Wednesday, September 12, 2007

Laterality intact, but a touch of asynchiria

Our friend Hardy the fireman, fell through a plate glass window and managed slice up his RIGHT forearm including a few tendons and the median nerve. His arm has been surgically repaired and is looking good at the 4 week stage. I was interested to see if there were any laterality deficits.

We ran the Recognise computer laterality programme. I ran it 3 times with 20 vanilla hand images by 5 seconds (therefore randomly picked left and right images came up sequentially on the screen to be identified as left or right).

Hardy did well. By the third test he was equal left and right in speed and accuracy of recognition. In the first two trials it took him longer to recognise LEFT hand images (over 1 second difference) and he was inaccurate recognizing LEFT sided images (60% LEFT compared with 90% RIGHT).

These results are worth a thought. In a CRPS state the opposite would be expected, i.e. difficulty and slowness recognizing an image of the painful/injured side (G. L. Moseley, 2004; Schwoebel et al., 2002) so I initially expected Hardy would have had similar responses if there was any left/right variation. Interestingly, in studies of acute experimental pain (G. L. Moseley et al., 2005), and expectation of pain responses (Hudson et al., 2006), this also occurs, suggesting a focus on the injured/painful side as opposed to the neglect often seen in CRPS.

Hardy was pretty cool with the whole arm problem, and although he was off work, he was not that concerned by it and could see he was making progress, or said another way, I thought that he wasn’t letting it get to him.

While it would be nice to know what these findings meant in terms of outcomes via research, my initial thoughts were that at this stage that Hardy didn’t need any graded motor imagery and he was progressing quite “normally”.

We tried a mirror box and noted that he experienced pain in the injured hand which was not moved (i.e. the one hidden in the mirror box). This phenomenon is called dysynchiria and its probably the best example of pain really being in the brain (Acerra & Moseley, 2005). I will discuss dysynchiria in later blogs.

Acerra, N. E., & Moseley, G. L. 2005. Dysynchiria: Watching the mirror image of the unaffected limb elicits pain on the affected side. Neurology, 65, 751-753.

Hudson, M. L. et al 2006. Expectation of pain replicates the effect of pain in a hand laterality recognition task: Bias in information processing towards the painful side. European Journal of Pain, 10, 219-224.

Moseley, G. et al 2005. Experimental hand pain delays recognition of the contralateral hand - evidence that acute and chronic pain have opposite effects on information processing. Cogn Brain Res, 25, 188-194.

Moseley, G. L. 2004. Why do people with complex regional pain syndrome take longer to recognize their affected hand? Neurology, 62, 2182-2186.

Schwoebel, J. et al 2002. Pain and the body schema: Effects of pain severity on mental representations of movement. Neurology, 59, 775-777.