Electromyographically triggered electric muscle stimulation for chronic hemiplegia.
Electromyographically triggered electric muscle stimulation (EMS) was evaluated in combination with conventional treatment in 69 consecutive postcerebrovascular accident outpatients whose onset of hemiplegia was four months to 14 years earlier. Six subjects initially exhibited no residual volitional activity in targeted muscles, and all patients had undergone conventional therapy with little or no functional recovery. Electromyographic (EMG) recordings and EMS directed to prime movers of impaired movements were accomplished by way of skin-surface electrodes. Prescribed treatment (patient compliance was frequently substandard) involved several months of four to five sessions per week, focusing on wrist extension and/or ankle dorsiflexion initially, and often other movements later. During 30 to 300 movement attempts per session, EMGs that exceeded a preset threshold triggered immediate stimulation to force movement completion. Over sessions, patients commonly realized substantially improved increases in voluntary EMG capabilities generally proportionate to the frequency of treatment sessions. Parallel improvements were also found for subjectively scaled functional measures of range-of-motion and ambulation. Motivation was important to success, but side and nature of stroke, age, and poststroke interval were not. Progress often far exceeded that of previous conventional therapy (each patient served as his/her own control). Regarding mechanisms, impaired proprioceptive feedback is considered central to stroke-disrupted sensorimotor control. EMG-triggered EMS is intended to improve brain relearning by reinstating proprioceptive feedback time-locked to each attempted movement. Clinical results were consistent with this theory; further assessment of the new EMG-triggered EMS modality intergrated into conventional treatment regimens seems warranted.