CSF Biomarkers in Patients With COVID-19 and Neurologic Symptoms

Objective To explore whether hospitalized patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and neurologic symptoms have evidence of CNS infection, inflammation, and injury using CSF biomarker measurements.

Methods We assessed CSF SARS-CoV-2 RNA along with CSF biomarkers of intrathecal inflammation (CSF white blood cell count, neopterin, β₂-microglobulin, and immunoglobulin G index), blood-brain barrier integrity (albumin ratio), and axonal injury (CSF neurofilament light chain protein [NfL]) in 6 patients with moderate to severe coronavirus disease 2019 (COVID-19) and neurologic symptoms who had undergone a diagnostic lumbar puncture. Neurologic symptoms and signs included features of encephalopathies (4 of 6), suspected meningitis (1 of 6), and dysgeusia (1 of 6). SARS-CoV-2 infection was confirmed by real-time PCR analysis of nasopharyngeal swabs.

Results SARS-CoV-2 RNA was detected in the plasma of 2 patients (cycle threshold [Ct] value 35.0–37.0) and in CSF at low levels (Ct 37.2, 38.0, 39.0) in 3 patients in 1 but not in a second real-time PCR assay. CSF neopterin (median 43.0 nmol/L) and β₂-microglobulin (median 3.1 mg/L) were increased in all. Median immunoglobulin G index (0.39), albumin ratio (5.35), and CSF white blood cell count (<3 cells/µL) were normal in all, while CSF NfL was elevated in 2 patients.

Conclusion Our results in patients with COVID-19 and neurologic symptoms suggest an unusual pattern of marked CSF inflammation in which soluble markers were increased but white cell response and other immunologic features typical of CNS viral infections were absent. While our initial hypothesis centered on CNS SARS-CoV-2 invasion, we could not convincingly detect SARS-CoV-2 as the underlying driver of CNS inflammation. These features distinguish COVID-19 CSF from other viral CNS infections and raise fundamental questions about the CNS pathobiology of SARS-CoV-2 infection.