Pathological plantar response: disturbances of the normal integration of flexor and extensor reflex components

Previous reports (Kugelberg, Eklund, and Grimby, 1960; Grimby, 1963) have presented the results of electromyographic studies ofspinal reflexes elicited in healthy subjects by painful brief electric stimuli applied to the plantar surface of the foot. Special attention was paid to the 'reflex pattern' obtained on simultaneous recording in the short hallux flexor and extensor muscles, since the strength of the response in the flexor has been shown to be a sensitive index of the tendency to plantar flexion, and the response in the extensor of the tendency to dorsiflexion of the great toe. The investigations of the reflexes obtained in healthy individuals revealed that the reflex pattern has a basic composition typical of the stimulus site. Thus, stimulation of the hollow of the foot gives rise to activity predominantly in the short hallux flexor, whereas hallux stimulation results in dominant extensor activity; as the stimulus is successively shifted from planta to hallux, the flexor activity is gradually replaced by extensor activity. In an area which was called the 'transition zone' and which roughly corresponds to the ball of the foot, the reflex pattern is composed of alternating flexor and extensor activity of equal strength; the site and width of the transition zone vary from individual to individual. Finally, changes in the subject's attention and expectancy may result in marked, but only occasional, deviations from the basic reflex pattern at a given stimulus site. The electromyographic responses to stimulation of the planta have previously been studied in certain patients with severe spinal cord lesions (Kugelberg et al., 1960); in these cases the reflex patterns consisted of pure short hallux extensor activity independently of the stimulus site. The present study has been undertaken to investigate the types of deviation from the normal reflex patterns that may appear in subjects with less severe lesions of the reflex mechanism, and a direct analysis of the Babinski sign in the common clinical sense is not within the scope of this work. The material has been chosen so as to give the widest possible range of variations, and no conclusions as to the frequency of the different types of deviation in unselected pathological material can be drawn from the results.