Pathophysiology of Peripheral Neuropathies

Connective tissue components: I. Endoneurium: consists of basal lamina surrounding Schwann cells. External to lamina is narrow zone of collagen fibrils which is endoneurium proper and contains few cells. II. Perineurium: ensheathes fascicles and ganglia and consists of lamellae of flattened cells. Larger diameter fascicles are covered by more layers. Perineurium provides diffusion barrier with tight junctions and metabolic activity. III. Epineurium: areolar connective tissue around fascicles. IV. Arrangement at spinal roots: A. Endoneurium continues to junction with CNS. B. Perineurium merges with pia mater. C. Epineurium merges with dura mater. V. Changes following degeneration: A. Basal lamina and endoneurium persist, viable for years for reinnervation. B. Little change in perineurium and epineurium.