Motor Imagery ability in adults with neurological conditions compared to healthy individuals: A systematic review and meta-analysis

There is growing but inconclusive evidence on the effects of motor imagery interventions in neurorehabilitation. Uncertainty regarding potential impairments in imagery ability in adults with neurological conditions may contribute to this controversy. We summarized the evidence on impairments across different aspects of motor imagery ability following Stroke, Traumatic Brain Injury (TBI), Parkinson’s disease (PD), or Multiple Sclerosis (MS). Six databases were searched up to February 2024. Studies comparing adults with these conditions to healthy individuals were included. Two reviewers independently conducted the study selection and Risk of Bias (RoB) assessment. Motor imagery generation, maintenance, and manipulation, assessed through questionnaires, mental chronometry, and mental rotation tasks respectively, were the outcomes extracted. Both quantitative and qualitative analyses were applied. Fifty-two studies with low or moderate RoB were included (Stroke: n=26; TBI: n=1; PD: n=14; MS: n=11). Meta-analyses revealed small-to-moderate effects of Stroke on generation of visual and kinesthetic motor imagery, respectively. A moderate effect of PD was found only for visual motor imagery. For imagery maintenance, qualitative syntheses indicated contradictory evidence for Stroke (although it was stronger towards impairment), with PD and MS showing impairment with moderate to strong evidence. Meta-analyses showed a large and moderate effect on the accuracy measures of imagery manipulation in Stroke and PD respectively, while qualitative analysis also supported this effect in MS. For TBI, a limited number of studies impeded performing a formal synthesis of the evidence. We conclude that impairments in motor imagery ability domains are likely present in people with neurological conditions.