Conference Coverage
CHICAGO—Transcranial direct-current stimulation (tDCS) reduces fatigue and improves aspects of verbal memory in patients with multiple sclerosis (MS), according to data from a pilot study presented at the 140th Annual Meeting of the American Neurological Association. The stimulation may not consistently improve working memory, however, contrary to the researchers’ expectations.
Cognitive dysfunction, including working memory deficits, and fatigue are common and debilitating symptoms of MS, said Tracy D. Vannorsdall, PhD, Assistant Professor of Neurology and Psychiatry and Behavioral Sciences at Johns Hopkins University School of Medicine in Baltimore. Prior studies have shown that tDCS enhances working memory in healthy adults. To see if tDCS might improve working memory in patients with MS, Dr. Vannorsdall and her research colleagues conducted a sham-controlled, single-blind crossover study.
A Sham Stimulation Control
The investigators recruited five patients with secondary progressive MS from the Johns Hopkins MS Center. All participants were right-handed native English speakers, and three of the participants were women. Participants were between the ages of 42 and 57, with an average age of 50. They had a mean estimated IQ of 119 and a mean 18.4 years of schooling.
Participants completed cognitive testing before and after receiving 2 mA of anodal or sham stimulation to the left dorsolateral prefrontal cortex for 30 minutes once per day for five consecutive days. Investigators administered the current using a NeuroConn Stimulator Plus. For the sham stimulation, researchers increased the anodal current to 2 mA and decreased it to 0 mA over 30 seconds. After a four-week washout period, participants repeated the study procedures under the stimulation condition to which they had not been assigned originally.
Evaluating Cognition
Participants completed the Minimal Assessment of Cognitive Functioning in MS, a seven-subtest battery that assesses verbal learning and memory, visuospatial learning and memory, working memory, processing speed, verbal fluency, executive functioning, and perceptual accuracy. Participants also completed self-report measures of mood and fatigue and responded to a mental and physical side effects questionnaire. The researchers performed two-tailed paired-samples t-tests to compare changes in scores across anodal and sham conditions.
No adverse events occurred. Depression scale ratings did not significantly change during tDCS, compared with sham stimulation.
Fatigue Severity Scale
Participants’ scores on the Fatigue Severity Scale increased by 7 points over the course of five days of sham stimulation, compared with a decrease of 4.6 points over the course of anodal stimulation.
In addition, researchers observed a trend toward improved verbal immediate recall under the anodal condition, compared with sham stimulation. Anodal stimulation also was associated with better performance across most cognitive tests, but the differences were not significant. The study was underpowered to detect whether reduced fatigue contributed to the improvements in cognition. “These preliminary findings suggest that tDCS may ameliorate fatigue and cognitive dysfunction in secondary progressive MS,” concluded the researchers. Future studies will investigate the mechanism of these effects.
—Jake Remaly