Quantifying associated reactions in the paretic arm in stroke and their relationship to spasticity

Objectives: (1) To present a measurement protocol for assessing associated reactions (AR) in the paretic arm and (2) to use it to investigate the patt ern of AR and its association with spasticity. Setting: Inpatient rehabilitation unit. Design: Associated reactions in 49 adults with stroke were measured in term s of force generated, electrical muscle activity and wrist movement in the paretic arm using hand dynamometry, surface electromyography and electrogon iometry respectively. Simultaneous recording of the effort used to elicit t he associated reaction was made using a second hand dynamometer. The magnit ude and persistence of AR was compared with the clinical assessment of spas ticity (using the modified Ashworth Scale, MAS). Results: There was poor correlation between peak AR and MAS, suggesting tha t AR are not confined to patients with severe spasticity. Go-activation of forearm flexors and extensors was evident during the AR. AR fluctuated duri ng a single period of effort in some patients. Only 12 out of 31 patients w ho maintained uniform effort over the measurement period produced a uniform AR. AR often persisted for some time after effort had ceased. Eight were c lassified as minimal (median AR 0.23 N), 25 as mild (median AR 2.7 N), 11 a s moderate (median AR 6.4 N) and 3 as severe (median AR 11.0 N). AR tended to persist in patients with higher MAS although this result was not statist ically significant. Conclusion: The magnitude, profile and persistence of AR varied considerabl y between individuals. Associated reactions were present in people with min imal spasticity. As this technique allows the magnitude of AR to be quantif ied in relation to effort it has the potential to be a useful outcome measu re in clinical trials evaluating the treatments (e.g. physiotherapy) direct ed at reducing associated reactions.