Peripheral nerve morphology and intraneural blood flow in chronic kidney disease with and without diabetes

Nerve cross-sectional area in advanced uremic neuropathy: A nerve ultrasound pilot study

BACKGROUND AND PURPOSE

Uremic neuropathy (UN) is a disabling neuropathy in end-stage kidney disease (ESKD) affecting the majority of patients receiving long-term hemodialysis (HD). One previous nerve ultrasound study reported an increased cross-sectional area (CSA) of the median nerve in moderate UN, while another study found enlarged sural nerves in small-fiber polyneuropathy associated with ESKD. The present cohort study aims to analyze bilateral CSA of multiple nerves in UN.

METHODS

Ten nondiabetic ESKD patients with UN on HD for at least 2 years and 10 healthy age-matched controls underwent bilateral ultrasound examinations with CSA measurements in 13 arm and leg nerve sites. Nerve conduction studies (NCS) and the total neuropathy score (TNS) were recorded. Pearson's coefficient and the Mann-Whitney U-test were used to analyze correlations and compare groups.

RESULTS

ESKD patients presented advanced neuropathic symptoms (mean TNS 15.9). NCS showed significantly reduced motor and sensory amplitudes in the UN group compared to the control group, and a slightly reduced nerve CSA was observed in 5 of 13 nerve sites (p < .05); the other nerve sites were not enlarged. Sural nerve CSA (p < .05) and sensory amplitude (p < .01) were negatively correlated with the TNS.

CONCLUSIONS

Nerve enlargement was not observed in the present study in advanced UN. A reduced nerve CSA observed in the sural nerve suggests an axonal loss associated with long-term HD in ESKD. During clinical workup of an acute disease of the peripheral nervous system in ESKD patients, nerve enlargement might be attributable to other causes than chronic UN.

Electrochemical Skin Conductance by Sudoscan in Non-Dialysis Chronic Kidney Disease Patients

BACKGROUND

Peripheral neuropathy is prevalent among patients with chronic kidney disease (CKD). Sudoscan non-invasively detects polyneuropathy by measuring electrochemical skin conductance (ESC). We conducted a study on sudomotor function in CKD patients across various stages based on their estimated glomerular filtration rate (eGFR).

METHODS

In this cross-sectional study of 700 CKD patients, all underwent Sudoscan. Pathological ESC was defined as hands < 40 μS or feet < 50 μS. Clinical neuropathy scores including Michigan Neuropathy Screening Instrument (MNSI) and Douleur Neuropathique en 4 questionnaire (DN4) were obtained.

RESULTS

Among participants, 344 had diabetes and 356 did not. Hands and feet ESC decreased with CKD progression (median (IQR) in stage 1-2, 3, 4-5: 54.0 (39.0-68.0), 45.5 (30.0-63.0), 41.8 (26.5-60.5), p trend < 0.001; 64.5 (53.5-74.0), 60.5 (43.0-72.5), 55.0 (39.0-69.8), p trend < 0.001). Pathological hands and feet ESC increased in later CKD stages (stage 1-2, 3, 4-5: 26.6%, 40.9%, 45.7%, p trend < 0.001; 21.7%, 34.0%, 40.6%, p trend < 0.001). Positive hands and feet ESC-eGFR correlation existed irrespective of diabetes. Diabetic patients had lower hands and feet ESC than non-diabetics as CKD progressed. However, multivariate regression found no significant ESC-eGFR association. Sudoscan correlated with clinical neuropathy scores.

CONCLUSION

Pathological sudomotor function was common in non-dialysis CKD stages 4-5. Diabetic patients had worse function. Sudomotor dysfunction progressed with renal disease but eGFR was not an independent risk factor.

Normative Reference Values of the Tibial Nerve in Healthy Individuals Using Ultrasonography: A Systematic Review and Meta-Analysis

BACKGROUND

High-resolution ultrasound of the tibial nerve has been used for screening of several neurologic disorders, but normative reference values of tibial nerve cross-sectional areas (CSA) have not been well established. Thus, the present meta-analysis was performed to generate normative estimates of tibial nerve CSA at various sites of the lower limb based on ultrasonography.

METHODS

Google Scholar, Scopus and PubMed were searched for potential studies. Studies were required to report tibial nerve CSA in healthy individuals to be included. A random-effect meta-analysis was performed to calculate tibial nerve CSA values. Subgroup and statistical analyses were performed to study covariates.

RESULTS

Forty-eight eligible articles consisting of 2695 limbs were included. The average tibial nerve CSA was found to be 10.9 mm2 at the ankle (95% CI: 9.9-11.8) and should not exceed 11.8 mm2 in healthy adults. At the popliteal fossa, the overall CSA was 21.7 mm2 (95% CI: 17.5-25.8) in healthy adults. At both sites, the average tibial nerve CSA was significantly larger in adults than in children, and the differences by geographical region were not statistically significant. At the ankle, tibial nerve CSA increased with age and body mass index, while at the popliteal fossa it increased with age and weight.

CONCLUSIONS

our findings indicate that the tibial nerve varied not only along its course but also among sub-variables. Establishing normal references values of tibial nerve CSA is helpful to differentiate healthy from diseased tibial nerves such as in diabetic peripheral neuropathy or tarsal tunnel syndrome.

The Effects of Indoxyl Sulfate and Oxidative Stress on the Severity of Peripheral Nerve Dysfunction in Patients with Chronic Kidney Diseases

Pieces of evidence support the view that the accumulation of uremic toxins enhances oxidative stress and downstream regulation of signaling pathways, contributing to both endothelial microangiography and cell dysfunction. This study is to address the impact of protein-binding uremic toxins on the severity of peripheral nerve function in patients with chronic kidney disease (CKD). Fifty-four patients with CKD were included in the Toronto Clinical Neuropathy Score (TCNS), nerve conduction study (NCS), and laboratory studies including protein-binding uremic toxin (indoxyl sulfate [IS] and p-cresyl sulfate [PCS]), oxidative stress (Thiol and thiobarbituric acid reacting substances [TBARS]), and endothelial dysfunction (serum intercellular adhesion molecule 1 [sICAM-1] and serum vascular adhesion molecule 1 [sVCAM-1]) at enrollment. We used composite amplitude scores (CAS) to analyze the severity of nerve conductions on peripheral nerve function. TCNS and CAS were higher in the diabetic CKD group (p = 0.02 and 0.01, respectively). The NCS revealed the compound muscle action potential of ulnar and peroneal nerves and the sensory nerve action potential of ulnar and sural nerves (p = 0.004, p = 0.004, p = 0.004, and p = 0.001, respectively), which was found to be significantly low in the diabetic group. CAS was significantly correlated with age (r = 0.27, p = 0.04), urine albumin-creatinine ratio (UACR) (r = 0.29, p = 0.046), free-form IS (r = 0.39, p = 0.009), sICAM-1 (r = 0.31, p = 0.02), sVCAM-1 (r = 0.44, p < 0.0001), TBARS (r = 0.35, p = 0.002), and thiols (r = −0.28, p = 0.045). Linear regression revealed that only TBARS and free-form IS were strongly associated with CAS. The mediation analysis shows that the sVCAM-1 level serves as the mediator between higher IS and higher CAS. IS and oxidative stress contribute to the severity of peripheral nerve dysfunction in patients with CKD, and chronic glycemic impairment can worsen the conditions.