Ultrasonographic measurements in cubital tunnel syndrome

Neuromuscular ultrasound: Impact on diagnosis and management

INTRODUCTION/AIM

High-resolution ultrasound (HRUS) is increasingly used in evaluating neuromuscular conditions. Its potential advantages include its ability to discern anatomic information and make specific etiological diagnoses. Although many studies have demonstrated HRUS effectiveness, especially in mononeuropathies, more information is needed to better determine how often and to what extent useful information is obtained; how it influences diagnosis, clinical decision-making, and patient management; and how it is used with electrodiagnostic (EDx) studies.

METHODS

A retrospective cohort study was performed on patients referred for HRUS at a university laboratory during 2021. Demographic information, referral diagnoses, clinical information, HRUS findings, and follow-up patient management were analyzed. For patients who had EDx, results were compared with HRUS. Determinations were made whether HRUS did or did not aid in the diagnosis. For patients in whom HRUS resulted in a diagnosis, determination was made whether it confirmed the diagnosis made clinically or by EDx but did not change management; added additional important information; and/or made a decisive impact on subsequent management.

RESULTS

Five hundred two patients were analyzed, most referred for mononeuropathy, brachial plexopathy, and polyneuropathy. HRUS was abnormal in 81.7% of patients. HRUS added additional useful information in 79.0% and was decisive in management in 62.7%. In patients who also had abnormal EDx, HRUS resulted in decisive management in 49.5%.

DISCUSSION

HRUS is an effective diagnostic tool that frequently adds localizing and structural information that is otherwise not obtainable by clinical and EDx evaluation. In a substantial number of patients selected for HRUS, it is decisive in guiding further management.

Ulnar nerve thickness at the elbow on longitudinal ultrasound view in control subjects

INTRODUCTION

Ulnar mononeuropathy at the elbow is the second most frequent neuropathy in humans. Diagnosis is based on clinical and electrophysiological criteria and, more recently, also on ultrasound. Cross-sectional ultrasound is currently the most valued, although longitudinal ultrasound allows assessment of the entire affected trajectory of the nerve in a single view, but always in a straight line with no changes in direction, as in the extended elbow. The main aim of this work is to propose normative values ​​for longitudinal ultrasound of the ulnar nerve at the elbow.

METHODS

The neurological exploration of upper extremity, and electrophysiological and ultrasound parameters at the elbow of ulnar nerve were evaluated in 76 limbs from 38 asymptomatic subjects.

RESULTS

The diameters of the nerve as well as the distal and proximal areas were larger at the proximal region of the ulnar groove, and even more so in older individuals. In most of these elderly subjects, we found a small, non-significant slowdown in motor conduction velocity at the elbow with respect to the forearm (less than 5 m/s).

CONCLUSIONS

We observed a good correlation between the longitudinal and cross-sectional ultrasounds of the ulnar nerve at the elbow. Longitudinal ultrasound proved to be sensitive, reliable, simple and rapid, but its greatest contribution was allowing the visualization of the entire nerve trajectory in an integrated way, providing an image with good definition of the outline, proportions and intraneural characteristics of the nerve.

Neuromuscular Ultrasound: Indications in the Electrodiagnostic Laboratory

ABSTRACT

Accurate assessment of neuromuscular disorders is critical to facilitate timely treatment and achieve the best outcomes. Historically, electrodiagnostic studies have filled this role, but recently, neuromuscular ultrasound is being used in the electrodiagnostic laboratory. This review discusses the uses of neuromuscular ultrasound in the electrodiagnostic laboratory that have strong evidence, emphasizing those that could be adopted in a typical electrodiagnostic laboratory with a reasonable level of equipment and training. The evidence currently supports using neuromuscular ultrasound to diagnose carpal tunnel syndrome and ulnar neuropathies at the elbow and as a supplementary test when electrodiagnostic studies are suspected to be falsely negative or in axonal nonlocalizing lesions. Neuromuscular ultrasound can identify the causes of focal mononeuropathies, which can change treatment in specific cases. It is sensitive at identifying fasciculations and providing complementary evidence of autoimmune demyelinating polyneuropathies. It is particularly helpful in assessing nerves after trauma. Neuromuscular ultrasound is likely to prove even more useful in the electrodiagnostic laboratory as the technology continues to advance.

