A morphometric study of myelinated fibers in the fifth lumbar ventral roots in patients with cerebrovascular diseases.

In order to evaluate the effects of lesions in the upper motor neuron on the lower one, a morphometric study of the 5th lumbar ventral roots was performed in 16 patients with cerebrovascular diseases (CVD) and 8 age-matched controls plus 7 patients with muscular disorders as pathological controls. As a lesion of the upper motor neuron, the degree of lateral corticospinal tract degeneration in the spinal cord were classified into 4 groups. Total fascicular area (TFA), total myelinated fibers (TF) and large fibers (LF) of the ventral roots were significantly (p less than 0.001) decreased in CVD patients who revealed severe degeneration in the lateral corticospinal tracts in affected sides compared with those of controls. The apparent unilateral fiber loss in the ventral root was also observed in some cases whose lateral corticospinal tracts were degenerated with ipsilateral predominance. Therefore, the degree of degeneration of the lateral corticospinal tracts seemed to parallel that of fiber loss of the ventral roots. On the other hand, there were no significant decreases of TFA and TF in the patients with muscular disorders, which makes less likely the possibility that fiber loss in the ventral roots of CVD cases is attributed to long-term bed rest or lack of muscle movements in extremities. These findings suggest a trans-synaptic effect of the degenerated upper motor neuron (lateral corticospinal tract) in CVD patients facilitating fiber loss in the ventral roots.