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How COVID-19 Affects the Brain

How COVID-19 Affects the Brain

What your doctor is reading on Medscape.com:

APRIL 17, 2020 — As of April 9, 2020, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had infected 1,436,198 people and caused 85,522 deaths. By the time you read this, those numbers will have increased. As the numbers grow, more and more neurologic symptoms are being reported in COVID-19 patients. Neurologists, in turn, may increasingly find themselves involved in caring for patients with the novel virus.

COVID-19 may affect the nervous system via four potential mechanisms, which may overlap. The first is direct viral injury of nervous tissue, such as occurs with herpes simplex encephalitis. Although there are some suggestive case reports, there is no definite proof that the SARS-CoV-2 virus directly damages the central nervous system (CNS).

The second type of injury results from an excessive immune response in the form of a “cytokine storm.” Cytokines can cross the blood-brain barrier and are associated with acute necrotizing encephalopathy. Only one case concurrent with COVID-19 has been reported.

The third mechanism of nervous tissue damage results from unintended host immune response effects after an acute infection. An example of this type of indirect CNS injury is Guillain-Barré syndrome (GBS). One case of GBS associated with COVID-19 has been reported, but the evidence for cause and effect is weak.

The fourth mechanism of indirect viral injury results from the effects of systemic illness. Neurologists are accustomed to seeing severely ill patients in the intensive care unit develop neurologic symptoms such as encephalopathy, critical illness myopathy, and neuropathy. Most cases of COVID-19-related neurologic complications appear to fall into this category.

In February of this year, Guan and colleagues reported the clinical characteristics of SARS-CoV-2 infection in 1099 patients. Neurologic symptoms in patients with COVID-19 included headache (13.6%) and myalgias (14.9%). Only 5% required intensive care unit admission. On the basis of this large series, there seemed little reason to worry that SARS-CoV-2 might directly or indirectly attack the CNS or peripheral nervous system (PNS).

However, a separate, nearly simultaneous retrospective case series reported a high incidence of neurologic symptoms in 214 hospitalized patients with confirmed COVID-19 in Wuhan, China. Seventy-eight (36.4%) patients had CNS (24.8%), PNS (8.9%), or skeletal muscle symptoms (10.7%). The two most common CNS symptoms were dizziness (16.8%) and headache (13.1%), with acute cerebrovascular disease, ataxia, epilepsy, and impaired consciousness also reported. Severely ill patients were more likely to develop neurologic symptoms such as altered mental status, ischemic or hemorrhagic stroke, and muscle injury.

Published at Mon, 20 Apr 2020 17:23:42 +0000

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