[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.[…]

 

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