F-waves persistence in peripheral sensory syndromes.

BACKGROUND: The distinction between sensory neuronopathies (SN), which is by definition purely sensory, and sensory polyneuropathies (SP) and sensory multineuropathies (SM) is important for etiologic investigation and prognosis estimation. However, this task is often challenging in clinical practice. We hypothesize that F-wave assessment might be helpful, since it is able to detect subtle signs of motor involvement, which are found in SP and SM, but not in SN. OBJECTIVE: The aim of the present study was to determine whether F-waves are useful to distinguish SN from SP and SM. METHODS: We selected 21 patients with SP (12 diabetes mellitus, 4 transthyretin familial amyloid polyneuropathy, 4 others), 22 with SM (22 leprosy), and 26 with SN (13 immune-mediated, 10 idiopathic, 3 others) according to clinical-electrophysiological-etiological criteria. For every subject, we collected data on height and performed 20 supramaximal distal stimuli in median, ulnar, peroneal, and tibial nerves, bilaterally, to record F-waves. Latencies (minimum and mean) and persistences were compared across groups using the Kruskal-Wallis and Bonferroni tests. P-values < 0.05 were considered significant. RESULTS: All groups were age, gender, and height-matched. Overall, there were no significant between-group differences regarding F-wave latencies. In contrast, F-wave persistence was able to stratify the groups. Peroneal F-wave persistence was higher, bilaterally, in the SN group compared to SM and SP (p < 0.05). In addition, F-waves persistence of the ulnar and tibial nerves was also helpful to separate SN from SP (p < 0.05). CONCLUSION: F-wave persistence of the peroneal nerves might be an additional and useful diagnostic tool to differentiate peripheral sensory syndromes.

ANTECEDENTES: A distinção entre neuronopatias sensitivas (SN) e polineuropatias sensitivas (SP) e multineuropatias sensitivas (SM) é importante para a investigação etiológica e para o prognóstico. Contudo, esta tarefa é desafiadora na prática clínica. Hipotetizou-se que a avaliação das ondas-F pode ser útil, por ser capaz de detectar envolvimento motor nas SP e SM, mas não nas SN. OBJETIVO: Determinar se as ondas-F podem ajudar a distinguir entre SN, SP e SM. MéTODOS: Selecionou-se 21 pacientes com SP (12 diabetes mellitus, 4 ATTR-FAP e 4 com outras neuropatias), 22 com SM (22 hanseníases) e 26 com SN (13 imunomediadas, 10 idiopáticas e 3 com outras neuronopatias), de acordo com critérios clínicos, etiológicos e eletrofisiológicos. Para cada indivíduo, foi aferida a altura e foram aplicados 20 estímulos distais supramáximos nos nervos mediano, ulnar, fibular e tibial, bilateralmente, para registrar as ondas-F. Uma comparação foi feita, por grupo, das latências (mínimas e médias) e persistências pelos testes Kruskal-Wallis e Bonferroni. Valores de p < 0.05 foram considerados estatisticamente significativos. RESULTADOS: Todos os grupos foram pareados por idade, sexo e altura. Não houve diferença estatística significativa entre os grupos quanto às latências das ondas-F. A persistência da onda-F foi capaz de estratificar os grupos, sendo as dos nervos fibulares bilateralmente maiores no grupo SN que nos grupos SM e SP (p < 0.05). Adicionalmente, a persistência das ondas-F dos nervos ulnares e tibiais também foi útil para distinguir SN de SP (p < 0.05). CONCLUSãO: A persistência das ondas-F dos nervos fibulares pode ser uma ferramenta adicional e útil para diferenciar síndromes sensitivas periféricas.

Inter-observer reliability in assessment of sensation of skin lesion and enlargement of peripheral nerves in leprosy patients.

The accurate diagnosis of leprosy is important to both individuals and to the community. The diagnosis of leprosy is based on clinical examination. However, the reliability of clinical assessment of sensation in skin lesions and thickness of peripheral nerves on palpation has not been well studied, due to the lack of a gold standard. We report an inter-tester reliability study of the clinical assessment of skin lesions and thickness of ulnar and popliteal nerves in leprosy patients by different staff. For sensory testing of skin lesions, the agreement between the leprologist and leprosy control staff, and between one student and leprosy control staff, was poor (kappa values < 0-4). The agreement between the leprologist and the two students, between the two students, and between the other student and local leprosy control staff were fair (kappa values > 0.4, but < 0-6). For the palpation of ulnar and popliteal nerves, the agreement ranged from 0.36 to 0.52 and from 0.02 to 0.29 in different pairs of testers, respectively. The reliability of clinical diagnostic skills based on both sensory testing of skin lesions with the cotton wool method and palpation of superficial peripheral nerves was unsatisfactory.

Damage and regeneration of peripheral nerves in advanced treated leprosy.

Despite the rapidly falling prevalence of leprosy, the disability and handicap resulting from loss of protective sensation, due to irreversible nerve damage, will remain a huge medical problem for many years. To elucidate the location and consequences of permanent nerve damage in treated leprosy, a prospective study involving nine patients who underwent leg amputation was conducted. Full-length nerves dissected from amputated legs were studied with histological and immunohistochemical methods. Our main findings were that: in both lepromatous and tuberculoid leprosy nerve damage increased distally, culminating in total destruction of dermal nerves and sensory nerve endings; after the therapy-related decrease of inflammation large-scale nerve regeneration took place; and that regenerating axons persisted for decades and in tuberculoid leprosy they might reach the subcutaneous fat of the plantar skin. We conclude that nerve regeneration was blocked by fibrous replacement of the distal-most nerves and nerve endings, and that the theoretical basis of nerve grafting in leprosy is in need of further clarification. In some patients, autologous transplantation of skin flaps, probably irrespective of the duration of loss of sensation, might help in regaining protective sensation.

Ultrastructural observations of small blood vessels in leprosy patients.

In lepromatous leprosy, blood vessels revealed the luminal protrusions of endothelial cells containing M. leprae and thickening of the basement membrane of endothelial and smooth cells. Endothelial projections with increased pinocytotic vesicles were more often encountered in lepromatous leprosy than in the other types of leprosy. On the other hand, in tuberculoid leprosy, the extensive rough endoplasmic reticulum suggesting protein synthesis was observed in the endothelial cells compared with the other types of leprosy and non-specific lesions. It seems that the blood vessels associated with hyperfunction and proliferation in the endothelium could aggravate the degenerative changes in peripheral nerve fibers including the Schwann cells.