By Megan Auld
In research and in clinical practice, I’m forever finding myself snagged on the details – missing the story by getting caught up with p-values, forgetting that the arm I’m treating is connected to a head. Which is perhaps why I remember so clearly when Lorimer first persuaded me to focus on treating the source of the problem – the brain. And also what amused me when I realised that I hadn’t given this a single thought when reading this paper he sent me…
Many of you would be familiar with Parsons’ laterality task, used to test motor imagery. This task involves looking at pictures of hands in various rotated positions and judging whether they are left or right hands. Using this task, an interesting paper by Van Elk et al. (2010) suggests that the movement planning deficits present in children with hemiplegia may be related to an impaired ability to use motor imagery.
Van Elk et al. measured “rotation-related negativity” (RRN) with EEG during the laterality task as a neural indicator of motor imagery activity. This showed that children with mild hemiplegia had a stronger “RRN” than those with more severe motor deficits, therefore suggesting a relationship between motor imagery ability and the biomechanical limitations of the impaired limbs. In other words, a more impaired arm leads to dodgier motor imagery (or perhaps the other way around?).
When I first read this paper, I was snagged again by those thinking-too-hard-about-the-detail questions– was it wise to only include children with right hemiplegia in the study, what about kids with left hemiplegia and is motor imagery really the same in children with right hemiplegia who are right dominant as those who are left dominant? (if you’re as anxious about these things as I was, you should probably read the paper).
If you are, however, able to look past the few worrisome details, this is what I think deserves our attention:
After years of stretching and strengthening and any other treatment we can think of to manage the motor problems of hemiplegia at the level of the hand, Van Elk et al. challenge us to look a bit closer at the source of the problem. We know that hemiplegia results from damage to the CNS, that it leads to motor deficits and that these motor deficits are at least in part due to difficulty in planning movements. But now, Van Elk et al. swing the spotlight completely away from the physical impairment for a moment and fix it on the brain to probe the neural foundations of some of these problems and perhaps the window to a whole new world of therapy for these children. And I’m reminded all over again to not get snagged on the details…
Megan Auld is a physiotherapist with a special interest and, by all reports, considerable expertise, in treating children with hemiplegia. This is why she works at the Cerebral Palsy League. She is also in the final stages of her PhD at the University of Queensland. Her doctoral work has investigated tactile function in children with hemiplegia. She is absolutely top-shelf. Megan did her honours in physiotherapy with Lorimer at UQ, which is why Lorimer felt able to put a little bit of pressure on her to squeeze this post into her end-of-phd-panic-striken-somehow-still-very-nice-and-tolerant-of-loud-noises timetable. We are very grateful indeed. Oh, Megan did not write this bio.
van Elk, M., Crajé, C., Beeren, M., Steenbergen, B., van Schie, H., & Bekkering, H. (2010). Neural Evidence for Compromised Motor Imagery in Right Hemiparetic Cerebral Palsy Frontiers in Neurology, 1 DOI: 10.3389/fneur.2010.00150