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MUSCLE STRENGTH IN MYASTHENIA GRAVIS: Effects of Exhaustion and Anticholinesterase Related to Muscle Fibre Size
Author(s) -
Ringqvist Ivar
Publication year - 1971
Publication title -
acta neurologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.967
H-Index - 95
eISSN - 1600-0404
pISSN - 0001-6314
DOI - 10.1111/j.1600-0404.1971.tb07514.x
Subject(s) - isometric exercise , biceps , myasthenia gravis , elbow , medicine , myofibril , neuromuscular transmission , muscle contraction , anesthesia , anatomy
Isometric muscle strength and the effects of anticholinesterase and exhaustion were measured in standardized ways in 14 myasthenia gravis patients and 50 controls. The muscle fibre size in m. biceps brachii sin was studied in 12 patients and 8 healthy controls. Significant (positive) response to anticholinesterase of elbow flexors was found in those patients where neuromuscular blocking at single fibre EMG had been found in an upper extremity muscle. In one or more of the six muscle groups tested positive response was found in 12 of the 14 patients. A low relative value of isometric muscle strength did not imply a positive response to anticholinesterase. Post‐tetanic potentiation of elbow flexion strength could only be demonstrated in the group of patients with positive response of elbow flexors to anticholinesterase. A pronounced exhaustion effect was seen in four of the seven patients with positive response. The remaining three patients showed small muscle fibres of type II (see below). The muscle fibres were divided into two groups on the basis of staining reactions for myofibrillar ATPase–type I, weak reaction, and type II, strong reaction. The female patients had significantly reduced type I muscle fibre size. Significantly reduced type II fibre size was found only in the female group with positive response of elbow flexors to anticholinesterase. The 4 male patients had essentially normal fibre sizes.