Predictive factors for improvement of gait by low-frequency stimulation in Parkinson's disease

After several years duration of Parkinson's disease, with or without deep brain stimulation, axial signs (such as postural instability, freezing of gait) may worsen. High-voltage, low-frequency stimulation has been shown to improve severe gait disorders in some patients.

To identify predictive factors for the efficacy of low-frequency stimulation.

We assessed the respective effects of low- and high-frequency stimulation using an acute stand-walk- sit test, and on motor performance in 22 patients with longstanding, bilateral sub-thalamic nucleus stimulation. We calculated the difference in the number of steps (delta steps) between high and low -frequency stimulation during the stand-walk-sit test. Our aim was to establish a profile for low-frequency responders, which was defined by a positive value for delta steps.

Low frequency responders presented higher age, a severe axial phenotype five years after surgery and a lower L-dopa responsiveness of (i) the Unified Parkinson's Disease Rating Scale part III score and its akinesia subscore before surgery and (ii) the axial subscore one year after surgery.

Here we defined a specific and severe axial profile of minority of patients who could benefit from low frequency stimulation parameters. Our findings challenge the conventional treatment approach (i.e. high-frequency stimulation) in patients who develop gait disorders after several years of stimulation.