Nerve Autograft: Preservation of a Lost Art.

Nerve autografts involve the transplantation of a segment of the patient's own nerve to bridge a nerve gap. Autografts provide biological compatibility, support for axonal regeneration, and the ability to provide an anatomic scaffold for regrowth that other modalities may not match. Disadvantages of the autograft include donor site morbidity and the extra operative time needed to harvest the graft. Nevertheless, nerve autografts such as the sural nerve remain the gold standard in reconstructing nerve gaps, but a multitude of factors need to be favorable in order to garner reliable, consistent outcomes.

Superficial Branch of the Radial Nerve Versus Sural Nerve Grafting After Traumatic Adult Brachial Plexus Injury.

The purpose of this study was to compare two sources of nerve graft for brachial plexus reconstruction: the denervated superficial branch of the radial nerve (SBRN) and the sural nerve. Ninety-seven patients who underwent brachial plexus reconstruction with denervated SBRN nerve (24 patients with 24 grafts) or with sural nerve grafting (73 patients with 83 nerve grafts) were included. The two groups were compared with respect to postoperative muscle reinnervation, disabilities of the arm, shoulder, and hand (DASH) scores. In the SBRN group, only four (17%) of the nerve grafts provided grade III or higher muscle function. In the sural nerve group, 31 (37%) of the nerve grafts provided grade III or higher muscle function. Smoking had a negative impact on muscle recovery. Denervated SBRN grafts are associated with inferior outcomes when compared with sural nerve grafts in the treatment of traumatic adult brachial plexus injuries. (Journal of Surgical Orthopaedic Advances 33(2):080-083, 2024).

Experimental Reconstruction of the Optic Nerve with a Sural Nerve Graft: An in Vivo Experimental Study.

BACKGROUND: Neurosurgical interventions and trauma are common causes of damage to the optic nerve. This determines the relevance of research for solutions aimed at restoration of the nerve's anatomical integrity, electrical conductivity, and subsequently - restoration of its function. Restore a damaged (cut) optic nerve using n. suralis autograft in vivo. METHODS: The experiment involved reconstruction of the optic nerve through injury modulation, graft placement and restored nerve harvest and evaluation. Injury modulation included removal of a fragment of the optic nerve. Autograft harvesting and placement involved resection of a fragment of the sural (sensory) nerve and its subsequent anastomosis in place of the removed fragment of the optic nerve. As an experimental model, a rabbit of the "Burgundy" breed was used. The animal was previously examined for the presence of infectious and other diseases to confirm its health. RESULTS: Four months post operatively when stimulating the operated right eye, low-amplitude components altered in shape are registered. Thus, signs of mild restoration of electrical conductivity on the treated optic nerve were seen. CONCLUSIONS: Our initial experience shows the technical feasibility of reconstructing the optic nerve using an autograft, the possibility of axonal growth through the graft and, in the future, using this method for direct optic nerve reconstruction, as well as a bypass method for damage to the optic nerve with various tumor diseases of the optic nerve, tumors of the chiasmatic-sellar localization, orbital injuries.

Development of a major histocompatibility complex class II conditional knockout mouse to study cell-specific and time-dependent adaptive immune responses in peripheral nerves.

