Neurogenic muscle involvement in myasthenia gravis: A clinical and histopathological study

Abstract

SUMMARY An investigation was made into the occurrence of muscular atrophy and muscular pathology in a series of 170 patients with myasthenia gravis. The results can be summarized as follows: (1) Of the 148 patients with generalized myasthenia gravis, 14 showed local muscular atrophies. Of 10 biopsies from atrophic muscles, eight showed neurogenic changes, with or without lymphocytic infiltrations. One biopsy showed lymphocytic infiltrations only, and one showed type IL-fibre atrophy ( diameter in the female patients than in the controls. In the male patients this could not be proven. (5) Of the eight patients who had died without disorders of ventilation, 90 muscle specimens were examined postmortem. Four of these patients had a thymoma. Lymphocytic infiltrations, found in 32 biopsy specimens, were mostly observed in the presence of a thymoma. Neurogenic changes were apparently unrelated to the presence of a thymoma (Tables 5 and 6). The post mortem examination included the spinal cord in five, and peripheral nerves in three cases. No abnormalities were found. (6) The muscular atrophy found in patients with myasthenia is not a myopathy but an affection of the lower motor neurone. Neurogenic changes were regularly found in the muscles of patients with myasthenia, even without muscular atrophy. The finding of these changes is no reason to reject the diagnosis. It is postulated that denervation occurs at the neuromuscular junction as a result of permanent absence of acetylcholine.

Canine myasthenia gravis

“…The former is thought to exert a trophic effect in the muscle fibre (Oosterhuis and Bethlem 1973). Experiments have shown that the contents of a single vesicle (quantum) produce a small subthreshold depolarisation of the post synaptic membrane (about 1 mV) called a miniature end-plate potential.…”

“…Spontaneous activity suggestive of denervation may be found on electromyographic evaluation (C. L. Chrisman, personal communication), Similar findings occur in humans and although neurogenic atrophy has been demonstrated by muscle biopsy in about 30 per cent of human myasthenia gravis patients, there is no obvious neuropathy or myopathy. Functional denervation because of the absence of trophic effects of acetylcholine on muscle membrane is suspected (Oosterhuis and Bethlem 1973).…”

Facial Muscular Atrophy in a Myasthenia Gravis Patient

“…2-C (1,2). In such cases, muscular atrophy usually involves the tongue, the scapulohumeral muscles, or the proximal limb muscles; facial muscular atrophy is relatively rare (2,3,9,10 (3,4).…”

“…In these cases, the facial muscles were relatively rarely involved (2)(3)(4). Since then, the number of papers dealing with muscle atrophy in MG patients has decreased significantly.…”

Atrophy and Fibrosis of Extra-Ocular Muscles in Anti-Acetylcholine Receptor Antibody Myasthenia Gravis

“…While the primary site of pathology in MG is the neuromuscular junction, muscle changes also occur. Lymphocyte infiltrates and muscle fiber atrophy are the most commonly described changes in the muscle of patients with MG [1]- [4]. While modern diagnostic techniques have made muscle biopsy obsolete in the diagnosis of MG, an understanding of the spectrum of muscle pathology in MG can still be pertinent to clinical practice.…”