Low-frequency Deep Brain Stimulation Reduces Freezing of Gait, Study Shows

Low-frequency subthalamic deep brain stimulation (STN-DBS), but not high-frequency STN-DBS, reduces freezing of gait in Parkinson’s patients while preserving their ability to simultaneously process motor and cognitive information, a recent study shows.

The study, “Decreasing subthalamic deep brain stimulation frequency reverses cognitive interference during gait initiation in Parkinson’s disease,” was published in the journal Clinical Neurosphysiology.

Many Parkinson’s patients (50-70 percent) will develop freezing of gait, which occurs when a patient temporarily feels as if his/her feet are glued to the floor and hesitates before stepping forward.

Freezing of gait mainly occurs when a patient wants to start walking or change direction, but also can occur in double-task situations, such as crossing the street or talking while walking. This often leads to falls and affects patients’ quality of life, making freezing of gait a major burden.

Increasing evidence suggests an association between freezing of gait and impaired attention, executive function, and cognitive control, supporting the additional involvement of non-motor brain regions in this motor symptom.

Deep brain stimulation often is used to treat patients with advanced Parkinson’s whose motor problems no longer improve with medication.

The technique involves surgically implanting an electrode in the brain that is connected to an implanted pulse generator through subcutaneous wires. The pulse generator is programmed to deliver charge-balanced, voltage-controlled electric pulses that stimulates the subthalamic nucleus, an area of the brain involved in motor function and which becomes hyperactive in Parkinson’s patients.

Several studies have shown that STN-DBS eases motor symptoms, reduces the necessary daily dose of medication, and improves patients’ quality of life.

While some studies have shown that high-frequency STN-DBS strongly alleviates motor symptoms in Parkinson’s patients, others suggest that it worsens freezing of gait and executive function, compared to low frequency STN-DBS.

French researchers now evaluated the therapeutic effects of low (80-Hz) and high (130-Hz) frequency STN-DBS on the walking initiation performance of Parkinson’s patients, with or without the combination of a cognitive task.

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This cognitive interference task consisted of initiating walking according to a visual cue, which involved  integrating an environmental cue and executing the motor task.

The study included 19 people (15 men and four women) with advanced Parkinson’s disease and a mean age of 59 years, and 20 healthy people (15 men and five women) with a mean age of 62 years.

While initiation of walking was recorded in all participants, only nine Parkinson’s patients performed the walking test combined with the cognitive interference task. The tests were conducted before DBS surgery, with or without dopaminergic medications, and after surgery without dopaminergic medications.

In the simple walking initiation task, Parkinson’s patients showed significant improvements in their walking ability after STN-DBS with either frequency and with prior dopaminergic treatment.

However, when coupled with the cognitive interference task, treatment with high frequency STN-DBS significantly impaired patients’ walking performance. These changes were not observed in patients treated with low-frequency STN-DBS, with or without prior dopaminergic medication, or in healthy people.

These findings suggest that “high frequency STN-DBS reduces the ability to simultaneously process motor and cognitive information while this seems preserved with low frequency STN-DBS,” researchers wrote.

Thus, the results support the use of low frequency STN-DBS to ease freezing of gait in Parkinson’s patients.

The team noted that different frequencies may act differently in the brain networks that regulate motor and cognitive functions, and that additional studies are necessary to clarify the mechanisms behind these different effects.