Preliminary evaluation of the sural nerve using 22-MHz ultrasound: a new approach for evaluation of diabetic cutaneous neuropathy

From Morphology to Therapeutic Strategies: Exploring New Applications of Ultrasound for Diabetic Peripheral Neuropathy Diagnosis and Management

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes that can result in severe lower limb pain and amputation. Early detection and treatment of DPN are vital, but this condition is often missed due to a lack of symptoms and the insensitivity of testing methods. This article reviews various ultrasound imaging modalities in the direct and indirect evaluation of peripheral neuropathy. Moreover, how ultrasound-related therapeutic strategies are playing a role in clinical treatment is discussed. Finally, the application of innovative methodologies in the diagnosis of DPN, including ultrasound attenuation, photoacoustic imaging, and artificial intelligence, is described.

Neuromuscular Ultrasound in Polyneuropathies

Neuromuscular ultrasound is a painless, radiation-free, high-resolution imaging technique for assessing the peripheral nervous system. It can accurately depict changes in the nerves and muscles of individuals with neuromuscular conditions, and it is therefore a robust diagnostic tool for the assessment of individuals with polyneuropathies. This review will outline the typical ultrasonographic changes found in a wide variety of polyneuropathies. In general, demyelinating conditions result in greater nerve enlargement than axonal conditions, and acquired conditions result in more patchy nerve enlargement compared to diffuse nerve enlargement in hereditary conditions. This review is data-driven, but more nuanced anecdotal findings are also described. The overall goal of this paper is to provide clinicians with an accessible review of the ultrasonographic approaches and findings in a wide variety of polyneuropathies.

The vagus nerve cross-sectional area on ultrasound in patients with type 2 diabetes

Diabetic neuropathy, including autonomic neuropathy is a serious complication related to type 2 diabetes mellitus (T2D). The vagus nerve (VN) is the longest nerve in the autonomic nervous system, and since diabetic neuropathy manifests first in longer nerves, the VN is commonly affected in early diabetic autonomic neuropathy. The use of high-resolution ultrasound for peripheral and cranial nerve imaging has significantly increased over the past 2 decades. The aim of the study is to compare the cross-sectional area of the VN in patients with T2D to that of a control cohort without T2D. A total of 52 VN cross-sectional areas were recorded from patients with T2D. A total of 56 VN cross-sectional areas were also recorded from asymptomatic subjects without T2D. In each subject, high-resolution ultrasound imaging of the bilateral VNs was performed in the short-axis between the common carotid artery and the internal jugular vein. The VN cross-sectional areas were recorded and compared. In the patients with T2D, HbA1c and fasting blood glucose levels were obtained as well as the duration of T2D in years and correlated with the cross-sectional areas. The bilateral VN cross-sectional areas were similar in both cohorts. Additionally, no correlation was seen between the VN cross-sectional areas, demographics, or clinical data of T2D. Our study demonstrated normal VN cross-sectional areas in patients with T2D without any significant relation with the patients' demographic or clinical data.

Effect of Surgical Release of Entrapped Peripheral Nerves in Sensorimotor Diabetic Neuropathy on Pain and Sensory Dysfunction-Study Protocol of a Prospective, Controlled Clinical Trial

BACKGROUND

Nerve entrapment has been hypothesized to contribute to the multicausal etiology of axonopathy in sensorimotor diabetic neuropathy. Targeted surgical decompression reduces external strain on the affected nerve and, therefore, may alleviate symptoms, including pain and sensory dysfunction. However, its therapeutic value in this cohort remains unclear.

AIM

Quantifying the treatment effect of targeted lower extremity nerve decompression in patients with preexisting painful sensorimotor diabetic neuropathy and nerve entrapment on pain intensity, sensory function, motor function, and neural signal conduction.

STUDY DESIGN

This prospective, controlled trial studies 40 patients suffering from bilateral therapy-refractory, painful (n = 20, visual analogue scale, VAS ≥ 5) or painless (n = 20, VAS = 0) sensorimotor diabetic neuropathy with clinical and/or radiologic signs of focal lower extremity nerve compression who underwent unilateral surgical nerve decompression of the common peroneal and the tibial nerve. Tissue biopsies will be analyzed to explore perineural tissue remodeling in correlation with intraoperatively measured nerve compression pressure. Effect size on symptoms including pain intensity, light touch threshold, static and moving two-point discrimination, target muscle force, and nerve conduction velocity will be quantified 3, 6, and 12 months postoperatively, and compared (1) to the preoperative values and (2) to the contralateral lower extremity that continues non-operative management.

CLINICAL SIGNIFICANCE

Targeted surgical release may alleviate mechanical strain on entrapped lower extremity nerves and thereby potentially improve pain and sensory dysfunction in a subset of patients suffering from diabetic neuropathy. This trial aims to shed light on these patients that potentially benefit from screening for lower extremity nerve entrapment, as typical symptoms of entrapment might be erroneously attributed to neuropathy only, thereby preventing adequate treatment.

Ultrasound evaluation of peripheral nerves of the lower limb in diabetic peripheral neuropathy

PURPOSE

Comparative evaluation of the cross-sectional area (CSA) of the sural and tibial nerves using ultrasound in diabetic peripheral neuropathy (DPN).