INTRODUCTION/AIMS: The precise relationship between molecular mimicry and tissue-specific autoimmunity is unknown. Major histocompatibility complex (MHC) class II antigen presenting cell-CD4+ T-cell receptor complex interactions are necessary for adaptive immunity. This study aimed to determine the role of endoneurial endothelial cell MHC class II in autoimmune polyneuropathy. METHODS: Cryopreserved Guillain-Barré syndrome (GBS) patient sural nerve biopsies and sciatic nerves from the severe murine experimental autoimmune neuritis (sm-EAN) GBS model were studied. Cultured conditional ready MHC Class II antigen A-alpha chain (H2-Aa) embryonic stem cells were used to generate H2-Aaflox/+ C57BL/6 mice. Mice were backcrossed and intercrossed to the SJL background to generate H2-Aaflox/flox SJL mice, bred with hemizygous Tamoxifen-inducible von Willebrand factor Cre recombinase (vWF-iCre/+) SJL mice to generate H2-Aaflox/flox; vWF-iCre/+ mice to study microvascular endothelial cell adaptive immune responses. Sm-EAN was induced in Tamoxifen-treated H2-Aaflox/flox; vWF-iCre/+, H2-Aaflox/flox; +/+, H2-Aa+/+; vWF-iCre/+ and untreated H2-Aaflox/flox; vWF-iCre/+ adult female SJL mice. Neurobehavioral, electrophysiological and histopathological assessments were performed at predefined time points. RESULTS: Endoneurial endothelial cell MHC class II expression was observed in normal and inflamed human and mouse peripheral nerves. Tamoxifen-treated H2-Aaflox/flox; vWF-iCre/+ mice were resistant to sm-EAN despite extensive MHC class II expression in lymphoid and non-lymphoid tissues. DISCUSSION: A conditional MHC class II knockout mouse to study cell- and time-dependent adaptive immune responses in vivo was developed. Initial studies show microvascular endothelial cell MHC class II expression is necessary for peripheral nerve specific autoimmunity, as advocated by human in vitro adaptive immunity and ex vivo transplant rejection studies.

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.

Frequent Sural Nerve Injury with Posterior Approach for Ankle Fracture Fixation.

INTRODUCTION: The purpose of this study was to report the incidence of iatrogenic sural nerve injury in a large, consecutive sample of surgically managed ankle fractures and to identify factors associated with sural nerve injury and subsequent recovery. We hypothesize that a direct posterior approach may be associated with higher risk of iatrogenic sural nerve injury. METHODS: A retrospective cohort study of 265 skeletally mature patients who sustained ankle fractures over a 2-year period was done. All were treated with open reduction and internal fixation of fractured malleoli. Patient, injury, and treatment features were documented. The presence (n = 26, 9.8%) of sural nerve injury and recovery of sural nerve function were noted. RESULTS: All 26 sural nerve injuries were iatrogenic, occurring postoperatively after open reduction and internal fixation. Patients who sustained sural nerve injuries had more ankle fractures secondary to motor vehicle collisions (23.1% versus 9.2%), more associated trimalleolar fractures (69.2% versus 33.9%), and more Orthopaedic Trauma Association/AO 44B3 fractures (57.7% versus 25.1%), all P < 0.05. A posterior approach to the posterior malleolus through the prone position was used in 20.4% of patients. All 26 of the sural nerve injuries (100%) occurred when the patient was placed prone for a posterior approach, P < 0.001. Therefore, 26 of the 54 patients (48%) treated with a posterior approach sustained an iatrogenic sural nerve injury. 62% of patients had full recovery of sural nerve function with no residual numbness, and patients with nerve recovery had fewer associated fracture-dislocations (23.1% versus 100%, P = 0.003). CONCLUSIONS: A posterior approach for posterior malleolus fixation was associated with a 48% iatrogenic sural nerve injury rate, with 62% recovering full function within 6 months of injury. Morbidity of this approach should be considered, and surgeons should be cautious with nerve handling. LEVEL OF EVIDENCE: Level III, Therapeutic.

The multiple roles of nerve biopsy in the diagnosis and prognosis of suspected immune neuropathies.

INTRODUCTION: The value of a sural nerve biopsy for the diagnosis of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is controversial. Evidence-based recommendations for its implementation are lacking. We investigated factors leading to biopsy and analyzed biopsy outcomes and consequences, assessed the predictability of biopsy outcomes through clinical parameters to avoid unnecessary biopsies, and compared results with electrophysiological and clinical severity to determine their prognostic value. METHODS: 190 sural nerve biopsies were analyzed in two cohorts. One consisted of 163 biopsies and the second of 72 biopsies from the prospective Immune-mediated Neuropathies Biomaterial and Data registry (INHIBIT). Both have an intersection of 45 patients. 75 data sets from patients without biopsy were used. Analysis of nerve conduction studies, treatment, overall disability sum score (ODSS), biopsy outcomes, and diagnosis was performed. RESULTS: 51% of biopsied patients received the diagnosis CIDP (77% fulfilled EFNS/PNS criteria), 21% were not CIDP typical, and 27% were unspecific. Biopsied patients responded less frequently to immunotherapies at time of biopsy than non-biopsied patients (p = 0.003). Immunotherapy was initiated more frequently after biopsy (p < 0.001) and more often with intravenous immunoglobulins (p < 0.0001). 76% of all biopsied patients met the electrophysiological criteria for CIDP. Sensory nerve action potential amplitudes of 0 µV still provide 73% of histological diagnostic value. Histologic signs of degeneration predicted ODSS worsening after 1 year (p = 0.028) but disease severity did not correlate with histological damage severity. DISCUSSION: The main indication for nerve biopsy was the treatment of refractory cases of autoimmune neuropathies with the therapeutic consequence of treatment initiation or escalation. Sural biopsy also provided prognostic information. Even with extinguished sural SNAP, the biopsy can still have diagnostic value.

