Degeneration and regeneration in teased nerve fibres. I. Leprous neuritis

Does clofazimine (B663) reach Mycobacterium leprae persisting in Schwann cells and endothelial cells of endoneurial blood vessels in peripheral nerves?

Peripheral nerve biopsies from 10 Lepromatous leprosy (LL) patients who were on multidrug treatment (MDT) were investigated by light and electron microscopy. Clofazimine (CLF) has been included as an essential component of MDT, which is the standard WHO regimen for treatment of leprosy. The patients receiving continuous MDT for a long period had viable bacilli in Schwann cells (SCs) of peripheral nerves whereas they had disappeared from the skin. Our ultrastructural observations clearly indicated the presence of CLF crystals in SCs. The crystals were in the form of osmiophilic rods of various shapes and sizes. On the other hand, the blood nerve barrier was clearly noticed in endoneurial blood vessels (EBV), and the barrier seems to play an important role for penetration of antileprosy drugs especially CLF.

Alterations in neurofilament protein(s) in human leprous nerves: morphology, immunohistochemistry and Western immunoblot correlative study

Using a specific antibody (SMI 31), the state of phosphorylation of high and medium molecular weight neurofilaments (NF-H and NF-M) was studied in 22 leprous and four nonleprous human peripheral nerves by means of immunohistochemistry, sodium dodecyl sulfate-poly acrylamide gel electrophoresis (SDS-PAGE) and Western immunoblot (WB). The results thus obtained were compared with morphological changes in the respective nerves studied through light and electron microscopy. Many of the leprous nerves showing minimal pathology revealed lack of or weak staining with SMI 31, denoting dephosphorylation. Remyelinated fibres stained intensely with SMI 31 antibody. The WB analysis of Triton X-100 insoluble cytoskeletal preparation showed absence of regular SMI 31 reactive bands corresponding to 200 and 150 kDa molecular weight (NF-H and NF-M, respectively) in 10 nerves. Three of the 10 nerves revealed presence of NF protein bands in SDS-PAGE but not in WB. Presence of additional protein band (following NF-M) was seen in four nerves. Two nerves revealed NF-H band but not NF-M band and one nerve showed trace positivity. In the remaining five nerves presence of all the three NF bands was seen. Thus, 77.3% (17/22) of human leprous nerves studied showed abnormal phosphorylation of NF protein(s). The ultrastructural study showed abnormal compaction and arraying of NF at the periphery of the axons in the fibres with altered axon to myelin thickness ratio (atrophied fibres) as well as at the Schmidt-Lantermann (S-L) cleft region. Such NF changes were more pronounced in the severely atrophied axons suggesting a direct correlation. The observed well-spaced NF in the remyelinated fibres under ultrastructural study was in keeping with both intense SMI 31 staining and presence of NF triplet bands seen in WBs in four of leprous nerves that showed a large number of regenerating fibres suggesting reversal of changes with regeneration. Findings in the present study suggest that atrophy, that is, the reduction in axonal calibre and paranodal demyelination, seen in leprous nerves may result from dephosphorylation of NF-H and NF-M proteins.

The diagnosis of leprosy among patients with symptoms of peripheral neuropathy without cutaneous lesions: a follow-up study

Forty-four patients with neuritic leprosy were individually followed for periods ranging from 4 months to almost 4 years for the purpose of ascertaining the presence and/ or absence of leprosy. The neural symptoms presented were sensory impairment (41), parasthesia (28), nerve enlargement (22), nerve tenderness (20), paresia (20), amyotrophy (8). Leprosy was diagnosed in ten out of the total number of patients studied. Leprosy was confirmed by the appearance of reactional neuritis (4), reversal reaction (2), biopsy of the hypoesthesic area (3) and the appearance of non-reactional cutaneous lesion. We reported an experience in the diagnosis of neuritic leprosy and its most frequent clinical presentation with which clinicians have to be acquainted. We can also state that the clinical follow-up was an effective strategy for the diagnosis of the disease when diagnostic facilities are not available or have not confirmed the diagnosis.

Teased fibre studies in leprous neuropathy

Nerve biopsies were taken from four cases of leprosy, which included borderline tuberculoid, borderline and lepromatous types. They were examined in 1-micron resin sections and in teased preparations. The most common finding in teased fibres from each leprosy type was paranodal demyelination affecting successive internodes. In transverse sections some fibres showed changes associated with axonal atrophy. Together, these findings suggest that demyelination in some cases may be secondary to axonal changes. In addition, there was evidence of focal areas of demyelination affecting whole internodes of many fibres at the same level across the nerve and which was possibly caused by local factors.

