Electromyography and histopathology of muscle and spinal cord: Analysis of 105 skeletal muscles from 31 autopsy cases

Abstract

The subject of our studies included 105 muscles from 31 cases; all cases had been subjected to detailed electromyographic examination before death, and histological studies could be made on the whole of the muscles and the spinal cords corresponding to them at autopsy. Histochemical methods were not applied. The diagnostic significance of EMG and muscle biopsy was investigated by making a comparison between the findings obtained by EMG and histological findings in muscles and spinal cords. The results are as follows: 1. (1) All 25 muscles that were histologically found to contain groups of small fibres showed neurogenic changes in the EMG. However, among the muscles showing neurogenic changes in the EMG, some had no distinctly discernible groups of small fibres and contained only muscle fibres of different sizes, or scattered small fibres. These pathological findings in muscle could also be interpreted as neurogenic because the anterior horn cells of the corresponding spinal segments showed some morbid changes. 2. (2) In a considerable number of the muscles having groups of small fibres, the groups were localized in small areas of the muscle bellies, and therefore, they might quite easily have been missed on sampling by muscle biopsy. 3. (3) The wider the range of the groups of small fibres, the more marked the decrease in the number of action potentials in maximum contractions, and the more grave was the muscular wasting, clinically. 4. (4) All the anterior horns of the spinal cords corresponding to the muscles with neurogenic changes, both in the EMG and in the histopathology, presented some abnormal findings in serial sections. 5. (5) Degeneration of isolated muscle fibres, if scattered, had little influence on the EMG, and myopathic changes were not revealed by the EMG until muscle fibre degeneration had become diffuse in the muscle atrophy due to disuse or ageing.