METHOD

This study involved 210 participants divided into 3 groups: type 2 diabetics with DPN, type 2 diabetics without DPN, and controls. Ultrasound evaluation of the sural and tibial nerves was done using a 5-17 MHz linear transducer. The CSA of both the nerves was recorded in both lower limbs. Nerve conduction studies (NCS) were also done in all diabetic patients.

RESULTS

There were 70 participants in each group. All the three groups were gender-matched and no significant difference was observed between CSA values of the sural and tibial nerves between males and females and also in right and left lower limbs within a group. The sural nerve CSA was significantly higher in the DPN group than in diabetic patients without DPN and controls. The sensitivity of the sural nerve CSA was higher than the tibial nerve with a cut-off value of 4.41 mm² for CSA of the sural nerve.

CONCLUSION

The sural nerve CSA at the superior border of lateral malleolus can be used for screening DPN. With well-established cut-off values may result in early initiation of the therapy even in NCS negative cases, thus reducing the morbidity associated with the disease. Ultrasound could be used as a first diagnostic tool for detection of DPN which can be followed by NCS in cases where ultrasound is non-diagnostic.

The Slipping Slipper Sign: A Poor Man's Test for Severe Diabetic Peripheral Neuropathy

BACKGROUND

Neuropathic feet are at very high risk for infection and amputation. The slipping slipper sign (SSS) is elicited by a simple questionnaire test reported to detect the presence of severe diabetic peripheral neuropathy. This test can be administered by non-medical staff. In this study, subjects with and without the SSS were evaluated by nerve conduction studies (NCS) and ultrasound measurements of the right sural nerve diameters as well as with traditional scoring systems for peripheral and autonomic neuropathy.

OBJECTIVE

To demonstrate that the Slipping Slipper Sign can be used as an index of severe diabetic peripheral neuropathyMethod:This was a prospective cross sectional study in which 74 patients with diabetes (38 positive and 36 negative for SSS) underwent ultrasonography and NCS of the right sural nerve by an examiner blinded to SSS status. Findings were evaluated against demography, clinical history, anthropometry as well as traditional clinical and autonomic neuropathic scores.

RESULTS

Patients without the SSS [median (IQR) = 10.0 years (4.0-20.3)] had a significantly shorter duration of diabetes compared with those with the SSS [median (IQR) = 15.0 years (8.5-25.0)], p = 0.028. The frequencies of retinopathy (36.8% vs 2.8%, p <  0.05) and cerebrovascular accidents (18.4% vs 13.9 %, p <  0.05) were higher among those with SSS compared with those without. Differences in nerve conduction characteristics were markedly significant. The amplitude of the sural sensory nerve action potential (SNAP) was ([median (IQR)] 0 microvolts vs 4.0 microvolts (0.0-10.8) p <  0.002) between those with and without SSS, respectively whilst none of patients with SSS had a recordable SNAP vs 78% without a SSS. Similarly, maximal thickness of the right sural nerve at the ankle 3.0 mm (2.3-3.4) vs 3.5 mm (3.0-3.9), and leg 3.4 mm (2.7-3.8) vs 3.9 mm (3.3-4.2) was reduced, p <  0.01 in patients with the SSS compared with those with a negative SSS.

CONCLUSION

The SSS identifies feet with objective neurophysiological and imaging characteristics of severe neuropathy.

High-resolution ultrasonography of the sural nerve in diabetic peripheral neuropathy

Aim of the study: To study the cross-sectional area, the maximum thickness of the nerve fascicle and the thickness/width ratio of the sural nerve in patients with diabetes mellitus and non-diabetic subjects using high-resolution ultrasonography and to correlate the results with nerve conduction studies. Material and methods: This prospective study was conducted among 60 patients divided into two groups: A and B. Group A consisted of 30 patients >18 years of age with a history of type 2 diabetes mellitus, and Group B consisted of 30 non-diabetic patients >18 years of age. High-resolution ultrasonography was performed using a linear transducer with the frequency of 5-18 MHz in all the patients in the prone position with the transducer placed in a transverse position at the junction of the middle and lower thirds of the calf. Nerve conduction studies were performed using Aleron 201 (RMS) in all the patients. Results: As compared to the control group, the sural nerve in the diabetic group showed increased cross-sectional area, maximum thickness of the nerve fascicle and thickness/width ratio (p <0.05). Nerve conduction studies showed decreased amplitude, increased latency and decreased velocity in the cases as compared to controls (p <0.05). The cross-sectional area, maximum thickness of the nerve fascicle and thickness/width ratio showed statistical significance when compared with amplitude, latency and velocity in the cases as well as controls (p <0.001). Conclusion: This study suggests that high-frequency ultrasound of the sural nerve is a useful tool for evaluating changes typical of peripheral neuropathy in patients with diabetes mellitus.

