Peripheral neuropathy is a disease involving damage to the peripheral nerves, causing symptoms of weakness, numbness, and pain in the extremities. The condition affects millions of Americans each year.

A small study in the journal Neurology: Neuroimmunology & Neuroinflammation may add to emerging evidence that peripheral neuropathy could be behind symptoms of long COVID in some people. If proven, this could create a path toward new treatments.

What The Researchers Did

Medical researchers from the Department of Neurology at Massachusetts General Hospital examined a cross-section of 17 patients with long COVID who were referred for evaluation of suspected peripheral neuropathy.

• The average patient age was roughly 43 years.
• Around 69% of patients were female.
• Approximately 94% of patients were Caucasian, and 19% were Latino.
• All but one patient experienced mild COVID-19.
• No patients had any nerve damage before coronavirus infection.

After ruling out all other possible causes, the researchers conducted a series of tests (electrodiagnostic, autonomic function, and skin biopsies) to see whether nerves were involved in their long COVID. Patients’ symptoms, test results, and outcomes were monitored for an average of 1.4 years.

“We looked with every single major diagnostic test,” said Lead investigator, Anne Louise Oaklander, M.D., Ph.D.

What They Found

Long-COVID patients they evaluated often presented with disabling nerve damage after just mild SARS-CoV-2 infection and within a month of COVID-19 onset. The vast majority had damage to their small nerve fibers consistent with small-fiber polyneuropathy, a type of peripheral neuropathy. These fibers detect sensations and control cardiovascular system activity, breathing, and other involuntary functions.

The findings align with a July study from Weill Cornell Medicine-Qatar in which nerve damage in the eye’s cornea was linked to long COVID. 

Eleven of the 17 patients were then treated with either steroids or intravenous immunoglobulin (standard treatment for small-fiber neuropathy caused by immune system dysfunction). While some showed improvement, no patients were cured.

What It Means

The authors say fragments of coronavirus or spike proteins may promote antibodies that target nerve cells. Though their study cannot confirm patients’ long-COVID symptoms were caused by immune dysfunction, their results provide baseline data for a larger study and may also help clinicians evaluate similar long-COVID patients in the meantime.

Other experts note the results would only apply to long-COVID patients with this kind of nerve damage. But they agree further research on these patients is warranted, using a randomized trial design to better assess immunotherapy treatment.

*Steenhuysen, J. (2022, March 2). Nerve damage may explain some cases of long COVID – U.S. study. Reuters. https://www.reuters.com/business/healthcare-pharmaceuticals/nerve-damage-may-explain-some-cases-long-covid-us-study-2022-03-01

Much about the novel coronavirus, i.e., COVID-19, is still not fully understood. As research progresses and our knowledge of the virus increases, information can change rapidly. We strive to update all of our articles as quickly as possible, but there may occasionally be some lag between scientific developments and our revisions.