Contribution of nerve biopsy findings to the diagnosis of disabling neuropathy in the elderly. A retrospective review of 100 consecutive patients.

Peripheral neuropathy is an important factor of disability in the elderly. In order to learn more on the usefulness of intensive evaluation of patients over 65 years of age with subacute or chronic disabling peripheral neuropathy, we reviewed the clinical and nerve biopsy findings of the last 100 patients of this age group who suffered from a peripheral neuropathy severe enough to justify performance of a nerve biopsy for a diagnostic or prognostic purpose. Normal nerve biopsy findings led to the diagnosis of lower motor neuron disease in three patients and pointed to lesions of the spinal roots in six other patients. Necrotizing arteritis was demonstrated in the biopsy specimens of 23 patients, and non-necrotizing vasculitis in five. In five additional patients the diagnosis of vasculitic neuropathy was kept in spite of non-contributive biopsy findings. In two diabetic patients who had a multifocal neuropathy the biopsy also revealed the presence of vasculitis. Thus 35% of the patients included in this series had one form or another of vasculitic neuropathy. Fourteen patients had a chronic inflammatory demyelinating polyneuropathy. In 11 patients the neuropathy was associated with monoclonal gammopathy, which was benign in nine and associated with malignant plasma cell dyscrasia in two. Among the six patients with diabetes mellitus, two patients who presented with a multifocal neuropathy were found to have vasculitis in the nerve specimen; in the others the biopsy was performed because of uncommonly severe pains or motor involvement due to an extremely severe diabetic neuropathy. Six patients suffered from a long-lasting disability secondary to a drug-induced neuropathy. The remaining 15% had neuropathies of different origin, including amyloidosis, lepromatous leprosy, carcinomatous neuropathy and alcoholic neuropathy. Six patients had a mild, non-progressive or slowly progressive axonopathy of unknown origin, ageing of the peripheral nervous system may have played a role in its development. Our findings show that vasculitis is an important and treatable cause of disabling neuropathy in the elderly and that the proportion of patients with severe neuropathy of unknown origin is small.

Detection of Mycobacterium leprae in nerve lesions by the polymerase chain reaction.

A simple procedure is described for the detection of Mycobacterium leprae by the polymerase chain reaction in nerve biopsies sectioned with a cryostat and then treated with proteinase K. All samples from lepromatous leprosy patients and the majority of samples from paucibacillary cases yielded positive results. This approach may be useful for differentiating between leprosy and other inflammatory neuropathies.

Infective neuropathies.

Infective neuropathies encompass neuropathies that are among the most common in the world. Retroviral infection, which includes infection with the human immunodeficiency virus, has now spread worldwide. This virus is responsible for a number of disabling peripheral neuropathies, either from the immune reaction that follows penetration of the virus into nervous system of the host, or by opportunistic infection secondary to the major cellular immunodeficit induced by gradual destruction of lymphocytes bearing the CD4 antigen on their surface. In the other class of retroviruses, human T lymphotrophic viruses (HTLV), which are responsible for the HTLV-I-associated myelopathy or tropical spastic paraparesis, peripheral nerve involvement and inflammatory myopathy are less common and milder than in HIV infection. Leprosy continues to pose problems concerning the understanding of the immune mechanisms that lead to the various patterns of nerve lesions encountered in this condition. Chagas' disease, which is due to infection with Trypanosoma cruzi, affects more than 15 million people in Latin America. It is accompanied by mostly subclinical peripheral nerve involvement and by cardiac manifestations from lesions of the autonomic nervous system and cardiac muscle.

Asymptomatic nerve hypertrophy in lepromatous leprosy: a clinical, electrophysiological and morphological study.

In order to learn more about early nerve lesions observed in leprosy, we performed a clinical, electrophysiological and morphological study in seven patients with untreated lepromatous leprosy, palpably enlarged radial cutaneous nerve and preserved sensation in the corresponding territory. The conduction velocity of the cutaneous radial nerve, which was decreased in all patients, did not significantly differ from that of a group of patients with lepromatous leprosy, hypertrophy of the radial cutaneous nerve and sensory loss. In contrast, the sensory action potential was significantly lower in patients with sensory loss, which demonstrates that axon loss is more important than demyelination in producing sensory loss. In all patients nerve enlargement was due to thickening of the epineurium and of the perineurium subsequent to inflammatory infiltrates and proliferation of fibroblasts and perineurial cells. In several fascicles, the inflammatory infiltrates and the infected cells infiltrated endoneurial connective tissue septa and blood vessels. Mycobacteria leprae were abundant in perineurial cells, fibroblasts, macrophages, Schwann cells and endothelial cells, and lymphocytic vasculitis present in all cases. The average density of myelinated fibres was 2600 SD 880 fibres/mm2 (control: 7700 fibres/mm2), with marked differences between individual fascicles, versus 420 fibres/mm2 in patients with nerve hypertrophy and sensory loss (range 0-2080 fibres/mm2). Single fibre preparations showed that segmental demyelination predominated in two patients, axonal degeneration in one, while inflammatory infiltrates and proliferation of connective tissue adhering to individual fibres were prominent in the others.(ABSTRACT TRUNCATED AT 250 WORDS)

Nerve lesions induced by macrophage activation.

The neuropathies associated with infectious processes, including leprosy, retroviral infections and Chagas' disease, represent the largest group of neuropathies in the world. Segmental demyelination and axonal degeneration of nerve fibres are associated with inflammatory infiltrates which contain a large number of mononuclear phagocytes. In order to learn more about the role played by macrophage activation in the nerve lesions observed in inflammatory neuropathies, we have performed a morphological study of nerves injected with products of activation of macrophages including proteolytic enzymes and cytokines (tumour necrosis factor and alpha beta-interferon). We have also studied the effects on nerve fibres of macrophages activated by ingestion of proteose-peptone, a foreign protein, and in the course of a delayed-type hypersensitivity (DTH) reaction. We have found that proteases and urokinase were potent demyelinating agents and that activated macrophages were also able to induce significant demyelination of neighbouring fibres. In contrast, injection of TNF alpha induced more severe nerve lesions consisting of axonal degeneration of the majority of nerve fibres. We thus conclude that infected macrophages which penetrate the endoneurium and macrophages activated in a DTH reaction can both cause neuropathy.

[Inflammatory neuropathies]. / Les neuropathies inflammatoires.

Inflammatory neuropathy is the term used for all neuropathies associated with an inflammatory infiltrate of the nerves and/or nerve roots. Broadly speaking, there are two types of inflammatory neuropathies: those caused by an identified infectious agent, and those of uncertain origin for which an autoimmune process is usually blamed. Among the neuropathies of infective origin, leprosy is the most important owing to its frequency and to the physiopathological and therapeutic problems it still poses to clinicians and researchers, since the form and severity of nerve lesions depend on cellular immunity to the bacillus' antigen rather than on the bacillus itself. Retroviral infections, caused by the virus of AIDS more than by the virus of tropical spastic paraplegia, are responsible for numerous neuropathies the mechanisms of which are discussed here. The principal inflammatory neuropathies of uncertain origin are polyradiculitis and its different forms, and the heterogeneous group of neuropathies associated with Sjögren's syndrome.