Low-frequency DBS May Help Parkinson’s Patients With Walking
But patients with significant tremor prior to starting DBS may not find the treatment tolerable, because it can lead to the re-emergence of tremor symptoms.
Trial findings were in the study “Low-frequency STN-DBS provides acute gait improvements in Parkinson’s disease: a double-blinded randomised cross-over feasibility trial,” published in the Journal of NeuroEngineering and Rehabilitation.
DBS is a surgical treatment for Parkinson’s that involves implanting an electrode in the brain, which delivers electrical stimulations to specific brain regions. DBS is known to be effective at easing certain Parkinson’s symptoms, like tremor.
However, standard DBS can also cause problems with dynamic postural stability that can, for instance, make it difficult to maintain balance when walking.
“Postural instability, a symptom strongly associated with falling in those with PD [Parkinson’s disease], declines following STN-DBS [DBS to the subthalamic nucleus brain region] and subsequently has been considered a contributing factor to the increased falls rate reported for those who are more than one year post-surgery,” the researchers wrote.
Recent research has indicated that low-frequency DBS (i.e., where stimulations are given more slowly) may be able to alleviate the risks of postural instability that the standard treatment provides. However, most research into its use has relied on relatively subjective measures of dynamic postural stability.
A team of researchers in Australia conducted a small clinical trial (ACTRN12618000944235) to test the effects of low-frequency DBS relative to high-frequency DBS on postural instability more objectively — through specialized sensors worn on the head and back of participants while walking.
These sensors measured the patients’ movements in detail, and data collected was then analyzed to assess aspects of participants’ walking ability, like how rhythmic their movements were (rhythmicity). More rhythmic movements are generally associated with better balance.
In all, the researchers reported findings for 14 people given a standard high-frequency DBS (more than 100 Hz) and a low-frequency DBS (starting at 60 Hz), with walking assessments after each treatment. Of note, when participants were assessed, they were required to be off their Parkinson’s medications.
Analyses showed that low-frequency DBS led to statistically and clinically significant improvements in rhythmicity compared high-frequency stimulation. These improvements were independent of factors like walking speed, and the placement of the DBS electrode.
No significant differences between the two DBS frequencies were evident for other factors, like walking speed, cadence, and step-to-step variability.
“Our results indicate that low-frequency [DBS] therapy … was effective at improving some aspects of gait rhythmicity in most people with PD following surgery,” the researchers concluded. “These findings provide evidence for the potential utility of low-frequency [DBS] stimulation parameters for post-operative patients who experience gait complications.”
Among these 14 participants, however, 10 experienced a worsening of tremor symptoms while on low-frequency DBS. For four of these people, the symptoms were severe enough that they were unable to complete trial assessments.
“It is noteworthy that the low-frequency stimulation strategy was not tolerated by all participants and, in some cases, the gait improvements came at the cost of a re-emergence of tremor,” the researchers wrote.
The team stressed, however, that the trial’s design required these patients to temporarily stop their standard medications while being assessed, which may have contributed to the re-emergence of symptoms.
“With advances in adaptive DBS technology, it may become feasible to deliver low-frequency stimulation to patients for the improvement of dynamic postural stability, while also having a high-frequency stimulation policy to initiate when symptoms of tremor reappear,” the researchers added.