Ultrasound Elastography Tracks Nerve Healing After Decompression in Diabetic Rats

Diabetic peripheral neuropathy, a symmetrical and length-dependent sensorimotor polyneuropathy, is one of the leading causes of chronic ulcers, gangrene, and amputation of the lower extremities, and painful manifestations attributable to diabetic neuropathy have been documented in up to 50% of individuals with diabetes mellitus. Surgical decompression of distal nerves has been shown to reduce ulceration and amputation rates, yet the risk of ulcer recurrence persists after surgery, which means patients require long-term postoperative follow-up. The problem is that the tools currently used to track recovery are blunt instruments: clinical scoring systems are inherently subjective, and nerve conduction studies, the acknowledged gold standard, are time-consuming and uncomfortable for patients. A research team at Peking University People’s Hospital in Beijing now reports that a rapid, noninvasive ultrasound technique may fill this gap, by measuring how stiff the nerve itself becomes as it heals.

The technique, known as shear wave elastography, or SWE, quantifies tissue stiffness by measuring how fast shear waves propagate within the tissue. Shear-wave velocity correlates positively with tissue stiffness, so a harder, more fibrotic nerve returns a higher velocity value than a healthy one. SWE has already been widely applied in organs such as the liver, breast, and thyroid, and in recent years it has emerged as a valuable modality for assessing diabetic peripheral neuropathy, with accumulating evidence indicating that peripheral nerve stiffness is substantially elevated in patients with diabetic neuropathy compared with both diabetic patients without neuropathy and healthy control subjects. What remained unclear was whether falling nerve stiffness after decompression surgery actually tracks the underlying biological recovery, or whether it merely reflects the mechanical release of external pressure. The new study, published in Frontiers in Neurology on 23 October 2026, was designed to answer exactly that question in an animal model, by correlating SWE measurements with electrophysiological testing and detailed histopathological examination of the same nerves.

The experiment used 24 male Sprague-Dawley rats aged 8 weeks and weighing 250 to 300 grams. Six rats served as normal controls, while the remaining 18 were made diabetic through a high-glucose and high-fat diet fed for 4 weeks, followed by a single intraperitoneal injection of streptozotocin at 40 mg/kg body weight. Diabetes was confirmed 7 days later by measuring random blood glucose from the tail vein, with values exceeding 16.7 mmol/L considered indicative of successful induction. Each diabetic rat then underwent surgical exposure of the left hind limb sciatic nerve, around which a 1-cm-long silicone tube with an internal diameter of 1.2 mm was placed at the middle third level and secured with 6-0 nylon sutures. The tube was longitudinally slit to allow atraumatic placement, and all surgical interventions were carried out by a single investigator to eliminate inter-operator variability. Four weeks after compression, 6 rats were randomly designated as the diabetic sciatic nerve compression 4-week group, while the other 12 received surgical decompression, in which the silicone tube was removed, adjacent inflammatory tissue was debrided, and the epineurium was carefully released by a single orthopedic surgeon experienced in peripheral nerve microsurgery. These decompressed rats were further subdivided into 2-week and 8-week post-decompression groups.

The choice of time points reflected the model’s established biology. At 4 weeks after compression, the researchers observed a significant decrease in motor nerve conduction velocity, along with notable reductions in myelinated fiber density, axon diameter, and myelin sheath thickness, all indicative of severe sciatic nerve damage. Previous work had shown that 2 weeks after decompression there is negligible functional recovery, whereas by 8 weeks post-decompression significant improvements in nerve conduction velocity, latency, and amplitude, as well as increases in myelinated fiber diameter, have been reported in streptozotocin-induced diabetic rats. An extended duration of compression might have caused substantial nerve injury and confounded the outcomes, so the 4-week mark was chosen for decompression, and 8 weeks post-decompression was selected as the second longitudinal observation point.

SWE imaging was performed with a 20 MHz linear-array transducer from SuperSonic Imagine in France. Before imaging, anesthetized rats were placed in the lateral decubitus position with the hind limb relaxed, and longitudinal nerve images were acquired with care taken to avoid transducer-induced compression, since external pressure would itself alter the stiffness reading. The region of interest was set at 0.01 cm2 and positioned within the epineurium, and SWE of the nerve was measured three times at the compression site, with the average value used for analysis. Two experienced operators, each with more than 5 years of ultrasound experience, independently evaluated all groups; the second operator repeated the measurements using the same protocol while blinded to the first operator’s results. The interobserver consistency was excellent, with an intraclass correlation coefficient of 0.862 for elasticity, meaning the stiffness values were reproducible across independent examiners.

The elastography results revealed a clear and progressive pattern. Sciatic nerve stiffness in the compressed diabetic group was significantly increased compared with the control group, with shear-wave velocity rising from 1.75 ± 0.05 m/s in controls to 2.48 ± 0.11 m/s after 4 weeks of compression. Two weeks after decompression, stiffness had already fallen markedly to 2.09 ± 0.13 m/s, a statistically significant decrease, and it fell further to 1.93 ± 0.09 m/s at 8 weeks. Yet even at 8 weeks the decompressed nerves remained significantly stiffer than normal controls, showing that recovery was real but incomplete. The stiffness values traced a dynamic curve of healing that could be sampled repeatedly without harming the nerve.

