Number and morphology of mechanoreceptors in the myotendinous junction of paralysed human muscle.

The mechanoreceptor system of the myotendinous junction (MTJ) of human palmaris longus muscle obtained at autopsy was studied histologically from six patients with flaccid paralysis (complete acute tetraplegia 4-6 weeks before the autopsy, due to a spinal cord injury), eight patients with spastic paralysis (chronic hemiplegia due to cerebral stroke) and ten neurologically normal controls. Four types of nerve endings, Ruffini and Pacini corpuscles, Golgi tendon organs, and free nerve endings, could be identified in the MTJs of the controls. In the MTJs of the patients with flaccid and spastic paralysis, the free nerve endings were not present and the mechanoreceptors that were found were few in number, degenerated, fibrotic, and atrophic. These mechanoreceptors had lost their connection with the muscle fibres and tendon bundles and were frequently located within pathological accumulations of fatty tissue in the myotendinous region. The number and distribution of mechanoreceptors in the MTJ were almost identical in patients with flaccid and spastic paralysis.