Neuromuscular Diseases

Neuromyopathies are similar to the dystrophies in that there is both nerve and muscular involvement, but there are also differences between the two categories. Some neuromyopathies start in childhood, while others begin later in life. Neuromyopathies involve more brain and spinal cord damage; causes can include infectious diseases, allergic conditions, immunologic problems, and toxic or traumatic injuries.

Amyotonia congenita of the Werdnig-Hoffmann type is the most prevalent condition in this group. In all types of amyotonia congenita, however, there is a failure of development or a degeneration of the motor neurons of the central nervous system or damage of the nerve pathways to the muscles. Since nerve activation of the muscles is diminished or lost completely, muscles atrophy. The condition is recognizable within the first few weeks of life. The child lies flaccid on his back with the head turned to one side, his cry is weak, and his reflexes are diminished or gone. In such severe cases, death occurs before the fifth year, but in some instances, a few years later. The condition is familial and affects both sexes equally. On biopsy the most striking microscopic characteristic of affected muscle tissue is the absence or loss of the development of "end plates," where the twig-like branches of the motor nerves dip into the muscle fibers. The motor nerves or axons also show some typical thickening. Several blood enzyme tests are available for differentiating neuromyopathy from dystrophy but, since neither condition can be effectively treated, the distinction has little therapeutic value.