Ultrasonographic cross‐sectional area normal values of the ulnar nerve along its course in the arm with electrophysiological correlations in 100 asian subjects

Introduction: Normative cross‐sectional areas (CSAs) have been obtained for the Western population. We obtained CSAs of normal ulnar nerves at predetermined sites and correlate them with electrophysiological variables in Asian subjects. Methods: One hundred healthy volunteers, mean age 39 ± 14 years (range, 18–75 years), were recruited for the study after obtaining informed consent. The ulnar nerve was examined ultrasonographically from wrist to axilla, and CSA was measured at predetermined sites. All subjects underwent a simultaneous standardized nerve conduction study. Results: Men had larger CSAs, and CSAs increased with advancing age. There was a statistically significant correlation between CSA at the wrist and distal ulnar motor latency (P = 0.005). Conclusions: Ulnar CSA correlated with age, gender, and distal motor latency. No correlations were observed with height, weight, or body mass index. Muscle Nerve 47: 673–676, 2013     

The effect of magnification on sonographically measured nerve cross‐sectional area

Introduction: The primary aim of this investigation was to determine whether use of write‐zoom magnification affects sonographically determined cross‐sectional area (CSA) of peripheral nerves. Methods: CSAs of the median (MN) and posterior interosseous (PIN) nerves were measured in 22 limbs from 11 asymptomatic volunteers using both standard imaging and write‐zoom magnification. CSA measurements were repeated on the same images 1 week later. Results: The average CSA of write‐zoomed images for the MN was significantly larger at both measurement sessions (week 1: 11.1 mm² write‐zoom vs. 10.0 mm² standard, P = 0.019; week 2: 11.8 mm² vs. 10.4 mm², P = 0.023). Similar differences were noted for the PIN (week 1: 2.3 mm² vs. 1.9 mm², P = 0.002; week 2: 2.5 mm² vs. 1.9 mm², P = 0.001). Conclusions: Write‐zoom magnification may significantly increase the measured CSA of peripheral nerves. These changes appear to be more substantial when smaller nerves are measured. Muscle Nerve 51 : 30–34, 2015     

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     

Multifocal motor neuropathy: correlation of nerve ultrasound,electrophysiological, and clinical findings

We present nerve ultrasound findings in multifocal motor neuropathy (MMN) and examine their correlation with electrophysiology and functional disability. Eighty healthy controls and 12 MMN patients underwent clinical, sonographic, and electrophysiological evaluation a mean of 3.5 years (standard deviation [SD] ± 2.1) after disease onset. Nerve ultrasound revealed significantly higher cross‐sectional area (CSA) values of the median (forearm, p < 0.001), ulnar (p < 0.001), and tibial nerve (ankle, p < 0.001) when compared with controls. Electroneurography documented signs of significantly lower values of the motor conduction velocity and compound muscle action potentials (cMAPs) in the upper arm nerves (median, ulnar, radial, p < 0.001). A significant correlation between sonographic and electrophysiological findings in the MMN group was found only between cMAP and CSA of the median nerve at the upper arm (r = 0.851, p < 0.001). Neither nerve sonography nor electrophysiology correlated with functional disability. MMN seems to show inhomogeneous CSA enlargement in various peripheral nerves, with weak correlation to electrophysiological findings. Neither nerve sonography nor electrophysiology correlated with functional disability. Multicentre, prospective studies are required to prove the applicability and diagnostic values of these findings.     

Measurement of cross‐sectional area of cervical roots and brachial plexus trunks

Introduction: The aim of this study was to determine normal reference values for cross‐sectional area (CSA) and the correlation between demographic factors and CSA in the cervical roots and brachial plexus trunks using ultrasonography. Methods: Ninety‐five age‐matched healthy individuals were studied. Ultrasonographic tests were performed via nerve tracing from the cervical root to the brachial plexus trunk. The CSA of each nerve was measured in the C5–8 ventral roots and brachial plexus (trunk level). Results: Normal values of each cervical root were: C5, 5.66 ± 1.02 mm²; C6, 8.98 ± 1.65 mm²; C7, 10.43 ± 1.86 mm²; and C8, 10.76 ± 2.02 mm². Values for the brachial plexus were: upper trunk, 16.70 ± 2.88 mm²; middle trunk, 14.01 ± 2.70 mm²; and lower trunk, 13.75 ± 2.57 mm². The side‐to‐side discrepancy was 11.91 ± 11.11%. Body mass index (BMI) and height correlated frequently with nerve CSA. Conclusions: These reference values may be helpful in investigating pathologies involving the cervical area. Muscle Nerve 46: 711–716, 2012     

