Neuromuscular complications have been reported in patients with COVID-19, but the effect of SARS-CoV-2 (the virus that causes COVID-19) on nerves and muscles is unclear. To address this question, two research groups examined nerve and muscle biopsies from autopsies of patients with COVID-19.

Aschman and colleagues performed a case–control study in which they obtained quadriceps, deltoid, heart, and lung tissue from 43 patients who died with COVID-19 and 11 patients without COVID-19 who died from critical illness. Compared with controls, COVID-19 patients had significantly more degenerating muscle fibers and inflammation on immunohistochemical analysis and a higher average creatine kinase level.

In people with COVID-19, the presence of neuromuscular conditions such as myositis, rhabdomyolysis, and Guillain-Barré syndrome has led to speculation that direct viral invasion of muscles, nerves, or both may underly neuromuscular complications of COVID-19. However, these two histopathology studies did not show direct viral invasion of muscles or nerves.

Muscle inflammation and necrosis are known features of viral myositis, which has been associated with many viruses. Future studies to examine which of these muscle biopsy features are specific to SARS-CoV-2 as opposed to other severe viral infections will be useful.