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CC BY 4.0 · Arq Neuropsiquiatr 2025; 83(01): s00451802961
DOI: 10.1055/s-0045-1802961
Original Article

Jitter and muscle fiber conduction velocity in long COVID fatigue

João Aris Kouyoumdjian 
1   Faculdade Estadual de Medicina de São José do Rio Preto (FAMERP), Departamento de Ciências Neurológicas, Psiquiatria e Psicologia Médica, Laboratório de Investigação Neuromuscular, São José do Rio Preto SP, Brazil.
,
Leticia Akemi Rama Yamamoto 
1   Faculdade Estadual de Medicina de São José do Rio Preto (FAMERP), Departamento de Ciências Neurológicas, Psiquiatria e Psicologia Médica, Laboratório de Investigação Neuromuscular, São José do Rio Preto SP, Brazil.
,
Carla Renata Graca 
1   Faculdade Estadual de Medicina de São José do Rio Preto (FAMERP), Departamento de Ciências Neurológicas, Psiquiatria e Psicologia Médica, Laboratório de Investigação Neuromuscular, São José do Rio Preto SP, Brazil.
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Funding Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil, supported this work (grant number 2022/02291-1 to JAK).
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Abstract

Background Long coronavirus disease (long COVID, LC) is defined as the continuation or development of new symptoms 3 months after the acute stage of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In LC, the rate of fatigue/postexertional malaise (F-PEM) has been described to be as high as 70%, regardless of age or severity of the acute symptoms.

Objective To evaluate the neuromuscular junction (NMJ) function and the isolated muscle fiber conduction velocity (MFCV) in situ in LC cases and controls.

Methods We studied 37 subjects without SARS-CoV-2 (controls) and 32 cases of SARS-CoV-2 infection, half with LC symptoms (LC-yes) and half without them (LC-no). Single-fiber electromyography (jitter measured with a concentric electrode), MFCV, the fast-to-slow MFCV ratio (F/S ratio), and the motor unit potentials (MUPs) were taken in the tibialis anterior muscle.

Results At least 1 jitter parameter was abnormal in 1/37 controls, in 1/16 LC-no patients, and in 2/16 LC-yes patients, without significant differences among them. None of the subjects with abnormal jitter presented fluctuation symptoms or positive acetylcholine-receptor antibody. The MFCV and F/S ratios did not show abnormalities in any of the participants. The MUPs did not show myopathic or neurogenic abnormality in needle electromyography. The most frequent symptom in LC was F-PEM, which occurred in all LC-yes patients and was significantly different from the other groups.

Conclusion Fatigue/postexertional malaise was found in all cases of LC, and the electrophysiological findings did not indicate the muscle fiber or the NMJ as a relevant factor in this condition.

Keywords

SARS-CoV-2 - Post-Acute COVID-19 Syndrome - Fatigue - Single-Fiber Electromyography - Muscle Fiber Conduction Velocity

Authors' Contributions

JAK: conceptualization and/or design of the work, data acquisition (neurophysiological tests), analysis and/or interpretation of data, writing – original draft, and writing –review and editing; CRG: data acquisition (interview), analysis and/or interpretation of data, writing – original draft, and writing –review and editing; LARY: participant selection and analysis and/or interpretation of data. All authors approved the final version of the manuscript and agree to be responsible for all aspects of the work.


Data Availability Statement

The data supporting the present study's findings are openly available upon reasonable request in the Data Center of Faculdade de Medicina de São José do Rio Preto, state of São Paulo, Brazil.


Editor-in-Chief: Hélio A. G. Teive.


Associate Editor: Carlos Otto Heise.




Publikationsverlauf

Eingereicht: 29. August 2024

Angenommen: 13. Oktober 2024

Artikel online veröffentlicht:
24. Februar 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International License, permitting copying and reproduction so long as the original work is given appropriate credit (https://creativecommons.org/licenses/by/4.0/)

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Bibliographical Record
João Aris Kouyoumdjian, Leticia Akemi Rama Yamamoto, Carla Renata Graca. Jitter and muscle fiber conduction velocity in long COVID fatigue. Arq Neuropsiquiatr 2025; 83: s00451802961.
DOI: 10.1055/s-0045-1802961