F‐wave latencies in patients with diabetes mellitus

Introduction: To evaluate the sensitivity of electrophysiologic assessments, we compared F‐waves and motor and sensory nerve conduction studies (MNCS and SNCS) in patients with diabetes mellitus (DM). Methods: We tested median, ulnar, tibial, and fibular nerves in 132 DM patients divided into those with and without clinical evidence of polyneuropathy. Results: Of 64 asymptomatic patients, 2 (3%) had MNCS or SNCS abnormalities, both of whom had F‐wave changes, whereas 21 (33%) had only delayed F‐waves, for a combined yield of 23 (36%). The corresponding values for 68 symptomatic patients consisted of 43 (63%), 14 (21%), and 57 (84%). In both groups, F‐wave latency had a higher (P < 0.05) frequency of abnormality than MNCS in all nerves. F‐wave study also surpassed SNCS in lower limb nerves. Conclusions: F‐waves of the tibial and fibular nerves are the most sensitive measure to detect subclinical or overt diabetic polyneuropathy. Muscle Nerve 49 : 804–808, 2014     

Ultrasound visualization of nerve remodeling after strenuous exercise

Introduction: The aim of this case study is to describe the use of nerve ultrasound to visualize the morphological changes that occur during conduction velocity alterations after strenuous exercise. Methods: A 32‐year‐old, healthy runner underwent clinical, electrophysiological, and ultrasound evaluation 24 hours before, 30 minutes after, and 24 hours after a marathon. Results: An increase in motor conduction velocity of the median, ulnar, radial, and tibial nerves and sensory conduction velocity of the median and ulnar nerves was found between pre‐ and post‐marathon studies. An increase in the cross‐sectional area of the median (carpal tunnel), ulnar (Guyon canal and elbow), fibular (fibular head), and tibial (ankle) nerves was documented. No changes in the MRC sum scale score of the various peripheral nerves were detected. Conclusion: The case described shows the morphological changes that occur in healthy peripheral nerves during conduction velocity alterations. Muscle Nerve 53: 320–324, 2016     

Muscle shear modulus measured with ultrasound shear‐wave elastography across a wide range of contraction intensity

Introduction: In this study we examine the repeatability of measuring muscle shear modulus using ultrasound shear‐wave elastography between trials and between days, and the association between shear modulus and contraction intensity over a wide range of intensities. Methods: Shear modulus of the biceps brachii was determined using ultrasound shear‐wave elastography during static elbow flexion (up to 60% of maximal contraction) in healthy young adults. Results: The correspondence of shear modulus was confirmed in phantoms between the manufacturer‐calibrated values and the shear‐wave elastography values. The intraclass correlation coefficient of muscle shear modulus was high: 0.978 between trials and 0.948 between days. Shear modulus increased linearly with elbow flexion torque across contraction intensity, and its slope was associated negatively with muscle strength. Conclusions: Muscle shear modulus measured with ultrasound shear‐wave elastography may be useful for inferring muscle stiffness across a wide range of contraction intensity. In addition, it has high repeatability between trials and between days. Muscle Nerve 50 : 103–113, 2014     

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     

Electrical somatosensory stimulation modulates hand motor function in healthy humans

In healthy people, electrical somatosensory stimulation modulates excitability in contralateral cortical motor areas. The question whether this is associated with a change in motor performance is still under debate. The effect of electrical somatosensory stimulation on motor performance of the hand was investigated in 14 healthy right-handed subjects. Subjects performed index finger and hand tapping movements as well as reach-to-grasp movements towards small and large cubes with each hand prior to (baseline condition) and following 2-hour electrical somatosensory stimulation (trains of 5 pulses at 10 Hz with 1 ms duration delivered at 1 Hz with an intensity on average 60 % above the individual somatosensory threshold) of the (i) right median nerve, (ii) left median nerve, (iii) right tibial nerve (control stimulation) and (iv) left tibial nerve (control stimulation) on separate occasions at least one week apart. The order of sessions was counterbalanced across subjects. Somatosensory stimulation of the median nerves, but not of the tibial nerves, reduced the frequency and velocity of index finger and hand tapping movements performed with the stimulated hand, compared to baseline. In contrast, the kinematics of reach-to-grasp movements remained unaffected by somatosensory stimulation. The data suggest that somatosensory stimulation interferes with the processing of highly automated open-loop motor output at the stimulated limb, as reflected by tapping movements, but not with the processing of closed-loop motor performance, as reflected by reach-to-grasp movements.     

