New Research Shows Promising Treatment for Long COVID Smell Loss
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One of the distinct symptoms of long COVID is a loss or distortion of smell. Research has documented people who said their coffee smelled like garbage or rotting meat. A person with long COVID quoted in WVU Today said that everything tasted like a burning cigarette. The symptom can last for months or even years after infection, negatively impacting appetite and overall quality of life.
Now research shows a promising way forward to restoring the olfactory sense. The findings, to be presented next week at the annual meeting of the Radiological Society of North America, indicate that an image-guided, minimally invasive procedure may bring back the sense of smell in some people living with long COVID.
“There is a subset of COVID patients who lose their taste for food, get nauseous from certain smells, and really struggle to live normally,” says Adam Zoga, MD, the lead author of the study and a professor of musculoskeletal radiology at Jefferson Health in Philadelphia. “I was absolutely shocked by the results [from our procedure] in the first few patients — including one early patient who could not bathe her 4-year-old daughter because the shampoos and soaps made her sick.”
Improvements Reported Within a Week Post-Injection
Dr. Zoga and colleagues recruited 54 patients who’d had COVID-19 and were desperately seeking help to regain normal smell after every conventional treatment failed. An ear, nose, and throat specialist referred the participants — all of whom reported cases of at least six months of post-COVID parosmia (distorted sense of smell) that was resistant to pharmaceutical and topical therapies.
The patients received a combination injection of anesthetic and steroid (a “special cocktail” of Depo Medrol, bupivicaine, and lidocaine) into the stellate ganglion, a group of nerves in the neck.
Called a stellate ganglion block, the anesthetic medication has been used with varying degrees of success to treat a number of conditions, including cluster headaches, phantom limb pain, Raynaud’s and Ménière’s syndromes, angina, and cardiac arrhythmia.
“Most of the nerves that supply the olfactory system contribute to the tangle of nerves in the anterior (front) neck that is the stellate ganglion,” says Zoga. “We felt that injecting this region could essentially ‘reboot’ the olfactory system.”
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Using CT image guidance, the scientists carefully direct a 3.5-inch needle deep into an area near the first rib next to the esophagus.
“We simply pass a 25-gauge needle through the neck,” says Zoga. “Patients feel a momentary pinch, and that’s it.” The entire procedure takes less than 10 minutes.
He and his colleagues were able to obtain follow-up information for 37 participants (65 percent). Nearly 60 percent reported improved symptoms one week after injection. Of these, over 80 percent reported significant progressive improvement by one month post-procedure.
At three months, there was an average of 49 percent improvement in symptoms among the participants.
At least six weeks after the first injection, 26 participants returned for a second shot. Participants who did not respond the first time still did not improve with the extra dose. Of those who did experience some benefit after the first dose, 86 percent reported additional improvement.
Patients experienced no complications or adverse events.
Resetting the Body to Restore Sense of Smell
Kristine Smith, MD, a rhinologist in the department of otolaryngology (a medical specialty focused on the ears, nose, and throat) at University of Utah Health in Salt Lake City, notes that the current study builds on previous research also showing that injections of local anesthetic into the stellate ganglion may improve sense of smell in people who had COVID-19.
A difference in the latest research is that CT guidance was used for the procedure rather than ultrasound, mentions Dr. Smith, who was not involved in the latest research. Although Zoga and his coauthors indicate that CT provides ideal efficiency and guidance, some radiation exposure is associated with CT imaging, according to Harvard Health Publishing, while ultrasound uses no radiation to create images.
Exactly why the procedure works remains unclear, according to Smith. She would like to see further research explore the actual physiology or the mechanism behind the approach.
“We think it works a bit like a reset of the nervous system — almost like turning your computer on and off again, and letting it reorient those abnormal sensations to something more normal,” says Smith.
The study was limited by its small number of participants, she adds. And, although the findings suggest benefits in the short term, more research is needed to determine if the procedure is long-lasting.
“To date, we do not know why some patients respond better than others, but with continued research on this patient population, we hope to find out,” says Zoga.
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