Dr. Marcia Bockbrader is assistant professor of physical medicine and rehabilitation at the Ohio State University Wexner Medical Center. Her research of the navigated Transcranial Magnetic Stimulator (TMS) was funded by NexStim, the technology's developer. Bockbrader contributed this article to Live Science's Expert Voices: Op-Ed & Insights.
More than 750,000 Americans experience a stroke each year in the United States. While most are not fatal, stroke kills someone every four minutes, equating to nearly 130,000 yearly deaths — and leaving a total of 7 million stroke survivors in need of some form of rehabilitation.
Those survivors face a range of potential side effects, including vision problems, memory loss and impairments in speech. The most prevalent side effect, however, is paralysis on either side of the body, which can cause loss of movement and diminished range of motion in the arms and legs. When one side of the brain is damaged by stroke, the healthy side tends to generate much more activity to compensate for the immobile side. This overcompensation can actually prevent the injured side from recovering. [Stroke: Symptoms, Tests and Treatment ]
In an effort to help patients regain movement on the side of their body affected by stroke, my colleagues at The Ohio State University Wexner Medical Center and I are taking part in a double-blind, randomized, placebo-controlled, Phase III trial to determine the effectiveness of repetitive transcranial magnetic stimulation (rTMS) using a device developed by NexStim, which funded our study.
After a stroke hits
Often, stroke patients can have a rapid partial recovery in the first few months after a stroke, then the spontaneous healing process slows down after about three to six months, and then slows even further after a year. This can be frustrating for patients who have a stroke that leaves one side of their body weak, making it difficult for them to do their usual everyday activities, like dressing and eating, or leisure activities like golfing.
Often, when those impairments have persisted even after completing 3 to 6 months of outpatient therapies, many patients lose hope of regaining the ability to use their weaker side. [Harsh Thoughts: Cynicism Linked to Stroke Risk]
Up to this point, doctors have not known how to reset the brain back into the state of rapid recovery that we see in the initial months after a stroke. We have been looking for a way to boost the benefits of physical and occupational therapy for motor recovery after stroke, and we think that using a powerful magnet to enhance brain plasticity prior to therapies may be the solution.
Doctors think that part of the problem is that the healthy and injured sides of brains of some stroke patients develop an imbalance over time, either as a direct result of the tissue injury from stroke or through lack of use of the weaker side of the body. The result appears to be overactivity on the healthy side of the brain that may actually prevent the injured side from recovering. The rTMS device helps even out this imbalance by reducing activity on the side of the brain that was not injured by stroke and giving the other side a more likely chance to recover and express itself once more.
We use the navigated rTMS to essentially map the participant's brain like a GPS system would, and then repeatedly stimulate specific areas of the motor cortex in a non-invasive manner. The rTMS device is a flat, water bottle-sized magnet that we hold against the patient's scalp while they are reclining comfortably in a chair. The process is painless, though participants may feel the snap of the magnet pulse against their scalp or the twitch of a muscle in their arm as the device works. [Video Game Therapy Proving Powerful for Stroke Patients (Op-Ed )]
The critical advance of this technology is the navigation tool, which allows us to more easily find the area of the brain that needs to be stimulated, which speeds up a patient's recovery and restores the brain balance. Adding navigation to TMS is the key to finding the exact location and orientation of the motor area in each person that needs inhibition, via the stimulation. The stimulation is then accurately repeated in every session, assuring the exact dose is applied to the correct place, within a tolerance of 2 millimeters.
The process helps improve the brain's receptiveness to activity-based therapy. The technology isn't limited solely to motor recovery after stroke — in fact, it seems to have the potential to affect many of the brain circuits that are injured in stroke.
From trials to technique
The current study involves 12 centers across the United States, and eligible participants are those who have not fully recovered motor strength on one side of their body three to 12 months after their stroke. Over the course of the eight-month trial, participants will have a total of 29 visits and receive six weeks of hand and arm therapy free of charge. The current Phase III clinical trial was launched in June 2014 and researchers will continue to conduct trials over the next 12 to 18 months. As a Phase III clinical trial, this technology is in the last phase of testing needed to obtain U.S. Food and Drug Administration (FDA) approval for use in clinical settings. In development since 2000, NexStim's non-invasive Navigated Brain Stimulation System is currently available for investigational use only.
Patients in the trial undergo occupational therapy rehab after each use of the device to improve flexibility, strength and use of weak arms or hands. We hypothesize that pretreatment with carefully dosed magnetic pulses to the motor cortex will predispose participants to make bigger gains with therapy than they would have with 6 weeks of therapy alone. The trial continues for 8 months so we can determine whether initial improvements in motor function persist 6 months after completing treatment.
Since the study is double-blind, patients are not sure if they're actually getting a stimulation dose from the device, but we've already encountered some who say everyday tasks like opening the refrigerator and getting around the house are much easier. Although we don't know for sure if these individuals have received the stimulation or placebo treatment, these indications give us hope that our trial will be successful and the device will be approved for general use in the near future.
The technology also has implications outside of post-stroke motor recovery. The rTMS treatment is a highly precise, yet non-specific, way of preparing the brain for all types of therapies, and depending on where the magnet is aimed, can potentially affect many of the brain circuits that are impaired during stroke or other types of brain injuries. Instead of targeting the motor cortex to promote recovery of arm movement, we can vary the location of magnetic stimulation to target the brain regions associated with other neurologic impairments, e.g., language areas, attention areas, chronic pain areas. Thus, rTMS treatment could be potentially improve aphasia, hemispatial neglect or pain perception resulting from stroke or brain injury. This bodes well for neurorehabilitation programs in the future, shedding light on the possibility that this technology might not be limited to stroke recovery alone.
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