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     

Peripheral nerve tractography in soft tissue tumors: A preliminary 3‐tesla diffusion tensor magnetic resonance imaging study

Introduction: This diffusion tensor magnetic resonance imaging (DTI) study aimed to clarify the relationship of peripheral nerves and soft tissue tumors (STTs) in 3D to optimize subsequent treatment. Methods: Twenty‐six consecutive STT patients (histologically malignant, n = 10; intermediate, n = 3; and benign, n = 13) underwent 3‐Tesla MRI using an echoplanar DTI sequence. Deterministic tractography was performed. Fractional anisotropy (FA) values were measured within peritumoral and distant regions of interest. Results: Tractography depicted the 3D course of the sciatic (n = 12), femoral (n = 2), tibial (n = 7), fibular (n = 2), median (n = 1), musculocutaneous (n = 1), and ulnar (n = 1) nerves in a regular (n = 8 of 18, 44.4%) or thinned (n = 7 of 18, 38.9%) fashion. The lowest peritumoral FA values, abrupt thinning, and/or complete discontinuity of trajectories were found in 2 cases with histologically proven tumoral nerve infiltration. Conclusions: DTI clarifies the 3D topography between major peripheral nerves and STTs and may be helpful in the assessment of peripheral nerve infiltration by malignant tumors. Muscle Nerve 51: 338–345, 2015     

Sonographic evaluation of the sciatic nerve in patients with lower‐limb amputations

Hypertrophy of the sciatic nerve after lower‐limb amputation in patients with sarcomas has been previously reported by magnetic resonance imaging; however, sonographic evaluation of the sciatic nerve after lower‐limb amputation due to nonmalignant causes has not been done before. Therefore, the aim of this study was to perform imaging of the sciatic nerve in lower‐limb amputees and to find out whether sonographic findings were related to clinical characteristics. Twenty‐three males with lower‐limb amputations due to traumatic injuries were enrolled. Sonographic evaluations were performed using a linear array probe (Aloka UST‐5524‐7.5 MHZ ). Sciatic nerve diameters were measured bilaterally at the same level, and the values of the normal limbs were taken as controls. Sciatic nerve width and thickness values were found to be greater on the amputated sides than the normal sides (P = 0.001). The thickness values were greater in above‐knee amputees than below‐knee amputees (P = 0.05). Subjects with a neuroma also had thicker sciatic nerves (P = 0.04). The diameters were found not to change between subjects with different liners (P > 0.05), but they were correlated with time after amputation (r = 0.6, P = 0.006; r = 0.4, P = 0.05, respectively). Our results clearly show that the sciatic nerves were wider and thicker on the amputated sides. Amputation level, duration, and the presence of a neuroma seem to affect the eventual diameters of the nerves. Muscle Nerve, 2010     

Diagnostic nerve ultrasound in Charcot–Marie–Tooth disease type 1B

Ultrasound is emerging as a useful tool for evaluation of neuromuscular conditions, because it can provide high‐resolution anatomic information to complement electrodiagnostic data. There have been few studies in which ultrasound was used to assess the peripheral nerves of individuals with Charcot–Marie–Tooth (CMT) disease and none involving CMT type 1B. In this study we compared nerve cross‐sectional area in individuals from a single large family with CMT 1B with normal, healthy controls. We also assessed for cranial nerve enlargement in those with CMT 1B with cranial neuropathies compared to those with CMT 1B without cranial neuropathies. Individuals with CMT 1B have significantly larger median and vagus nerves than healthy controls, but no difference was seen in cranial nerve size between those with versus those without cranial neuropathies. This is the first study to characterize the ultrasonographic findings in the peripheral nerves of individuals with CMT 1B. Muscle Nerve 40: 98–102, 2009     

