A clinical trial at St. Joseph's Health Care in London, Ontario, is investigating the use of stellate ganglion block (SGB) to treat parosmia, a condition characterized by the distortion of smell following a COVID-19 infection. The trial offers hope for individuals experiencing altered or phantom smells after recovering from the virus.
The Burden of Post-COVID Smell Distortion
Parosmia can significantly impact a person's quality of life. Patients often report once-pleasant odors becoming repulsive, and the emergence of disturbing phantom smells. One patient, Rebecca Bruzzese, described experiencing smells of burning cigarettes and excrement, leading to a 30-pound weight loss and mental health challenges. Early in the pandemic, about half of COVID-19 patients reported a loss of smell. Most recovered, but a “significant number” never got it back, Sowerby said. The loss of smell happens when an organ inside the nose, filled with cells responsible for smelling, is injured by COVID. It can take a long time to regenerate, Sowerby said, and even when the sense of smell returns, patients sometimes report symptoms of parosmia.
Stellate Ganglion Block (SGB) as a Potential Treatment
The clinical trial utilizes stellate ganglion block (SGB), a procedure involving the injection of a local anesthetic into the stellate ganglion, a cluster of nerves in the neck. Dr. Leigh Sowerby, a head and neck surgeon and scientist at the Lawson Health Research Institute, is leading the randomized, double-blind trial. The stellate ganglion controls signals to the head, neck, arms, and part of the chest, and the injection aims to "reset" overstimulated nerves by temporarily blocking them.
Trial Design and Methodology
Participants in the trial are randomized to receive either the anesthetic or a saline placebo. Neither the participants nor the investigators know who is receiving the active treatment. While the nerves targeted by the injection are not directly responsible for the sense of smell, Dr. Sowerby explains that they play a crucial role in how the brain interprets olfactory signals. A diagnosis of parosmia considers the patient’s COVID-19 history, including a smell test, but other health problems such as chronic infection can also trigger the disorder, Sowerby said.
Early Patient Experiences
Bruzzese, who participated in the trial, reported a return to her normal sense of smell. She also found support and validation through social media, connecting with others experiencing similar issues. "It’s really hopeful not just for myself, but for other people dealing with this," she said.
Next Steps
The next phase of the trial involves a follow-up with 44 patients to assess the effectiveness of SGB in treating post-COVID parosmia. The results of this trial could provide a significant advancement in the treatment of this debilitating condition.
