Amiostatic Symptonom-Complex

AMIOSTATIC SYMPTONOM-COMPLEX, a concept introduced by Strümpell (1915), encompassing all disorders of muscle tone regulation. - In a voluntary motor act, two parallel processes must be distinguished: 1) voluntary contraction of muscles and the resulting movement of body parts; this is the external manifestation of myodynamic, or myomotor, innervation; 2) the complex work of the muscle tone apparatus with a special organization of myostatic innervation. The latter changes the tone of voluntarily contracting muscles and their antagonists in the direction necessary for voluntary movement, fixes the limb in the most favorable position for this purpose, and through movement ensures the achievement of the intended goal. This role of myostatic innervation in normally proceeding voluntary movement is not as externally noticeable as the role of myodynamic innervation and is only revealed upon careful analysis, but it becomes particularly clear when the integrity of the muscle tone apparatus is impaired. The following groups of amiostatic symptoms can be established. 1. Increased myostatic innervation leads to increased muscle tone, a peculiar rigidity of muscles, limited joint mobility, and the formation of active contractures that fix the limb in an unusual position. As a result of such changes in muscle tone, a peculiar fixed position of the body and limbs is created, the characteristic posture of the patient, and an immobile facial expression (amimia). Myomotor innervation, as a result, encounters unfavorable conditions for motor effect and may appear insufficient. Voluntary movements become difficult and become unusually poor, rare, slow, and monotonous. This increase in muscle tone in lesions of the myostatic system, unlike that in disorders of the myodynamic apparatus, affects both agonists and antagonists uniformly, so that a passively moved limb freezes in the position given to it (catalepsy). With passive movement of the limb, whether rapid or slow, the impression of equal "wax-like" resistance is obtained (plastic tone of Sherrington); moreover, there is no element of increased reflex irritability. As a special case of such a state of muscle tone, the paradoxical phenomenon of Westphal is observed. - 2. If the disorder of myostatic innervation spreads to the corresponding muscles unevenly and not simultaneously, as in the cases described above, then a disorder of muscle tone balance arises. Since the fixation of any member depends on the equal intensity and timing of static innervation of antagonists, a violation of this equality must lead to defects in fixation. Here two cases are possible: a) if the static innervation of antagonists ceases to be simultaneous and becomes alternating, then alternating but equal in intensity tension of antagonists arises; this creates oscillation of the corresponding body part, tremor (true tremor of antagonists, oscillatory tremor); b) if this unevenness of static innervation concerns the intensity of muscle tension, then instead of uniform oscillatory tremor, a series of uneven, alternating, involuntary contractions throughout the muscle group arises, i.e., athetosis develops. - 3. Decreased myostatic innervation leads to decreased muscle plastic tone and, consequently, to excessive freedom of both passive and active movements. Such a condition occurs in chorea (chorea minor). In it, the disorder of muscle tone regulation leads to involuntary movements, but, unlike athetosis, rapid, disorderly, and scattered (choreiform movements). The group of myostatic disorders also includes Bálint's adiadochokinesia, Schilder's bradyteleokinesia, and Rossolimo's cerebral amyotaxia. Negative signs of pure A. s. are the absence of "pyramidal symptoms" (the favorite type of contractures, increased tendon reflexes, Babinski's reflex, etc.). Anatomically, myostatic innervation is connected with the extrapyramidal apparatus of the central nervous system and with the vegetative part of the peripheral nervous system. Therefore, A. s. is observed in such diseases as paralysis agitans, Wilson's disease, pseudosclerosis, arteriosclerotic muscular rigidity, postencephalitic and CO poisoning parkinsonism, bilateral athetosis, chorea, as well as in focal processes affecting the entire extrapyramidal system or its individual parts - from the striatum to the cerebellum. As a transient phenomenon, A. s. can be observed in epilepsy.