Evaluation Of freehand high‐resolution 3‐dimensional ultrasound of the median nerve

Introduction: In this study we evaluated freehand 3D ultrasound (3DUS) of the median nerve in comparison to 2D ultrasound (2DUS) and assessed the influence of tilting the transversal plane on cross‐sectional area (CSA) measurement. Methods: Two examiners investigated the median nerves of 22 healthy subjects over a distance of 20 cm using 3DUS. Image quality and CSA were assessed at random points within the virtual 3D volume and compared with 2DUS. Results: Image quality within the virtual 3D volume was good/sufficient/poor in 53.0%/40.2%/6.8% (examiner 1) and 21.6%/69.6%/8.8% (examiner 2), respectively. CSA measurements with 3DUS were smaller than with 2DUS (–12% and –17%; Wilcoxon test, P < 0.001). Interrater agreement for 3DUS and intermethod agreement between 2DUS and 3DUS were moderate. Stepwise tilting of the transversal plane increased CSA significantly. Conclusion: Freehand 3DUS of the median nerve over 20 cm is feasible and may help overcome some of the limitations and pitfalls of 2DUS. Muscle Nerve 55 : 206–212, 2017     

F-wave latency,the most sensitive nerve conduction parameter in patients with diabetes mellitus

In this study we examined the diagnostic sensitivity of minimal F-wave latency, F-wave persistence, motor nerve conduction velocity (MCV), and amplitude of the compound motor action potential (CMAP) of the median, ulnar, tibial, and peroneal nerves, and of sensory conduction velocity (SCV) and sensory nerve action potential (SNAP) amplitude of the sural nerve in 82 diabetic patients. For the median, ulnar, and tibial nerves the Z scores of the minimal F-wave latency were significantly larger than those of the MCV, and for all four motor nerves the Z scores of the minimal F-wave latency were significantly larger than those of the amplitude of the CMAP. The Z scores of the peroneal minimal F-wave latency exceeded those of peroneal MCV, sural SCV, and sural SNAP. F-wave persistence did not differ significantly from the reference values. In conclusion, minimal F-wave latency is the most sensitive measure for detection of nerve pathology and should be considered in electrophysiological studies of diabetic patients. © 1997 John Wiley & Sons, Inc. Muscle Nerve 20: 1296–1302, 1997     

Between‐day reliability of the trapezius muscle H‐reflex and M‐wave

Introduction: The aim of this study was to investigate the between‐day reliability of the trapezius muscle H‐reflex and M‐wave. Methods: Sixteen healthy subjects were studied on 2 consecutive days. Trapezius muscle H‐reflexes were evoked by electrical stimulation of the C3/4 cervical nerves; M‐waves were evoked by electrical stimulation of the accessory nerve. Relative reliability was estimated by intraclass correlation coefficients (ICC_2,1). Absolute reliability was estimated by computing the standard error of measurement (SEM) and the smallest real difference (SRD). Bland–Altman plots were constructed to detect any systematic bias. Results: Variables showed substantial to excellent relative reliability (ICC = 0.70–0.99). The relative SEM ranged from 1.4% to 34.8%; relative SRD ranged from 3.8% to 96.5%. No systematic bias was present in the data. Conclusions: The amplitude and latency of the trapezius muscle H‐reflex and M‐wave in healthy young subjects can be measured reliably across days. Muscle Nerve 52 : 1066–1071, 2015     

Utility of minimum F‐wave latencies compared with F‐estimates and absolute reference values in S1 radiculopathies: Are they still needed?

