J Appl Biomed 22:149-154, 2024 | DOI: 10.32725/jab.2024.020

Olfactory event-related potentials (OERPs) and trigeminal event-related potentials (TERPs) in subjects after Covid-19 infection: single-center prospective study

Richard Holý^{1, 2, *}, David Kalfeřt^{3, 4}, Libor Vašina^{2, 5, 6}, Oleksii Vorobiov^{1, 2}, Petra Dytrych^{7, 8}, Karla Janoušková^{1, 2}, Eva Augste⁹, Shahriar Kashiri⁴, Nikola Pastorková⁵, Kristýna Mamiňák^{1, 2}, Jiří Hložek^{1, 2}, Daniel Kovář^{1, 2}, Jan Vodička^{10, 11}, Jaromír Astl^{1, 2}

¹ Military University Hospital Prague, Department of Otorhinolaryngology and Maxillofacial Surgery 3rd Faculty of Medicine Charles University and Military University Hospital, Prague, Czech Republic

² Charles University, Third Faculty of Medicine, Prague, Czech Republic

³ University Hospital Motol, Department of Otorhinolaryngology and Head and Neck Surgery, Prague, Czech Republic

⁴ Charles University, First Faculty of Medicine, Prague, Czech Republic

⁵ Military University Hospital Prague, Department of Neurology, Prague, Czech Republic

⁶ Military Hospital Brno, Department of Neurology, Brno, Czech Republic

⁷ University Hospital Motol, Department of Ear, Nose and Throat, Prague, Czech Republic

⁸ Charles University, Second Faculty of Medicine, Prague, Czech Republic

⁹ University of Ostrava, Faculty of Medicine, Institute of Physiology and Pathophysiology, Ostrava-Vítkovice, Czech Republic

¹⁰ Regional Hospital Pardubice, Department of Otorhinolaryngology and Head and Neck Surgery, Pardubice, Czech Republic

¹¹ University of Pardubice, Faculty of Health Studies, Pardubice, Czech Republic

Objectives: Olfactory dysfunction (OD) is a common symptom associated with Covid-19. During the Covid-19 pandemic, the importance of psychophysical olfactory tests and electrophysiological olfactory assessment increased. The purpose of the study was to analyze the psychophysical olfactory tests and the post-covid curves of olfactory event-related potentials (OERPs) and trigeminal event-related potentials (TERPs).

Methods: The prospective study included 98 subjects (62 females / 36 males). The average age was 42 years (range 21-84 years). Group I (n = 77) contained participants who had been infected with Covid-19. They were enrolled in the study at least 1 year after Covid-19. Group II (n = 21) was the healthy normosmic control group.

Results: In Group I, the OERPs of 18% participants were absent. Patients in Group I were statistically more likely to have an absence of OERPs (p = 0.036) than subjects in Group II. We did not detect a statistical difference in amplitudes and latencies of the OERPs between Group I and Group II. In Group I, N1 latency of the TERPs was significantly longer (p = 0.002) than in Group II. The amplitude of the N1-P2 interval of the TERPs was significantly lower (p = 0.025) in Group I than in Group II. According to the psychophysical Sniffin stick identification test, hyposmia was detected in 39% in Group I versus 0% in the control Group II.

Conclusion: OD is a common post-covid symptom. The presence of OERPs is a significant prognostic factor for olfactory function after Covid 19. We detected a lower percentage of absence of OERPs after Covid-19 compared to the previously published studies of post-viral OD and post-infectious OD. For TERPs, we detected a longer N1 latency and a lower amplitude for the N1-P2 interval after Covid-19. OERPs and TERPs can be considered valid biomarkers to evaluate the progress of post-covid OD.

Keywords: Chemosensory functions; Covid-19; OERPs; Olfactory dysfunction; Post-covid; Smell; TERPs

Grants and funding:

This paper was funded by Project MO 1012 of the Ministry of Defence of the Czech Republic. Our prospective study was approved by the Ethics Committee of the Military University Hospital Prague – Reference Number 108/16-24/2021 (Project MO 1012). All patients signed an informed consent form.

Conflicts of interest:

The authors have no conflict of interest to declare.

Received: August 1, 2024; Revised: August 25, 2024; Accepted: September 16, 2024; Prepublished online: September 23, 2024; Published: September 26, 2024  Show citation