Histochemical study of the muscle spindles in parkinsonism, motor neuron disease and myasthenia. An examination of the pathological fusimotor endings by the acetylcholinesterase technic.

Pathological changes of the fusimotor endings in parkinsonism, motor neuron disease and myasthenia were examined by the acetylcholinesterase technic on serial sections. In parkinsonism, the diffuse endings, which are thought to be supplied by the static gamma nerve fibers, showed remarkable enlargement, while en plaque and en grappe endings were atrophic. In motor neuron disease, en plaque and en grappe endings, which are thought to be innervated by the beta nerve fibers and dynamic gamma nerve fibers respectively, revealed marked atrophy. However the diffuse endings were normal. In myasthenia gravis and myasthenic syndrome (Eaton-Lambert syndrome), en plaque and en grappe endings were atrophic, though only the diffuse endings were spared. The significance of these changes in the fusimotor endings is discussed.