Median nerve ultrasound as a screening tool in carpal tunnel syndrome: Correlation of cross‐sectional area measures with electrodiagnostic abnormality

Introduction: Sonographically measured median nerve cross‐sectional area (CSA) at the wrist is increased in patients with carpal tunnel syndrome (CTS). Ultrasound of the median nerve may be useful in screening for electrodiagnostic (EDx) abnormalities. Methods: EDx studies were performed on all participants. Sonographic evaluation of median nerve CSA at the wrist and in the forearm was performed by a physician blinded to the EDx results. Multivariate and receiver operating characteristic (ROC) analysis were used to assess the data. Results: Fifty control wrists and 192 symptomatic wrists were analyzed. Sensitivity of ultrasound in excluding EDx abnormality was 99% for CSA of 9 mm² and 97% for a wrist–forearm ratio (WFR) of 1.4. There was no clinically significant correlation between ultrasound parameters and EDx severity. Conclusions: Median nerve ultrasound is a highly sensitive screening tool for EDx abnormality, but it cannot determine severity. This may lead to changes in the current standards for evaluating CTS. Muscle Nerve, 2012     

Ultrasonographic measurement of median nerve cross-sectional area in idiopathic carpal tunnel syndrome: Diagnostic accuracy

Severity-correlated enlargement of the median nerve occurs in idiopathic carpal tunnel syndrome (CTS). We determined whether measurement of the nerve cross-sectional area was useful in making the diagnosis of CTS. In 414 wrists of 275 patients with clinically diagnosed idiopathic CTS and 408 wrists of 408 controls, we made ultrasonographic measurements of the nerve area at the distal (distal edge of the flexor retinaculum), mid (hook of the hamate), and proximal carpal tunnel (wrist crease). Criteria based on the area at a single level yielded sensitivities of 43-57% and specificities of 96-97%. Use of the mean carpal nerve area (average of the areas at the three levels) improved the results (sensitivity, 67%; specificity, 97%), which was as sensitive as the nerve conduction studies (NCS). In the NCS, we obtained sensitivities of 66% for the distal motor nerve latency and 67% for the distal sensory nerve latency, with specificities of 97% for each. A combination of the mean carpal nerve area and NCS criteria yielded a sensitivity of 84% and a specificity of 94%. The clinical implications of these findings for the diagnosis of CTS are discussed.     

Posture‐induced changes in peripheral nerve stiffness measured by ultrasound shear‐wave elastography

Introduction: Peripheral nerves slide and stretch during limb movements. Changes in nerve stiffness associated with such movements have not been examined in detail but may be important in understanding movement‐evoked pain in patients with a variety of different musculoskeletal conditions. Methods: Shear‐wave elastography was used to examine stiffness in the median and tibial nerves of healthy individuals during postures used clinically to stretch these nerves. Results: Shear‐wave velocity increased when limbs were moved into postures that are thought to increase nerve stiffness (mean increase: median nerve = 208% in arm, 236% in forearm; tibial nerve = 136%). There was a trend toward a negative correlation between age and shear‐wave velocity (r = 0.58 for tibial nerve). Conclusions: Shear‐wave elastography provides a tool for examining nerve biomechanics in healthy individuals and patients. However, limb position, age, and effects of nerve tension on neural architecture should be taken into consideration. Muscle Nerve 55 : 213–222, 2017     

Physiological cross‐sectional area of the oblique head of the adductor pollicis is greater than its transverse counterpart: Implications for functional testing

Introduction: Despite structural distinction between the transverse and oblique heads of the adductor pollicis, in vivo testing continues to consider the adductor pollicis as functionally simplistic. As a muscle's architecture is a strong indicator of function, in this study we aimed to determine whether the physiological cross‐sectional areas (PCSAs) of both heads were uniform. Methods: Classical, microdissection, and chemical dissection procedures were conducted on 10 cadaveric left hands to determine structural origin and insertions. Architectural measures of muscle length (L_m), muscle weight (W_m), fascicle length (L_f), sarcomere length (L_s), and pennation angle (θ) were used to calculate PCSA and fascicle length:muscle length ratio (L_f:L_m). Results: The oblique head had greater variation in attachments, significantly greater PCSA (P = 0.008), and smaller L_f:L_m (P = 0.001) than its transverse counterpart. Conclusions: Muscle architecture suggests the oblique head has greater potential for force generation, and the transverse has greater potential for joint excursion. Muscle Nerve 49 :405–412, 2014     