Mitochondrial DNA and Electron Transport Chain Protein Levels Are Altered in Peripheral Nerve Tissues from Donors with HIV Sensory Neuropathy: A Pilot Study.

Distal sensory polyneuropathy (DSP) and distal neuropathic pain (DNP) remain significant challenges for older people with HIV (PWH), necessitating enhanced clinical attention. HIV and certain antiretroviral therapies (ARTs) can compromise mitochondrial function and impact mitochondrial DNA (mtDNA) replication, which is linked to DSP in ART-treated PWH. This study investigated mtDNA, mitochondrial fission and fusion proteins, and mitochondrial electron transport chain protein changes in the dorsal root ganglions (DRGs) and sural nerves (SuNs) of 11 autopsied PWH. In antemortem standardized assessments, six had no or one sign of DSP, while five exhibited two or more DSP signs. Digital droplet polymerase chain reaction was used to measure mtDNA quantity and the common deletions in isolated DNA. We found lower mtDNA copy numbers in DSP+ donors. SuNs exhibited a higher proportion of mtDNA common deletion than DRGs in both groups. Mitochondrial electron transport chain (ETC) proteins were altered in the DRGs of DSP+ compared to DSP- donors, particularly Complex I. These findings suggest that reduced mtDNA quantity and increased common deletion abundance may contribute to DSP in PWH, indicating diminished mitochondrial activity in the sensory neurons. Accumulated ETC proteins in the DRG imply impaired mitochondrial transport to the sensory neuron's distal portion. Identifying molecules to safeguard mitochondrial integrity could aid in treating or preventing HIV-associated peripheral neuropathy.

Role of tactile stimulation during the preweaning period on the development of the peripheral sensory sural (SU) nerve in adult artificially reared female rat.

Maternal deprivation, as a result of the artificial rearing (AR) paradigm, disturbs electrophysiological and histological characteristics of the peripheral sensory sural (SU) nerve of infant and adult male rats. Such changes are prevented by providing tactile or social stimulation during isolation. AR also affects the female rat's brain and behavior; however, it is unknown whether this early adverse experience also alters their SU nerve development or if tactile stimulation might prevent these possible developmental effects. To assess these possibilities, the electrophysiological and histological characteristics of the SU nerve from adult diestrus AR female rats that: (i) received no tactile stimulation (AR group), (ii) received tactile stimulation in the anogenital and body area (AR-Tactile group), or (iii) were mother reared (MR group) were determined. We found that the amplitude, but not the area, of the evoked compound action potential response in SU nerves of AR rats was lower than those of SU nerves of MR female rats. Tactile stimulation prevented these effects. Additionally, we found a reduction in the outer diameter and myelin thickness of axons, as well as a large proportion of axons with low myelin thickness in nerves of AR rats compared to the nerves of the MR and AR-Tactile groups of rats; however, tactile stimulation only partially prevented these effects. Our data indicate that maternal deprivation disturbs the development of sensory SU nerves in female rats, whereas tactile stimulation partially prevents the changes generated by AR. Considering that our previous studies have shown more severe effects of AR on male SU nerve development, we suggest that sex-associated factors may be involved in these processes.

Glycemic variability is associated with sural nerve conduction velocity in outpatients with type 2 diabetes: Usefulness of a new point-of-care device for nerve conduction studies.

