Regeneration at the predilective damage sites of nerve trunks in treated leprosy

Superficially located large and medium sized mixed peripheral limb nerves in active leprosy have previously been shown to have well-recognized fusiform swellings. It is generally agreed that these are the sites of predilective nerve involvement where the severest degeneration and fibrosis occur. A semiquantitative histopathological study on one of these sites the flexor retinaculum region of the posterior tibial nerve, has been carried out on 14 treated leprosy patients who suffered from total sensory loss to the root for between 2 and 40 years. The following observations were made: (1) large-scale nerve regeneration was present as characterized by numerous Schwann cells and unmyelinated axons which formed regeneration clusters; (2) thick myelinated axons were either absent or present only in very low numbers; (3) the intraneurial fibrosis was usually not severe; (4) the presence of active inflammation probably interfered with nerve regeneration; (5) it appeared that this regeneration started shortly after the onset of therapy and persisted for decades; (6) lepromatous cases were characterized by evenly distributed pathology whereas borderline tuberculoid cases had an unevenly distributed pathology; (7) the massive nerve regeneration observed was functionally ineffective - these findings indicate that the total nerve damage may affect the more peripheral nerve branches.