Aim of the study: To study the cross-sectional area, the maximum thickness of the nerve fascicle and the thickness/width ratio of the sural nerve in patients with diabetes mellitus and non-diabetic subjects using high-resolution ultrasonography and to correlate the results with nerve conduction studies. Material and methods: This prospective study was conducted among 60 patients divided into two groups: A and B. Group A consisted of 30 patients >18 years of age with a history of type 2 diabetes mellitus, and Group B consisted of 30 non-diabetic patients >18 years of age. High-resolution ultrasonography was performed using a linear transducer with the frequency of 5–18 MHz in all the patients in the prone position with the transducer placed in a transverse position at the junction of the middle and lower thirds of the calf. Nerve conduction studies were performed using Aleron 201 (RMS) in all the patients. Results: As compared to the control group, the sural nerve in the diabetic group showed increased cross-sectional area, maximum thickness of the nerve fascicle and thickness/width ratio (p <0.05). Nerve conduction studies showed decreased amplitude, increased latency and decreased velocity in the cases as compared to controls (p <0.05). The cross-sectional area, maximum thickness of the nerve fascicle and thickness/width ratio showed statistical significance when compared with amplitude, latency and velocity in the cases as well as controls (p <0.001). Conclusion: This study suggests that high-frequency ultrasound of the sural nerve is a useful tool for evaluating changes typical of peripheral neuropathy in patients with diabetes mellitus.

Feasibility of Point Shear Wave Elastography for Evaluating Diabetic Peripheral Neuropathy

OBJECTIVES

In the mode of Virtual Touch quantification (Siemens AG, Erlangen, Germany), point shear wave elastography (p-SWE) is widely used for noninvasive assessments of tissue stiffness, which may be useful in the evaluation of diabetic peripheral neuropathy (DPN).

METHODS

Thirty patients with type 2 diabetes and 20 control participants (7 with myoma of the uterus and 13 with kidney stones) were enrolled in this prospective study. The 30 patients were further divided into patients with DPN and patients without DPN. Conventional ultrasound examinations and p-SWE were used to examine the tibial nerve in the popliteal fossa.

RESULTS

Tibial nerve stiffness values in the overall patient group, patients with DPN, and patients without DPN were all significantly higher than in the control group (P < .05). The cutoff value of p-SWE for assessing DPN was 2.60 m/s; at that threshold, sensitivity was 63.33%, and specificity was 92.50%.

CONCLUSIONS

Point SWE was useful for the noninvasive assessment of DPN and had high specificity. The increased stiffness in patients without DPN indicated that the tibial nerve might be affected by diabetes.

Clinical outcome and ultrasonographic evaluation of treatment using polyglycolic acid-collagen tube for chronic neuropathic pain after peripheral nerve injury

BACKGROUND

A novel polyglycolic acid (PGA)-collagen tube has been available in Japan since March 2013, and the development of high-resolution ultrasonography has recently allowed detailed evaluation of nerves. The purpose of this study was to report the clinical outcomes and evaluations of in-vivo changes under high-resolution ultrasonography for treatment using PGA-collagen tube for painful chronic nerve injury.

METHODS

Four patients underwent surgical management of peripheral nerve neuroma, with nerve defects after neuroma resection reconstructed using PGA-collagen tube. Mean duration of follow-up was 30 months. Patients were surveyed to determine visual analog scale scores for pain before surgery and at final follow-up. At final follow-up, sensory function was evaluated using the Semmes-Weinstein test, static 2-point discrimination (2PD), and moving 2PD. Furthermore, we performed ultrasonography for all patients every 1 month after surgery.

RESULTS

In all cases, resting pain, radicular pain, and dysesthesia were improved immediately after the operation and remained improved until the last follow-up. At the time of final follow-up, the Semmes-Weinstein test was red in 2 cases and blue in 2 cases. Mean static 2PD was 15.5 ± 5.3 mm and mean moving 2PD was 11.5 ± 5.3 mm. Ultrasonography revealed that the PGA outer wall had disappeared by 3 months postoperatively, and a hypoechoic linear shadow bridged the proximal and distal stumps. Swelling of the junction between nerve and nerve conduits was revealed at 4 months after surgery and remained until last follow-up.

CONCLUSIONS

All patients were very satisfied with pain relief, but recovery of sensory function was insufficient. Ultrasonographic evaluation after using PGA-collagen tube for painful chronic peripheral nerve injury was useful for observing in-vivo changes.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Ultrasound assessment of the sural nerve in patients with neuropathic pain after ankle surgery

INTRODUCTION

The sural nerve may be damaged after ankle injury. The aim of our study was to determine the diagnostic utility of high-resolution sonography in patients with ankle fractures treated by open reduction and internal fixation in whom there was a clinical suspicion of sural neuropathy.

METHODS

We examined the ultrasound (US) characteristics of patients with and without postsurgical sural neuropathic pain and healthy volunteers. Cross-sectional area (CSA), echogenicity, and vascularization of the sural nerves were recorded.

RESULTS

Fourteen participants and all sural nerves were identified. CSA (P < 0.001) and vascularization (P = 0.002) were increased in symptomatic patients when compared with asymptomatic patients and healthy volunteers. There were no significant differences in nerve echogenicity (P = 0.983).

DISCUSSION

US may be a valuable tool for evaluating clinically suspected sural nerve damage after ankle stabilization surgery. Sural nerve abnormalities are seen in patients with postsurgical neuropathic pain. Muscle Nerve 57: 407-413, 2018.

The use of ultrasound in neuromuscular diagnoses

Purpose of review

The use of ultrasonography for diagnosis of neuromuscular disorders is a relatively new but rapidly expanding field. This review covers key ultrasound findings in primary disease of muscle and nerve.

Recent findings

Ultrasonography is used routinely for evaluation of entrapment neuropathies, hereditary and inflammatory neuropathies, polyneuropathies, myopathies, and motor neuron disease. When used in association with other electrodiagnostic testing, ultrasound has allowed physicians to increase the yield of clinical evaluation in diagnostic laboratories.