AIMS/INTRODUCTION: Although several studies have shown the association between continuous glucose monitoring (CGM)-derived glycemic variability (GV) and diabetic peripheral neuropathy, no studies have focused on outpatients or used NC-stat®/DPNCheck™, a new point-of-care device for nerve conduction study (NCS). We investigated the association between CGM-derived GV and NCS using DPNCheck™ in outpatients with type 2 diabetes, and further analyzed the difference in results between patients with and without well-controlled HbA1c levels. MATERIALS AND METHODS: All outpatients with type 2 diabetes using the CGM device (FreeStyle Libre Pro®) between 2017 and 2022 were investigated. Sural nerve conduction was evaluated by sensory nerve action potential (SNAP) amplitude and sensory conduction velocity (SCV) using DPNCheck™. Associations of CGM-derived GV metrics with SNAP amplitude and SCV were investigated. RESULTS: In total, 304 outpatients with type 2 diabetes were included. In a linear regression model, most CGM-derived GV metrics except for the mean amplitude of glucose excursion and low blood glucose index were significantly associated with SCV, but not with SNAP amplitude. The significant associations of most CGM-derived GV metrics with SCV remained after adjustment for possible confounding factors, but not after adjustment for glycated hemoglobin (HbA1c). Most CGM-derived GV metrics were significantly associated with SCV after adjustment for HbA1c in patients with a HbA1c ≤ 6.9%, but not in those with a HbA1c ≥ 7.0%. CONCLUSIONS: In outpatients with type 2 diabetes, multiple CGM-derived GV metrics were significantly associated with SCV obtained by DPNCheck™. GV may have independent impacts on peripheral nerve function, particularly in patients with well-controlled HbA1c levels.

Analgesic effect of a cholinergic agonist (carbachol) in a sural nerve ligation-induced hypersensitivity mouse model.

OBJECTIVES: Neuropathic pain is characterized by long-lasting, intractable pain. Sciatic nerve ligation is often used as an animal model of neuropathic pain, and the spared nerve injury (SNI) model, in which the common peroneal nerve (CPN) and tibial nerve (TN) are ligated, is widely used. In the present study, we evaluated the analgesic effect of a cholinergic agonist, carbachol, on a neuropathic pain model prepared by sural nerve (SN) ligation in mice. METHODS: The SN was tightly ligated as a branch of the sciatic nerve. Mechanical and thermal allodynia, and hyperalgesia were assessed using von Frey filaments and heat from a hot plate. The analgesic effects of intracerebroventricularly-administered morphine and carbachol were compared. RESULTS: SN ligation resulted in a significant decrease in pain threshold for mechanical stimulation 1 day after ligation. In response to thermal stimulation, allodynia was observed at 50°C and hyperalgesia at 53 and 56°C 3 days after ligation. Content of thiobarbituric acid reactive substances (TBARS) in the spinal cord increased significantly at 6 and 12 h after ligation. Acetylcholine content of the spinal cord also increased at 5 and 7 days after ligation. Intracerebroventricular administration of carbachol at 7 days after ligation produced a marked analgesic effect against mechanical and thermal stimuli, which was stronger and longer-lasting than morphine at all experimental time points. CONCLUSION: These findings suggest that cholinergic nerves are involved in allodynia and hyperalgesia of the SN ligation neuropathic pain model.

Anatomical considerations of the sural nerve in the distal leg: Side branch patterns and significance in nerve harvesting procedures.

BACKGROUND: The sural nerve is a somatosensory nerve that provides sensation to the posterolateral aspect of the lower leg and the lateral part of the ankle and foot. Due to its location and anatomical properties, it is often used as an autologous nerve graft. However, the nerve harvest can be complicated by the presence of side branches. The objective of this study was to investigate the anatomy of the sural nerve and to map its side branches. This information can be used to predict the localization of separate incisions during the stair-step incisions technique for nerve harvest, thereby reducing the risk of complications. METHODS: The study involved the dissection of 50 adult cadaveric legs (25 left and 25 right) obtained from 27 Central European cadavers. The focus of the dissection was to identify the sural nerve, small saphenous vein, and surrounding anatomical structures. Detailed measurements were taken on the side branches of the sural nerve, tributaries of the small saphenous vein, and their interrelationship. RESULTS: The average number of sural nerve side branches in a single leg was 4.2±1.9. These side branches were categorized into six groups based on their location and course: mediodistal, medioproximal, lateroproximal, laterodistal, medial perpendicular, and lateral perpendicular. Specific patterns of combination of these side branches were also identified and described. The branching point of the sural nerve was found to be 5.8±2.7 cm proximal to the lateral malleolus, whereas the small saphenous vein branching point was located more distally, 4.5 ± 2.8 cm proximal to the lateral malleolus. The highest density of sural nerve side branches was found 2.1-6.0 cm above the lateral malleolus. CONCLUSION: This study presents valuable data about the relationship between the sural nerve and the surrounding anatomical structures in the distal part of the leg, including the identification of its side branches and their relevance during nerve harvest procedures. On the basis of the most frequent locations of side branches, a three-incision-technique for nerve harvest is proposed.