The striking finding was how this curve compared with the conventional measures. Motor nerve conduction velocity in the 2-week group was 40.83 ± 4.67 m/s, which did not differ significantly from the 35.83 ± 2.93 m/s recorded in the compressed group before decompression. Histopathology told the same story: myelinated fiber density in the 2-week group was 7,979 ± 687 fibers/mm2, not significantly different from the 6,522 ± 476 fibers/mm2 in the compressed group, and average axon diameter and myelin sheath thickness in the 2-week group, 4.36 ± 1.50 μm and 0.83 ± 0.18 μm respectively, also failed to differ from the compressed group’s 3.89 ± 0.96 μm and 0.84 ± 0.17 μm. In other words, elastography detected a change in the nerve at 2 weeks that neither electrophysiology nor microscopy could see.

By 8 weeks after decompression, the conventional measures had caught up with the elastography signal. Motor nerve conduction velocity rose to 49.17 ± 4.71 m/s, significantly improved compared with the compressed group, though still substantially lower than the control value of 65.5 ± 5.43 m/s. Myelinated fiber density increased markedly to 11,008 ± 1,413 fibers/mm2, significantly higher than both the compressed group and the 2-week group, while remaining inferior to the control density of 12,780 ± 1,202 fibers/mm2. Average axon diameter and myelin sheath thickness in the 8-week group, 4.71 ± 0.93 μm and 0.99 ± 0.22 μm, were significantly greater than in the compressed group but still below control values. The progressive decrease in neural stiffness after decompression therefore correlated with functional recovery of the sciatic nerve, and the authors conclude that dynamic SWE assessment of decreasing neural stiffness predicts postoperative functional improvement in diabetic rats.

The interpretation of the early stiffness drop is mechanistically interesting. The decrease in neural tissue stiffness at 2 weeks likely results from the release of pressure following decompression surgery, since neither histopathological nor electrophysiological findings indicated recovery of nerve function at that stage. This is consistent with previous strain elastography work showing that nerve stiffness decreased at 3 months after carpal tunnel release, accompanied by improvements in nerve conduction velocity and clinical symptoms. Nerve decompression is thought to reduce neural edema, improve microcirculation and regenerative capacity, and partially reverse the underlying pathological process. The incomplete recovery at 8 weeks fits the multifactorial pathophysiology of diabetic neuropathy: hyperglycemia drives mitochondrial reactive oxygen species overproduction, inflammation, and endoneurial edema; dyslipidemia exacerbates neural injury via free fatty acid-induced inflammatory signaling; and metabolic disturbances disrupt endoplasmic reticulum proteostasis and calcium homeostasis, triggering neuronal apoptosis.

The clinical context makes the result potentially significant. The prevalence of carpal tunnel syndrome in diabetes patients is as high as approximately 30%, and diabetes patients with carpal tunnel syndrome undergo nerve decompression surgery 4 to 14 times more frequently than the general population. Nerve entrapment has been demonstrated to accelerate the progression of diabetic foot syndrome, and the widely cited double crush hypothesis is considered a major contributing factor to the increased susceptibility to nerve entrapment in diabetes. Dellon was the first to introduce nerve decompression surgery for distal diabetic neuropathy and demonstrated its effectiveness in reducing the risk of ulceration and amputation. A complementary assessment method that enables repeated, noninvasive evaluation of postoperative neurological recovery is urgently needed, and SWE, being cost-effective and rapid, could serve that role if the animal findings translate to patients.

The researchers are careful about the limits of their work. This was a preclinical animal-based investigation with a relatively limited sample size, restricted to an 8-week postoperative follow-up, so the long-term benefit of nerve decompression for diabetic peripheral neuropathy remains indeterminate. The use of streptozotocin-induced diabetic rats without glycemic management does not completely mirror clinical conditions, and gait analysis, mechanical pain threshold, and thermal pain threshold were not assessed after decompression; the inclusion of these behavioral parameters in future studies would strengthen the evidence. Even so, the study establishes a preliminary theoretical basis for clinical research: a falling shear-wave velocity after decompression appears to be an early, quantifiable, and reproducible marker that the nerve is on the road to recovery, visible weeks before the nerve’s electrical performance or microscopic structure confirm it.

Subject of Research: Shear wave elastography assessment of sciatic nerve stiffness after decompression in diabetic rats

Article Title: Shear wave elastography for quantitative assessment of nerve tissue stiffness after sciatic nerve decompression in diabetic rats

Article References: Li, D.-C., Li, W.-X., Xin, Y.-W., Li, D.-D., & Zhu, J.-A. (2026). Shear wave elastography for quantitative assessment of nerve tissue stiffness after sciatic nerve decompression in diabetic rats. Frontiers in Neurology, 17, Article 1962826. https://doi.org/10.3389/fneur.2026.1962826

Image Credits: AI Generated

DOI: 10.3389/fneur.2026.1962826

Keywords: shear wave elastography, diabetic peripheral neuropathy, nerve decompression, sciatic nerve, rat model, tissue stiffness, nerve conduction velocity, histopathology, ultrasound, peripheral nerve entrapment, preclinical study, Shear