Summary

While ultrasonography has not yet replaced the need for electrodiagnostic studies, it has become a useful accompaniment.

Neuromuscular Ultrasound in the Assessment of Polyneuropathies and Motor Neuron Disease

Neuromuscular ultrasound is an emerging technology for the evaluation of conditions affecting nerve and muscle, with most of the research focusing on focal neuropathies. Despite this focus, researchers have also investigated the ultrasonographic changes that occur in the nerves and muscles of those with more diffuse polyneuropathies and motor neuron diseases, and this review will detail the findings in these conditions. Specific findings are discussed in this article, but general themes will also be presented and include the following: hereditary polyneuropathies show diffuse nerve enlargement, whereas immune-mediated polyneuropathies show more patchy involvement; nerve enlargement is more profound in demyelinating than axonal polyneuropathies; and muscle changes in motor neuron diseases include heterogeneous increases in echogenicity, atrophy, readily detectable fasciculations, and increased subcutaneous tissue thickness.

Diabetic peripheral neuropathy: Correlation between nerve cross-sectional area on ultrasound and clinical features

BACKGROUND AND OBJECTIVE

To evaluate the correlations of the cross-sectional area (CSA) of peripheral nerves in diabetic peripheral neuropathy (DPN) patients based on ultrasound (US) with clinical and demographic characteristics.

METHODS

A DPN patient group (n= 53) and a matched healthy control group (n= 53) underwent US imaging of the sciatic, tibial and median nerves. The CSAs of these nerves were recorded, and their associations with pain intensity according to the visual analog scale (VAS) score and the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) pain scale score, diabetes mellitus (DM) duration, body mass index (BMI), HbA1c level and blood glucose levels were evaluated.

RESULTS

The CSAs of the examined nerves in diabetic patients were larger than those in healthy individuals (p< 0.05). No correlations were detected between the CSAs of the examined nerves and the parameters of interest (p> 0.05), including the VAS and LANSS pain scale scores (p= 0.32 and p= 0.31, respectively).

CONCLUSIONS

US is a sensitive diagnostic technique for detecting DPN; however, it does not indicate disease severity.

Peripheral nerve high-resolution ultrasound in diabetes

INTRODUCTION

High-resolution ultrasound (HRU) is used in the diagnosis of peripheral neuropathies. There are conflicting data regarding HRU findings in patients with diabetic sensorimotor polyneuropathy (DSP). Our purpose in this study was to measure nerve cross-sectional areas (CSAs) in patients with diabetes, with and without DSP.

METHODS

We performed a prospective peripheral nerve HRU study of 100 diabetic subjects, assessed the CSA at predefined sites, and compared the results with those of 100 normal subjects. We evaluated the use of individual CSA values and various summary scores for diagnosis of DSP.

RESULTS

Diabetic subjects had higher CSA values than healthy volunteers, and those with DSP had higher CSA values. Three or more enlarged CSA sites predicted DSP with 64% sensitivity and 77% specificity.

CONCLUSIONS

Peripheral nerves are enlarged diffusely in diabetic patients, including sites not susceptible to bony compression. The number of enlarged CSA values can help predict the presence of DSP. Muscle Nerve, 2016 Muscle Nerve 55: 171-178, 2017.

Sonographic features of peripheral nerves at multiple sites in patients with diabetic polyneuropathy

OBJECTIVE

Diabetic polyneuropathy (DPN) is one of the major complications of diabetes mellitus. Ultrasound has been frequently used for evaluation of peripheral nerves. However, there are few studies that have evaluated multiple peripheral nerves in DPN. In this study, ultrasonographic features of multiple peripheral nerves in upper and lower extremities of DPN patients were investigated and compared with those of healthy controls.

METHODS

This study was a case-control study that enrolled 20 patients with confirmed diagnosis of DPN and 20 healthy controls. The ultrasonography was performed on the sural, tibial, fibular, sciatic, median, ulnar, radial, and musculocutaneous nerves. Nerve cross-sectional area (CSA) was measured at multiple points for each peripheral nerve. The CSAs were compared between DPN and control groups, and analyzed in relation to the clinical characteristics and electrophysiologic findings.

RESULTS

The CSAs were significantly larger in the DPN group for sural nerve, fibular nerve at the fibular head level, median nerve at the carpal tunnel and mid-humerus level, ulnar nerve at the cubital tunnel outlet and mid-humerus level, and radial nerve at the spiral groove. The CSAs of sural nerve, tibial nerve and median nerve were significantly correlated with electrophysiologic findings. The sural nerve CSA revealed significant correlation with HbA1c.

CONCLUSIONS

These results suggest that the ultrasonography can provide useful information in diagnosis and evaluation of DPN.

