Posts Tagged Weakness

[ARTICLE] Upper Limb Motor Impairment Post Stroke – Full Text

Synopsis

Understanding upper limb impairment after stroke is essential to planning therapeutic efforts to restore function. However determining which upper limb impairment to treat and how is complex for two reasons: 1) the impairments are not static, i.e. as motor recovery proceeds, the type and nature of the impairments may change; therefore the treatment needs to evolve to target the impairment contributing to dysfunction at a given point in time. 2) multiple impairments may be present simultaneously, i.e., a patient may present with weakness of the arm and hand immediately after a stroke, which may not have resolved when spasticity sets in a few weeks or months later; hence there may be a layering of impairments over time making it difficult to decide what to treat first. The most useful way to understand how impairments contribute to upper limb dysfunction may be to examine them from the perspective of their functional consequences. There are three main functional consequences of impairments on upper limb function are: (1) learned nonuse, (2) learned bad-use, and (3) forgetting as determined by behavioral analysis of tasks. The impairments that contribute to each of these functional limitations are described.

The nature of upper limb motor impairment

According to the International Classification of Functioning, Disability and Health model (ICF) (Geyh, Cieza et al. 2004), impairments may be described as (1) impairments of body function such as a significant deviation or loss in neuromusculoskeletal and movement related function related to joint mobility, muscle power, muscle tone and/or involuntary movements, or (2) impairment of body structures such as a significant deviation in structure of the nervous system or structures related to movement, for example the arm and/or hand. A stroke may lead to both types of impairments. Upper limb impairments after stroke are the cause of functional limitations with regard to use of the affected upper limb after stroke, so a clear understanding of the underlying impairments is necessary to provide appropriate treatment. However understanding upper limb impairments in any given patient is complex for two reasons: 1) the impairments are not static, i.e. as motor recovery proceeds, the type and nature of the impairments may change; therefore the treatment needs to evolve to target the impairment contributing to dysfunction at a given point in time. 2) multiple impairments may be present simultaneously, i.e., a patient may present with weakness of the arm and hand immediately after a stroke, which may not have resolved when spasticity sets in a few weeks or months later; hence there may be a layering of impairments over time making it difficult to decide what to treat first. It is useful to review the progression of motor recovery as described by Twitchell (Twitchell 1951) and Brunnstrom (Brunnstom 1956) to understand how impairments may be layered over time (Figure 1).

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Sequential progression of motor recovery as described by Twitchell and Brunstrumm. Note that while recovery is proceeding from one stage to the next, residual impairment from preceding stages may still be present leading to the layering of impairment. Also note the underlying physiological processes that may account for progression from one stage to the next.

Understanding motor impairment from a functional perspective

The most useful way to understand how impairments contribute to upper limb dysfunction may be to examine them from the perspective of their functional consequences. There are three main functional consequences of stroke on the upper limb: (1) learned nonuse, (2) learned bad-use, and (3) forgetting as determined by behavioral analysis of a task such as reaching for a food pellet and bringing it to the mouth in animal models of stroke (Whishaw, Alaverdashvili et al. 2008). These are equally valid for human behavior. Each of the functional consequences and the underlying impairments are elaborated below.[…]

 

Continue —>  Upper Limb Motor Impairment Post Stroke

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[ARTICLE] Brain-machine Interface in Robot-assisted Neurorehabilitation for Patients with Stroke and Upper Extremity Weakness – the Therapeutic Turning Point – Full Text HTML

Abstract

Activity and participation after stroke can be increased by neurorehabilitation of upper extremity. As the technology advances, a robot-assisted restorative therapy with/without a brain-machine interface (BMI) is suggested as a promising therapeutic option. Understanding the therapeutic point of view about robots and BMIs can be linked to the patient-oriented usability of the devices. The therapeutic turning point concept of robot-assisted rehabilitation with BMIs, basics of robotics for stroke and upper extremity weakness and consequent neuroplasticity/motor recovery are reviewed.

