Wave-form characteristics and spatial distribution of evoked spinal electrogram in man

Area of Science:

• Neuroscience
• Spinal Cord Physiology
• Electrophysiology

Background:

• The evoked spinal electrogram (SEG) is a measure of spinal cord activity.
• Comparing human SEG with animal models like rabbit cord dorsum potential (CDP) can provide valuable insights into spinal cord function.

Purpose of the Study:

• To record and characterize the evoked spinal electrogram (SEG) in humans using epidural recordings.
• To compare human SEG with rabbit cord dorsum potential (CDP).
• To investigate the neural pathways and characteristics of the evoked SEG.

Main Methods:

• Recording of evoked spinal electrograms (SEG) from the epidural space in humans.
• Utilizing continuous epidural block technique.
• Comparison with cord dorsum potentials (CDP) recorded from wakeful rabbits.
• Stimulation of segmental nerves and skin receptors.

Main Results:

• Evoked SEG waveform characteristics were consistent across cervical and lumbar regions in humans.
• SEG generation was primarily linked to stimulation of large nerve fibers (tibial nerve) rather than small fibers (toe skin).
• Observed central latencies suggest a long feedback loop contributing to the P2 wave components.
• Amplitude decline of the N1 wave differed from P2, indicating distinct origins.
• Waveform polarity reversed with anterior epidural electrode placement.
• Human SEG closely resembled rabbit CDP.

Conclusions:

• The evoked spinal electrogram in humans shares significant waveform similarities with rabbit cord dorsum potentials.
• Large diameter afferent nerve fibers play a crucial role in generating the evoked SEG.
• The study provides evidence for a long feedback loop influencing spinal cord activity and highlights differences in the origins of N1 and P2 wave components.