Corneal confocal microscopy in patients with distal symmetric polyneuropathy compared to controls

Abstract

Background Diabetic neuropathy (DN) is a very common clinical condition throughout the world. The diagnostic tests currently recommended have low sensitivity, such as electromyography, or are invasive, such as skin biopsy. New techniques have been developed to identify the early involvement of the peripheral nerve. With the advent of corneal confocal microscopy (CCM), a reduction in corneal innervation in patients with DN has been observed.

Objective To compare, through CCM, diabetic patients with symptomatic distal symmetric polyneuropathy (DSP) and controls.

Methods In the present study, through CCM, we compared the morphological changes in the sub-basal epithelial corneal plexus of 35 diabetic patients with symptomatic DSP with 55 controls. Moreover, we sought to determine a pattern of change regarding the severity stages of DSP, comparing the clinical, laboratory, and nerve-conduction (NC) variables.

Results Differences between the control and diabetic groups were observed for the following variables, respectively: age (44.9 ± 13.24 years versus 57.02 ± 10.4 years; p < 0.001); fiber density (29.7 ± 10.2 versus 16.6 ± 10.2; p < 0.001); number of fibers (4.76 ± 1.30 versus 3.14 ± 1.63; p < 0.001); number of Langerhans cells (4.64 ± 8.05 versus 7.49 ± 10.3; p = 0.035); tortuosity (p < 0.05); and thickness (p < 0.05). Furthermore, inverse relationships were found regarding fiber density and age (p < 0.01) and fiber density and the severity of the disease (p < 0.05). A positive relationship between the conduction velocity of the fibular nerve and fiber density (p < 0.05) was also observed.

Conclusion Corneal confocal microscopy proved to be a fast, noninvasive and reproducible method for the diagnosis, staging, and monitoring of diabetic DSP.

Resumo

Antecedentes A neuropatia diabética (ND) é condição clínica muito frequente no mundo inteiro. Os testes diagnósticos atualmente preconizados são pouco sensíveis, como a eletroneuromiografia, ou invasivos, como a biópsia de pele. Novas técnicas de investigação complementares têm sido desenvolvidas a fim de identificar o acometimento precoce do nervo periférico. Com o advento da microscopia confocal de córnea (MCC), observou-se redução da inervação da córnea em pacientes com ND.

Objetivo Comparar, por meio da MCC, pacientes diabéticos com polineuropatia simétrica distal (PSD) sintomática e controles.

Métodos Neste estudo, por meio da MCC, comparamos as alterações morfológicas do plexo sub-basal epitelial da córnea de 35 pacientes diabéticos com PSD sintomática com 55 indivíduos controles. Além disso, buscamos determinar um padrão de alteração entre os estágios de gravidade da PSD, comparando variáveis clínicas, laboratoriais e de neurocondução.

Resultados Diferenças entre os grupos controle e diabéticos foram verificadas com relação às seguintes variáveis, respectivamente: idade (44,9 ± 13,24 anos versus 57,02 ± 10,4 anos; p < 0,001); densidade das fibras (29,7 ± 10,2 versus 16,6 ± 10,2; p < 0,001); número de fibras (4,76 ± 1,30 versus 3,14 ± 1,63; p < 0,001); número de células de Langerhans (4,64 ± 8,05 versus 7,49 ± 10,3; p = 0,035); tortuosidade (p < 0,05), e espessura (p < 0,05). Além disso, relações inversamente proporcionais foram verificadas entre a densidade das fibras e a idade (p < 0,01), e entre a densidade das fibras e a gravidade da doença (p < 0,05). Observou-se ainda uma relação positiva entre a velocidade de condução do nervo fibular e a densidade das fibras (p < 0,05).

Conclusão A MCC constitui um método rápido, não invasivo e reprodutível para o diagnóstico, o estadiamento, e o acompanhamento da PSD diabética.

Keywords

Diabetes Mellitus - Peripheral Nervous System Diseases - Confocal Microscopy

Palavras-chave

Diabetes Mellitus - Doenças do Sistema Nervoso Periférico - Microscopia Confocal

Authors' Contributions

CP: conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, and project administration; GD, RD: data curation, review; and ON: review.

Support

The present study was supported by the Brazilian federal agency called Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Coordination for the Improvement of Higher Education Personnel).

Publication History

Received: 16 September 2021

Accepted: 06 December 2021

Article published online:
17 October 2022

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