High-Resolution Ultrasonography of the Superficial Peroneal Motor and Sural Sensory Nerves May Be a Non-invasive Approach to the Diagnosis of Vasculitic Neuropathy

High-resolution ultrasonography (HRUS) is an emerging new tool in the investigation of peripheral nerves. We set out to assess the utility of HRUS performed at lower extremity nerves in peripheral neuropathies. Nerves of 26 patients with polyneuropathies of different etiologies and 26 controls were investigated using HRUS. Patients underwent clinical, laboratory, electrophysiological assessment, and a diagnostic sural nerve biopsy as part of the routine work-up. HRUS was performed at the sural, tibial, and the common, superficial, and deep peroneal nerves. The superficial peroneal nerve longitudinal diameter (LD) distinguished best between the groups: patients with immune-mediated neuropathies (n = 13, including six with histology-proven vasculitic neuropathy) had larger LD compared to patients with non-immune-mediated neuropathies (p < 0.05) and to controls (p < 0.001). Among all subgroups, patients with vasculitic neuropathy showed the largest superficial peroneal nerve LD (p < 0.001) and had a larger sural nerve cross-sectional area when compared with disease controls (p < 0.001). Enlargement of the superficial peroneal and sural nerves as detected by HRUS may be a useful additional finding in the differential diagnosis of vasculitic and other immune-mediated neuropathies.

Neuroprotective effects of ultrasound-guided nerve growth factor injections after sciatic nerve injury

Nerve growth factor (NGF) plays an important role in promoting neuroregeneration after peripheral nerve injury. However, its effects are limited by its short half-life; it is therefore important to identify an effective mode of administration. High-frequency ultrasound (HFU) is increasingly used in the clinic for high-resolution visualization of tissues, and has been proposed as a method for identifying and evaluating peripheral nerve damage after injury. In addition, HFU is widely used for guiding needle placement when administering drugs to a specific site. We hypothesized that HFU guiding would optimize the neuroprotective effects of NGF on sciatic nerve injury in the rabbit. We performed behavioral, ultrasound, electrophysiological, histological, and immunohistochemical evaluation of HFU-guided NGF injections administered immediately after injury, or 14 days later, and compared this mode of administration with intramuscular NGF injections. Across all assessments, HFU-guided NGF injections gave consistently better outcomes than intramuscular NGF injections administered immediately or 14 days after injury, with immediate treatment also yielding better structural and functional results than when the treatment was delayed by 14 days. Our findings indicate that NGF should be administered as early as possible after peripheral nerve injury, and highlight the striking neuroprotective effects of HFU-guided NGF injections on peripheral nerve injury compared with intramuscular administration.

Percutaneous Ultrasound-Guided Hydrodissection of a Symptomatic Sural Neuroma

Symptomatic neuromas of the sural nerve are a rare but significant cause of pain and debilitation in athletes. Presentation is usually in the form of chronic pain and dysesthesias or paresthesias of the lateral foot and ankle. Treatment traditionally ranges from conservative measures, such as removing all external compressive forces, to administration of nonsteroidal anti-inflammatory drugs, vitamin B6, tricyclic antidepressants, antiepileptics, or topical anesthetics. This article reports a case of sural nerve entrapment in a 34-year-old male triathlete with a history of recurrent training-induced right-sided gastrocnemius strains. The patient presented with numbness in the right lateral foot and ankle that had persisted for 3 months, after he was treated unsuccessfully with extensive nonoperative measures, including anti-inflammatory drugs, activity modification, and a dedicated physical therapy program of stretching and strengthening. Orthopedic assessment showed worsening pain with forced passive dorsiflexion and manual pressure applied over the distal aspect of the gastrocnemius. Plain radiographs showed normal findings, but in-office ultrasound imaging showed evidence of sural nerve entrapment with edema and neuromatous scar formation in the absence of gastrocnemius or soleus pathology. Percutaneous ultrasound-guided hydrodissection of the sural nerve at the area of symptomatic neuroma and neural edema was performed the same day. The patient had complete relief of symptoms and full return to the preinjury level of participation in competitive sports. This case report shows that hydrodissection, when performed by an experienced physician, can be an effective, minimally invasive technique for neurolysis in the setting of sural nerve entrapment, resulting in improvement in clinical symptoms.

Ultrasound in the diagnosis of peripheral neuropathy: structure meets function in the neuromuscular clinic

Peripheral nerve ultrasound (US) has emerged as a promising technique for the diagnosis of peripheral nerve disorders. While most experience with US has been reported in the context of nerve entrapment syndromes, the role of US in the diagnosis of peripheral neuropathy (PN) has recently been explored. Distinctive US findings have been reported in patients with hereditary, immune-mediated, infectious and axonal PN; US may add complementary information to neurophysiological studies in the diagnostic work-up of PN. This review describes the characteristic US findings in PN reported to date and a classification of abnormal nerve US patterns in PN is proposed. Closer scrutiny of nerve abnormalities beyond assessment of nerve calibre may allow for more accurate diagnostic classification of PN, as well as contribute to the understanding of the intersection of structure and function in PN.

Elasticity of the tibial nerve assessed by sonoelastography was reduced before the development of neuropathy and further deterioration associated with the severity of neuropathy in patients with type 2 diabetes

Aims/Introduction

To measure the elasticity of the tibial nerve using sonoelastography, and to associate it with diabetic neuropathy severity, the cross‐sectional area of the tibial nerve and neurophysiological findings in type 2 diabetic patients.

Materials and Methods

The elasticity of the tibial nerve was measured as the tibial nerve:acoustic coupler strain ratio using high‐resolution ultrasonography in 198 type 2 diabetic patients stratified into subgroups by neuropathy severity, and 29 control participants whose age and sex did not differ from the diabetic subgroups.

