Primary Motor Cortex Representation of Handgrip Muscles in Patients with Leprosy

Author(s)

Batista e Sa, Vagner Wilian ^{[1, 2, 3, 4]} ; Gomes, Maria Katia ^{[2, 3]} ; Rangel, Maria Luiza Sales ^[1] ; Sanchez, Tiago Arruda ^{[2, 3]} ; Moreira, Filipe Azaline ^{[2, 3]} ; Hoefle, Sebastian ^{[1, 5, 6]} ; Souto, Inaiacy Bittencourt ^{[2, 3]} ; Ledo Alves da Cunha, Antonio Jose ^{[2, 3]} ; Fontana, Ana Paula ^{[2, 3]} ; Vargas, Claudia Domingues ^{[1, 7]}

Affiliation

^[1] Univ Fed Rio de Janeiro, Inst Biofis Carlos Chagas Filho, Lab Neurobiol 2, Rio De Janeiro, RJ - Brazil

^[2] Univ Fed Rio de Janeiro, Hosp Univ Clementino Fraga Filho, Programa Posgrad Clin Med, Rio De Janeiro, RJ - Brazil

^[3] Univ Fed Rio de Janeiro, Fac Med, Dept Med Familia & Comunidade, Rio De Janeiro, RJ - Brazil

^[4] Univ Castelo Branco, Nucleo Pesquisas Fisioterapia, Rio De Janeiro, RJ - Brazil

^[5] DOr Inst Res & Educ, Cognit & Behav Neurosci Unit, Rio De Janeiro, RJ - Brazil

^[6] DOr Inst Res & Educ, Neuroinformat Workgrp, Rio De Janeiro, RJ - Brazil

^[7] Univ Fed Rio de Janeiro, Inst Neurol Deolindo Couto, Rio De Janeiro, RJ - Brazil

• Document type: Journal article
• Source: PLoS Neglected Tropical Diseases; v. 9, n. 7 JUL 2015.
• Web of Science Citations: 0

Abstract

Background Leprosy is an endemic infectious disease caused by Mycobacterium leprae that predominantly attacks the skin and peripheral nerves, leading to progressive impairment of motor, sensory and autonomic function. Little is known about how this peripheral neuropathy affects corticospinal excitability of handgrip muscles. Our purpose was to explore the motor cortex organization after progressive peripheral nerve injury and upper-limb dysfunction induced by leprosy using noninvasive transcranial magnetic stimulation (TMS). Methods In a cross-sectional study design, we mapped bilaterally in the primary motor cortex (M1) the representations of the hand flexor digitorum superficialis (FDS), as well as of the intrinsic hand muscles abductor pollicis brevis (APB), first dorsal interosseous (FDI) and abductor digiti minimi (ADM). All participants underwent clinical assessment, handgrip dynamometry and motor and sensory nerve conduction exams 30 days before mapping. Wilcoxon signed rank and Mann-Whitney tests were performed with an alpha-value of p<0.05. Findings Dynamometry performance of the patients' most affected hand (MAH), was worse than that of the less affected hand (LAH) and of healthy controls participants (p = 0.031), confirming handgrip impairment. Motor threshold (MT) of the FDS muscle was higher in both hemispheres in patients as compared to controls, and lower in the hemisphere contralateral to the MAH when compared to that of the LAH. Moreover, motor evoked potential ( MEP) amplitudes collected in the FDS of the MAH were higher in comparison to those of controls. Strikingly, MEPs in the intrinsic hand muscle FDI had lower amplitudes in the hemisphere contralateral to MAH as compared to those of the LAH and the control group. Taken together, these results are suggestive of a more robust representation of an extrinsic hand flexor and impaired intrinsic hand muscle function in the hemisphere contralateral to the MAH due to leprosy. Conclusion Decreased sensory-motor function induced by leprosy affects handgrip muscle representation in M1. (AU)

• FAPESP's process: 13/07699-0 - Research, Innovation and Dissemination Center for Neuromathematics - NeuroMat
• Grantee: Oswaldo Baffa Filho
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC