Walking can be one of the biggest challenges for people living with Parkinson’s disease. Deep brain stimulation (DBS) is already used to help with motor symptoms, but its impact on walking is still being explored.
This study looked at two DBS approaches to see how they affect gait and freezing in everyday situations.
The study includes 12 Parkinson’s disease patients and the same number of control participants. They were matched in age and gender. To see details of the inclusion criteria, check out the original paper linked.
Experimental procedure with different gate and brain stimulation conditions
The assessment includes three tasks:
- Freezing of gait course (FoG-Course)
It includes four maneuvers – standing up from a chair, start walking for 1 m, turn 360 degrees clockwise and counterclockwise, open and walk through the door.
Each maneuver a rater assigns a score from 0-3 points. Zero is given if there’s no FoG and three if the patient needs help to overcome the FoG episode.
Participants had to do this task three times: without additional tasks (“walking”), with carrying a tray with a cup of water (“carrying”), and with a mathematical calculation + the tray (“carrying and calculation”).
- Movement Disorder Society – Unified Parkinson’s Disease Rating Scale III (MDS-UPDRS III)
- Walking course
This was a standardized 115-meter walking course, through the floors of the neurology dept. The course included passing doors, elevators, turning and climbing stairs.
The tasks were all repeated in three different brain stimulation conditions: no stimulation OFF-DBS, conventional cDBS and high-frequency TBS-DBS.
Explaining the different stimulation conditions
Authors had two approaches to subthalamic nucleus DBS. First one is the conventional stimulation – cDBS. And the second one is theta burst stimulation TBS-DBS.
Authors compared them because the two approaches may affect gait and FoG in Parkinson’s disease through different mechanisms.
cDBS at 130 Hz is the clinical standard and works well for tremor and rigidity, as well as some aspects of gait. But its benefits on gait and FoG tend to decline over time. This can be due to disease progression in non-dopaminergic systems, suboptimal programming, or even maladaptive neuroplasticity.
TBS-DBS, however, is a newer approach adapted from transcranial magnetic stimulation. It delivers high-frequency pulses grouped into bursts at a 5 Hz rhythm. These are thought to engage cortical–subcortical networks differently than cDBS. Early studies suggested TBS-DBS might produce stronger or more durable effects on motor symptoms.
EEG and Kinematic recordings
EEG is recorded using the portable Smarting EEG system. Since researchers distributed brain stimulation at the same time as collecting EEG, they had to clean the data from artifacts.
They used the open source DBSFilt toolbox for this purpose.
After processing and cleaning the data, authors defined 2 regions of interest: central and frontal ROI. Central represents the motor execution in motor cortex, and frontal represents motor planning in premotor cortex.
With the help of 6 kinematic sensors, researchers were able to derive important metrics. First, they marked the heel strikes from both feet. Then, calculated the stepping frequency, mean step duration, variation of step duration and many more.
For detecting FoG episodes, they used the coefficient of variation of step duration + stepping asymmetry.
Comparing movement-related EEG activity between participants and conditions
EEG frequency spectrum analysis for (A) frontal ROI and (B) central ROI. The plots represent the difference in spectrum power between resting and walking condition. If the plot is above value 0, then we’re detecting suppression of that power. Different frequency bands are divided with dashed lines. We can see the plots in different colors for all stimulation conditions (Parkinson’s patients) and healthy controls.During movement, we expect to see suppression of power in the alpha and beta bands.
However, authors reported this suppression to be less in Parkinson’s disease patients than healthy controls. This was the case for all stimulation conditions (TBS-DBS, cDBS and OFF).
When comparing frontal ROIs in TBS-DBS condition to the other two, beta suppression is more pronounced. This can suggest improvement in information flow between basal ganglia and cortex, according to previous studies.
Alpha suppression was present in both stimulation modes with slightly different patterns. This indicates potential improvement of attentional access during gait.
Topographic view of movement related cortical activity. Movement-induced alpha and beta suppression is less pronounced in Parkinson’s participants compared to controls. TBS-DBS and cDBS reveal different patterns of movement-induced cortical activity patterns.Dividing Parkinson’s disease patients into two groups: non-TBS and TBS preference
The researchers wanted to understand why some Parkinson’s patients responded well to TBS-DBS and others didn’t. They asked each patient (while still blinded to the stimulation type) to rank the three tested conditions. Rating was in terms of how much their gait and FoG improved.
Based on these subjective rankings:
- TBS-preference group = patients who rated TBS-DBS as better or equal to cDBS.
- Non-TBS-preference group = patients who rated TBS-DBS worse than cDBS.
When looking at the cortical activity between these groups, no significant difference appeared. We can see the line plots in the image below:
EEG frequency spectrum analysis for (A) frontal ROI and (B) central ROI. We can see the plots in different colors for non-TBS preference and TBS-preference groups. As well as the previously mentioned groups.cDBS vs. TBS-DBS in FoG episodes
cDBS produced slightly better results on the FoG-Course than TBS-DBS. cDBS significantly reduced FoG compared to no stimulation, while TBS-DBS didn’t show a clear group-wide benefit.
But, in the subgroup of TBS-preference patients, both stimulation types worked equally well. And only TBS-DBS led to a significant improvement compared to no stimulation.
This means TBS-DBS might target gait irregularities more effectively in some patients.
Objective gait parameters from Kinematic measures
Even though patients improved subjectively, DBS (in either mode) didn’t normalize gait to the level of controls. Most gait measure like speed, symmetry, or variability, remained impaired.
The only measurable gain was that cDBS reduced total stepping time compared to no stimulation. Still, responses varied strongly between individuals.
Table represents gait parameter values for all participant groups, as well as statistical analysis between them.Final thoughts
These results highlight that while cDBS remains the standard, TBS-DBS could be especially valuable for certain patients. Future studies with larger groups and longer follow-ups are needed to better understand which patients benefit most. Also, how DBS settings can be tailored to improve walking and reduce freezing in daily life.
You can read more on the study in the original paper.
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