Comment on small fiber neuropathy associated with SARS-CoV-2 infection: Author response.

Guillain‐Barré syndrome

nerve conduction study/electromyography

We appreciate Dr Finsterer's letter to the editor regarding our recent work, as well as Dr Gemignani's editorial. We have several responses.

According to the US Centers for Disease Control and Prevention, post‐COVID conditions are new, recurring, or ongoing symptoms and clinical findings present 4 or more weeks after infection, and are referred to by different names, including post‐acute COVID syndrome and long COVID. The patients in our study developed new‐onset paresthesia with or without autonomic symptoms 2 weeks to 2 months after the onset of COVID‐19. The long‐term follow‐up of these patients showed persistence of painful small fiber neuropathy symptoms for at least 5 to 12 months. Therefore, our study patients have post‐COVID syndrome, and they are COVID long haulers.

Multiple studies have shown that Guillain‐Barré syndrome (GBS) may be seen in association with SARS‐CoV‐2 infection, , and dysautonomia can be present in GBS patients. However, our patients showed no evidence of conventional GBS by history, examination findings, or nerve conduction study/electromyography (NCS/EMG) findings. All had NCS/EMG studies that showed no evidence of a large fiber polyneuropathy, but all had paresthesia that prompted skin biopsy evaluation for small fiber neuropathy. We agree and discussed in our work that post‐infectious autoimmune neuropathy limited to small fibers appears the likely mechanism.

Dr Finsterer raised the interesting possibility that the autonomic dysfunction may be caused by hypothalamic‐pituitary axis dysfunction due to SARS‐CoV‐2 infection. Nine of 13 patients had brain imaging showing no abnormality in the hypothalamus or pituitary gland. Although autonomic symptoms were present in 7 of 13 patients, none of these patients had pure dysautonomia and 4 had biopsy‐proven small fiber neuropathy.

Some of the antiviral therapies mentioned by Dr Finsterer have the potential for neurotoxicity. At the time of assessment (May 2020 to May 2021), antiviral therapies specific for SARS‐CoV‐2 were not available for the cohort of patients in our study. These medications are currently approved only for patients with severe disease or those likely to progress to severe disease. Although they may be associated with adverse neurotoxic drug effects, the use of these drugs is only short term, and the treatment may in fact limit the development of post‐COVID conditions by suppressing acute SARS‐CoV‐2 infection.

CONFLICT OF INTEREST

None of the authors have any conflict of interest to disclose.

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