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Immunoglobulin Testing in the CSF Can Confirm the Presence of Coronavirus in the Brain
Immunoglobulin Testing in the CSF Can Confirm the Presence of Coronavirus in the Brain
Written By: Paphapin Pairojtanachai
A recent study involving three case studies of patients with severe COVID-19 and encephalitis (inflammation of the brain) at an inner city US hospital shows that antibody testing of the cerebrospinal fluid (CSF) can confirm whether the coronavirus has entered a patient’s brain. The cases included a 31-year-old woman diagnosed with sickle cell anemia and pulmonary embolism (a blockage of an artery in the lungs) and two men of ages 34 and 64 who have hypertension and typical respiratory symptoms. The spinal fluids of all of these patients underwent immunoglobulin M (IgM) assessment as well as the analysis of inflammatory proteins and molecular testing for the SARS-CoV-2 using reverse transcription polymerase chain reaction (RT-PCR). Among the three patients, only one of them had an abnormal amount of white blood cells and proteins present in their CSF. However, IgM antibodies for the virus were present in all of their tested CSF.
From this discovery, Karima Benameur, MD, a neurologist and associate professor at the Department of Neurology, Emory University School of Medicine, stated that “The only reason we could actually diagnose [the patients] with COVID encephalitis is because we were able to measure the IgM in their spinal fluid. IgM, the acute phase reactant against COVID, … is a direct indicator [that] they had COVID in their brain.” Therefore, simply using PCR and finding that there are normal white blood cell counts and protein levels in the CSF doesn’t mean that the SARS-CoV-2 has not entered the brain, as proven by the patients who did not have unusual numbers of white blood cells. While PCR is a good technique for testing for herpes virus, it is poorly suitable for testing for the coronavirus, said Benameur. She recommends that CSF IgM testing should be done to confirm whether or not the virus has entered the brain.
The mechanism as to how the SARS-CoV-2 enters the brain remains unclear, but animal research indicates that the virus can be transported to the brain through the olfactory nerve in the nose, explaining why some COVID-19 patients lose their ability to taste or smell.
Andrew Wilner, MD, an associate professor of neurology at the University of Tennessee Health Science Center, mentioned that “To date, most, if not all, of the neurological complications can be explained by inflammatory changes such as thrombosis or cytokine storm as well as post-infectious causes such as antibody-related Guillain-Barré.” Other secondary conditions are “nonspecific” and are “related to acute, severe systemic [illnesses]” similar to those of the three patients described. Wilmer also pointed out the fact that in the study, only the antibodies specific to the coronavirus were detected in the patients’ CSF, but the virus’ RNA itself wasn’t present. “As such, this paper is consistent with prior observations that suggest the SARS-CoV-2 virus may cause neurologic injury by secondary mechanisms,” but the virus doesn’t specifically attack the nervous system.
Sources:
https://wwwnc.cdc.gov/eid/article/26/9/20-2122_article
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