Morphological Changes in the Denervated Muscle

Abstract

The first histological studies of denervated muscles were clinical-pathological in character, and were associated with the rapid development of neurological diagnostic methods of peripheral nerve lesions, especially with electrodiagnostic changes developing during denervation, as studied by Erb (1868). In general there was agreement about the morphological changes in denervation which corresponded to the description given, for example, by Oppenheim (1894), who repeatedly investigated questions of muscle diseases: “From the histological aspect the muscle fibres are smaller in diameter, the content of muscle fibres disintegrates into granulated and lipid particles, which are resorbed, so that only sarcolemmal tubes containing nuclei remain.” And further: “Primitive muscle fibres become thinner, lose their cross-striation, their content undergoes granular disintegration combined with waxlike degeneration and there is proliferation of subsarcolemmal nuclei and perimysium.” The description of denervation changes is only very brief, and more attention was paid to degenerative changes in the peripheral nerve stump occurring, for example, after nerve injuries. This is quite natural when taking into account how important at this time were the findings of Waller (1852), concerning degeneration of the nerve, which led to the formulation of laws of neurotrophic relations (so-called “Waller’s degeneration”). The main aim of authors at this time was evidently to show corresponding degenerative changes also in the muscle. It is probably for this reason that Erb (1868) used the term “reaction of degeneration” when describing excitability changes of denervated muscle to galvanic stimulation and Oppenheim similarly concluded in 1894: “Alterations in electrical excitability of the muscle, reaction of degeneration, the course of which have been studied in considerable detail by Erb, Ziemssen and Weiss, correspond to degenerative changes in the peripheral nerve” and further: “Where the reaction of degeneration is present, severe anatomical changes must also be expected, and the degree of these degenerative changes can be anticipated, to a great extent, by evaluation of the degenerative reaction” (see Kopits 1929). The description of degenerative changes in the atrophic muscle is usually stressed in pathological-anatomical literature, so that, for example, in the text-book by Beattie and Dickson (1943) it is stated that: “Cross-striation in the atrophic muscle is less evident or missing, fibres exhibiting vacuolization and fragmentation and having a granular or hyaline appearance.”