Results

The elasticity of the tibial nerve in patients without neuropathy (P < 0.001) was reduced compared with controls (0.76 ± 0.023), further decreasing (0.655 ± 0.014 to 0.414 ± 0.018) after developing neuropathy. The cut‐off value of elasticity of the tibial nerve that suggested the presence of neuropathy was 0.558. The area under the curve (0.829) was greater than that for the cross‐sectional area (0.612). The cross‐sectional area of the tibial nerve in diabetic patients without neuropathy (6.11 ± 0.13 mm²) was larger than that in controls (4.84 ± 0.16 mm²), and increased relative to neuropathy severity (P < 0.0001). The elasticity of the tibial nerve was negatively associated with neuropathy severity (P < 0.0001), cross‐sectional area (P = 0.002) and 2000 Hz current perception threshold (P = 0.011), and positively associated with nerve conduction velocities (P < 0.0001).

Conclusions

Determining the elasticity of the tibial nerve in type 2 diabetic patients could reveal early biomechanical changes that were likely caused by thickened fibrous sheaths of peripheral nerves, and might be a novel tool for characterizing diabetic neuropathy.

Peripheral nerves and plexus: imaging by MR-neurography and high-resolution ultrasound

PURPOSE OF REVIEW

The purpose of this study is to review advances in magnetic resonance (MR)-neurography and nerve-ultrasound for the precise visualization and localization of nerve lesions not only in nerve trauma or mass lesions, but also in entrapment-related and spontaneously occurring intrinsic neuropathies. These advances may improve the understanding and classification of peripheral neuropathies.

RECENT FINDINGS

Diagnostic studies of MR-neurography and high-resolution ultrasound in entrapment-neuropathies consistently report accurate determination and localization of symptomatic nerve entrapment. Additionally, the longitudinal sampling of nerve-T2-signal over larger areas of coverage has become technically feasible. With this approach, more complex patterns of spatial lesion dispersion in nonfocal neuropathies could be observed with reliable lesion image contrast at the level of individual nerve fascicles. Imaging detection of fascicular lesions allows for more accurate localization, because fascicular lesion types represent a specific pitfall for clinical-electrophysiological examinations. Fascicular hypoechogenicity of high-resolution ultrasound is the correlate of nerve-T2-signal lesions, but contrast is inferior and difficult to quantify. Therefore, nerve enlargement remains the main diagnostic criterion in high-resolution ultrasound. Diffusion-tensor-MR-neurography provides quantitative estimates of fiber structure, which were shown to correlate with aging and focal entrapment.

SUMMARY

High-resolution nerve imaging with extended anatomical coverage is feasible and improves the topographic description of spatial lesion dispersion which is particularly relevant for the discrimination between focal and nonfocal neuropathies.

Morphological changes of the peripheral nerves evaluated by high-resolution ultrasonography are associated with the severity of diabetic neuropathy, but not corneal nerve fiber pathology in patients with type 2 diabetes

Aims/Introduction

To evaluate the morphological changes of the median and posterior tibial nerve using high-resolution ultrasonography, and the corneal C fiber pathology by corneal confocal microscopy in type 2 diabetic patients.

Materials and Methods

The cross-sectional area, hypoechoic area and maximum thickness of the nerve fascicle of both nerves were measured by high-resolution ultrasonography in 200 type 2 diabetic patients, stratified by the severity of diabetic neuropathy, and in 40 age- and sex-matched controls. These parameters were associated with corneal C fiber pathology visualized by corneal confocal microscopy, neurophysiological tests and severity of diabetic neuropathy.

Results

The cross-sectional area, hypoechoic area and maximum thickness of the nerve fascicle of both nerves in patients without diabetic neuropathy were larger than those in control subjects (P < 0.05 to P < 0.001), and further increased relative to the severity of neuropathy (P < 0.0001). All morphological changes of both nerves were negatively associated with motor and sensory nerve conduction velocity (P = 0.01 to P < 0.0001), and directly associated with 2,000-Hz current perception threshold (P = 0.009 to P < 0.001). The significant corneal C fiber pathology occurred before developing the neuropathy, and deteriorated only in patients with the most severe neuropathy. The association between the morphological changes of both nerves and corneal C fiber pathology was poor.

Conclusions

The morphological changes in peripheral nerves of type 2 diabetic patients were found before the onset of neuropathy, and were closely correlated with the severity of diabetic neuropathy, but not with corneal C fiber pathology.

High-resolution ultrasonographic evaluation of "hourglass-like fascicular constriction" in peripheral nerves: a preliminary report

An hourglass-like constriction is a focal fascicular lesion observed in one or a few places in one or a few fascicles of a peripheral nerve trunk, and usually affects the anterior interosseous (AIN) or posterior interosseous (PIN) nerve. Constrictions have previously been discovered only by surgical exploration, and have been unable to be recognized on pre-operative imaging. We encountered some cases in which the lesion was able to be diagnosed pre-operatively by high-resolution ultrasonography; these findings were then confirmed intra-operatively. Five consecutive cases were included in this study. In three cases with constrictions revealed on pre-operative ultrasound, the findings were confirmed intra-operatively. In the remaining two cases in which no constrictions were detected pre-operatively, no constriction was revealed intra-operatively. High-resolution ultrasonography may play a significant role in the diagnosis of hourglass-like constrictions, and may thus lead to significant changes in treatment strategies for AIN and PIN palsy.

