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Charcot on “provoked trepidation”, or clonus
  1. J M S Pearce
  1. 304 Beverley Road, Anlaby, Hull HU10 7BG, UK; jmspearce{at}freenet.co.uk

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    The classic signs of upper motor neurone lesions became recognised in the second half of the 19th century. Charcot and his colleagues first distinguished them from the flaccid weakness of poliomyelitis, posterior column lesions (locomotor ataxy), neuropathic, and myopathic lesions. The contributions of Erb,1 Marshall Hall,2 and Westphal3 to the related tendon reflexes are well know, but the origins of clonus are less clearly portrayed. The import of these signs can hardly be overestimated. In Charcot’s lectures (references as in his text)4 he said of clonus:

    “. . .known in France under the name of provoked trepidation, or provoked spinal epilepsy. German writers call it the foot-phenomenon (Fussphoenomen) or ankle clonus. But the discovery of this sign belongs to French clinical observers. Since 1863. . .it has been practised daily in the wards of La Salpêtrière by M. Vulpian, by myself, and by our pupils.”

    “. . .it is habitually absent in the motor inability connected with locomotor ataxy, infantile spinal paralysis, and in other conditions of the same kind, whereas it is never wanting in paralysis of cerebral or spinal origin, in which contracture exists or tends to become established.”5

    “The phenomenon may be described as follows. The paralysed lower limb of a hemiplegic patient is supported by placing one hand beneath the ham so that the patient’s leg may hang loose and swing; if now, with the other hand, the point of the foot is suddenly raised, a series of shakes is at once provoked, which collectively constitute a kind of rhythmical movement or oscillatory trembling more or less regular and persistent. Spinal trepidation presents the more interest from the fact that, as a rule, no trace of it exists in the normal state. Thus Herr Berger,6 who has made some observations on the matter, only discovered it three times in 14 000 apparently healthy subjects (mostly soldiers).”

    “I must, however, repeat emphatically that, in the domain of pathology, this is not a constant phenomenon, since in certain spinal affections it is absent, whilst in others the rule is for it to be present. Briefly, it is one of the characteristic features of the group of spasmodic [Charcot often uses the term spasmodic for spastic] paralyses; and to this category belongs central hemiplegia with secondary degeneration of the pyramidal tract.”

    “When late contracture has taken place, this phenomenon is nearly constant, but it frequently

    precedes the contracture by several weeks. In a patient, now an inmate in the infirmary of La Salpêtrière, it began to manifest its presence a week after the attack, and a fortnight later rigidity of the lower limb first made its appearance.”

    “In another patient, it did not appear until a month after the attack, and the muscular rigidity began to be evident in the course of the second month.”

    “M. Dejerine has recently pointed out that this symptom is occasionally present in both lower limbs, and we shall see that this is sometimes the case with contracture.”

    “In hemiplegic patients possessing some slight power of movement, this same trepidation which, in certain cases extends to the entire limb, may also manifest itself in consequence of a voluntary movement. The phenomenon in question is reflex, as I purpose to demonstrate at greater length on a subsequent occasion. . .”

    “An analogous phenomenon is occasionally produced when the hand of a hemiplegic patient is suddenly lifted up by the tips of the fingers. Moreover, these patients, on raising the paralysed arm, often experience a trembling similar to that which occurs in the lower limb under like circumstances. But the wrist-phenomenon, provoked or spontaneous, is much more uncommon than the corresponding effect which we call the foot–phenomenon.”

    “These two signs, as we shall show, belong to the same category as those recently introduced into the semeiotics of spinal affections by Westphal, and afterwards by Erb, under the collective term of tendon-reflexes.”

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