Trunk performance after stroke: an eye catching predictor of functional outcome

Background and aim

Trunk performance is an important predictor of functional outcome after stroke. However, the percentage of explained variance varies considerably between studies. This may be explained by the stroke population examined, the different scales used to assess trunk performance and the time points used to measure outcome. The aim of this multicentre study was to examine the predictive validity of the Trunk Impairment Scale (TIS) and its subscales when predicting the Barthel Index score at 6 months after stroke.

Methods

A total of 102 subjects were recruited in three European rehabilitation centres. Participants were assessed on admission (median time since stroke onset 20 days) and 6 months after stroke. Correlation analysis and forward stepwise multiple regression analysis were used to model outcome.

Results

The best predictors of the Barthel Index scores at 6 months after stroke were total TIS score (partial R² = 0.52, p<.0001) and static sitting balance subscale score (partial R² = 0.50, p<.0001) on admission. The TIS score on admission and its static sitting balance subscale were stronger predictors of the Barthel Index score at 6 months than the Barthel Index score itself on admission.

Conclusions

This study emphasises the importance of trunk performance, especially static sitting balance, when predicting functional outcome after stroke. The TIS is recommended as a prediction instrument in the rehabilitation setting when considering the prognosis of stroke patients. Future studies should address the evolution of trunk performance over time and the evaluation of treatment interventions to improve trunk performance.Although the age specific incidence of major stroke has fallen over the past few years,¹ it is still the main cause of long term disability in adults, with a growing number of survivors being dependent for activities of daily living (ADL).^2,3 Frequently identified variables predicting ADL after stroke are age and initial severity of motor and functional deficits.⁴ Trunk performance has also been identified as an important independent predictor of ADL after stroke.^5,6,7,8,9 However, based on multiple regression analyses, the reported variance of functional outcome after stroke explained by trunk performance ranges from 9% to 71%.^5,6,7,8,9 Differences in reported variance could be explained by the stroke population included, the various scales used to measure trunk performance and the time points used to measure outcome.Previous studies evaluating the predictive validity of trunk performance after stroke were performed in a single rehabilitation setting, warranting caution when generalising results.^5,6,7,8,9,10 Clinical tools used to assess trunk performance are the Trunk Control Test,^5,6,10 trunk control items of the Postural Assessment Scale for Stroke patients^7,8 and trunk assessment of Fujiwara et al.⁹ A limitation of the first two tests is that they both have a ceiling effect, which makes their use less suitable in long term outcome studies.^5,11,12,13 Furthermore, the trunk control items of the Trunk Control Test and Postural Assessment Scale for Stroke patients are largely comparable with the items of the trunk measure of Fujiwara et al.⁹ All previously mentioned clinical tools include items in the supine position which involve rolling as well as only basic balance movements in sitting. Finally, with the exception of the trunk control items of the Postural Assessment Scale for Stroke patients,⁸ no study has evaluated the prognostic value of trunk performance when predicting functional outcome at 6 months after stroke.The Trunk Impairment Scale (TIS) for patients after stroke was designed to measure ADL related selective trunk movements rather than participation of the trunk in gross transfer movements.¹⁴ The TIS assesses static and dynamic sitting balance and trunk coordination. Reliability, validity, measurement error, internal consistency and discriminant ability of the TIS have been reported elsewhere.^14,15 The TIS has no ceiling effect in subacute and chronic stroke patients and already appeared to be strongly related to measures of gait, balance and functional ability in a cross sectional study.¹² To the best of our knowledge, the predictive value of the TIS and its subscales has not been evaluated. Including age and other measures of motor and functional performance could provide a useful combination of variables predicting outcome after stroke. The Barthel Index score is a widely accepted measure in stroke rehabilitation research and assesses functional milestones in stroke recovery. Predicting Barthel Index scores at 6 months after stroke based on measurements taken on admission to a rehabilitation centre would further establish the importance of trunk performance when predicting long term outcome after stroke. Experts in the field of neurological rehabilitation have addressed the trunk as the central key point of the body.¹⁶ Proximal stability of the trunk is a prerequisite for distal head and limb movement and therefore expected to be related to functional ADL.In summary, there is still a lack of clarity regarding the importance of trunk performance in functional outcome after stroke. Scales which have been used in previous studies have important statistical limitations and are likely to be a comprehensive measure of motor performance of the trunk. Therefore, the aim of this multicentre study was to examine the predictive validity of the TIS and its subcomponents, together with other known predictors, in predicting functional outcome measured as a Barthel Index score at 6 months after stroke.