Ultrasound Ulnar Nerve Measurement in a Healthy Population

Introduction

Ulnar tunnel syndrome at the elbow is a common pathology. The ultrasound cross-sectional area is a well-known metric widely accepted in radiology for the description of nerve entrapment. However, the pathological cut-off value remains challenging. The objectives of this study were to (1) describe the ultrasound cross-sectional area measurement of the ulnar nerve at three locations, and (2) to evaluate the inter-observer reliability by two independent ultrasonographers.

Methods

One-hundred ulnar nerves of 50 asymptomatic individuals were scanned using B-mode and power Doppler ultrasonography. The ultrasound cross-sectional area measurements of the ulnar nerve were performed at three different levels: 2 cm proximal to the epicondyle, at the level of the epicondyle, and 2 cm distal to the epicondyle.

Results

In our healthy population, we found 21, 24 and 7% of ultrasound cross-sectional area ulnar nerve > 8 mm², respectively, at three different levels of measurement and 4, 7, and 0% US-CSA ulnar nerve > 10 mm². The intraclass correlation coefficient measured at three different site levels were good (0.7943, 0.7509) to moderate (0.5701).

Conclusions

Almost one-quarter of our healthy population had an ultrasound cross-sectional area ulnar nerve more than 8 mm² and few more than 10 mm². A cut-off of ultrasound cross-sectional area ulnar nerve measurement more than 10 mm² could be considered as pathological. No abnormal elbow ulnar nerve vascularization has been seen. This is the first step towards normal B-mode ulnar nerve values at the elbow to further detect pathological US findings as ulnar nerve entrapment.

Ultrasound Measurements and Assessments of the Ulnar Nerve at the Elbow and Cubital Tunnel: A Scoping Review

Ulnar neuropathy at the elbow (UNE) is the second most frequent peripheral nerve entrapment neuropathy in the upper extremity. The diagnosis is determined through a combination of history, physical examination, and electrodiagnostic testing. However, the use of high-resolution sonography is increasing, with sonographic measurements of ulnar nerve dimension established as a reliable diagnostic criterion for UNE. Sonographic imaging can describe anatomical features beyond ulnar nerve size, and therefore additional observations could potentially be used in UNE diagnosis and treatment follow-up. This review was a scoping of the literature on different sonographic measurements and assessments that have been reported to evaluate the ulnar nerve and cubital tunnel. This should provide a guide to scanning protocols for sonographers.

Ultrasound biomechanical anatomy of the soft structures in relation to the ulnar nerve in the cubital tunnel of the elbow

BACKGROUND

Chronic ulnar nerve entrapment worsened by elbow flexion is the most common injury, but rare painful conditions may also be related to ulnar nerve instability. The posterior bundle of the medial collateral ligament (pMCL) and the retinaculum, respectively form a soft floor and a ceiling for the cubital tunnel. The aim of our study was to dynamically assess these soft structures of the cubital tunnel focusing on those involved in the biomechanics of the ulnar nerve.

METHODS

Forty healthy volunteers had a bilateral ultrasonography of the cubital tunnel. Elbows were scanned in full extension, 45° and 90°, and maximal passive flexion. Morphological changes of the nerve and related structures were dynamically assessed on transverse views.

RESULTS

Both the pMCL and the retinaculum tightened with flexion. During elbow flexion, the tightening of the pMCL superficially moved the ulnar nerve remote from the osseous floor of the retroepicondylar groove. A retinaculum was visible in all 69 tunnels with stable nerves (86.3%), tightened in flexion, but absent in 11 tunnels with unstable nerves (13.7%). The retinaculum was fibrous in 60 elbows and muscular in nine, the nine muscular variants did not significantly influence the biomechanics of stable nerves. Stable nerves flattened in late flexion between the tightened pMCL and retinaculum, whereas unstable nerves transiently flattened when translating against the anterior osseous edge of the groove.

