FIG. 3.

Uninjured myelinated axon and motoneuron estimates by spinal level. (A) Mean (+ standard error) myelinated axon counts (A), percentage of large diameter myelinated axons (> 7 μm; B), and number of motoneurons (C) from C1 to L5 (n = 1 to n = 5 ventral roots per level), compared with motoneuron estimates for two cervical, thoracic and lumbar segments (cases 1–5). Current data from one uninjured spinal cord (case 1), and cervical and thoracic ventral roots taken from two cases of SCI beyond S2 (cases 6 and 7) were similar across cords suggesting that ventral roots remain intact many segments above a SCI. Data from Ingbert³¹ are plotted for comparison.