Antibodies against SARS-CoV-2 in cerebrospinal fluid: Clinical features and laboratory findings of hospitalized patients with neurologic symptoms in the pandemic era.

Background and purpose: High titers of anti-SARS-CoV-2 immunoglobulin G (IgG) have been reported in cerebrospinal fluid (CSF) samples of patients with COVID-19, but the data are limited. Our purpose is to report the clinical features and CSF findings of patients with neurologic symptoms in the pandemic era, and to discuss the origin and importance of anti-SARS-CoV-2 IgG in CSF.

Methods: The data of 100 patients hospitalized in neurology inpatient clinics and tested for anti-SARS-CoV-2 IgG antibodies in CSF samples, between May 2021 and March 2022, were evaluated in a retrospective manner. Demographic features, presence of coronavirus disease 2019 (COVID-19) and/or COVID-19 history, vaccination, vaccine type, and neurologic diagnoses were noted. CSF and serum anti-SARS-CoV-2 antibody ratio (AR) were assessed using a Euroimmun ELISA assay. CSF cytology, CSF protein level, oligoclonal band, IgG index, and albumin quotient (QAlb) were analyzed and compared between CSF AR positive and negative groups.

Results: QAlb and CSF protein levels were higher in the CSF anti-SARS-CoV-2 AR-positive group compared with CSF anti-SARS-CoV-2 AR-negative group (p.

Conclusion: Anti-SARS-CoV-2 antibodies in CSF seem to be related to a past immunization or a pre-existing cross reactive immunity and passive diffusion through a disrupted blood-brain-barrier, but not to an intrathecal antibody synthesis.