Less is more - Pulse width dependent therapeutic window in deep brain stimulation for essential tremor

Area of Science:

• Neurology
• Neurosurgery
• Biomedical Engineering

Background:

• Deep brain stimulation (DBS) is a therapeutic option for essential tremor (ET).
• Conventional pulse widths in DBS may be associated with side effects.
• Shorter pulse widths are being explored to potentially reduce side effects in DBS for ET.

Purpose of the Study:

• To compare the efficacy and safety of a shorter pulse width (40 μs) versus a conventional pulse width (60 μs) for DBS in ET patients.
• To evaluate the impact of pulse width on the therapeutic window, defined by efficacy and side effect thresholds.
• To assess the volume of neural activation (VNA) at different pulse widths.

Main Methods:

• A prospective, randomized, double-blind, crossover study involving 9 ET patients with VIM/PSA DBS.
• Therapeutic window was determined by assessing efficacy and side effect thresholds for 40 μs and 60 μs pulse widths.
• Clinical efficacy was measured using Tremor Rating Scales and Kinesia tremor analyses; VNA was calculated.

Main Results:

• DBS with a 40 μs pulse width demonstrated a significantly larger therapeutic window than DBS with a 60 μs pulse width, primarily due to higher side-effect thresholds.
• Both pulse widths significantly improved tremor compared to DBS-OFF, with comparable clinical efficacy.
• The 40 μs pulse width resulted in a smaller VNA at the efficacy threshold and required less energy for tremor suppression.

Conclusions:

• Ventral intermediate nucleus/posterior subthalamic area DBS using a short pulse width (40 μs) is a promising programming strategy for ET.
• This approach effectively reduces side effects while maintaining tremor suppression efficacy.
• The findings suggest that pulse width influences selective modulation of fiber tracts, widening the therapeutic window in DBS for ET.