Pathology and pathogenesis of predilective sites of nerve damage in leprous neuritis. Nerves in the arm and the face

A very brief review of the literature on the clinicopathological aspects of leprosy is given; mainly through references. The salient features of the two main types of leprosy--tuberculoid and lepromatous--are presented in a Table. The surgical and pathological findings are briefly described and the pathogenesis of involvement of the facial nerve (a motor nerve) is discussed. On the basis of (i) the severe histopathologic changes (degeneration) of the most distal part of the zygomatic branch of the facial nerve (innervating the orbicularis oculi), with sparing of the roots of all branches and the trunk of the nerve; (ii) the concurrent loss of cutaneous sensations in the territory of the maxillary division of the trigeminal nerve (the region of the zygoma and the lower eyelid); and (iii) the close approximation or even anastomoses occurring between the ultimate branches of these two nerves, it is postulated that paralysis of orbicularis oculi occurs secondarily to the sensory nerve damage, i.e. due to spread of infection from the sensory branches of the trigeminal to the motor branches of the facial nerve. The surgical and pathological findings of the nerves in the arm, especially the ulnar and the median and their branches are described, in tuberculoid and lepromatous leprosy. The forms of nerve degeneration, the occasional axon regeneration, and the role of the Schwann cell in harbouring the bacilli, are illustrated. The lysosomal enzyme activity in the Schwann cells of nerve fibres, particularly of unmyelinated fibres which preferentially phagocytose the M. leprae, and their role, albeit not very successful, in degrading the bacilli and controlling the infection, are also stressed, through light and electronmicrographs. The constellation of secondary factors of the terrain operating to produce further damage to primarily diseased nerves, is discussed. These factors include indirect compression from unyielding fibroosseous tissues, minor traumata, stretching of the nerves, and their exposure to lower temperatures in subcutaneous tissues.

The Hoffmann reflex of the soleus muscle. A study in leprosy

The H reflex of the soleus muscle was used to investigate the monosynaptic reflex arc of two groups of leprosy patients compared with a similar group of normal subjects. The H reflex recordings show two abnormalities: (1) An increase in the latency of the reflex without difference between lepromatous and borderline patients. (2) A decrease of the Hmax:Mmax amplitude ratio more pronounced in the lepromatous group. The discrepancy between these results and the commonly described preservation of the deep tendon reflexes in leprosy is discussed and the hypothesis that leprosy neuropathy would affect all nerve trunks related to blood vessel changes in suggested.

Electrophysiological evidence for motor unit impairment during the treatment of leprosy

Although neuropathy is the most striking feature in leprosy, the effects of various drugs are usually assessed by dermatological and bacteriological improvement. This short term electrophysiological study shows that both antileprosy drugs, DDS and Sulforthomidine, do not affect the insidious deterioration of motor unit condition in lepromatous and borderline BT patients. Differences observed in the results of the two groups were discussed.

Respective importance of different nerve conduction velocities in leprosy

Motor and sensory nerve conduction studies were performed in the distal part of the ulnar, median and radial nerves of 12 tuberculoid and 12 lepromatous leprosy patients, compared with 15 normal subjects. Slowing of sensory conduction velocity (SCV) was shown in all nerves with no difference between tuberculoid and lepromatous patients. The radial SCV slowing is correlated (P less than 0.001) with the clinical findings. Impairment of motor distal latencies was observed only in tuberculpoid patients. It is concluded that the radial SCV is the most reliable conduction test and is proposed as an early diagnostic test for leprosy.

Teased fibre study of early nerve lesions in leprosy and in contacts, with electrophysiological correlates

A teased fibre technique was used to study 19 biopsies of the index finger branch of the radial cutaneous nerve of leprosy patients and contacts. These were compared with four normal nerves. Five nerves were from patients with preclinical nerve lesions, five from leprosy patients with minimal sensory nerve impairment, and five from contacts of lepromatous leprosy. The extent of demyelination in preclinical nerve lesions in leprosy and in contacts of leprosy is recorded. The usefulness of nerve conduction velocity studies in early leprosy patients and in contacts is discussed.