Native paraneurial tissue and paraneurial adhesions alter nerve strain distribution in rat sciatic nerves

Abstract

Paraneurial adhesions have been implicated in the pathological progression of entrapment neuropathies. Surgical decompression of adhesions is often performed, with the intent of restoring nerve kinematics. The normal counterpart of adhesions, native paraneurium, is also thought to influence nerve deformation and mobility. However, influences of native or abnormal paraneurial structures on nerve kinematics have not been investigated. We measured regional strains in rat sciatic nerves before and immediately after decompression of native paraneurial tissue, and before and after decompression of abnormal paraneurial adhesions, which formed within 6 weeks of the initial decompression. Strain was significantly higher in the distal-femoral than in the mid-femoral region of the nerve before either decompression. Decompression of native and abnormal paraneurial tissue removed this regional strain difference. Paraneurial tissues appear to play a major role in distributing peripheral nerve strain. Normal nerve strain distributions may be reconstituted following decompression, even in the presence of paraneurial adhesions.

Decoupled epineurial and axonal deformation in mouse median and ulnar nerves

“…The observed homogenization of strain distributions after decompressing the mesoneurium (Fig. E and F) is consistent with a similar redistribution observed in rat sciatic nerves and in patients with cubital tunnel syndrome after circumferential decompression . The concurrent reduction in strain, also noted by Foran et al ., is likely due to the longitudinal relocation of the strain to proximal or distal regions that could not be visualized.…”

“…E and F) is consistent with a similar redistribution observed in rat sciatic nerves and in patients with cubital tunnel syndrome after circumferential decompression . The concurrent reduction in strain, also noted by Foran et al ., is likely due to the longitudinal relocation of the strain to proximal or distal regions that could not be visualized. Alternatively, although we did not observe obvious subluxation of the nerve during joint manipulation, reduced strain may also reflect subtle alterations to the nerve course through its bed.…”

“…Our observations that mesoneurial decompression affects epineurial strain imply a coupled meso‐epineurium (Fig. A) . In addition, earlier studies have dictated that physical viscoelastic connections at the core–sheath interface disallow excessive epiperineurial gliding.…”

“…5A). 24 In addition, earlier studies have dictated that physical viscoelastic connections at the coresheath interface 39,44 disallow excessive epiperineurial gliding. Finally, the endoneurium and nerve fiber must be coupled to the perineurium.…”

“…In addition, variability in fascicular number or spacing has also been posited as an explanation for local compliance, yet results in support of this hypothesis are conflicting . More recently, a major role for the mesoneurium (paraneurium) in regulating regional epineurial strains was described in rat sciatic nerves, suggesting that structures that tether the epineurium to the nerve bed contribute to the response of a nerve to imposed deformation.…”