Blink reflex changes in patient with long COVID headache

Abstract

Background: Headache is a common symptom of long COVID. Blink Reflex (BR) may indicate possible brainstem dysfunction or changes in excitability in the headache. In this study, we aimed to reveal whether one of the underlying mechanisms of headache in long COVID is dysfunction in the nociceptive centers in the brainstem. Methods: The study included 29 individuals with confirmed 2019 coronavirus disease (COVID-19) and 17 healthy volunteers. Individuals were divided into 3 groups: post-COVID-19 headache (Group 1), post-COVID-19 headache-free (Group 2) and healthy individuals (Group 3). Individuals in the groups were subjected to BR and the parameters obtained with BR were compared between the 3 groups. Results: Accordingly, when Group 1 and Group 2 were compared, the mean latency of the R1 component of the BR and the mean latency of the ipsilateral R2 component obtained via right-sided electrical stimulation were found to be longer in Group 1. When Group 1 and Group 3 were compared, the latency differences of the ipsilateral R2 component and contralateral R2 component of the BRs were found to be longer in Group 3, indicating distinct patterns of neural response between the two groups. Conclusion: In long COVID patients experiencing headache symptoms, the underlying cause of the pain symptom may be brain stem dysfunction.