Neurological symptoms and axonal damage in COVID-19 survivors: are there sequelae?

Abstract

The persistence of neurological symptoms after SARS-CoV-2 infection, as well as the presence of late axonal damage, is still unknown. We performed extensive systemic and neurological follow-up evaluations in 107 out of 193 consecutive patients admitted to the COVID-19 medical unit, University Hospital of Verona, Italy between March and June 2020. We analysed serum neurofilament light chain (NfL) levels in all cases including a subgroup (n = 29) of patients with available onset samples. Comparisons between clinical and biomarker data were then performed. Neurological symptoms were still present in a significant number (n = 49) of patients over the follow-up. The most common reported symptoms were hyposmia (n = 11), fatigue (n = 28), myalgia (n = 14), and impaired memory (n = 11) and were more common in cases with severe acute COVID-19. Follow-up serum NfL values (15.2 pg/mL, range 2.4-62.4) were within normal range in all except 5 patients and did not differentiate patients with vs without persistent neurological symptoms. In patients with available onset and follow-up samples, a significant (p < 0.001) decrease of NfL levels was observed and was more evident in patients with a severe acute disease. Despite the common persistence of neurological symptoms, COVID-19 survivors do not show active axonal damage, which seems a peculiar feature of acute SARS-CoV-2 infection.

Keywords: COVID-19; Hypogeusia; Hyposmia; Neurofilament; NfL; SARS-CoV-2.

Fig. 1

Comparison between NfL levels measured during the acute COVID-19 stage and over the follow-up. A significant decrease of serum NfL values was observed on follow-up measurement in patients with available onset and follow-up samples (n = 29), thus suggesting the absence of persistent active axonal damage. The boxes show median values and interquartile range for each group