Challenges in sciatic nerve repair: anatomical considerations

Object

The object of this study was to highlight the challenge of insufficient donor graft material in peripheral nerve surgery, with a specific focus on sciatic nerve transection requiring autologous sural nerve graft.

Methods

The authors performed an anatomical analysis of cadaveric sciatic and sural nerve tissue. To complement this they also present 3 illustrative clinical cases of sciatic nerve injuries with segmental defects. In the anatomical study, the cross-sectional area (CSA), circumference, diameter, percentage of neural tissue, fat content of the sural nerves, as well as the number of fascicles, were measured from cadaveric samples. The percentage of neural tissue was defined as the CSA of fascicles lined by perineurium relative to the CSA of the sural nerve surrounded by epineurium.

Results

Sural nerve samples were obtained from 8 cadaveric specimens. Mean values and standard deviations from sural nerve measurements were as follows: CSA 2.84 ± 0.91 mm2, circumference 6.67 ± 1.60 mm, diameter 2.36 ± 0.43 mm, fat content 0.83 ± 0.91 mm2, and number of fascicles 9.88 ± 3.68. The percentage of neural tissue seen on sural nerve cross-section was 33.17% ± 4.96%. One sciatic nerve was also evaluated. It had a CSA of 37.50 mm2, with 56% of the CSA representing nerve material. The estimated length of sciatic nerve that could be repaired with a bilateral sural nerve harvest (85 cm) varied from as little as 2.5 cm to as much as 8 cm.

Conclusions

Multiple methods have been used in the past to repair sciatic nerve injury but most commonly, when a considerable gap is present, autologous nerve grafting is required, with sural nerve being the foremost source. As evidenced by the anatomical data reported in this study, a considerable degree of variability exists in the diameter of sural nerve harvests. Conversely, the percentage of neural tissue is relatively consistent across specimens. The authors recommend that the peripheral nerve surgeon take these points into consideration during nerve grafting as insufficient graft material may preclude successful recovery.

Follow-up evaluation with ultrasonography of peripheral nerve injuries after an earthquake

Published data on earthquake-associated peripheral nerve injury is very limited. Ultrasonography has been proven to be efficient in the clinic to diagnose peripheral nerve injury. The aim of this study was to assess the role of ultrasound in the evaluation of persistent peripheral nerve injuries 1 year after the Wenchuan earthquake. Thirty-four patients with persistent clinical symptoms and neurologic signs of impaired nerve function were evaluated with sonography prior to surgical repair. Among 34 patients, ultrasonography showed that 48 peripheral nerves were entrapped, and 11 peripheral nerves were disrupted. There was one case of misdiagnosis on ultrasonography. The concordance rate of ultrasonographic findings with those of surgical findings was 98%. A total of 48 involved nerves underwent neurolysis and the symptoms resolved. Only five nerves had scar tissue entrapment. Preoperative and postoperative clinical and ultrasonographic results were concordant, which verified that ultrasonography is useful for preoperative diagnosis and postoperative evaluation of injured peripheral nerves.

Biologic Basis of Nerve Decompression Surgery for Focal Entrapments in Diabetic Peripheral Neuropathy

The most recent (2011) National Diabetes Fact Sheet states the combined diagnosed and undiagnosed number of diabetes cases in the United States is approaching 25 million, and another 79 million are prediabetic. Of the diabetes patients, 60-70% suffer from mild to severe neuropathy. This combined loss of sensory and motor control in diabetic limbs is usually considered an irreversible, progressive process. Patients suffering from these losses are at a significantly higher risk for development of foot ulceration, frequently leading to infection and partial or major limb amputation. However, a review of focal nerve entrapment surgical decompression literature suggests that several diabetic sensorimotor polyneuropathy (DSPN) symptoms and complications are potentially partially reversible or preventable. Decompression surgery represents a paradigm shift in treatment protocols because it both relieves pain and restores protective sensation, while providing significant protection against a cascade of serious foot complications. This review surveys current research regarding the biological basis for diabetic focal entrapment neuropathy. Metabolic dysfunction related to aldose reductase, oxidative stress, and advanced glycation end products are considered and correlated to peripheral nerve enlargement and entrapment. In addition, observational studies correlated to that biological basis are presented as well as surgical outcomes illustrating the effect of decompression on DSPN symptomatic relief, nerve function, and protection against complications.

Measurement of ultrasonic attenuation in diabetic neuropathic sciatic nerves for diagnostic and therapeutic applications

Measurements of ultrasonic attenuation in the sciatic nerves of rats were performed to verify the feasibility of ultrasound diagnosis of peripheral neuropathy and to avoid damage to the nerves caused by overheating in pain management applications. A rat model of diabetic peripheral neuropathy was established. The proximal-segment and middle-segment sciatic nerves of control and neuropathic rats were dissected for the attenuation measurement. Two commercial ultrasound transducers and a self-developed experimental platform were used in the measurements. Using H&E staining and transmission electron (TE) microscopy, morphological analysis of the control and neuropathic nerves was performed to determine the relationship between attenuation and the histology of the nerves. The experimental results showed that the attenuation coefficients of the control, second-week, fourth-week, and eighth-week neuropathic nerves were -6.68 ± 0.50, -5.61 ± 0.34, -6.27 ± 0.40, and -7.10 ± 0.35 dB/cm at 2.68 MHz, respectively. The respective values at 7.50 MHz were -14.96 ± 0.79, -12.65 ± 0.28, -13.98 ± 1.07, and -16.00 ± 0.54 dB/cm. The changes in the attenuation coefficients were significantly different among the second-week, fourth-week, and eighth-week DN nerves. Additionally, the ultrasonic attenuation coefficient of the rat sciatic nerve was fourfold that of the cat brain and cow liver and twofold that of human muscle.

