Deep brain stimulation , or DBS, may help improve speech and swallowing problems caused by traumatic brain injury (TBI), according to a new University of Pittsburgh School of Medicine study published in Nature Communications .
The proof-of-concept study found that low-frequency electrical stimulation of the motor thalamus, a deep brain region connected to the motor cortex, improved control of facial and tongue muscles involved in speaking and swallowing. The findings suggest that DBS may be able to strengthen remaining communication pathways between the brain and muscles after TBI , with the potential to improve and partially restore a person's ability to communicate verbally.
The study, led by Elvira Pirondini, Ph.D., assistant professor of physical medicine and rehabilitation at Pitt's Rehab Neural Engineering Laboratory , and Jorge A. Gonzalez-Martinez, M.D., Ph.D., professor of neurological surgery at Pitt, builds on the group's previous work using neuromodulation to improve arm and hand movement after brain injury.
"Rehabilitating speech deficits after an injury is a top priority for many people, often even more than mobility," said Pirondini, co-senior and corresponding author of the study. "For many people, losing speech affects work, independence and relationships. It can have a profound effect on a person's life."
Speech and swallowing depend on coordinated signals between the brain and the muscles of the face, tongue, throat and respiratory system. Brain injuries can disrupt those pathways, causing dysarthria, or impaired speech, and dysphagia, or difficulty swallowing. The paper notes that more than 5 million people in the United States live with dysphagia or dysarthria.
While current treatments, which often rely on speech-language therapy and compensatory behavioral techniques, can help, outcomes vary and external communication devices do not restore natural speech production.
To understand whether speech deficits could respond to DBS treatment, researchers applied their knowledge of brain physiology and experience in studying the neural networks responsible for arm control. While DBS has been tested extensively and used as a therapy for neurological conditions, including tremors due to Parkinson's disease, its utility for speech restoration remained controversial. Unlike previous trials, the Pitt group used low-frequency stimulation and tested the immediate effects of the stimulation on helping control the muscles used for speech and swallowing.
Unlike high-frequency stimulation, which has been shown by other groups to have a suppressive, negative effect on speech, the protocol used by Pitt scientists shifted stimulation parameters to lower the frequency by almost three-fold – to the 50-80 Hz range, compared to 130 Hz for high-frequency DBS.
In eight participants with intact speech and swallowing pathways who were undergoing DBS implantation for essential tremor, low-frequency DBS in the 50 to 80 Hz range increased activation of face and throat muscles without worsening speech. In one participant with TBI, chronic moderate dysphagia and severe dysarthria, low-frequency DBS improved facial muscle movement, swallowing and speech control.
The TBI participant's word intelligibility improved by 8%, 20% and 16% across three testing sessions when stimulation was on, compared with stimulation off. The study notes that a 7% change is considered a small clinically significant improvement and a 15% change is considered large.
"This study shows that stimulation parameters matter," said Gonzalez-Martinez, co-senior author of the study. "By targeting the correct brain circuit with low-frequency stimulation, we may be able to support the remaining pathways that help patients speak and swallow after brain injury."
The findings suggest that low-frequency motor thalamus DBS deserves further study as a potential neuromodulation strategy for dysarthria and dysphagia after TBI and other brain lesions. The study is not a clinical trial and involved one participant with TBI and speech and swallowing deficits. The authors write that larger studies are needed to test safety, effectiveness and long-term therapeutic effects across more patients and injury types, including stroke .
The group is currently testing whether DBS can produce lasting improvements in speech and motor function of the hand and arm. In a new clinical trial , which is recruiting study participants, researchers will be measuring the effects of stimulation for a period of four weeks.
Other authors of this research are Lilly Tang, Erinn Grigsby, Ph.D., Arianna Damiani, M.Sc., Jonathan Ho, M.D., Isabella Montanaro, Sirisha Nouduri, Scott Ensel, Ph.D., Sara Trant, M.A., Theodora Constantine, P.A.-C., Gregory Adams, Denise Balason, Tracey Thomas, M.S., Jordyn Ting, Ph.D., George Wittenberg, M.D., Ph.D., Kevin Franzese, D.O., Julie Fiez, Ph.D., Donald Crammond, Ph.D., and Kaila Stipancic, Ph.D., all of Pitt; Kelly Zdrowak, M.A., of the University at Buffalo; and Bradford Mahon, Ph.D., of Carnegie Mellon University.
The study was executed through the support of internal funding from the Department of Physical Medicine and Rehabilitation and the Department of Neurological Surgery at Pitt. The study was also supported by the University of Pittsburgh Hunter Family Foundation Traumatic Brain Injury Translational Research Program.