Morphometry of the sural nerve in diabetic neuropathy: a systematic review.

PURPOSE: The aim of this systematic review is to evaluate the usefulness of sural nerve ultrasonography in diagnosing diabetes mellitus (DM) and diabetic polyneuropathy (DPN), the latter of which is a common long-term complication for diabetic patients that frequently involves the sural nerve. METHODOLOGY: A meta-analysis of the cross-sectional areas (CSAs) of sural nerves in healthy individuals and patients with diabetes mellitus based on a total of 32 ultrasonographic-based studies from 2015 to 2023 was performed. Sub-analyses were performed for factors such as geographical location and measurement site. RESULTS: The meta-analysis showed that the mean CSA of the sural nerve was significantly larger in DM patients with DPN only compared to healthy individuals across all regions and when pooled together. An age-dependent increase in the CSA of healthy sural nerves is apparent when comparing the paediatric population with adults. CONCLUSION: Sural nerve ultrasonography can distinguish diabetic adults with DPN from healthy adults based on cross-sectional area measurement. Future studies are needed to clarify the relationships between other parameters, such as body metrics and age, with sural nerve CSAs. Cut-offs for DPN likely need to be specific for different geographical regions.

Automated whole slide morphometry of sural nerve biopsy using machine learning.

AIM: The morphometry of sural nerve biopsies, such as fibre diameter and myelin thickness, helps us understand the underlying mechanism of peripheral neuropathies. However, in current clinical practice, only a portion of the specimen is measured manually because of its labour-intensive nature. In this study, we aimed to develop a machine learning-based application that inputs a whole slide image (WSI) of the biopsied sural nerve and automatically performs morphometric analyses. METHODS: Our application consists of three supervised learning models: (1) nerve fascicle instance segmentation, (2) myelinated fibre detection and (3) myelin sheath segmentation. We fine-tuned these models using 86 toluidine blue-stained slides from various neuropathies and developed an open-source Python library. RESULTS: Performance evaluation showed (1) a mask average precision (AP) of 0.861 for fascicle segmentation, (2) box AP of 0.711 for fibre detection and (3) a mean intersection over union (mIoU) of 0.817 for myelin segmentation. Our software identified 323,298 nerve fibres and 782 fascicles in 70 WSIs. Small and large fibre populations were objectively determined based on clustering analysis. The demyelination group had large fibres with thinner myelin sheaths and higher g-ratios than the vasculitis group. The slope of the regression line from the scatter plots of the diameters and g-ratios was higher in the demyelination group than in the vasculitis group. CONCLUSION: We developed an application that performs whole slide morphometry of human biopsy samples. Our open-source software can be used by clinicians and pathologists without specific machine learning skills, which we expect will facilitate data-driven analysis of sural nerve biopsies for a more detailed understanding of these diseases.

Ultrahigh-frequency ultrasound of fascicles in the common fibular, superficial fibular, and sural nerves.