Ultrasound findings after surgical decompression of the tarsal tunnel in patients with painful diabetic polyneuropathy: a prospective randomized study

OBJECTIVE

It has been hypothesized that the development of diabetic polyneuropathy (DPN) is due to swelling of the nerve, as well as thickening and stiffening of the surrounding ligaments, causing chronic compression of nerves. We aimed to examine the effect of surgical decompression of the tibial nerve on the mean cross-sectional area (CSA).

RESEARCH DESIGN AND METHODS

We performed a randomized controlled trial of 42 subjects with painful DPN diagnosed using the Diabetic Neuropathy Score. A computer randomized for the surgery arm of the study. A control group consisting of 38 healthy subjects was included. An experienced sonographer measured the CSA and thickness-to-width (T/W) ratio of the tibial nerve, as well as the thickness of the flexor retinaculum.

RESULTS

CSA is significantly larger in patients with painful DPN (8.4 ± 3.9 mm(2)) than in control subjects (6.4 ± 1.3 mm(2)), P = 0.007. The T/W ratio in patients with painful DPN is 0.64 and in control subjects 0.59, P = 0.03. Patients with DPN have a significantly thicker retinaculum (1.07 mm) than control subjects (0.84 mm), P < 0.001. Mean follow-up was 28.2 weeks (range 23-45). Difference between baseline and follow-up in the operated leg was 1.49 mm(2) and in the control leg 1.81 mm(2), P = 0.674.

CONCLUSIONS

Decompression of the tibial nerve does not result in a significant difference between baseline and follow-up in CSA using ultrasound between the operated and control leg. Ultrasound measurements show a significantly increased CSA, a significantly thicker retinaculum, and a significantly increased T/W ratio in patients with painful DPN compared with healthy control subjects. Clinical trial reg. no. NTR2344, www.trialregister.nl.

Imaging of temperature dependent hemodynamics in the rat sciatic nerve by functional photoacoustic microscopy

Background

Vascular hemodynamics is central to the regulation of neuro-metabolism and plays important roles in peripheral nerves diseases and their prevention. However, at present there are only a few techniques capable of directly measuring peripheral nerve vascular hemodynamics.

Method

Here, we investigate the use of dark-field functional photoacoustic microscopy (fPAM) for intrinsic visualizing of the relative hemodynamics of the rat sciatic nerve in response to localized temperature modulation (i.e., cooling and rewarming).

Results and conclusion

Our main results show that the relative functional total hemoglobin concentration (HbT) is more significantly correlated with localized temperature changes than the hemoglobin oxygen saturation (SO₂) changes in the sciatic nerve. Our study also indicates that the relative HbT changes are better markers of neuronal activation than SO₂ during nerve temperature changes. Our results show that fPAM is a promising candidate for in vivo imaging of peripheral nerve hemodynamics without the use of contrast agents. Additionally, this technique may shed light on the neuroprotective effect of hypothermia on peripheral nerves by visualizing their intrinsic hemodynamics.

Ultrasound assessment of sural nerve in Charcot-Marie-Tooth 1A neuropathy

OBJECTIVE

Nerve ultrasound (US) has been used to study peripheral nerve disease, and increase of the cross-sectional area (CSA) has been described in demyelinating polyneuropathy. The objective of the current study is to characterise the US features of the sural nerve in a sample of Charcot-Marie-Tooth (CMT) 1A patients.

METHODS

A total of 20 CMT1A patients were enrolled. As control group we studied 37 age- and sex-matched subjects. All patients underwent clinical examination, neurophysiology and US evaluation of the bilateral sural nerve and right ulnar nerve. US results were correlated with neurophysiology and clinical data.

RESULTS

Sural nerve CSA was not increased in the majority of patients (70%), whereas an increased ulnar nerve CSA was present in the whole sample. Inverse relations were found between CSA of the ulnar nerve and body mass index (BMI) (p<0.0002, R=-0.8) and CSA of the sural nerve and age (right 0.006, R=-0.6, left 0.002, R=-0.6 and left and right p=0.00003, R=-0.4).

CONCLUSIONS

US showed ulnar CSA enlargement and normal sural nerve CSA.

SIGNIFICANCE

The significance of normal sural nerve CSA in CMT1A patients need to be further investigated, possibly through longitudinal studies.

Ultrasound in diagnosis of retroperitoneal femoral nerve injury: a case report

We present a case of retroperitoneal femoral nerve injury after cut wounds at the lower abdomen. Electrodiagnostic tests revealed impaired function of nerve and muscles. A mass was observed at the retroperitoneal part of the femoral nerve by ultrasound, indicating that a traumatic neuroma composed of disordered fascicles was configurated after the injury. Postoperative pathology confirmed hypertrophic and hyperplastic nerve bundles of the mass. Great improvements were shown in the patient's symptoms and electrodiagnostic tests in the subsequent 3 months. This case presented a rare position of neuroma formation by ultrasound.