Introduction: The utility of F‐waves in assessing radiculopathies is debated. The aim of this study is to determine the frequency of abnormal minimum tibial F‐wave latencies compared to an F‐estimate and an absolute reference value in patients with electromyography (EMG) confirmed S1 radiculopathies. Methods: A retrospective review of F‐waves in patients with an EMG‐confirmed isolated S1 radiculopathy was performed. The minimum and mean latencies of 8 tibial F‐waves were compared with the calculated F‐estimate and to an absolute reference value, and the frequencies of abnormal responses were determined. Results: Of the 50 patients with an S1 radiculopathy, 4% had prolongation of the minimum reproducible F‐wave latency, and 8% had prolongation of the mean latency relative to the calculated F‐estimate. Conclusions: The minimum and mean F‐wave latencies are infrequently abnormal when compared with an estimated F‐wave latency in S1 radiculopathies and are insensitive in the assessment of S1 nerve root injury. Muscle Nerve 49 : 809–813, 2014     

Nerve ultrasound reliability of upper limbs: Effects of examiner training

Introduction: Duration of training to reliably measure nerve cross‐sectional area with ultrasound is unknown. Methods: A retrospective review was performed of ultrasound data, acquired and recorded by 2 examiners—an expert and either a trainee with 2 months (novice) or a trainee with 12 months (experienced) of experience. Data on median, ulnar, and radial nerves were reviewed for 42 patients. Results: Interrater reliability was good and varied most with nerve site but little with experience. Coefficient of variation (CoV) range was 9.33%–22.5%. Intraclass correlation coefficient (ICC) was good to excellent (0.65–95) except ulnar nerve‐wrist/forearm and radial nerve‐humerus (ICC = 0.39–0.59). Interrater differences did not vary with nerve size or body mass index. Expert–novice and expert–experienced interrater differences and CoV were similar. The ulnar nerve‐wrist expert–novice interrater difference decreased with time (r_s = ?0.68, P = 0.001). Discussion: A trainee with at least 2 months of experience can reliably measure upper limb nerves. Reliability varies by nerve and location and slightly improves with time. Muscle Nerve 57 : 189–192, 2018     

Sonographic features in hereditary neuropathy with liability to pressure palsies

Introduction: Diagnostic nerve ultrasound is becoming more commonly used by both radiologists and clinicians. The features of different neuromuscular conditions must be described to broaden our understanding and ability to interpret findings. Methods: Our study examines the sonographic features of 7 subjects with hereditary neuropathy with liability to pressure palsies (HNPP) in comparison to 32 controls by measuring the nerve cross‐sectional area (CSA) of the median, ulnar and tibial nerves. Results: Significant differences (P < 0.05) in nerve size were found. The HNPP group had a larger CSA for the median nerve at the wrist and ulnar nerve at the elbow (entrapment sites), but not the forearms. The tibial nerve at the ankle was also larger in the HNPP group, suggesting possible concomitant tibial neuropathy at the ankle. Conclusion: These results will help shape imaging protocols to better detect conditions with non‐uniform nerve enlargements. Muscle Nerve 2011     

Bifid median nerve in carpal tunnel syndrome: Do we need to know?

Introduction: We tested the hypothesis that a bifid median nerve predisposes to development of carpal tunnel syndrome (CTS) and investigated differences in electrophysiological findings and outcome. Methods: A total of 259 consecutive patients with clinically defined CTS were included and investigated clinically, electrophysiologically, and ultrasonographically. Fifty‐four healthy asymptomatic volunteers were investigated ultrasonographically. Results: The prevalence of bifid median nerves is equal in patients with CTS and controls. Electrophysiological and ultrasonographic abnormalities are more pronounced in patients with non‐bifid median nerves. Some outcome data are better in patients with non‐bifid median nerves, but others do not show significant differences. Conclusions: A bifid median nerve is not an independent risk factor for development of CTS. Some of our data suggest outcome after surgical decompression to be different, but others do not. The surgical technique in these patients may therefore have to be reevaluated. Muscle Nerve 50 : 835–843, 2014     

