Patients who have suffered a stroke often experience dysphagia, a swallowing disorder after the event. Dysphagia leads to a higher rate of complications, such as dehydration, malnutrition and pneumonia, and greater subsequent healthcare costs. Researchers have now discovered in a new study featured in the July issue of Restorative Neurology and Neuroscience that transcranial direct current stimulation (tDCS) can improve the outcome of swallowing therapy for post-stroke dysphagia. tDCS involves applying weak electrical currents to the patient’s affected area of the brain.
Lead researcher Nam-Jong Paik, MD, PhD, from Seoul National University College of Medicine’s Department of Rehabilitation Medicine, South Korea explains:
Our pilot study demonstrated that ten daily sessions of tDCS over the affected esophageal motor cortex of the brain hemisphere affected by the stroke, combined with swallowing training, improved post-stroke dysphagia. We observed long-lasting effects of anodal tDCS over three months.”
The trial involved 16 patients with acute post-stroke dysphagia who had difficulty in swallowing caused by reduced tongue movement, coughing and choking whilst eating, and vocal cord palsy. They received ten 30-minute sessions of swallowing therapy and were randomly assigned to either a treatment group or control group.
The researchers fitted all patients with an electrode that was attached on the their scalp on the side of the brain affected by the stroke, as well as in the region linked to swallowing. The treatment group was administered tDCS for the first 20 minutes of their sessions, with swallowing training alone for the remaining 10 minutes, whilst those in the control group, the researchers tapered down the direct current and turned it off after thirty seconds.
The scientists measured outcomes before and immediately after the experiment, and again three months later. Just before and after treatment, the team took a PET scan from a patient in each group to see whether the treatment had any effect on metabolism.
None of the patients suffered any discomfort or fatigue during the interventions and the researchers observed no significant differences in age, sex, stroke lesion site, or extent of brain damage.
At the end of the sessions, the authors found that all patients had showed an improvement in dysphagia, with no significant difference between the two groups, although the results at the 3-month follow-up showed a significantly greater improvement in the treatment group compared with the control group.
The PET study showed significant differences in cerebral metabolism between the first and second PET scans in the patients who had received tDCS. The researchers found a higher metabolism of glucose in the unaffected hemisphere of the brain, even though they only applied tDCS to the affected hemisphere. This suggests that tDCS appears to activate a larger area of the cortical network involved in swallowing recovery, instead of just those areas that were stimulated by the electrode.
Dr. Paik concludes:
“The results indicate that tDCS can enhance the outcome of swallowing therapy in post-stroke dysphagia. As is always the case in exploratory research, further investigation involving a greater number of patients is needed to confirm our results. It will be important to determine the optimal intensity and duration of the treatment to maximize the long-term benefits.”
Written by Petra Rattue