Procedure Might Restore Proper Sense of Smell to Folks With Long COVID

By Ernie Mundell HealthDay Reporter  |  Copyright © 2023 HealthDay. All rights reserved.

MONDAY, Nov. 20, 2023 (HealthDay News) -- A minimally invasive procedure that's long been used to ease headaches and irregular heartbeats might also restore a typical sense of smell to people who lost it after COVID, new research shows.

The 10-minute procedure is called a stellate ganglion block, with doctors injecting an anesthetic into the stellate ganglion, a nerve bundle at the side of the neck. Researchers say this can stimulate the autonomic nervous system to resolve parosmia -- the medical term for a distortion of sense of smell. That's distinct from anosmia, which is a loss of the sense of smell

It's a common complaint, especially among folks suffering from long COVID.

“Post-COVID parosmia is common and increasingly recognized,” said study lead author, Dr. Adam Zoga, a professor of musculoskeletal radiology at Jefferson Health in Philadelphia.

“Patients can develop a distaste for foods and drinks they used to enjoy," Zoga said. His team presented its findings Monday at the annual meeting of the Radiological Society of North America (RSNA), in Philadelphia.

With parosmia, many people may also imagine unpleasant smells that aren't there, a condition called phantosmia.

According to an RSNA news release, stellate ganglion block is a treatment that's already been used successfully for years to ease conditions such as cluster headaches, heart arrhythmias and phantom limb pain.

The stellate ganglia are nerves found on each side of the neck that are involved in the body's autonomic nervous system. They're crucial to transferring signals to the brain from the head, neck, arms and a portion of the upper chest.

Zoga's study involved 58 patients who'd complained of COVID-linked distortion of smell for at least six months. They'd all tried -- and failed -- other treatments.

The Philadelphia team first used CT scans to guide a needle to the base of the neck of each patient. They then injected a combination of anesthetic and corticosteroid into the stellate ganglia.

The steroid was added because the researchers suspected that lingering COVID virus might be driving the parosmia.

The first patient this treatment was attempted in "had a tremendously positive outcome, almost immediately, with continued improvement to the point of symptom resolution at four weeks,” Zoga said in the RSNA news release. “We have been surprised at some outcomes, including near 100% resolution of phantosmia in some patients, throughout the trial.”

Follow-up data was obtained from 37 of the patients, with 22 (59%) reporting improvements in smell just one week after their treatment, the team said. Eighty-two percent of those 22 patients were still reporting "significant" improvement a month out.

Twenty-six of the original 59 patients underwent a second injection, on the opposite side of their neck, beginning at least six weeks after they'd gotten the first treatment.

This second ganglion block did not help people who hadn't responded to the first attempt, Zoga's group said, but it boosted outcomes for most of those who said the first dose had helped them.

Because this study was small and presented at a medical meeting, its findings should be considered preliminary until published in a peer-reviewed journal.

More information:

Find out more about parosmia at the Cleveland Clinic.

SOURCE: Radiological Society of North America, news release, Nov. 20, 2023