COVID-19-Related Smell Loss Can Be Cured By Nasal Injections

20 Jan 2023 • In a trial led by Stanford Medicine researchers, more than half of patients with persistent smell loss saw improvement with injections of platelet-rich plasma. Early in the pandemic, when people with COVID-19 began reporting that they lost their sense of smell, Zara Patel, MD, figured as much. A professor of otolaryngology at Stanford Medicine, Patel has, for years, studied loss of smell as a symptom of viral infections. According to a 2022 survey by Patel and colleagues, about 15% of people who experienced smell loss from COVID-19 continued to have problems six months later. Now Patel’s team has tested a new treatment for long-term, COVID-19-related smell loss using injections of platelet-rich plasma derived from a patient’s own blood. In a trial of 26 participants, those who received the treatment were 12.5 times more likely to improve than patients who received placebo injections. The study was published Dec. 12 in the International Forum of Allergy and Rhinology. Patel was skeptical of such a cure-all but was intrigued by a study showing that platelet-rich plasma injections were as effective as surgery in treating carpal tunnel syndrome, which is caused by compressing and injuring a nerve in the wrist. She knew that COVID-19-related smell loss also was a neurological problem, in which long-term effects of the virus prevent nerves deep in the nasal cavity from regenerating correctly. The SARS-CoV-2 virus doesn’t target nerve cells directly; it attacks supporting cells known as sustentacular cells, which have the ACE-2 receptor the virus uses to infect cells. These cells play a role in correct nerve regeneration, so persistent inflammation and damage to these cells may lead to long-term loss of function.Patel had already completed a small pilot study demonstrating the safety of platelet-rich plasma injections in the nasal cavity when the pandemic hit, so she pivoted her plans for a larger trial to focus specifically on COVID-19-associated smell loss. Half the participants received platelet-rich plasma injections into the tissue deep inside their nasal cavity every two weeks for six weeks, while the other half received placebo injections (of saline) on the same schedule. Neither the participants nor the researchers knew who received what. The Sniff Test - The researchers assessed smell ability using a standard olfactory test known as Sniffin’ Sticks. The test includes a range of odors, both pleasant (flowers) and terrible (rotten eggs), and participants are scored on their ability to identify the odors, tell odors apart and determine their strength, for a possible score of 48.
When the researchers checked in with the participants three months after their first injection, those in the platelet-rich plasma group scored on average 6.25 points higher than they did before treatment, which was 3.67 points greater than the placebo group. They gained most in their ability to tell different odors apart, known as smell discrimination. At three months, 57.1% of the platelet-rich plasma group had shown a clinically significant improvement, compared with just 8.3% in the placebo group. Patel is now offering platelet-rich plasma injections to patients outside the trial. “Our olfactory systems can be resilient,” Patel said. “But the sooner you perform some sort of definitive intervention, probably the better chance you have of improvement.” Source : Stanford Medicine | Read full story

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