FROM MOVEMENT DISORDERS
The application of transcranial direct-current stimulation and spinal cord stimulation alleviated freezing of gait in two separate studies of patients with idiopathic Parkinson’s disease published online in Movement Disorders.
In the first study, Moria Dagan of Tel Aviv University and her colleagues reported that transcranial direct-current stimulation (tDCS) applied simultaneously to the primary motor cortex (M1) and the left dorsolateral prefrontal cortex (DLPFC) improved freezing of gait (FOG) more than M1 stimulation alone or sham stimulation in a double-blind, randomized trial of 20 patients. The second study, reported by Olivia Samotus and her associates at the London (Ont.) Health Sciences Centre, found that open-label, midthoracic epidural spinal cord stimulation (SCS) in five patients produced significantly reduced FOG episodes and also provided sustained improvement in gait measurements.
The tDCS study used a crossover design to show that, over the course of four separate, 20-minute tDCS sessions, FOG-provoking test scores improved in 15 of 17 patients who received multitarget stimulation and were significantly improved on average, whereas the scores of patients who had M1 stimulation alone or sham stimulation did not improve. Improvement in FOG severity nearly reached statistical significance when compared with M1 only and sham stimulation (P = .06). Three patients were unable to complete the FOG-provoking test and were excluded from the analysis.
The investigators tested simultaneous tDCS of the M1 and left DLPFC because a previous study showed improvement in FOG after M1 stimulation, and other evidence suggests that FOG might also arise through deficits in executive function mediated by the DLPFC. Previous research in other patient populations has also shown that tDCS improves cognition, gait, and postural control, and a prior study using transcranial magnetic stimulation of the M1 and left DLPFC improved gait and cognition in patients with FOG.
“We suggest that the results move this emerging approach a key step forward, as they support the idea that the cognitive executive circuit plays a role in FOG and the possibility that multitarget stimulation may have value as an intervention for ameliorating FOG,” Ms. Dagan and her colleagues wrote.
In a separate, nonrandomized pilot trial, SCS produced improvements in stride velocity, step length, and single- and double-support phases in follow-up visits out to 6 months post surgery, in addition to significantly decreasing FOG episodes. The study is the first to use objective gait technology to assess the efficacy of SCS for gait in advanced Parkinson’s disease patients. Ms. Samotus and her associates observed these changes after testing a range of pulse width and frequency combinations in each of the five participants to determine which settings best improved gait for each participant. Overall, the results suggest that pulse widths of “300-400 microseconds and frequencies of 30-130 Hz may be safe and possibly effective for reducing FOG frequency and improving gait dysfunction in advanced Parkinson’s disease patients.”
The tDCS trial was supported by the Michael J. Fox Foundation for Parkinson’s Research. One investigator disclosed that he is cofounder and shareholder of Neuroelectrics, which makes brain stimulation technologies such as the ones used in the study. No outside funding was reported for the SCS study. One investigator in the SCS study reported ties to pharmaceutical companies and device manufacturers.
SOURCES: Dagan M et al. Mov Disord. 2018 Feb 13. doi: 10.1002/mds.27300 ; Samotus O et al. Mov Disord. 2018 Feb 14. doi: 10.1002/mds.27299 .
