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Simple treatment restores sense of smell in long COVID patients

Using a cutting-edge, minimally invasive technique, researchers are on the brink of a breakthrough in treating long COVID patients who have lost their sense of smell. This promising development will be presented at the upcoming annual meeting of the Radiological Society of North America (RSNA).

Post-COVID parosmia

Parosmia, a condition that disrupts the normal functioning of smell, has emerged as a prevalent symptom among COVID-19 sufferers. Recent studies reveal that up to 60 percent of COVID-19 patients experience this condition. 

While many recover their olfactory senses over time, a subset of long COVID patients continues to struggle with these symptoms for an extended period, impacting their appetite and overall quality of life.

“Post-COVID parosmia is common and increasingly recognized,” said lead author Adam C. Zoga, M.D., M.B.A., a professor of Musculoskeletal Radiology at Jefferson Health in Philadelphia. “Patients can develop a distaste for foods and drinks they used to enjoy.”

In addition to a distorted sense of smell, some affected individuals may experience phantosmia, where they perceive smells that are not present in their environment.

Stellate ganglion block 

The researchers focused on the effectiveness of CT-guided stellate ganglion block as a potential remedy for persistent post-COVID parosmia. The stellate ganglia, part of the autonomic nervous system, are nerve clusters located on each side of the neck, playing a role in sending signals to various parts of the upper body.

In their approach, the team employed a stellate ganglion block, a procedure involving the injection of anesthetic directly into the ganglion to activate the regional autonomic nervous system. This quick, minimally invasive technique requires no sedation or pain relief. 

Previously, stellate ganglion block has been applied in treating diverse conditions like cluster headaches, phantom limb pain, Raynaud’s and Meniere’s syndromes, angina, and cardiac arrhythmia.

“Parosmia has previously been reported as a rare disorder occurring after brain trauma, brain surgery, stroke, viral syndromes, and with some head and neck tumors,” Zoga explained. The team was initially uncertain about the procedure’s efficacy for parosmia.

Focus of the study

In the study, 54 patients with at least six months of persistent post-COVID parosmia, unresponsive to conventional treatments, were referred for the procedure. Using CT guidance, the researchers accurately positioned a spinal needle at the neck base for the injection. They included a corticosteroid dose with the anesthetic, hypothesizing that COVID-19 might trigger nerve inflammation.

“The initial patient had a tremendously positive outcome, almost immediately, with continued improvement to the point of symptom resolution at four weeks,” Zoga said. The trial witnessed significant outcomes, including near-total resolution of phantosmia in some patients.

Critical insights 

Among the 37 patients (65 percent) followed up, 22 (59 percent) reported symptom improvement within a week post-injection. Of these, 18 (82 percent) experienced substantial ongoing improvement a month after the procedure. At three months, these 22 patients noted an average 49 percent symptom improvement.

A second injection was administered to 26 patients on the opposite neck side after a six-week gap. While ineffective for those unresponsive to the first injection, 86 percent of those who had initial improvement reported further progress post-second injection. No complications or adverse events were reported.

“Other treatments have failed to date. This injection is working,” Zoga concluded.

More about long COVID

Long COVID, also known as post-acute sequelae of SARS-CoV-2 infection (PASC), refers to a range of symptoms that continue for weeks or even months after the acute phase of a COVID-19 infection has resolved.

This phenomenon has been observed in a subset of individuals who have contracted the COVID-19 virus, caused by SARS-CoV-2.


Long COVID can affect nearly any organ system. Symptoms include fatigue, brain fog or cognitive impairment, shortness of breath, chest pain, joint or muscle pain, depression or anxiety, fever, loss of taste or smell, and more. These symptoms may fluctuate or relapse over time.

Unknown cause

While the exact cause of long COVID was not yet known, it’s thought to be a combination of factors. These include direct damage caused by the virus, a prolonged inflammatory response, an autoimmune response, or persistent presence of low-level virus.

The probability of developing long COVID does not necessarily correlate with the severity of the initial infection. Even individuals with mild or asymptomatic COVID-19 can experience these prolonged symptoms.

Public health concern

Long COVID has been increasingly recognized as a significant public health concern. For some individuals, this condition can significantly impact the quality of life and ability to perform daily activities or work.

There is ongoing research into long COVID, including its causes, risk factors, and potential treatments. Care for patients involves managing symptoms and supportive treatments.

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