The number and sizes of reconstructed peripheral autonomic, sensory and motor neurons in a case of dysautonomia

Motor, spinal ganglion, intermediolateral and sympathetic trunk neurons were reconstructed by morphometric sampling of their cell bodies at L5 and T7 segments and at various levels of spinal roots and peripheral nerves in a 31 year-old patient with dysautonomia and compared to reference cases. The patient had strikingly fewer intermediate motoneuron column neurons and intermediate ventral root axons (probably gamma motoneurons), spinal ganglion neurons, preganglionic autonomic neurons and sympathetic trunk neurons than did controls (˜ 10-30% of reference values). The striking agreement between selective absence of intermediate-diameter cytons (Ci) and of intermediate diameter myelinated fibers (Ai), which are thought to be gamma efferent, of L5 motoneuron columns provides further confirmation to our previous suggestion that the Ci peak of motoneuron columns are somas of gamma efferent neurons. The number and size of alpha motoneuron cell bodies and their proximal axons were like those of controls but their distal axons were probably atrophic. This finding probably explains the small reduction in maximum conduction velocity of motor nerve fibers found in this disorder. The brunt of the pathologic process in this disorder has been borne by intermediate and small neurons preferentially.