Transcranial stimulation parameters to elicit motor evoked potentials.

Area of Science:

• Neurosurgery
• Neurophysiology

Background:

• Transcranial electrical stimulation (TES) is a technique used to modulate cortical excitability.
• Activating the motor cortex is crucial for monitoring descending motor tracts during complex surgeries like spinal procedures.

Purpose of the Study:

• To compare the effectiveness of single, paired, and repetitive transcranial electrical stimulation (TES) in activating the motor cortex.
• To determine the optimal TES method for intraoperative motor pathway monitoring during spine surgery.

Main Methods:

• Ten patients undergoing spine surgery provided consent for the study.
• Muscle action potentials from the abductor pollicis brevis were measured following cortical stimulation.
• Latency and amplitude of evoked potentials were analyzed for different TES paradigms.

Main Results:

• Repetitive TES elicited significantly more responses than single-pulse TES (p=0.0001).
• Paired-pulse TES also showed a significant increase in responses compared to single-pulse TES (p=0.0191).
• Repetitive TES was more effective than paired-pulse TES (p=0.0253), with no significant changes in latency or amplitude based on interstimulus interval or pulse number.

Conclusions:

• Intraoperative repetitive transcranial electrical stimulation (TES) is the most effective method for activating descending motor tracts.
• This finding supports the use of repetitive TES for enhanced neurophysiological monitoring during spine surgery under anesthesia.