Cross-sectional area reference values for nerve ultrasonography

Ultrasound allows for a non-invasive structural assessment of nerves, muscles, and surrounding tissues, and therefore it is increasingly being used as a supplement to traditional electrodiagnostic studies. As investigators have begun to use ultrasound to explore peripheral nerves, it has become clear that conditions such as entrapment, hereditary neuropathies, acquired neuropathies, trauma, and nerve tumors result in an increase in nerve cross-sectional area. Reference values have not been published for the cross-sectional area of many nerves commonly studied in diseases of the peripheral nervous system, so our goal was to obtain reference values for the nerve cross-sectional area at the following sites: radial at antecubital fossa; radial at distal spiral groove; musculocutaneous in upper arm; trunks of the brachial plexus; vagus at carotid bifurcation; sciatic in distal thigh; tibial in popliteal fossa; tibial in proximal calf; tibial at ankle; peroneal in popliteal fossa; peroneal at fibular head; and sural in distal calf. Mean cross-sectional area, as well as side-to-side differences, are reported for each site, and qualitative data are provided to guide imaging at each site. The information provided in this study should serve as the starting point for quantitatively evaluating these nerve sites with ultrasound.     

Nerve ultrasound reference data in children from two to seven years

ObjectiveWe examined selected peripheral and spinal nerves of children aged between two and seven years.MethodHigh resolution ultrasound was performed in 116 children (2–7 years of age) at 19 predefined landmarks of median, ulnar, tibial, fibular, sural and radial nerves, the vagus as well as cervical spinal nerve 5 and 6. Further, side-to-side measuring and grey-scale analysis was done at selected nerve sites.ResultsNerves of children were on average smaller than those of adults. Nerve growth correlates significantly with age in all nerves, the mean values were similar in the age of two to four years and five to seven years. Body mass index (BMI) and gender showed moderate effect at some nerve sites, however not uniformly in all. A side-to-side difference of up to 30% in median, and up to 20% in tibial nerve can occur in healthy individuals. Grey-scale analysis for echointensity has been performed in median, ulnar and tibial nerves.ConclusionNerve size increases with age, BMI and gender have moderate effect. A side-to-side-difference of up to 30% can exist.SignificanceReference values of nerve cross-sectional area, side-to-side-difference and echo intensity are necessary to detect nerve pathology in children as well as in adults.     

Nerve,muscle, and neuromuscular junction electrophysiology at high temperature

Although the effect of low temperature on the peripheral nervous system has been systematically studied, the effect of high temperature has not. We investigated the effect of elevating limb temperature from 32°C to 42°C by performing sequential motor studies, antidromic sensory studies, and 3-Hz repetitive stimulation in normal subjects. In addition, we recorded single motor units by using threshold stimulation. On average, motor amplitude and duration decreased by 27% and 19%, respectively, whereas sensory amplitude and duration decreased by 50% and 26%, respectively. Neuromuscular transmission remained normal at 42°C. Single motor unit recordings revealed a reduction in amplitude of 26%, similar to the overall reduction in compound motor amplitude. These findings demonstrate that significant reductions in sensory and motor amplitudes can occur in normal nerves at high temperature; we hypothesize that these changes are secondary to alterations in nerve and muscle ion channel function. © 1997 John Wiley & Sons, Inc. Muscle Nerve, 20, 431–436, 1997     

Reference values for ultrasonograpy of peripheral nerves

Introduction: High‐resolution ultrasonography (HRU) is a novel method that provides morphological information about peripheral nerves. We aimed to determine reference values for nerve cross‐sectional area (CSA) on HRU. Methods: One hundred healthy volunteers had HRU of median, radial, ulnar, fibular, tibial, sural, and superficial fibular nerves at defined sites. The CSA was measured and the effects of age, gender, and body mass index (BMI) were evaluated. Results: CSA values in healthy subjects are described. CSA is larger in lower limb motor nerves than in sensory nerves at similar sites, and the CSA tends to be symmetrical. The strongest effect on CSA was for age, although gender and BMI had some effects. Conclusions: This study provides normative values for HRU, and it suggests that further research with age‐ and gender‐specific distributions must be a key priority in the development of HRU for use as a diagnostic test for peripheral nerve diseases. Muscle Nerve 53 : 538–544, 2016     

Lower touch sensibility in the extremities of healthy Indians: further deterioration with age

Abstract   Touch sensibility testing is a cost-effective, psychophysical measure of peripheral nerve function and impairment. However, there is limited information regarding the natural variability in touch sensibility across different populations and different age groups. We studied 568 healthy Indian volunteers without any clinical evidence of peripheral nerve disease. Touch sensibility was evaluated bilaterally in palms, feet, and heels, using Semmes-Weinstein monofilaments, with target forces ranging from 0.008 to 300 g. No differences were observed between the right and the left limbs. The lowest target force detected ranged from 0.4 to 2 g in the palms and 1.4 to 15 g in the feet. These values showed further increase with age. Women compared with men had higher sensibility in the palms in most age groups. Touch sensibility thresholds recorded in a large group of Indians were higher than that reported in other populations. These findings have clinical implications for the diagnosis of early nerve impairment in the elderly and in disease states drawing attention to geographic variations in touch sensation.     

