A group of patients with persistent COVID have managed to recover their sense of smell thanks to a “minimally invasive” image-guided procedure that lasts just 10 minutes. The study that has shown the effectiveness of this new technique will be presented at the next annual meeting of the Radiological Society of North America (RSNA).
Anosmia or loss of the sense of smell is one of the typical symptoms of SARS-CoV-2 coronavirus infection, while parosmia is characterized by alterations in smell that cause the individual to perceive odors differently and this can affect also to taste. Both disorders continue to affect many long-COVID patients, months or even years after they overcome the initial infection.
“Post-COVID parosmia is common and increasingly recognized,” said the study’s senior author, Dr. Adam C. Zoga, professor of musculoskeletal radiology at Jefferson Health in Philadelphia, Pennsylvania. “Patients may develop a dislike for foods and beverages they previously enjoyed.” Distortion in the sense of smell can also affect the perception of smell and some patients may suffer from phantosmia, which is an olfactory hallucination that causes people to detect odors (pleasant or unpleasant) that do not exist.
What does the procedure to recover your sense of smell consist of?
The researchers carried out a study to evaluate a possible treatment for patients with long-term post-COVID parosmia, and to this end they analyzed the possible benefits of blocking the stellate ganglia, which are part of the autonomic nervous system that regulates involuntary processes such as heart rate, blood pressure, breathing and digestion, and are nerves located on both sides of the neck that send signals to the head, neck, arms and part of the chest.
“We have been surprised with some results, including close to 100% resolution of phantosmia in some patients, throughout the trial”
They performed a stellate ganglion block, which includes injecting anesthetic directly into the stellate ganglion on one side of the neck to stimulate the regional autonomic nervous system. This minimally invasive procedure takes less than 10 minutes and does not require sedation or intravenous analgesia. Stellate ganglion block has been used with varying success to treat a variety of conditions, including cluster headache, phantom limb pain, Raynaud and Meniere syndromes, angina, and cardiac arrhythmia.
“Parosmia has previously been described as a rare disorder that occurs after brain trauma, brain surgery, stroke, viral syndromes and with some head and neck tumors,” explained Zoga. “We weren’t totally sure the procedure would work for parosmia.”
To verify this, 54 patients were referred by an otolaryngologist after experiencing post-COVID parosmia resistant to pharmaceutical and topical treatments for a minimum of six months. They used computed tomography (CT) guidance to place a spinal needle at the base of the neck for injection into the stellate ganglion. They added a small dose of corticosteroid to the anesthetic in the pharmacological preparation, suspecting that the coronavirus could be causing inflammation of the nerves.
“The initial patient had a tremendously positive result, almost immediately, with continued improvement to the point of resolution of symptoms at four weeks,” said Dr. Zoga. “We have been surprised by some results, including close to 100% resolution of phantosmia in some patients, throughout the trial.”
Thirty-seven patients (65%) were followed up, and 22 (59%) of the 37 reported improvement in symptoms one week after injection. Of these 22, 18 (82%) reported significant progressive improvement one month after the procedure. At three months, there was a mean 49% improvement in symptoms (range 10% to 100%) among the 22 patients.
After an interval of at least six weeks, 26 patients returned to receive a second injection on the other (contralateral) side of the neck. Although this second injection was not effective in patients who did not respond to the first injection, 86% of patients who reported some improvement after the first injection also reported further improvement after the contralateral injection. No complications or adverse events were observed. “Other treatments have failed to date,” Zoga concludes. “This injection is working.”
