[Contribution of histochemistry to the classification of neuromuscular diseases]

For a long time after the first muscle biopsy performed on man by Bilroth in 1965, histological study of the muscle has been linked to out of date patterns of interpretation most of them without any importance for clinical diagnosis. The use of histochemical techniques in the study of muscle was introduced quite recently and consequently in the last 15 years it has been possible to collect an enormous amount of very important data for the clinical diagnosis of many neuromuscular disorders. The classification of muscle fibers into different types which was possible first of all using the myofibrillar ATPase reaction by Padykula and Hermann permitted pathological interpretation leading to specific correlations between histological and EMG results. Furthermore the use of different histoenzymological methods in the study of mitochondrial enzymes activity and of the enzymes for the glycogen breakdown and synthesis, promoted a more elaborate fibre typing system. Thank to the development of cryostatic microtomy, the above mentioned methods became easy to be performed in the laboratory routine work. The use of the cryostat, which allows a better preservation of muscular tissue, led to a more accurate diagnostic interpretation particularly in relation to morphology. The study of fiber typing revealed many alterations: single fiber type atrophy, type one or type two predominance, type grouping, hypertrophy of a single fiber type and so on, giving to the clinicians the possibility not only of a more elaborate pathogenetic interpretation, but also of a much more precise diagnosis than in the past. Important results have been achieved using the above mentioned histoenzymological methods in the study of the single muscle fibers. Anglo-Saxon Authors provided us with many significant terms, in order to point out alterations of the enzymes distribution within the single muscle fiber: moth eaten, target fiber, rods, central core, subsarcolemmal blebs. Some of these alterations, seen in specific neuromuscular disorders, still represent the only distinguishing feature of these disorders from the nosographic point of view. It is possible to assert without any doubts that in the last 15 years the use of histochemical methods in the study of human muscular tissue has allowed a nosografic classification of neuromuscular disorders very different from that in use before the histochemical age. Thanks to histochemistry the consequent diagnostic and therapeutic advantages have led to very interesting results in such an important field of Neurology.