Research Reveals Potential Connection Between Long COVID and Peripheral Neuropathy

Exploring the Connection Between Long COVID and Peripheral Neuropathy

Understanding Long COVID

Long COVID is a significant area of research, characterized by the persistence of symptoms following a COVID-19 infection. According to the World Health Organization, long COVID symptoms can emerge within 90 days of the initial COVID-19 symptoms and must last for over two months.

Peripheral Neuropathy in Long COVID Patients

One notable symptom observed in some long COVID patients is peripheral neuropathy, which involves nerve damage leading to numbness and weakness in various body regions, excluding the brain and spinal cord. A study conducted by researchers at Massachusetts General Hospital and Harvard Medical School specifically explored the relationship between long COVID and small-fiber polyneuropathy (SFN).

Defining Small-Fiber Polyneuropathy

Small-fiber polyneuropathy (SFN) occurs when the axons of small nerves are damaged. These small nerves include sensory nerves, responsible for transmitting sensations, and autonomic nerves, which manage involuntary functions such as digestion.

Study Findings on SFN in Long COVID Patients

The study, published in Neurology Neuroimmunology & Neuroinflammation, assessed 17 patients who had contracted SARS-CoV-2 and were experiencing symptoms of neuropathy. Participants had contracted COVID-19 between February 21, 2020, and January 19, 2021, and were monitored for an average of 1.4 years. Notably, all participants had no prior history of neuropathy before their COVID-19 infection.

Detection of neuropathy involved skin biopsies from the lower leg and upper thigh, electrodiagnostic tests to measure nerve activity, and autonomic function tests. The results indicated that 62% of lower leg biopsies showed signs of SFN, while 17% of electrodiagnostic tests and 50% of autonomic function tests confirmed the diagnosis. Among the participants, 16 experienced mild COVID-19, while one required hospitalization due to severe illness. Symptoms of SFN typically developed within one month following mild COVID-19.

Treatment Options for SFN

Available treatments for SFN include intravenous immunoglobulins and corticosteroids, both of which are classified as immunotherapies that modify the immune system’s response. However, the study found no clear trend regarding the success rates of these treatments, indicating that approaches should be tailored to individual cases. The evidence suggests that SARS-CoV-2 infection may lead to immune dysregulation, potentially contributing to the development of SFN.

The Need for Larger Studies

The researchers highlighted that small nerve fibers are particularly susceptible to damage due to their lack of myelin, the protective layer surrounding nerve axons. Although small-fiber axons can regenerate relatively quickly, suggesting that symptoms may improve over time, the limitation of this study lies in its small sample size of 17 participants. Nevertheless, the findings indicate a plausible connection between long COVID and SFN, warranting further research with larger sample sizes to confirm this association.

Reference

Oaklander, A.L. et al. (2022). Peripheral Neuropathy Evaluations of Patients With Prolonged Long COVID. Neurology Neuroimmunology & Neuroinflammation; 9(3). Doi: 10.1212/NXI.0000000000001146.