction, there are two different load types: maintenance of a constant limb angle while supporting an inertial load (position task) and maintenance of a constant force by pushing against a rigid restraint (force task). Previous studies demonstrated that performing the position task requires more proprioceptive information. The purpose of this study was to investigate whether there would be a difference in cutaneous information processing between the position and force tasks by assessing the gating effect, which is reduction of amplitude of somatosensory evoked potentials (SEPs), and cutaneomuscular reflex (CMR). Eighteen healthy adults participated in this study. They contracted their right first dorsal interosseous muscle by abducting their index finger to produce a constant force against a rigid restraint that was 20% maximum voluntary contraction (force task), or to maintain a target position corresponding to 10° abduction of the metacarpophalangeal joint while supporting a load equivalent to 20% maximum voluntary contraction (position task). During each task, electrical stimulation was applied to the digital nerves of the right index finger, and SEPs and CMR were recorded from C3' of the International 10-20 system and the right first dorsal interosseous muscle, respectively. Reduction of the amplitude of N33 component of SEPs was significantly larger during the force than position task. In addition, the E2 amplitude of CMR was significantly greater for the force than position task. These findings suggest that cutaneous information processing differs with load type during static muscle contraction.

Effect of novel training to normalize altered finger force direction post-stroke: study protocol for a double-blind randomized controlled trial

BACKGROUND

Functional task performance requires proper control of both movement and force generation in three-dimensional space, especially for the hand. Control of force in three dimensions, however, is not explicitly treated in current physical rehabilitation. To address this gap in treatment, we have developed a tool to provide visual feedback on three-dimensional finger force. Our objective is to examine the effectiveness of training with this tool to restore hand function in stroke survivors.

METHODS

Double-blind randomized controlled trial. All participants undergo 18 1-h training sessions to practice generating volitional finger force of various target directions and magnitudes. The experimental group receives feedback on both force direction and magnitude, while the control group receives feedback on force magnitude only. The primary outcome is hand function as measured by the Action Research Arm Test. Other outcomes include the Box and Block Test, Stroke Impact Scale, ability to direct finger force, muscle activation pattern, and qualitative interviews.

DISCUSSION

The protocol for this clinical trial is described in detail. The results of this study will reveal whether explicit training of finger force direction in stroke survivors leads to improved motor control of the hand. This study will also improve the understanding of neuromuscular mechanisms underlying the recovery of hand function.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03995069 . Registered on June 21, 2019.

Concomitant sensory stimulation during therapy to enhance hand functional recovery post stroke

Background

Post-stroke hand impairment is prevalent and persistent even after a full course of rehabilitation. Hand diminishes stroke survivors’ abilities for activities of daily living and independence. One way to improve treatment efficacy is to augment therapy with peripheral sensory stimulation. Recently, a novel sensory stimulation, TheraBracelet, has been developed in which imperceptible vibration is applied during task practice through a wrist-worn device. The objective of this trial is to determine if combining TheraBracelet with hand task practice is superior to hand task practice alone.

Methods

A double-blind randomized controlled trial will be used. Chronic stroke survivors will undergo a standardized hand task practice therapy program (3 days/week for 6 weeks) while wearing a device on the paretic wrist. The device will deliver TheraBracelet vibration for the treatment group and no vibration for the control group. The primary outcome is hand function measured by the Wolf Motor Function Test. Other outcomes include the Box and Block Test, Action Research Arm Test, upper extremity use in daily living, biomechanical measure of the sensorimotor grip control, and EEG-based neural communication.

Discussion

This research will determine clinical utility of TheraBracelet to guide future translation. The TheraBracelet stimulation is delivered via a wrist-worn device, does not interfere with hand motion, and can be easily integrated into clinical practice. Enhancing hand function should substantially increase stroke survivors' independence and quality of life and reduce caregiver burden.

Trial registration

NCT04569123. Registered on September 29, 2020

Effect of Sensory Impairment on Hand Functional Improvement with Therapy and Sensory Stimulation

Sensory impairment may impact individual stroke survivors' motor recovery as well as their response to peripheral sensory stimulation treatment. The objective of this study was to determine the effect of sensory impairment level of individual stroke survivors on motor improvement with therapy and peripheral sensory stimulation. A secondary analysis of a pilot triple-blind randomized controlled trial was used. Twelve chronic stroke survivors were randomly assigned to the treatment group receiving peripheral sensory stimulation or the control group receiving no stimulation during 2-week hand task practice therapy. Sensory impairment level was quantified as the pre-intervention sensory threshold. Motor improvement was assessed as change in the Box and Block Test score from pre- to post-intervention. The association between sensory impairment level and motor improvement was examined using a regression analysis, accounting for groups. This study found that participants with better sensation (i.e., with lower sensory threshold) had better motor improvement than patients with worse sensation (i.e., with higher sensory threshold). Sensory impairment level did not alter the effect of peripheral sensory stimulation. These findings suggest that the level of sensory impairment may predict recovery potentials and direct rehabilitation treatment for stroke survivors.

