Auditory Mirror Therapy for Tinnitus with Clas Linnman, PhD

tinnitus mirror therapy
April 30, 2023

Mirror therapy has been used with amputees for many years. In this episode of TWiH. Dr. Clas Linnman, assistant professor at the Spaulding Rehabilitation Hospital discusses his patent-pending auditory mirror therapy device for tinnitus patents. Dr. Linnman recently conducted a pilot trial with 18 participants who wore the headphone device for two hours per day for two weeks.

Results showed a significant reduction in the Tinnitus Handicap Inventory, which measures self-rated levels of bother from tinnitus, as well as a reduction in awareness of the condition. Dr. Linnman notes that the reductions were dose-dependent, meaning that longer use of the headphones led to greater reductions in tinnitus. A second clinical trial is currently underway with more rigorous measures and a control condition, and it’s hoped that the initial results may become available by the end of the summer. Dr. Linnman suggests that mirror therapy for tinnitus may offer a new approach to targeting multisensory integration in the brain, rather than just targeting the auditory system.

Full Episode Transcript

Hello, and welcome to another episode of This Week In Hearing. I’m Brian Taylor, and this week we’re discussing mirror therapy for tinnitus with Clas Linnman. Dr. Linnman, we’re really pleased to have you with us this week. And before we talk about mirror therapy for tinnitus, I thought it’d be a really good idea if you could kind of tell our audience a little bit about your background, about your research interest and maybe what got you involved in mirror therapy for tinnitus. Thank you. And thanks for the introduction and the opportunity to speak to you guys. Yes, my background is in chronic pain. I mostly study patients with spinal cord injury. And so after spinal cord injury, there’s no sensory inflow from below the lesion level, but from your your paralyzed legs. But patients still experience a lot of patients still experience neuropathic pain as if it was arising from their legs. And this is thought of and in some ways, it can be thought of as a phantom sensation. So there’s no actual peripheral sensory inflow. We think rather, the brain reinterprets those signals and makes sense of those signals by turning it into a pain signal. So one of the ways we treat both spinal cord injury and then primarily amputees is through mirror therapy. So, basically, you put up, you take a card. It’s very low tech. It’s a cardboard box with a mirror inside it. You stick your hand in, and you stick your good hand in and your amputated limb in behind the mirror. And that way, when you look into the box, it looks as if you have your hand back, because your good hand is mirrored as if it were in the spot of the amputated hand. And this actually helps a lot of patients with phantom limb pain, because we think the mechanism is that the brain reinterprets the peripheral signals from the amputated limb. You know, you get your visual feedback, oh, my hand is back, then that doesn’t make sense to the brain. So it introduces what’s called a prediction error that forces us to reinterpret and reevaluate the peripheral signals from the amputated limb. So this was discovered more than 20 years ago, and it’s a common therapy in rehab clinics. And then we were thinking about tinnitus, and that can also be seen as a phantom sound. There’s no external source. There’s no ringing. Sound in the background, although you experience it as an external source. So can we do something similar for tinnitus? And basically, I built the first prototype into my garage. It’s a pair of headphones that records sound at the left ear and projects it into the right ear and records sound at the right ear and projects it into the left ear. So basically, you flip the soundscape 180 degrees. So if I snap my fingers at my right ear, I would hear it in my left ear. Now, obviously, we rely more on vision than on our ears to localize sounds. If you think of a ventriloquist, for example, the puppet is talking, you know that the ventriloquist is doing the talking and that the puppet is just moving its lips. But since we tend to rely more on our vision than our ears for sound localization, we actually experience that the puppet is doing the talking because this little trick that our brain is very good at making sense of the world, even though our senses are not fully calibrated. So with this flipping of the soundscape 180 degrees, we really mess up how the brain interprets its auditory signals. Basically telling or our eyes are basically telling us that there’s something wrong with our ears. Everything is off by 180 degrees. So it’s a fun little experiment just to think of the psychology of perception. But we also think it may work to treat phantom sounds or tinnitus. So we did a pilot trial that’s published. Now, it was only 18 people. Two people dropped out. But in the 18 people that continued, it was two weeks of wearing these headphones at home for about 2 hours per day. And in them we saw a significant reduction in what’s called the Tinnitus Handicap Inventory. So self ratings of how much how bothered they were of tinnitus and also a big reduction in the awareness of tinnitus. So how many hours per day are you aware that you hear ringing in the ears? And we saw reductions that seem to be kind of