Motor neuron disease: quantitative morphological and microdensitophotometric studies of neurons of anterior horn and ventral root of cervical spinal cord with special reference to the pathogenesis.

Spinal anterior horn and ventral roots from C6 of spinal cord 6 patients with motor neuron disease (MND) and those from 6 controls were studied morphologically and biochemically, using microscopic observation, morphometry and microdensitophotometry. Spinal anterior horns in MND showed various kinds of morphological changes in nerve cells, and a significant decrease in cellular, nuclear and nucleolar cross-sectional areas in normal and abnormal cells. Microdensitophotometry revealed a significant decrease in the cellular RNA content, of both large cells and small cells, and also of histologically normal appearing cells and abnormal cells. Those findings point to an abnormality of RNA synthesis which precedes the earliest light microscopic changes seen in nerve cells. The cross-sectional areas of myelinated fibers and axons of spinal ventral roots in MND cases showed a significant decrease in the numbers of both total myelinated fibers and large axons. The abnormalities in myelinated fibers and axons of spinal ventral roots in MND cases might be secondary to those in both large nerve cells and small ones of spinal anterior horns in most MND cases and/or primary in some cases.