CONCLUSION

The retinaculum and the pMCL are key structures in the biomechanics of the ulnar nerve in the cubital tunnel of the elbow.

Sonography of Carpal Tunnel Syndrome According to Pathophysiologic Type: Conduction Block Versus Axonal Degeneration

OBJECTIVES

The purpose of this study was to investigate sonographic findings according to the pathophysiologic type in patients with carpal tunnel syndrome.

METHODS

We retrospectively reviewed the records of 80 patients (148 hands) with carpal tunnel syndrome. Patients were classified into 3 groups according to electrophysiologic findings: (1) conduction block and conduction delay; (2) axonal degeneration; and (3) mixed. We used sonographic evaluations to assess the cross-sectional area at the distal wrist crease and the distal forearm and the wrist-to-forearm ratio of the median nerve.

RESULTS

Patients with axonal degeneration had significantly larger cross-sectional areas and wrist-to-forearm ratios than those with a conduction block (P < .05). The increased wrist-to-forearm ratio correlated with a reduced amplitude of the sensory nerve action potential, which reflects the degree of axonal degeneration.

CONCLUSIONS

The cross-sectional area and wrist-to-forearm ratio were associated with the pathophysiologic type of carpal tunnel syndrome, with larger nerve swellings seen in patients with axonal degeneration compared with those with demyelinating lesions. In addition to helping in the localization of the nerve lesion, sonography may indicate the type of nerve lesion.

Use of High-Resolution Ultrasonography in Anterior Subcutaneous Transposition of the Ulnar Nerve for Cubital Tunnel Syndrome

OBJECTIVES

Cubital tunnel syndrome (CTS) is the most common form of ulnar nerve entrapment. In this study, ultrasonography (US) was used not only for diagnosis but also for operation. US findings could be used to establish the diagnosis of CTS and could demonstrate the pathological anatomy in the cubital tunnel region to guide anterior subcutaneous transposition of the ulnar nerve.

METHODS

Sixty-two patients with clinical and electrophysiological evidence of ulnar nerve entrapment were included. All patients received ultrasonographic examination and anterior subcutaneous transposition of the ulnar nerve. The maximal diameter of the ulnar nerve (MDU) was measured in longitudinal views and the range of the hypoechoic area around the nerve was observed. The cross-sectional area (CSA) was also measured on transverse scans. The actual MDU was measured during operation.

RESULTS

The actual MDU was 6.4 ± 0.4 mm, measured during operation. The preoperative MDU was 3.1 ± 0.2 mm. The MDU values recorded in CTS patients were greater than those in normal subjects. The range of the hypoechoic area observed on longitudinal US scans was 2.9-5.6 mm (mean, 4.1 ± 0.4 mm).

CONCLUSIONS

High-resolution US can be used not only in the diagnosis of CTS, also for providing effective preoperative evaluation for the anterior subcutaneous transposition of the ulnar nerve in CTS.

MR anatomy and pathology of the ulnar nerve involving the cubital tunnel and Guyon's canal

Ulnar neuropathy is a common and frequent reason for referral to hand surgeons. Ulnar neuropathy mostly occurs in the cubital tunnel of the elbow or Guyon's canal of the wrist, and it is important for radiologists to understand the imaging anatomy at these common sites of impingement. We will review the imaging and anatomy of the ulnar nerve at the elbow and wrist, and we will present magnetic resonance imaging examples of different causes of ulnar neuropathy, including trauma, overuse, arthritis, masses and mass-like lesions, and systemic diseases. Treatment options will also be briefly discussed.

