Brain changes during COVID-19 infections are not caused by the virus

Most brain changes after a COVID-19 infection are not caused by the virus, but by the body's immune response. The findings are from a study that examined 43 deceased people infected with SARS CoV-2.

Immune reaction originates from the body itself

The majority of brain changes observed after a COVID-19 infection are not caused by the virus itself, but by the body's immune response. In a German study carried out by the Institute of Neuropathology (Hamburg-Eppendorf University Medical Centre or UKE) together with researchers from the Institute of Forensic Medicine, Medical Microbiology, Virology and Hygiene (UKE), the Clinic and Polyclinic for Neurology (UKE) and the Institute of Neuropathology at the Freiburg University Medical Centre, 43 deceased people infected with SARS CoV-2 were examined.

21 of the 43 deceased had the SARS-CoV-2 pathogen in the brain, namely in the brainstem and also in nerves originating from the brainstem. However, the viral amounts were very small and the brains of patients with the highest virus levels did not show more changes than those who were not infected. Nevertheless, an immune reaction was triggered in the brains of the deceased COVID-19 patients. Inflammatory cells in the brain could be involved in the development of the neurological symptoms, according to the research group.

Wide range of neurological symptoms 

"In addition to complications in the lungs, heart, and kidneys, COVID-19 can also cause neurological symptoms. These are broad in spectrum and range from mild diffuse symptoms to severe strokes. However, it has not yet been clear whether and how the pathogen enters the brain and can multiply there. We have now been able to show that it is not the novel coronavirus itself that damages the brain, but that the neurological symptoms are probably an indirect consequence of the virus infection," says Prof. Dr. Markus Glatzel, Director of the Institute of Neuropathology at the UKE.

"The clear virus detection in individual cells and nerves was of particular interest, which indicates a localized proliferation and impairment of specific brain functions," sums up Prof. Dr. Martin Aepfelbacher, Director of the Institute of Medical Microbiology, Virology, and Hygiene at the UKE and study co-author.

Patients with a typical risk level

The 16 deceased women and 27 men examined were on average 76 years old and had age-related pre-existing conditions. The patient cohort thus represents typical COVID-19 patients in Germany. "COVID-19 patients usually show a significantly altered immune response in their blood. We could now also detect a clear inflammatory reaction in the brain, which was not known to this extent," says Prof. Dr. Marco Prinz, Medical Director of the Institute for Neuropathology at the University Hospital Freiburg and study co-author.

Further research to clarify the causes of neurological symptoms with COVID-19 is necessary to develop treatment options for patients with severe neurological symptoms.

Jakob Matschke, Markus Glatzel et. al. Neuropathology of patients with COVID-19 in Germany: a post-mortem case series. The Lancet Neurology. 2020,