The phenomenon known as ankle clonus consists in alternate extension and flexion of the foot on the leg, repeated a varying number of times, following passive flexion of the foot effected rather rapidly and forcibly and maintained somewhat firmly. It is best induced with the leg flexed slightly on the thigh and supported in the palm of one hand, although it can at times be elicited—as with the patient lying supine in bed—when the leg is fully extended on the thigh. Its presence is, in general, an expression of excessive irritability on the part of the motor path in the lumbosacral segment of the spinal cord, and while it is occasionally observed in cases of neurasthenia and hysteria, it is, as a rule, a sign of organic disease. It can at times be induced in healthy persons by supporting the weight of the body on the ball of the partially
ESHNER AA. SOME GRAPHIC OBSERVATIONS OF ANKLE CLONUS. JAMA. 1904;XLII(19):1202–1205. doi:10.1001/jama.1904.92490640008001b
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