Correlation of nerve ultrasound,electrophysiological, and clinical findings in post Guillain‐Barré syndrome

We aimed to correlate functional disability, electrophysiology, and nerve ultrasound in patients after Guillain‐Barré syndrome (GBS). Seventy‐five healthy controls and 41 post‐GBS patients (mean 3.4 years, SD ± 2.91 years after onset) underwent clinical, sonographic, and electrophysiological evaluation. Compared to healthy controls, the post‐GBS patients showed: (1) a mean Rasch‐built Overall Disability Scale score of 31.8 (SD ± 11.6), modified Rasch‐built fatigue severity scale score of 15.6 (SD ± 3.2), Medical Research Council sum score of 22 (SD ± 5.6); (2) electrophysiological signs of permanent axonal loss in the majority of the peripheral nerves; (3) sonographical evidence of higher cross‐sectional area values (CSA) of the ulnar (elbow, p < 0.001), radial (spiral groove, p < 0.001), tibial nerve (popliteal fossa, p < 0.001) and brachial plexus (supraclavicular space, p < 0.001). No correlation between sonographic and electrophysiological findings was found. Neither nerve ultrasound nor electrophysiology correlated with muscle strength, overall disability, and fatigue scale. Compared to healthy controls, post‐GBS patients had significant functional disability. Despite significant abnormalities in both electrophysiology and ultrasound compared to healthy controls, neither electrophysiology nor nerve ultrasound correlated with functional disability of these patients.     

Platelet‐rich plasma limits the nerve injury caused by 10% dextrose in the rabbit median nerve

Introduction: We evaluated the effect of platelet‐rich plasma (PRP) injection in a rabbit model of dextrose‐induced median nerve injury. Methods: New Zealand white rabbits (n = 15) were divided randomly into 3 groups. Three different regimens (group 1: 0.1 ml saline; group 2: 10% dextrose with PRP; group 3: 10% dextrose with saline) were injected within the carpal tunnel. Electrophysiological and histological findings were evaluated 12 weeks after the injection. Results: The mean median motor latency in group 3 was significantly longer than that in groups 1 and 2. The cross‐sectional area of the median nerve and subsynovial connective tissue thickness in group 3 were significantly larger than those in groups 1 and 2. Conclusions: PRP injection may be effective in controlling median nerve injury, as demonstrated by improvement in electrophysiological and histological findings 12 weeks after dextrose injection. Muscle Nerve 49 : 56–60, 2014     

Direct current stimulation modulates the excitability of the sensory and motor fibres in the human posterior tibial nerve,with a long‐lasting effect on the H‐reflex

Several studies demonstrated that transcutaneous direct current stimulation (DCS) may modulate central nervous system excitability. However, much less is known about how DC affects peripheral nerve fibres. We investigated the action of DCS on motor and sensory fibres of the human posterior tibial nerve, with supplementary analysis in acute experiments on rats. In forty human subjects, electric pulses at the popliteal fossa were used to elicit either M‐waves or H‐reflexes in the Soleus, before (15 min), during (10 min) and after (30 min) DCS. Cathodal or anodal current (2 mA) was applied to the same nerve. Cathodal DCS significantly increased the H‐reflex amplitude; the post‐polarization effect lasted up to ~ 25 min after the termination of DCS. Anodal DCS instead significantly decreased the reflex amplitude for up to ~ 5 min after DCS end. DCS effects on M‐wave showed the same polarity dependence but with considerably shorter after‐effects, which never exceeded 5 min. DCS changed the excitability of both motor and sensory fibres. These effects and especially the long‐lasting modulation of the H‐reflex suggest a possible rehabilitative application of DCS that could be applied either to compensate an altered peripheral excitability or to modulate the afferent transmission to spinal and supraspinal structures. In animal experiments, DCS was applied, under anaesthesia, to either the exposed peroneus nerve or its Dorsal Root, and its effects closely resembled those found in human subjects. They validate therefore the use of the animal models for future investigations on the DCS mechanisms.