The prolonged effects of COVID-19 are as baffling as they are alarming, with scientists still unsure how the virus produces these lingering symptoms in certain individuals. In spite of this lack of understanding regarding the cause of the syndrome, however, some doctors are beginning to speculate that long COVID could be treated using neurostimulation, which involves the electrical activation of the brain and peripheral nerves. At present, data regarding the efficacy of this approach remains scarce, yet early findings have led to a demand for larger-scale clinical trials.

Long COVID – or post-acute sequelae of SARS-CoV-2 infection (PASC) – can involve an array of different symptoms including brain fog, respiratory complications, heartbeat irregularities, and mood dysregulation. Finding a one-size-fits-all treatment for such a heterogeneous condition seems like a long shot, although there is reason to believe that brain stimulation could help to alleviate many of these complaints.

For instance, a type of neurostimulation known as transcranial direct current stimulation (tDCS) has previously been shown to attenuate depression, boost memory, and enhance learning. Stimulation of the vagus nerve, meanwhile, has been associated with increased focus and attention and has even resulted in the partial restoration of consciousness in one patient who had been in a vegetative state for 15 years.

In August 2020, a small study involving just two patients provided the first evidence that the stimulation of the vagus nerve (nVNS) may help to treat respiratory issues in COVID-19 patients. “In case 1, the patient used nVNS to expedite symptomatic recovery at home after hospital discharge and was able to discontinue use of opioid and cough suppressant medications,” write the study authors.

“In case 2, the patient experienced immediate and consistent relief from symptoms of chest tightness and shortness of breath, as well as an improved ability to clear his lungs.”

Exactly how neurostimulation brings about such benefits is not fully understood, although there is good reason to believe that the activation of the vagus triggers a reduction in inflammation. Given that inflammation is a major hallmark of COVID-19, it seems plausible that this approach may prove useful in the treatment of the condition.

To investigate, researchers at the Université Libre de Bruxelles in Belgium provided nVNS to 20 long COVID patients for a period of ten days, publishing their findings in May of last year. All participants experienced reductions in symptoms such as fatigue and depression, while also gaining muscle strength and benefiting from an increase in blood oxygenation.

However, contrary to the researchers’ expectations, nVNS failed to bring about reductions in pro-inflammatory cytokines. They, therefore, speculate that the treatment may help to treat COVID-19 symptoms by “resetting” the sympathetic nervous system – which coordinates the body’s fight-or-flight response – rather than by dampening inflammation.

Across the pond, researchers at New York University are currently preparing to conduct larger-scale studies into tDCS as a potential treatment for long COVID, while an as yet unpublished study from Brazil is expected to reveal that the technology speeds up recovery in hospitalized patients.

As research progresses, scientists hope to learn more about how neurostimulation impacts patients’ neurology, while at the same time deepening their understanding of the biological mechanisms behind long COIVD. In a best-case scenario, these studies will also lead to the development of effective new treatments for the condition that don’t involve pharmaceuticals.

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