Electromyographic permutation entropy quantifies diaphragmatic denervation and reinnervation.

Area of Science:

• Neuroscience
• Physiology
• Biomedical Engineering

Background:

• Diaphragmatic paralysis can occur due to trauma, surgery, tumors, or spinal cord injuries.
• Spontaneous reinnervation is often observed, potentially explained by collateral reinnervation due to the diaphragm's double innervation by the phrenic nerve.
• Permutation entropy (PeEn) is a time series complexity measure that can reflect neuromuscular transmission by quantifying network interactions.

Purpose of the Study:

• To investigate collateral reinnervation of the diaphragm after unilateral phrenicotomy in a rat model.
• To assess the utility of electromyographic permutation entropy (PeEn) in quantifying diaphragm denervation and reinnervation.
• To correlate PeEn changes with histological findings of reinnervation.

Main Methods:

• Electromyographic (EMG) signals from different diaphragm areas of 33 rats were analyzed using PeEn after unilateral phrenicotomy.
• Measurements were taken at 1, 3, 9, 27, and 81 days post-surgery.
• Diaphragm muscle samples were dissected for fiber type evaluation to identify signs of reinnervation.

Main Results:

• A significant decrease in normalized PeEn was observed in the sternal and mid-costal diaphragm areas at day 1 post-phrenicotomy, indicating denervation.
• The crural area, innervated by the accessory phrenic nerve, showed no change in PeEn, suggesting intact innervation.
• PeEn normalized in the mid-costal area by day 81, correlating with histological evidence of collateral reinnervation (fiber type grouping).

Conclusions:

• Collateral reinnervation can effectively restore diaphragm activity following phrenicotomy.
• Electromyographic PeEn serves as a novel and distinct method for assessing intramuscular function during denervation and reinnervation processes.
• This technique offers a valuable tool for understanding neuromuscular recovery in the diaphragm.