The Ipsilesional Upper Limb Can Be Affected following Stroke

Objective. Neurological dysfunction commonly occurs in the upper limb contralateral to the hemisphere of the brain in which stroke occurs; however, the impact of stroke on function of the ipsilesional upper limb is not well understood. This study aims to systematically review the literature relating to the function of the ipsilesional upper limb following stroke and answer the following research question: Is the ipsilesional upper limb affected by stroke? Data Source. A systematic review was carried out in Medline, Embase, and PubMed. Review Methods. All studies investigating the ipsilesional upper limb following stroke were included and analysed for important characteristics. Outcomes were extracted and summarised. Results. This review captured 27 articles that met the inclusion criteria. All studies provided evidence that the ipsilesional upper limb can be affected following stroke. Conclusion. These findings demonstrate that clinicians should consider ipsilesional upper limb deficits in rehabilitation and address this reduced functional capacity. Furthermore, the ipsilesional upper limb should not be used as a “control” measure of recovery for the contralateral upper limb.


Introduction
Neurological dysfunction commonly occurs in the upper limb contralateral to the hemisphere of the brain in which stroke occurs; however, the effect on the ipsilesional upper limb (iUL) is poorly understood [1,2]. Contralateral deficits increase reliance on the iUL for function and for maintaining independence [3,4]. Recognising the impact of stroke on the iUL is an important step towards implementing effective rehabilitation and to improve our understanding of the challenges faced following stroke [5,6].
Health professionals commonly use the iUL as a measure of reference for recover, and frequently refer to it as "nonaffected" or "unaffected" [2,7]. For health professionals to simply presume that the iUL is not affected by stroke, as our current terminology infers, may fail to adequately recognise the contribution of a functionally important component of upper limb recovery.
In this study, the term iUL refers to the arm and hand on the same side of the body as the lesioned hemisphere. This study will systematically review the research investigating the iUL following stroke to determine if the iUL is affected or not affected by stroke. This study hypothesises that following stroke the iUL can be adversely affected.

Search Strategy.
A systematic search of the literature was carried out in October 2012 using the following databases: Medline, Embase, and PubMed. Search strategies were developed in accordance with the requirement of each database to locate studies for inclusion. The following search terms were used: stroke, upper limb, upper extremity, arm, less affected, nonaffected, and ipsilateral. An example search strategy has been included ( Table 2). A further manual search was conducted from the reference lists of the "captured" studies to identify other relevant studies for inclusion.  survivors. It excluded studies not initially published in English, conference publications, and those that used animal modelling. It also excluded studies which only recruited patients with a left or a right hemispheric stroke, studies which aimed to analyse the role of each hemisphere and/or the function of the iUL, and studies which explored neuroanatomical causes for iUL deficit (Figure 1).

Selection of Studies.
From the initial search, titles and abstracts were reviewed for relevance. Studies which appeared to meet the inclusion criteria were then analysed using the full text. Once the inclusion criteria were confirmed, relevant data was then extracted by the review panel in accordance with a customised data collection form. Where discrepancies arose, the review panel reached agreement through discussion.

Results
This systematic review found that the iUL can be affected following stroke. The search captured 27 studies which assessed iUL motor and/or sensory deficits following stroke ( Table 1).
The iUL was reported as affected in all of the 27 studies captured by this review. The publication dates ranged from 1971 to 2012, with eight (29.6%) studies published before the year 2000. The number of participants with stroke ranged from seven participants to 100; mean (SD) participant cohort was 33.2 (22.8) years. Participant ages ranged from 50.1 to 72.4 years; mean (SD) age was 60.7 (6.1). Isolated deficits of the iUL were not reported; contralateral upper limb deficits were present in all participants recruited to the stroke cohort across the 27 included studies.
Only Noskin et al. [1] and Spaulding et al. [8] compared a stroke cohort to normative data, whilst all the remaining studies ( = 25, 92.6%) compared results to age-matched healthy controls. A mixed cohort of left-handed and righthanded participants was recruited in six studies, whilst 18 studies (66.7%) recruited right-handed participants only. Hand dominance data was incomplete in the remaining three studies [2,9,10].
A dynamometer was the most frequently used assessment tool to determine strength ( = 5, 18.5%) [1,7,10,13,18]. Noskin et al. [1] reported that grip strength was not significantly affected at the time points assessed: 24-48 hours, one week, three months, and one year after stroke. Sunderland et al. [7] reported that grip strength was reduced within one month of stroke ( < 0.001), and in a subsequent study [19] they reported that grip strength had significantly improved at six months after stroke. McCrea et al. [10] reported that 12 months after a stroke event, strength remained affected in the iUL ( < 0.001).

