Physicians are experimenting with a numbing procedure which may restore or improve smell and taste disorders in people with long COVID-19, NBC News reported March 31.
The procedure, a stellate ganglion block, involves a temporary, local anesthetic injected into the stellate ganglion bundle of nerves on both sides of a person's neck. The nerves are part of the sympathetic nervous system and are not known to impact how a person perceives odors; however, some physicians are reporting improvement in patients with long COVID-19 smell disorders.
Some experts theorize the block may work by increasing blood flow to the brain. Others say the block could be a "reset button" for the sympathetic nervous system.
A survey last year found 15 percent of people with COVID-related olfactory loss still had smelling problems six months later. Few treatments are available for smell disorders, according to the report.
Two physicians have treated patients with a stellate ganglion block and reported positive results.
Christina Shin, MD, a pain management physician at the Cleveland Clinic, says she treated roughly 30 long COVID-19 patients with the block. About half reported improvement levels in smell or taste between 25 percent and 90 percent.
Nyssa Farrell, MD, an assistant professor of otolaryngology–head and neck surgery at Washington University School of Medicine in St. Louis, conducted a small study to test the block. Among 20 patients with smelling troubles, half reported "slight to moderate" improvement from the stellate ganglion block. It was enough to start planning a large study "to see if this is a placebo effect or if this is real," Dr. Farrell said.
However, some experts are skeptical of the treatment.
Stem cells in the nasal cavity replace olfactory receptor neurons every three to four months, Zara Patel, MD, a professor of otolaryngology at Stanford University in California, told NBC News. As many as 80 percent will recover on their own within about six months, she said.
The lack of scientific evidence is an issue for many.
"Given the lack of data suggesting efficacy, it's really hard to advocate for this for patients who have a problem that typically resolves with time," Justin Turner, MD, PhD, an associate professor in the department of otolaryngology–head and neck surgery at Vanderbilt University Medical Center in Nashville, Tenn., told NBC News.