Highlights

  • Robot with BMI therapy for arm after stroke has closed feedback and more chance of neural plasticity.
  • Understanding of the new rehabilitation technologies such as robot with BMI therapy for arm after stroke shall give the therapeutic turning point.

INTRODUCTION

Stroke is a sudden neurologic deficit caused by disturbance of vascular supply to the brain by ending up ischemic/hemorrhagic lesions on it. A large proportion of disease burden of stroke can be explained by the loss of motor function causing decreased activity of daily living and participation restriction for the patient. Affected brain regions in stroke, especially in sensorimotor areas, could show various kinds of motor deficits such as weakness, incoordination and changes of muscle tone. For the execution of activity of daily living, those motor deficits need to be properly intervened, which would be the reason why we claim an intensive neurorehabilitation for the recovery of functions during long survival period after stroke [1, 2, 3].

In Merriam-Webster (http://merriam-webster.com; accessed on 26 August 2016), one simple definition of robot is a machine that do the work of a person and that works automatically or is controlled by a computer. Some kinds of a robot can move human body parts, and the purpose of the robot can be the neurorehabilitation and the improvement of the function of that body parts.

Robot-assisted arm rehabilitation can give the patient repetitive, controlled motion of upper extremity without exhaustion of therapist. Level of difficulty for the training task can be adjusted according to the status of the patient [4]. Through robot-assisted upper extremity training of movement, neural plasticity and motor recovery can be facilitated [5].

The motivation for the use of devices and the study of psychological stability would be important in terms of efficacy in all kinds of therapies, including robot therapy. Closed feedback during the robot therapy can elevate the patient’s emersion to the task and increase the motivation. Among many methods of closed feedback, brain-machine interface (BMI) system can give the direct and immediate feedback to the patient [5]. The BMI is a system that picks up the brain signal, by extracting a useful characteristic, and develop some logics to control other devices using that characteristic, which ideally congruent with the patient’s intention [6]. Many logics of current BMI are used for controlling robots. Through such robot-assisted rehabilitation with BMI system, closed feedback from patient’s immediate, not preprogrammed, intention can be completed. Even though robotic devices or BMIs do not give any haptic sensory feedback, visual or proprioceptive observation of the robotic arm to perform the intended movement will give the BMI-controlling patients more appropriate feedback. In this review, non-invasive electroencephalogram based BMI combined with robot-assisted rehabilitation technique is considered.

Continue —> KoreaMed Synapse

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[ARTICLE] Contributions of voluntary activation deficits to hand weakness after stroke

Abstract

Background: Hemiparetic stroke survivors often exhibit profound weakness in the digits of the paretic hand, but the relative contribution of potential biomechanical and neurological impairment mechanisms is not known. Establishing sources of impairment would help in guiding treatment.

Objective: The present study sought to quantify the role of diminished capacity to voluntarily active finger flexor and extensor muscles as one possible neurological mechanism.

Methods: Two groups of stroke survivors with “severe” (N = 9) or “moderate” (N = 9) hand impairment and one group of neurologically intact individuals (N = 9) participated. Subjects were asked to create isometric flexion force and extension force, respectively, with the tip of the middle finger. The maximum voluntary force (MVF) and the maximum stimulated force (MSF) produced by an applied train of electrical current pulses (MSF) were recorded for flexion and extension. Percent voluntary activation (PVA) was computed from MVF and MSF.

Results: Significant deficits in both MVF and PVA were observed for stroke subjects compared to control subjects. For example, activation deficits were >80% for extensor digitorum communis (EDC) for the “severe” group. Maximum voluntary force and PVA deficits were greater for EDC than for flexor digitorum superficialis (FDS) for stroke subjects with severe impairment. Maximum voluntary force and PVA correlated significantly for stroke subjects but not for control subjects.

Conclusions: Although extrinsic finger muscles could be successfully recruited electrically, voluntary excitation of these muscles was substantially limited in stroke survivors. Thus, finger weakness after stroke results predominantly from the inability to fully activate the muscle voluntarily.

Source: Maney Online – Maney Publishing

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