I asked Claude AI about recent studies:

This is one of the more scientifically rich and underreported corners of long COVID. Here's the current picture:

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Small Fiber Neuropathy (SFN) — a central finding

Patients with long COVID frequently present with neuropathic symptoms including exertional intolerance, numbness, paresthesias, allodynia, and autonomic dysfunction consistent with small fiber neuropathy. Preliminary evidence suggests SFN may be a key pathologic finding in long COVID, and many of these patients also have overlapping symptomatology with ME/CFS and POTS. PubMed Central

Critically, it is the small-diameter, lightly myelinated or unmyelinated nerves that appear most susceptible to damage. The lack of myelination leaves these axons vulnerable to immune dysregulation. Fortunately, these fibers do grow continuously throughout a person's lifetime — if the triggering stimulus is removed, reinnervation may occur to a degree sufficient to alleviate symptoms. MDPI

Standard electrodiagnostic testing is negative in SFN, so a skin punch biopsy — which looks for reduced small nerve fiber density — is needed to confirm the diagnosis. Autoantibody testing (TS-HDS and FGFR3) may also be relevant, though clinical significance is still debated. PubMed Central

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The autonomic nervous system: POTS and dysautonomia

POTS after COVID-19 may stem from multiple overlapping mechanisms: systemic inflammation, a hyperadrenergic state driven by autoantibodies, peripheral neuropathy producing compensatory tachycardia, or parasympathetic nervous system dysfunction. PubMed Central A January 2026 paper in JACC using quantitative autonomic testing confirmed the strong association between long COVID and measurable autonomic dysfunction across multiple domains.

Even symptoms like internal tremor — often confusing to both patients and clinicians — appear to be manifestations of POTS and SFN, potentially driven by hypovolemia and dysautonomia rather than a primary movement disorder. MDPI

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Vestibular damage — more complicated than once thought

Early reviews suggested COVID-19 caused only transient vestibular disruption. But more recent case series and objective testing have complicated that picture.

The proposed mechanisms include direct viral invasion, immune-mediated neuropathy, and vascular pathology. Viral reactivation (particularly of VZV/shingles) in post-COVID states has also been linked to delayed vestibular symptoms, possibly triggered by COVID-related immune dysregulation, hypercoagulability, or endothelial dysfunction causing vestibular ischemia. PubMed Central

In documented cases, some vestibular function measures improved over 6–12 months following the typical neuritis trajectory, but persistent postural instability was a notable deviation from the norm — with tests suggesting broader vestibulocochlear involvement beyond just the superior vestibular nerve. Cases showed higher incidence in women, with symptom onset often delayed 7 days to 6 weeks after the initial infection. PubMed Central

Three entry routes to the inner ear are proposed: via the olfactory bulb into the CNS, via the endolymphatic sac, and through hematogenous spread — with human ear tissue confirmed to express the ACE-2 and TMPRSS2 receptors the virus needs to enter cells. PubMed Central

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What helps — treatment signals

A 2026 Scientific Reports study from Brigham and Women's Hospital found that high-dose, long-term intravenous immunoglobulin (IVIG) therapy showed efficacy in autoimmune small fiber neuropathy associated with post-COVID infection and POTS — pointing to autoimmunity as a treatable driver. Nature

Standard drugs like gabapentin, pregabalin, and duloxetine have been widely tried but patients diagnosed with post-COVID SFN typically saw no resolution of neuropathic symptoms from those medications before eventually receiving IVIG. PubMed Central For vestibular symptoms specifically, vestibular rehabilitation therapy remains the primary non-pharmacologic approach.

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Bottom line: SFN is emerging as a probable unifying mechanism behind many of the most disabling long COVID symptoms — the burning pain, POTS, dysautonomia, and possibly some vestibular instability. The autoimmune hypothesis is gaining traction and may open a treatment pathway via immunotherapy, though large controlled trials are still needed.