Jitter and muscle fiber conduction velocity in long COVID fatigue

Kouyoumdjian, João Aris; Akemi Rama Yamamoto, Leticia; Renata Graca, Carla

doi:10.1055/s-0045-1802961

person João Aris Kouyoumdjian

conceptualization and/or design of the work · data acquisition (neurophysiological tests) · analysis and/or interpretation of data · writing – original draft · writing –review and editing · approved the final version of the manuscript and agree to be responsible for all aspects of the work

schoolFaculdade 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.

0000-0002-9384-9964

person Leticia Akemi Rama Yamamoto

participant selection and analysis and/or interpretation of data · approved the final version of the manuscript and agree to be responsible for all aspects of the work

schoolFaculdade 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.

0009-0004-5915-2030

person Carla Renata Graca

data acquisition (interview) · analysis and/or interpretation of data · writing – original draft · writing –review and editing · approved the final version of the manuscript and agree to be responsible for all aspects of the work

schoolFaculdade 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.

0000-0003-3818-168X

personAddress for correspondence João Aris Kouyoumdjian (email:
jaris@famerp.br).

Conflict of Interest

The authors have no conflict of interest to declare.

Editor-in-Chief:

Hélio A. G. Teive.

Associate Editor:

Carlos Otto Heise.

Figures (5)
Tables (2)

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Figure 1 (A) Motor unit potentials from the tibialis anterior muscle in semiquantitative electromyography, showing a mean amplitude of 1,750 μV. (B) Muscle fiber conduction velocity in situ, showing a complex of isolated muscle fiber action potentials with a conduction velocity varying from 3.70 m/s to 5.26 m/s. The mean consecutive differences were displayed above each spike and were shorter than 5 μs, defining direct isolated muscle fiber stimulation. (C) Isolated muscle fiber action potential after electrical activation, showing a mean consecutive difference (jitter) of 15.1 μs, defining indirect muscle fiber stimulation.

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Figure 2 Plot with the mean jitter in all groups. Observe one abnormal jitter in the group without long coronavirus disease (LC-no) and another in the group with LC (LC-yes). Both groups presented acetylcholine receptor antibodies within the normal range, and none presented fluctuation weakness.

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Figure 3 Plot with the abnormal individual jitter above 10% in all groups. Observe one abnormal percentage in the control group, one in the LC-no group, and two abnormal in the LC-yes group. All presented acetylcholine receptor antibodies within the normal range, and none presented fluctuation weakness.

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Figure 4 Plot with the muscle fiber conduction velocity in situ in all groups. Observe that none of the groups were outside the reference limits. None presented proximal fixed weakness nor abnormal motor unit potentials in needle electromyography.

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Figure 5 Plot with the mean fatigue/postexertional malaise score frequency in all groups (95% confidence interval for the mean). There are five questions and, for each of them, the scores are as follows: 0–without symptoms; 1–sometimes; 2–about half of the time; 3–most of the time; and 4–continuous.

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Table 1 Variables analyzed in the study sample

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Table 2 Comparison of the mean jitter, MFCV, and F-PEM using the Mann-Whitney U-test

Variables	Group	Mean	SD	Minimum	Median	Maximum
Age (years)	Controls	40.89	12.24	21	40	60
	LC-no	36.56	12.28	20	33	60
	LC-yes	42.38	14.12	24	42.50	68
Body mass index (kg/m²)	Controls	27.32	5.68	18.50	26	40.57
	LC-no	27.61	5.44	20.90	25.30	37.55
	LC-yes	28.75	6.32	18.83	28.45	41.21
Motor unit potential (μV)	Controls	1,920	607	1,256	1,698	3,438
	LC-no	1,699	540	1,129	1,583	3,391
	LC-yes	1,813	471	1,167	1,591	2,872
Mean jitter (abnormal: ≥ 26 μs)	Controls	20.79	2.48	15.82	21.09	25.13
	LC-no	19.94	3.13	14.42	19.71	26.32
	LC-yes	21.55	3.38	16.43	21.75	32.31
Percentage of individual jitter > 34 μs	Controls	4.78	4.22	0	4.99	16.66
	LC-no	2.49	3.94	0	0	13.33
	LC-yes	5	9.81	0	1.67	36.67
Muscle fiber conduction velocity (m/s)	Controls	4.11	0.37	3.33	4.06	5.05
	LC-no	4.11	0.25	3.71	4.14	4.69
	LC-yes	4.12	0.52	3.12	4.16	5.01
Muscle fiber conduction velocity: fast-to-slow ratio	Controls	1.73	0.49	1.27	1.62	3.74
	LC-no	1.64	0.22	1.24	1.65	2.03
	LC-yes	1.82	0.45	1.29	1.72	3.20

Group comparison	Variable	p value	Confidence	Significance
Controls versus LC-no	F-PEM	0.368	95.08%	No
Controls versus LC-yes	F-PEM	0	95.08%	High
LC-no versus LC-yes	F-PEM	0	95.21%	High
Controls versus LC-no	MFCV	0.774	95.15%	No
Controls versus LC-yes	MFCV	0.579	95.15%	No
LC-no versus LC-yes	MFCV	0.692	95.21%	No
Controls versus LC-no	Mean jitter	0.269	95.22%	No
Controls versus LC-yes	Mean jitter	0.768	95.22%	No
LC-no versus LC-yes	Mean jitter	0.147	95.21%	No

[TFN1] Abbreviations: LC, long coronavirus disease; SD, standard deviation.

[TFN2] Note: The numbers in bold represent parametric (mean) or non-parametric (median), according to the normality test of the variable sample.