Cerebrospinal fluid in COVID-19 neurological complications: Neuroaxonal damage, anti-SARS-Cov2 antibodies but no evidence of cytokine storm

Abstract

Objective: To study in cerebrospinal fluid (CSF) of COVID-19 subjects if a "cytokine storm" or neuroinflammation are implicated in pathogenesis of neurological complications.

Methods: Cross-sectional study of CSF neuroinflammatory profiles from 18 COVID-19 subjects with neurological complications categorized by diagnosis (stroke, encephalopathy, headache) and illness severity. COVID-19 CSF was compared with CSF from healthy, infectious and neuroinflammatory disorders and stroke controls (n = 82). Cytokines (IL-6, TNFα, IFNγ, IL-10, IL-12p70, IL-17A), inflammation and coagulation markers (high-sensitivity-C Reactive Protein [hsCRP], ferritin, fibrinogen, D-dimer, Factor VIII) and neurofilament light chain (NF-L), were quantified. SARS-CoV2 RNA and SARS-CoV2 IgG and IgA antibodies in CSF were tested with RT-PCR and ELISA.

Results: CSF from COVID-19 subjects showed absence of pleocytosis or specific increases in pro-inflammatory markers (IL-6, ferritin, or D-dimer). Although pro-inflammatory cytokines (IL-6, TNFα, IL-12p70) and IL-10 were increased in CSF of stroke COVID-19 subjects, a similar increase was observed in non-COVID-19 stroke subjects. Anti-SARS-CoV2 antibodies in CSF of COVID-19 subjects (77%) were observed despite no evidence of SARS-CoV2 viral RNA. CSF-NF-L was elevated in subjects with stroke and critical COVID-19 as compared to controls and other COVID-19 severity categories. CSF-hsCRP was present in all subjects with critical stages of COVID-19 (7/18) but only in 1/82 controls.

Conclusion: The paucity of neuroinflammatory changes in CSF of COVID-19 subjects and lack of SARS-CoV2 RNA do not support the presumed neurovirulence of SARS-CoV2 or neuroinflammation in pathogenesis of neurological complications in COVID-19. The role of CSF SARS-CoV2 IgG antibodies and mechanisms of neuronal damage are still undetermined.

Keywords: COVID-19; Cerebrospinal fluid; Cytokine storm; Cytokines; Neuroinflammation.

Graphical abstract

Fig. 1

Timeline of clinical features in patients with COVID-19 with neurological complications. Temporal profile of COVID-19 and neurological symptoms as related with the time of CSF analysis (vertical blue line) for the 18 subjects included in the study. Patients were classified based on the NIH disease severity classification [33]. Eight subjects presented with neurological symptoms as the first manifestation of COVID-19 (light pink bar), eight exhibited systemic illness symptoms preceding neurological symptoms (dark pink bar) and two presented with mixed neurological and systemic symptoms (diagonal stripes).

Fig. 2

Profile of CSF inflammatory markers in COVID-19 diagnostic groups and controls. Profiles of inflammatory markers in the CSF from 18 COVID-19 subjects categorized by diagnosis (yellow box) as compared with healthy controls (n = 14), acute meningitis (n = 12) and encephalitis (n = 14), autoimmune encephalitis (n = 12), neuromyelitis optica (n = 11) and neurosarcoidosis (n = 14) and non-COVID-19 strokes (n = 8). Boxes indicate the interquartile range and whiskers show the minimum and maximum values for analytes in each group, and median (red line in box plot). A significant difference (P < 0.05) in which the COVID-19 diagnostic group was significantly higher than the control group is denoted as an orange line. A significant difference (P < 0.05) when the disease control group was significantly higher than the COVID-19 diagnostic group is denoted by the blue line. Significance for D-dimer and hsCRP was obtained by categorical analysis, present or absent. The significance for hsCRP was represented by the COVID-19 stroke and encephalopathy groups (yellow bracket) vs. the healthy controls and the overall disease control groups (gray bracket).

Fig. 3

Heatmap of significance analysis of COVID-19 cases vs. controls. Heatmap description of the significance P < 0.05 and P < 0.005 after comparative analysis of (A) COVID-19 CSF diagnostic groups vs. healthy and disease controls, (B) COVID-19 disease severity groups vs. healthy and disease controls, and (C) timing of the CSF sampling in COVID-19 group vs. healthy and disease controls. (D) Heatmap description after exclusion of the COVID-19 group comparing the non-COVID-19 stroke group with other control groups. Analytes that are significantly higher in the COVID-19 group are denoted as orange (P < 0.05) or red (P < 0.005). Analytes that are significantly higher in the control groups are denoted as light blue (P < 0.05) or dark blue (P < 0.005) (A, B and C). A heat map in D shows analytes the were significantly elevated in the non-COVID-19 stroke group as compared with controls are shown as orange (P < 0.05) or red (P < 0.005). Analytes that were significantly higher in the control groups vs. non-COVID-19 stroke group were denoted light blue (P < 0.05) or dark blue (P < 0.005). Significance for D-dimer and hsCRP was obtained by categorical analysis, present or absent.