Electromyographic differentiation of diplegic cerebral palsy from idiopathic toe walking: Involuntary coactivation of the quadriceps and gastrocnemius

Clinical differentiation of patients with mild diplegic cerebral palsy (CP) and idiopathic toe walking (ITW) can be difficult. However, an involuntary extensor pattern may be a distinguishing sign. The purpose of this study was to determine if selected gait parameters or patterns of electromyogram (EMG) timing of quadriceps, gastrocnemius, and tibialis anterior during knee extension while sitting can distinguish between these patients. The hypothesis was that EMG testing for selective control of the quadriceps and gastrocnemius could differentiate patients with diplegic CP from normal controls and from patients with ITW. We evaluated 10 control, eight CP, and eight ITW subjects. Measurements included walking speed, energy expenditure index (EEI), ankle position during stance, and EMG of the quadriceps, gastrocnemius, and tibialis anterior during gait and during knee extension while sitting. Dynamic EMG timing during gait showed significant differences in the mean onset of the gastrocnemius between subjects with CP and ITW, but there was considerable overlap. More consistent differences were found during active and active-resisted knee extension while sitting. Mean values for gastrocnemius EMG timing recorded as a percentage of duration of quadriceps EMG while sitting were 0 and 0.4% for controls, 0 and 3.9% for ITW subjects, and 84.3% and 93.4% for CP subjects. Patterns of EMG timing of the quadriceps and gastrocnemius during knee extension while sitting can help to differentiate patients with mild diplegic CP from those with ITW.