COVID-19 has brought new technology such as mRNA vaccines into the limelight. But it’s also called attention to long overlooked medical conditions such as post-viral syndromes and loss of smell.
David Rosen, an otolaryngologist at Thomas Jefferson University, has been treating patients with smell loss since the 1990s. He is frustrated that it took a pandemic to call attention to the problem, but he’s happy that physicians and researchers are more interested in developing new therapies for these patients since they currently have few treatment options. He’s about to begin a phase II clinical trial testing a biologic that those outside of otolaryngology may be surprised by: a patient’s own platelet-rich plasma.
Why were you interested in studying smell?
Research and treatments for taste and smell are underrepresented in the nose, ear, and throat field of medicine. Prior to COVID-19, people weren’t that concerned about smell loss, especially when I started doing smell research around the year 2000. Once I started seeing these patients, I realized that they’re absolutely miserable when they lose their sense of smell. Food’s aroma is the main source of taste, so they struggle to eat. Things that should smell pleasant smell unpleasant, and that makes life really difficult. We really didn’t have much to offer these patients. The platelet-rich plasma treatment is a game changer. People are over the moon when they’re better. They’re like new people, and it’s a very gratifying thing. I’m always happy to find new things for treating these patients.
What are the current available treatments for smell loss?
The gold standard — and the only thing that has any kind of scientific support — is smell retraining therapy, where we repeatedly expose a patient to different smells over the course of a few months. But this treatment only restores someone’s sense of smell by about 35%.
Why is platelet-rich plasma a valid treatment option?
Platelet-rich plasma therapy is not new; it's been out for 40 years. In the olfactory system, the olfactory neurons, which sense and send information about smell to the central nervous system, are the only neurons that can repair themselves. For example, if a nerve that goes to the finger and allows it to move gets cut, it probably won’t work again if we put it back together because these nerves can’t regenerate very well. But we can regenerate olfactory neurons by jumpstarting the body’s own ability to repair itself with plasma. Platelets have a lot of growth factors that tell the body, “okay, start making stem cells and start differentiating those into neurons.” Damaged neural tissue is not easy to repair, but in this instance, we get away with it because of the neuroplasticity already in this system.
Anecdotally, I have incredible stories from nearly two dozen patients who are completely back to normal after the platelet-rich plasma treatment. We just need more data to back up our findings. Next, we’re going to compare patients who receive platelet-rich plasma therapy with patients who only undergo smell retraining therapy.
What is the treatment process?
Olfactory neurons reside high in the back of the nose. I take these little widgets made from cellulose and soak them with platelet-rich plasma, which looks like a straw-colored fluid. I use an endoscope to visualize the back of the nose and pack the widget up as high as I can, and it just sits up there. Eighty percent of the plasma absorbs in the first minute. If the widget falls out or the patient squeezes it out, it doesn’t matter because a majority of it is absorbed before they even leave the office. The patient doesn’t have problems breathing because it’s so high in the nose that it doesn’t obstruct the airway. It degrades on its own within a day or two.
The nice thing about the way I designed the delivery is that I’m not adding anything new to the patient’s system. The platelet-rich plasma is their own blood. We could have changed the consistency of the plasma into a gel that is easier to put up the nose, but I wanted there to be little buy in for patients. The only downside is the blood draw.
Do you treat many patients who have recovered from COVID-19?
Ninety-five percent of the people I see who have lost their sense of smell had COVID-19. Luckily, the way I deliver the platelet-rich plasma therapy is probably better than other previously used delivery methods such as by injection. In my pilot study, I discovered that patients who received plasma via injection didn’t regain their sense of smell as well as patients who received the widget. Additionally, patients who received the injection weren’t as keen to get a second injection.
What are you most excited about moving forward?
I’m excited to start the placebo-controlled study so that I can actually prove to people that this works. I have more than enough patient success stories to feel confident. We are waiting on IRB approval for a phase II trial right now, but I continue to treat people who already started the therapy. I hope we can get enough patients willing to go through the double blinded study. Many people who have lost their smell would rather simply take the therapy than take the chance of ending up in the placebo group.
I hope that my work can help these patients because no one listens to them. Many doctors don’t understand why someone without smell won’t eat or feels nauseated. Sometimes food smells like garbage to these patients, so it makes them feel sick. That’s why it’s so exciting to see people get better. I saw a patient yesterday who had only received two treatments so far, and she told me that grass smelled like grass to her again and chocolate tasted like chocolate. I’m excited to see people getting back to their normal lives.
This interview has been edited and condensed for clarity.
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