Nerve conduits and growth factor delivery in peripheral nerve repair

Peripheral nerves possess the capacity of self-regeneration after traumatic injury. Transected peripheral nerves can be bridged by direct surgical coaptation of the two nerve stumps or by interposing autografts or biological (veins) or synthetic nerve conduits (NC). NC are tubular structures that guide the regenerating axons to the distal nerve stump. Early synthetic NC have primarily been made of silicone because of the relative flexibility and biocompatibility of this material and because medical-grade silicone tubes were readily available in various dimensions. Nowadays, NC are preferably made of biodegradable materials such as collagen, aliphatic polyesters, or polyurethanes. Although NC assist in guiding regenerating nerves, satisfactory functional restoration of severed nerves may further require exogenous growth factors. Therefore, authors have proposed NC with integrated delivery systems for growth factors or growth factor-producing cells. This article reviews the most important designs of NC with integrated delivery systems for localized release of growth factors. The various systems discussed comprise NC with growth factors being released from various types of matrices, from transplanted cells (Schwann cells or mesenchymal stem cells), or through genetic modification of cells naturally present at the site of injured tissue. Acellular delivery systems for growth factors include the NC wall itself, biodegradable microspheres seeded onto the internal surface of the NC wall, or matrices that are filled into the lumen of the NC and immobilize the growth factors through physical-chemical interactions or specific ligand-receptor interactions. A very promising and elegant system appears to be longitudinally aligned fibers inserted in the lumen of a NC that deliver the growth factors and provide additional guidance for Schwann cells and axons. This review also attempts to appreciate the most promising approaches and emphasize the importance of growth factor delivery kinetics.     

Reliability of side‐to‐side ultrasound cross‐sectional area measurements of lower extremity nerves in healthy subjects

Introduction: In peripheral nerve ultrasound, the healthy contralateral side may be used as internal control. Therefore, inherent side‐to‐side differences must be minimal. The goal of this study was to assess intrastudy, intraobserver, and interobserver reproducibility of ultrasound in comparative side‐to‐side evaluation of lower limb nerves. Methods: Lower limb nerves of 60 normal subjects were evaluated by 3 radiologists. Bilateral sciatic, tibial, common fibular, sural, lateral femoral cutaneous, femoral, obturator, and saphenous nerves were evaluated. Results: Overall, side‐to‐side differences were not statistically significant at any level. In the lower limb nerves, in a between‐limb comparison, the minimum detectable difference of cross‐sectional area ranged from 16.4 mm² (sciatic nerve at the level of piriformis muscle) to 0.4 mm² (saphenous nerve). Conclusion: In general, the healthy contralateral side can be used as an internal control. Muscle Nerve 46: 717–722, 2012     

Maximal isometric muscle strength values obtained By hand‐held dynamometry in children between 6 and 15 years of age

Introduction: In this study we aimed to determine the maximal isometric muscle strength of a healthy, normal‐weight, pediatric population between 6 and 15 years of age using hand‐held dynamometry to establish strength reference values. The secondary objective was determining the relationship between strength and anthropometric parameters. Methods: Four hundred normal‐weight Chilean children, split into 10 age groups, separated by 1‐year intervals, were evaluated. Each age group included between 35 and 55 children. Results: The strength values increased with increasing age and weight, with a correlation of 0.83 for age and 0.82 for weight. The results were similar to those reported in previous studies regarding the relationships among strength, age, and anthropometric parameters, but the reported strength differed. Conclusions: These results provide normal strength parameters for healthy and normal‐weight Chilean children between 6 and 15 years of age and highlight the relevance of ethnicity in defining reference values for muscle strength in a pediatric population. Muscle Nerve 55 : 16–22, 2017     

Morphological changes of the epineurium in leprosy: a new finding detected by high-resolution sonography

Introduction: From histopathological studies of peripheral nerves in leprosy, it is known that the epineurium can be thickened. We measured the epineurial thickness of the ulnar nerve by high resolution sonography (HRUS). Methods: The epineurium of the ulnar nerve was measured above the elbow on transverse scan in 25 healthy controls and 26 leprosy patients. Results: The mean epineurial thickness was 0.77 mm (95% confidence interval [CI] 0.66–0.88) in symptomatic ulnar nerves (n = 20), 0.58 mm (CI 0.51–0.65) in asymptomatic nerves (n = 30), and 0.49 mm (CI 0.44–0.54) in healthy controls (n = 25) (P = 0.0001). This thickening was related to the cross‐sectional area of the ulnar nerve, but not with increased blood flow. Conclusions: The epineurium of the ulnar nerve can be measured with the use of HRUS, and it is often strikingly thickened in leprosy patients, especially in those with ulnar involvement. Muscle Nerve 46:38–41, 2012     

The median to ulnar cross-sectional surface area ratio in carpal tunnel syndrome

Objective

To investigate the use of a sonographic median-to-ulnar cross-sectional area ratio (MUR) in diagnosis of carpal tunnel syndrome (CTS); and to compare the MUR with currently used sonographic parameters, and electrophysiology.

Ultrasound of peripheral nerves in neuralgic amyotrophy

Introduction: Neuralgic amyotrophy (NA) can often be difficult to diagnose. Nerve ultrasound (US) is potentially useful, but it is operator-dependent, especially for small nerves. Methods: Fifty-one consecutive patients with NA (mean duration 16 months) and 50 control subjects underwent US of the brachial plexus and major nerves of the upper extremity at predefined sites. We compared cross-sectional areas (CSAs) of affected and unaffected sides with controls and sides within patients. Results: The median nerve and radial nerve at the level of the upper arm were enlarged on the affected sides compared with controls and the unaffected sides of patients. Enlargement was most pronounced for affected sides vs. controls (median 44%, radial 67%). Discussion: NA patients showed increased CSAs, especially in the major nerves of the upper limb, even after longer disease duration. This could make US a useful adjunct in diagnosing NA. Muscle Nerve 59 :55–59, 2019