Pathophysiology of the Tonic Innervation Phenomenon in the Foot

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Abstract
THE VARIETIES of exaggerated flexion movements in the hand resulting from forebrain lesions have received much detailed study.1-7Most authors have pointed out that related flexion in the foot may be present in some patients, but less investigation has been focused upon the lower extremity, and one may infer that this is partially because the phenomenon is less conspicuous there. Wilson and Walshe1described a behavior of prolonged innervation of the finger flexors which the patient was unable to relax. Adie and Critchley3emphasized the reflex nature of pathological grasping but indicated that it may be triggered by voluntary effort. Later studies by Walshe4,5concluded that there are two phenomena, one an exaggerated volitional contraction and the other a reflex response to proprioceptive stimulation of the fingers. A similar reflex was also described in the foot. The most detailed study is that of Seyffarth and