Integrated Characterization of Proximal and Distal Nerve Stumps in a Model of Chronic Motor Nerve Transection

In Lewis rats with 10-week chronic facial motor nerve transection, proximal and distal stumps develop distinct pathology: proximal neuroma and myelin loss versus distal endoneurial atrophy, collagen I increase, and immune-cell accumulation.

• Why it matters: Delayed peripheral motor nerve repair can fail because chronic axotomy proximally and denervation distally remodel the nerve environment, but histopathology in pure motor models is incompletely defined.
• What they did: The buccal branch of the facial nerve was transected and secured to adjacent muscle to prevent reconnection; proximal and distal stumps were compared at 10 weeks post-injury using histology, immunofluorescence, and morphometrics versus uninjured nerves.
• The result: Proximal stumps showed traumatic neuroma formation, altered axonal morphology, and loss of myelin integrity with largely preserved architecture, while distal stumps showed reduced neurofilament expression, small-caliber axon clusters, increased myelinated axon density, endoneurial tube atrophy, collagen I deposition, vascular remodeling, and immune-cell accumulation.

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