Pathological plantar response. I. Flexor and extensor components in early and late reflex parts.

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Abstract
Pathological changes of the plantar reflex were studied in 120 patients with lesions of the central nervous system. Reflex responses of the short hall-uxflexor and extensor evoked by means of painful repetitive electrical shocks of 10 msec. to the plantar surface of the foot were electro-myographically recorded. Normally flexor activity is strongly predominant in the reflex pattern but following injury there is a tendency to dominant extensor activity. In some of the cases studied the reflex pattern consisted of early predominant extensor activity and late predominant flexor activity. The short latency of the extensor dominant part inducated that it must be a purely spinal reflex. Its strength is completely dependent on stimulus strength. The latency of the flexor dominant part corresponds to that of fast voluntary reactions with strength sometimes completely dependent upon cerebral factors. In other pathological cases there is early predominant flexor activity and late predominant extensor activity. The flexor part must be purely spinal. The extensor component in this pattern varys. At times it is fully dependent upon long-lasting spinal excitatory states which can be built up by repetitive weak stimuli. Reflex patterns of antagonistic extensor-flexor components were only seen in the cases where cerebrospinal connections were intact. This investigation shows that extensor activity may appear early or late in the plantar pattern following injury of the reflex mechanism. It is presumed that a regular dominant extensor activity, whether occurring early or late in the reflex pattern, is of pathological significance and this technique may be of value in clinical examination.