dose dependent so that the longer people wore the headphones, the greater their reductions were. So we think this is a new approach to tinnitus in some way by maybe not just targeting the auditory system, but going up one level and targeting. Multisensory integration. And we’re now doing our second clinical trial a little bit more rigorous with more audiology measures and a control condition or a placebo control or a sham control device. I can’t really argue any results from that, but understood. When might those results be available? I hope we’ll be finished with data collection within a month, and then there will be some data analysis and processing and it takes a while to get it published, but hopefully by I don’t want to promise anything, but maybe end of the summer if all goes well. Understood, but I understand it’s early in the process here. I’m kind of curious to know a couple of things. Number one, who might be a good candidate for something like this, if you had any thoughts on that? And then secondly, do you have any ideas or any thoughts on maybe how many hours a day somebody would have to wear the headphones before they would see some if they would see any residual inhibition or anything like that? Yeah, no, those are all part of the questions we’re addressing now. So by recruiting a larger sample, we can differentiate patients a little bit more and we’re doing some hearing testing and some tinnitus matching in these patients as well to kind of get to more objective measures of how we might be changing the experience of tinnitus we did not see in the pilot trial. We thought, well, maybe the the unilateral subjects would be it would be more beneficial if you have, you know, one sided tinnitus as opposed to two in both ears. But we didn’t see any difference between the unilateral and the bilateral. So maybe it was just too small of a sample. I think it was ten with unilateral and nine or eight with bilateral. But yeah, there was no trend there. And the patients we’ve been recruiting have been just anyone interested from the community. So not the worst cases and probably not the lightest cases either. Just the general sort of population type of tinnitus That’s interesting. Do you think that there is potential that something like this could be built into hearing aids? I hope so. I mean, one of the next steps here is after our second trial, we’re reaching out to hearing aid makers and to, well, medical device makers in general to see what. What a path forward might be. We have a patent pending on the utility patent on the approach. I think that commercializing this and making it available to a lot of people quickly would be the best way to get it out there, since I’m a science is not that good of a salesman, but if it can help one in ten, then I’d be thrilled. Well, and I think clinicians and the public in general, people that suffer from tinnitus, I think they’re always looking for some new solution, some new device that might help. Because I think we all know in the field that there’s no one solution, that you need several different kinds of tools in your toolbox to help people with tinnitus. So I think it’s really great to see something like this. And you mentioned to me offline mirror therapy is on the show, Dr. House. Yeah. If anybody wants to learn more about it in the world with phantom limbs I guess that’d be a place to look. It’s a fun episode. It’s Dr. House, so he’s maybe not the most empathetic doctor, but he helps his neighbor. I put it that way. My hope is that this is quite non invasive. We’re not giving drugs, and there’s no surgery or anything like that involved, which are some other approaches. So my hope is that this can be useful for a lot of people. Yeah, no, I think it’s great. Yeah. We’re pleased that you were able to take some time out of your schedule to be with us. And Dr. Clas linman, we’re talking about mirror therapy for tinnitus. Thanks for being on our broadcast today. We appreciate it. Thank you so much.

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About the Panel

Clas Linnman, PhD, is an Assistant Professor in Physical Medicine and Rehab, Spaulding Rehab Hospital, Harvard Medical School. Dr. Linnman is a highly experienced psychologist with 15 years of expertise in multimodal imaging of pain and negative affect using Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI). His groundbreaking work has utilized multiple tracers to study the monoaminergic, peptidergic, and inflammatory aspects of clinical pain and anxiety, as well as combining PET-fMRI to study emotional circuits in psychiatric disease states. Dr. Linnman is currently focused on developing cutting-edge fMRI, PET, and simultaneous PET-MR techniques to visualize and quantify nociceptive processes, from peripheral lesions to behavioral consequences. Additionally, he has extensive experience in neuroimaging of animal models of spinal cord injury and other complex neurological, pain, and psychiatric conditions.


Brian Taylor - Editor-at-Large, Co-Host, This Week in HearingBrian Taylor, AuD, is the senior director of audiology for Signia. He is also the editor of Audiology Practices, a quarterly journal of the Academy of Doctors of Audiology, editor-at-large for Hearing Health and Technology Matters and adjunct instructor at the University of Wisconsin.


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