INTRODUCTION/AIMS: While ultrasound assessment of cross-sectional area and echogenicity has gained popularity as a biomarker for various neuropathies, there is a scarcity of data regarding fascicle count and density in neuropathies or even healthy controls. The aim of this study was to determine whether fascicles within select lower limb nerves (common fibular, superficial fibular, and sural nerves) can be counted in healthy individuals using ultrahigh-frequency ultrasound (UHFUS). METHODS: Twenty healthy volunteers underwent sonographic examination of the common fibular, superficial fibular, and sural nerves on each lower limb using UHFUS with a 48 MHz linear transducer. Fascicle counts and density in each examined nerve were determined by a single rater. RESULTS: The mean fascicle number for each of the measured nerves included the following: common fibular nerve 9.85 (SD 2.29), superficial fibular nerve 5.35 (SD 1.59), and sural nerve 6.73 (SD 1.91). Multivariate linear regression analysis revealed a significant association between cross-sectional area and fascicle count for all three nerves. In addition, there was a significant association seen in the common fibular nerve between fascicle density and height, weight, and body mass index. Age and sex did not predict fascicle count or density (all p > .13). DISCUSSION: UHFUS enabled the identification and counting of fascicles and fascicle density in the common fibular, superficial fibular, and sural nerves. Knowledge about normal values and normal peripheral nerve architecture is needed in order to further understand and identify pathological changes that may occur within each nerve in different disease states.

Reference values for nerve conduction studies of the peroneal, tibial, and sural nerve derived from a large population-based cohort: Associations with demographic and anthropometric characteristics-The Maastricht study.

INTRODUCTION/AIMS: Nerve conduction studies (NCSs) are widely used to support the clinical diagnosis of neuromuscular disorders. The aims of this study were to obtain reference values for peroneal, tibial, and sural NCSs and to examine the associations with demographic and anthropometric factors. METHODS: In 5099 participants (aged 40-79 years) without type 2 diabetes of The Maastricht Study, NCSs of peroneal, tibial, and sural nerves were performed. Values for compound muscle action potential (CMAP) and sensory nerve action potential amplitude, nerve conduction velocity (NCV), and distal latency were acquired. The association of age, sex, body mass index (BMI), and height with NCS values was determined using uni- and multivariate linear regression analyses. RESULTS: Detailed reference values are reported per decade for men and women. Significantly lower NCVs and longer distal latencies were observed in all nerves in older and taller individuals as well as in men. In these groups, amplitudes of the tibial and sural nerves were significantly lower, whereas a lower peroneal nerve CMAP was only significantly associated with age. BMI showed a multidirectional association. After correction for anthropometric factors in the multivariate analysis, the association between sex and NCS values was less straightforward. DISCUSSION: These values from a population-based dataset could be used as a reference for generating normative values. Our findings show the association of NCS values with anthropometric factors. In clinical practice, these factors can be considered when interpreting NCS values.

Values and diagnostic accuracy of sensory nerve action potentials in control participants and participants with diabetes with and without clinical diabetic neuropathy, based on neuropathy scale measurements.

BACKGROUND: The assessment of the normative values of sensory nerve action potentials (SNAP) and their diagnostic accuracies using validated neuropathy-assessment tools to classify participants into groups with and without neuropathy was not previously described in the literature. METHODS: The Utah Early Neuropathy Scale (UENS), Michigan neuropathy-screening instrument, and nerve conduction data were collected prospectively. We described and compared the values of the sural, superficial peroneal sensory (SPS), and superficial radial SNAP amplitude in different age groups for three groups. Group 1 (G1)-control participants (UENS <5), group 2 (G2)-participants with diabetes without clinical diabetic neuropathy (UENS <5), and group 3 (G3)-participants with clinical diabetic neuropathy (UENS ≥5). We also described the diagnostic accuracy of single-nerve amplitude and a combined sensory polyneuropathy index (CSPNI) that consists of four total points (one point for each of the following nerves if their amplitude was <25% lower limit of normal: right sural, left sural, right SPS, and left SPS potentials). RESULTS: We assessed 135 participants, including 41, 37, and 57 participants in G1, G2, and G3, respectively, with age median (interquartile ranges) of 51 (45-56), 47 (38-56), and 54 (51-61) years, respectively, whereas 19 (46.3%), 18 (48.7%), and 32 (56.14%) of them were males, respectively. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) scores were 68.4%, 92.3%, 86.7%, and 80% for the sural amplitude; 86%, 58.3%, 62%, and 84% for the SPS amplitude; 66.7%, 94.4%, 90.5%, and 78.2% for the CSPNI of 3; and 54.4%, 98.6%, 96.9%, and 73.2% for the CSPNI of 4, respectively. CONCLUSION: Sural nerve had a high specificity for neuropathy; however, the CSPNI had the highest specificity and PPV, whereas the SPS had the highest sensitivity and NPV.