While most COVID patients did recover their sense of smell over time, some patients however continue to have these symptoms for months, or even years, after infection.

Lead author professor Adam Zoga said that post-COVID parosmia is increasingly being recognized, and that patients can develop distaste for foods or drinks they used to enjoy.

"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," said Zoga. "We were not entirely confident that the procedure would work for parosmia."

The treatment involves injecting anesthetic directly into the stellate ganglion on one side of the neck to stimulate the autonomic nervous system, which is accurately achieved with CT guidance.

The minimally invasive procedure takes less than 10 minutes, and no sedation is necessary. It's been used to treat several other conditions including cluster headaches, phantom limb pain, Raynaud's and Meniere's syndromes, angina, and cardiac arrhythmia.

For the study, 54 patients were referred by an ear, nose, and throat specialist after at least six months of post-COVID parosmia that was resistant to pharmaceutical and topical therapies.

The researchers added a small dose of corticosteroid to the anesthetic, suspecting that the COVID virus may be causing nerve inflammation.