Assessment of muscle stiffness using a continuously scanning laser‐Doppler vibrometer

Introduction: A stand‐alone and low‐cost elastography technique has been developed using a single continuously scanning laser Doppler vibrometer. Methods: This elastography technique is used to measure the propagation velocity of surface vibrations over superficial skeletal muscles to assess muscle stiffness. Results: Systematic variations in propagation velocity depending on the contraction level and joint position of the biceps brachii were demonstrated in 10 subjects. Conclusions: This technique may assist clinicians in characterizing muscle stiffness (or tone) changes due to neuromuscular disorders. Muscle Nerve 50 : 133–135, 2014     

Nerve conduction studies in spastic paraplegia,optic atrophy,and neuropathy (SPOAN) syndrome

Introduction: SPOAN (spastic paraplegia, optic atrophy, and neuropathy) syndrome is an autosomal recessive neurodegenerative disorder identified in a large consanguineous Brazilian family. Methods: Twenty‐seven patients with SPOAN syndrome (20 women), aged 4–58 years, underwent nerve conduction studies (NCS) of the median, ulnar, tibial, and fibular nerves, and sensory NCS of the median, ulnar, radial, sural, and superficial fibular nerves. Results: Sensory nerve action potentials were absent in the lower limbs and absent in >80% of upper limbs. Motor NCS had reduced amplitudes and borderline velocities in the upper limbs and absent compound muscle action potentials (CMAPs) in the lower limbs. Conclusions: The neuropathy in SPOAN syndrome is a severe, early‐onset sensory–motor axonal polyneuropathy. Normal NCS seem to rule‐out this condition. Muscle Nerve 49 : 131–133, 2014     

Role of sodium channels in recovery of sciatic nerve‐stretch injury in rats

Introduction: To elucidate the mechanism of functional recovery after gradual nerve‐stretch injury, we used rats in which the femur length was increased by 15 mm at 1.5 mm/day. Methods: We performed electrophysiology, mRNA analysis of tetrodotoxin‐resistant voltage‐gated sodium channels (TTX‐R VGSCs) in dorsal root ganglia, and histology of unmyelinated sciatic nerve fibers and examined pain thresholds at 1, 10, 20, and 30 days after cessation of lengthening. Results: Electrophysiology revealed conduction block after cessation that recovered after 30 days. TTX‐R VGSC levels decreased immediately after cessation but were restored after 10 (Nav1.9) or 20 (Nav1.8) days. Histology revealed that injured unmyelinated nerve fibers regenerate 30 days after cessation. Pain threshold decreased gradually during lengthening but had not recovered to the control group level after 30 days. Conclusions: Early restoration of TTX‐R VGSC mRNA in dorsal root ganglia preceded functional recovery of stretched nerves before regeneration of injured unmyelinated nerve fibers. Muscle Nerve 50 : 425–430, 2014     

Use of collision tests to identify physiological differences between the median and ulnar nerves

Introduction: Median and ulnar nerves are used in comparative electrophysiological studies. We analyzed the conduction values in these hand nerves in healthy volunteers to find any physiological differences between them. Methods: We performed standard conduction studies and conduction velocity distribution (CVD) tests with estimation of 3 quartiles in 31 healthy right-handed volunteers (17 women, 14 men) with a mean age of 44.8 ± 15.5 years. Results: The conduction velocities in all quartiles of CVD tests were statistically faster in the ulnar nerve (P < 0.00001), with no differences in the spread of conduction values and no differences between sides. In the ulnar nerve, CVD velocities in all quartiles were faster in the female group (P < 0.05). Discussion: The ulnar nerve has more fibers conducting with high velocities than does the median nerve. Electrophysiological comparisons between hand nerves must be performed carefully. Muscle Nerve 59:470–474, 2019