Discussion
This review found evidence that stroke can adversely affect the iUL. To our knowledge, this is the first systematic review of iUL performance to date. This review demonstrates that iUL deficits can be present in the acute, subacute, and chronic phases of stroke recovery. Of the 27 studies reviewed, eight were published before the year 2000 demonstrating that this is not a new concept in stroke research; however, despite current supportive evidence, it continues to be poorly recognised and understood [2,7]. This evidence challenges the current clinical vocabulary which refers to the "nonaffected" or "unaffected" iUL [2,7]. It also reinforces the fact that health professionals should not be using the iUL as a "control" measure for dysfunction in the contralateral upper limb.
This review has demonstrated that, as with the contralesional upper limb, there is a broad range of measures that can be used to assess iUL impairment. It provides evidence that the 9HPT [1,4,12,15] and JHFT [3,4,[7][8][9]14] are sensitive to motor impairment in the iUL. Both assessments are used routinely in patients recovering from stroke, and the 9HPT has been validated for use in this cohort in a systematic literature review [31]. In contrast, grip strength of the iUL was reported to be both affected [7,10] and unaffected [1,18] across the acute, subacute, and chronic phases of stroke recovery. These conflicting results may be reflective of between-study differences in the participant cohort, or they may reflect the fact that this type of measure is, in fact, a crude de facto measure of corticospinal tract integrity [32].

Clinical
Relevance. The current systematic review finds evidence of abnormal patterns of movement and strength in the iUL. These deficits can be linked to reduced functional capacity following stroke and may impact patient outcomes [1,5,11]. These findings indicate that clinicians need to assess, consider, and if relevant, treat impairment of the iUL to effectively manage upper limb rehabilitation after stroke. While the contralateral limb should remain the primary focus of upper limb rehabilitation, this review provides evidence to support the importance of bilateral interventions thereby addressing deficits of both the contralateral upper limb and the iUL [32].
The results of this review validate a change in upper limb vocabulary, and we recommend that the term "less affected" be used when referring to the iUL and the term "more affected" be used when referring to the contralateral upper limb. Health professionals should cease using the terms "unaffected" and "nonaffected" to describe the iUL following stroke, as these terms are misleading at best.

Study Limitations.
Heterogeneity between studies is a limitation of this systematic review. Table 1 illustrates the variances of cohort characteristics. Lesion size and location are not documented in this review; however, it is worth noting that while some researchers took this into consideration when recruiting participants, some made no mention of this at all. The time from stroke onset was another notable limitation with the majority of participants recruited in the chronic phase of stroke (≥six months). Handedness was another between-study inconsistency. Right handed cohorts made up the majority of participants across studies with only some studies considering the association between upper limb function and handedness by comparing the iUL to the equivalent upper limb in control groups.

Further Research.
Sunderland et al. [7] are the only authors who describe the effect of cognition on the deficits of the iUL. Therefore, further research is required to establish the impact of cognition on performance of the iUL. Further research is also needed to explore the pathophysiological mechanisms underpinning deficits of the iUL following stroke, and the role each hemisphere may play in the particular deficits exhibited.

Pathophysiological Mechanisms.
The pathophysiological mechanisms which result in deficits of the iUL are largely unknown. Evidence at this time suggests various hypotheses; however, further research is needed to provide a definitive explanation. A dominant theory suggests that the ipsilesional uncrossed descending corticospinal pathways may play a role in the movement of the iUL [33]. Alternatively, a body of evidence supports the importance of interhemispheric, transcallosal interactions [17,[34][35][36][37]. This suggests that activation of the ipsilateral hemisphere during unilateral upper limb movements might be related to excitatory or inhibitory effects in the contralateral hemisphere [35][36][37][38].

Conclusion
This systematic review finds that people who have experienced stroke can have a deficit of the iUL. Therefore, function in the iUL must be considered in rehabilitation to ensure maximum recovery and opportunities for increased 6 The Scientific World Journal independence. The clinical community needs to update the terminology associated with the iUL to acknowledge that it can be adversely affected and that it should not be used as a benchmark for recovery of function in the contralateral upper limb. While the contralateral limb should remain the primary focus of upper limb rehabilitation, this review provides evidence to support the importance of bilateral interventions thereby addressing deficits of both the contralateral upper limb and the iUL.