Leprosy neuropathy evaluated by NCS is independent of the patient's infectious state.

INTRODUCTION: Leprosy causes nerve injury, which mimics clinical and neurophysiological conditions, rendering it an excellent model of peripheral neuropathy. METHODS: A retrospective study including 822 nerve conduction studies (NCS) of 509 patients was developed to appraise the electrophysiological pattern of leprosy neuropathy. NCS of motor and sensory nerves performed before, during, and after multidrug therapy (MDT) were analyzed. RESULTS: During the three periods of MDT, while NCS alterations were similar regarding extension, topography, damage severity, and type of lesion, NCS showed that sensory was more frequent (sural nerve) (92-96%) than motor impairment (70-77%) (ulnar nerve). CONCLUSION: Once axonal loss has been installed, nerve function is little affected by inflammatory, immune and/or bacterial events since chronic neuropathy has been established, inevitably leading to the well-known leprosy sequelae occurring at any time before and/or after leprosy diagnosis.

Normal threshold values for a monofilament sensory test in sural and radial cutaneous nerves in Indian and Nepali volunteers.

The monofilament test (MFT) is a reliable method to assess sensory nerve function in leprosy and other neuropathies. Assessment of the radial cutaneous and sural nerves, in addition to nerves usually tested, can help improve diagnosis and monitoring of nerve function impairment (NFI). To enable the detection of impairments in leprosy patients, it is essential to know the monofilament threshold of these two nerves in normal subjects. The radial cutaneous, sural, ulnar, median and posterior tibial nerves of 245 volunteers were tested. All nerves were tested at three sites on both left and right sides. Normal monofilament thresholds were calculated per test-site and per nerve. We assessed 490 radial cutaneous and 482 sural nerves. The normal monofilament was 2 g (Filament Index Number (FIN) 4.31) for the radial cutaneous and 4 g (FIN 4.56) for the sural nerve, although heavy manual laborers demonstrated a threshold of 10 g (FIN 5.07) for the sural nerve. For median and ulnar nerves, the 200 mg (FIN 3.61) filament was confirmed as normal while the 4 g (FIN 4.56) filament was normal for the posterior tibial. Age and occupation have an effect on the mean touch sensitivity but do not affect the normal threshold for the radial cutaneous and sural nerves. The normal thresholds for the radial cutaneous and sural nerves are determined as the 2 g (FIN 4.31) and the 4 g (FIN 4.56) filaments, respectively. The addition of the radial cutaneous and sural nerve to sensory nerve assessment may improve the diagnosis of patients with impaired sensory nerve function.

Near nerve potential of sural nerve in leprosy

Na hanseníase, as fibras de pequeno calibre são acometidas antes que as fibras mais grossas, ocasião em que o estudo da condução torna-se anormal. Neste estudo, utilizou-se a técnica de registro com eletrodos justa-nervo com a finalidade de aumentar a precocidade e a acurácia diagnóstica, devido à sua capacidade de detectar potenciais oriundos de fibras com cerca de 3-6 mm. Contrário às nossas expectativas, o componente principal do potencial sensitivo do nervo sural foi anormal em todos os pacientes, enquanto a velocidade de condução mínima foi normal ou discretamente alterada em 3 pacientes. Além disso, os resultados são sugestivos de degeneração axonal e não mielinopatia, como seria esperado em uma doença que compromete inicialmente a bainha de mielina. Para um melhor entendimento da fisiologia e fisiopatologia, e para aumentar a precocidade diagnóstica, é fundamental estudar casos bem precoces e correlacionar os dados neurofisiológicos com a respectiva anatomia patológica.

Near nerve potential of sural nerve in leprosy.

Leprosy neuropathy is characterized by initial involvement of the small nerve fibers, later followed by involvement of the large fibers, when routine nerve conduction studies become abnormal. To increase the diagnostic yield and precocity of these studies, we applied the near nerve technique to the sural nerve of 8 leprosy patients. Contrary to our expectations, the main component of the sural nerve sensory action potential was abnormal in all patients, but the minimum conduction velocity originating from small 3-6 mm fibers was normal or only mildly involved in three patients. Also, although Schwann cells are the first to be involved in leprosy, the results are suggestive of axonal degeneration instead of demyelination. To better understand the neurophysiology and physiology of leprosy and to increase the accuracy and precocity of the diagnosis, it will be necessary to investigate patients in the very early stages of the disease and to correlate these findings with the corresponding nerve pathology.

Electrophysiologic and histologic studies in leprosy and some acrodystrophic neuropathies.

In vitro electrophysiologic and light microscopic studies were carried out on the sural nerve in six patients with non-leprous neuropathy with plantar ulceration and in six patients with various types of leprous neuropathy. In the non-leprous group (with congenital and acquired neuropathy) the abnormalities in the compound action potentials of the myelinated (large and small) fibers were usually more striking than those in the unmyelinated fibers potentials. In the leprous neuropathies, on the other hand, the three major fiber groups tended to be involved indiscriminately, the unmyelinated fiber potential being as liable to abnormality as the myelinated fiber potentials. Histologically the nerve fiber damage in the congenital neuropathies appeared to be moderate to gross involvement of the myelinated fibers without the prominent demyelination and degeneration/regeneration seen in leprosy and the other acquired neuropathies. Leprous neuropathy showed, besides fiber abnormalities, the simultaneous deleterious effects of inflammation and fibrosis. It is a matter for speculation whether disturbed conduction in the large myelinated touch-pressure mediating fibers contributes significantly to impaired pain perception (mediated by small fibers) and plantar ulceration in leprosy and other acrodystrophic neuropathies.

Nerve conduction studies in leprosy.

Motor and sensory nerve conduction studies have been performed on the peripheral nerves in the upper and lower limbs of 30 control subjects, and 36 subjects with leprosy from the Aboriginal population of the Northern Territory of Australia. Impairment of conduction was demonstrated in the vast majority of clinically abnormal nerves, and a large proportion of nerves which appeared clinically to be uninvolved. In a third group of subjects, abnormal conduction was demonstrated in a significant number of nerves which were considered to be clinically enlarged but in whom the diagnosis was initially in doubt. The majority of these patients were subsequently proven to have leprosy. It is concluded that nerve conduction studies are of considerable value in the diagnosis and management of leprosy.