Loss of haptic feedback impairs control of hand posture: a study in chronically deafferented individuals when grasping and lifting objects

Previous work has highlighted the role of haptic feedback for manual dexterity, in particular for the control of precision grip forces between the index finger and thumb. It is unclear how fine motor skills involving more than just two digits might be affected, especially given that loss of sensation from the hand affects many neurological patients, and impacts on everyday actions. To assess the functional consequences of haptic deficits on multi-digit grasp of objects, we studied the ability of three rare individuals with permanent large-fibre sensory loss involving the entire upper limb. All three reported difficulties in everyday manual actions (ABILHAND questionnaire). Their performance in a reach-grasp-lift task was compared to that of healthy controls. Twenty objects of varying shape, mass, opacity and compliance were used. In the reach-to-grasp phase, we found slower movement, larger grip aperture and less dynamic modulation of grip aperture in deafferented participants compared to controls. Hand posture during the lift phase also differed; deafferented participants often adopted hand postures that may have facilitated visual guidance, and/or reduced control complexity. For example, they would extend fingers that were not in contact with the object, or fold these fingers into the palm of the hand. Variability in hand postures was increased in deafferented participants, particularly for smaller objects. Our findings provide new insights into how the complex control required for whole hand actions is compromised by loss of haptic feedback, whose contribution is, thus, highlighted.

Mirror Illusion for Sensori-Motor Training in Stroke: A Randomized Controlled Trial

BACKGROUND

Poststroke, sensory deficits are not uncommon. In spite of the close association between the sensory and motor recovery, the deficits are usually underemphasized. Mirror therapy (MT), a neural-based approach for the motor deficit has not been explored for the sensory impairment. The objective of the present study was to develop and determine the effect of a MT program for sensori-motor impairment among poststroke subjects.

METHODS DESIGN

Randomized controlled trial.

SETTING

Functional therapy laboratory of Rehabilitation Institute.

PARTICIPANTS

Thirty-one chronic poststroke subjects (17 experimental and 14 controls), aged between 30 and 60years, with ≤ diminished light touch in the hand.

OUTCOME MEASURE

Semmes Weinstein Monofilament (cutaneous threshold), 2-Point discrimination test (touch discrimination) and Fugl-Meyer Assessment (hand motor recovery).

INTERVENTION

The experimental group received sensory stimulus such as tactile perception and motor tasks on the less-affected hand using mirror box. The control counterparts underwent only dose-matched conventional program. 30 sessions with a frequency of 5/week were imparted to the groups.

RESULTS

Post intervention, there was a significant (P < .004) increase up to 30% positive touch-response for the hand quadrants among the experimental group in comparison to only 13.5% rise for the same among the controls. The cutaneous threshold of the less-affected palm also improved significantly among the experimental subjects in comparison to the controls (P = .04).

CONCLUSION

MT may be considered as a promising regime for enhancing cutaneous sensibility in stroke. The mirror illusion induced by MT may be utilized for sensory and motor deficits as well as for the more-affected and less-affected hands.

Gating of Sensory Input at Subcortical and Cortical Levels during Grasping in Humans

Afferent input from the periphery to the cortex contributes to the control of grasping. How sensory input is gated along the ascending sensory pathway and its functional role during gross and fine grasping in humans remain largely unknown. To address this question, we assessed somatosensory-evoked potential components reflecting activation at subcortical and cortical levels and psychophysical tests at rest, during index finger abduction, precision, and power grip. We found that sensory gating at subcortical level and in the primary somatosensory cortex (S1), as well as intracortical inhibition in the S1, increased during power grip compared with the other tasks. To probe the functional relevance of gating in the S1, we examined somatosensory temporal discrimination threshold by measuring the shortest time interval to perceive a pair of electrical stimuli. Somatosensory temporal discrimination threshold increased during power grip, and higher threshold was associated with increased intracortical inhibition in the S1. These novel findings indicate that humans gate sensory input at subcortical level and in the S1 largely during gross compared with fine grasping. Inhibitory processes in the S1 may increase discrimination threshold to allow better performance during power grip.SIGNIFICANCE STATEMENT Most of our daily life actions involve grasping. Here, we demonstrate that gating of afferent input increases at subcortical level and in the primary somatosensory cortex (S1) during gross compared with fine grasping in intact humans. The precise timing of sensory information is critical for human perception and behavior. Notably, we found that the ability to perceive a pair of electrical stimuli, as measured by the somatosensory temporal discrimination threshold, increased during power grip compared with the other tasks. We propose that reduced afferent input to the S1 during gross grasping behaviors diminishes temporal discrimination of sensory processes related, at least in part, to increased inhibitory processes within the S1.