From Big Medical Encyclopedia

CLONUS (clonus; Greek klonos turmoil, a crush) — the bystry rhythmic movements caused by tolchkoobrazny reduction of a separate muscle or group of muscles. The term is used for the characteristic of the movements caused as spontaneous muscular contractions (clonic spasms), and the reductions caused by certain techniques. To spontaneous clonic spasms, heterogeneous on the mechanism of the origin, belong To. a soft palate, language, clonic spasms at epileptic seizures, etc. (see. Hyperkinesias , Epilepsy ).

At inspection of the patient To. cause special receptions which cornerstone the bystry tolchkoobrazny muscle strain and her sinews is; at the same time emergence To. points to partial or full loss of suprasegmentarny, first of all pyramidal, influences.

Disturbance of suprasegmentarny regulation is followed by reduction of the threshold of segmented reflexes therefore the muscle strain and her sinews leads to reflex reduction of a muscle — to its shortening. The shortening of a muscle counteracting its artificial stretching limits inflow of facilitating and increases inflow of brake impulses to motor-neuron, and then excitement of motor-neuron stops, the muscle relaxes. As the muscle strain and sinews artificially proceeds, the muscle stretches again and the arising excitement of motor-neuron leads to its repeated reduction. There occurs rhythmical alternation of reduction and relaxation of a muscle. Emergence To. it is combined with sharp increase in tendon jerks therefore To. is considered as one of manifestations of a hyperreflexia (see. Reflexes, pathological ).

Distinguish To. patella, foot, thumb of a leg, brush, chin, etc.

To. a patella it is possible to cause at position of the patient on spin with the kicked bucket. Having clamped a patella between big and index fingers, the doctor makes bystry tolchkoobrazny shift it down and holds in this situation, in reply there is a rhythmical alternation of reduction and relaxation by the four-head of a muscle. To. feet is caused in the same pose of the patient, the leg is bent in coxofemoral and knee joints, the bystry tolchkoobrazny dorsiflexion of foot and its deduction in this situation is made; in reply foot rhythmic is bent and unbent. To. feet it can be caused at the same pose by blow of a hammer in a calcaneal (akhillova) sinew. To. a thumb of a leg, a brush cause them bystry, tolchkoobrazny extension and keeping in this situation; To. a chin — bystry tolchkoobrazny procrastination down and keeping of a mandible in such situation. Force of active extension of muscles during the calling To. shall not counteract reduction of muscles.

Existence To. confirms organic lesion of a head or spinal cord. At patients with neurosises (see), in particular with hysteria, attempt to cause To. can lead to tolchkoobrazny reductions of muscles of the changing speed, amplitude and a rhythm (pseudoclonus) that allows to distinguish> them from To. as symptom of organic lesion of a head and spinal cord.

Bibliography: M. B. and Fedorov E. A. crawl. Main neuropathological syndromes, page 370, M., 1966, bibliogr.; A. V triumphs. Topical diagnosis of diseases of a nervous system, page 18, L., 1974; G h u s i d J. G. Correlative neuroanatomy functional neurology, Los Altqs, 1970.

H. H. Anosov.