Diagnostic cutoff value for ultrasonography in the ulnar neuropathy at the elbow

Objective

To determine the diagnostic cutoff values of ultrasonographic measurements in ulnar neuropathy at the elbow (UNE).

Methods

Twenty-five elbows of 23 patients (9 females, 16 males) diagnosed with UNE and 30 elbows of 30 healthy controls (15 females, 15 males) were included in our study. The ulnar nerve cross-sectional area (CSA) was measured at the Guyon canal, midforearm, and maximal swelling point (MS) around the elbow (the cubital tunnel inlet in healthy controls). CSA measurements of the ulnar nerve at each point, the Guyon canal-to-MS ulnar nerve area ratio (MS/G), and the midforearm-to-MS ulnar nerve ratio (MS/F) were calculated.

Results

Among the variables, only CSA at MS, MS/G, and MS/F displayed significant differences between the control and patient groups. The cutoff value for diagnosing UNE was 8.95 mm² for the CSA at MS (sensitivity 93.8%, specificity 88.3%), 1.99 for the MS/G (sensitivity 75.0%, specificity 73.3%), and 1.48 for the MS/F (sensitivity 93.8%, specificity 95.0%).

Conclusion

These findings may be helpful to diagnose UNE.

Cross-sectional area reference values of nerves in the lower extremities using ultrasonography

INTRODUCTION

Cross-sectional area (CSA) reference values of lower extremity nerves using ultrasonography have only been reported in a few studies and have been limited to white populations.

METHODS

For this study, 94 healthy Korean volunteers were recruited for measurement of the CSA at 7 sites of lower extremity nerves. The side-to-side difference in CSA was calculated for each nerve, and reference ranges were derived. External validity evaluation for the reference values was performed with 10 newly recruited volunteers at a different institution.

RESULTS

Nerve CSA was correlated significantly with body mass index, weight, and height; however, the absolute value of the side-to-side difference had no significant correlation with demographic factors. The external validity was adequate for all sites, ranging from 80% to 100%.

CONCLUSIONS

The lower extremity nerve CSA values obtained in this study may provide normal reference values for the Asian population.

Contribution of static and dynamic ultrasound in cubital tunnel syndrome

INTRODUCTION

Electroneuromyography (ENMG) is the gold standard examination in cubital tunnel syndrome (CuTS), but sheds no light on etiology. High-resolution ultrasound (HRU) analyzes the anatomic abnormalities and physical properties of the ulnar nerve (UN) and enables dynamic study. The present non-randomized prospective study compared HRU with clinical, ENMG and intraoperative findings.

MATERIAL AND METHODS

Sixty patients were included. The McGowan clinical classification as modified by Goldberg was employed, and ENMG lesions were ranked for severity. HRU screened for morphologic abnormalities of the ulnar nerve and cubital tunnel, measuring UN cross-sectional area (UNCSA) and flattening index (FI) in the cubital tunnel, in extension and flexion. UN stability was assessed.

RESULTS

Ultrasound found 2 stenoses, 29 pseudoneuromas 25 dedifferentiations. There were 16 morphologic abnormalities. Mean cubital tunnel UNCSA (in cm(2)) and FI were respectively 0.112 and 1.549 in extension and 0.117 and 1.827 in flexion. Nineteen cases of UN instability were found on HRU, versus 17 intraoperatively. Only 8 patients showed no abnormality on HRU. Pseudoneuroma or dedifferentiation on HRU correlated with clinical stage (P=0.2579 and 0.2615, respectively). Dedifferentiation was associated with severe abnormality on ENMG (P<0.5). Thirty-two stenoses, 18 pseudoneuromas and 10 epitrochlearis anconeus muscles were found intraoperatively, matching HRU abnormalities.

DISCUSSION

The present findings were comparable to those of the literature. Cubital tunnel UNCSA was elevated in case of CuTS, with cut-off at 0.112 cm(2). FI was elevated in flexion (P=0.0063). The rate of UN instability was 32%, compared to 21-60% in the literature. HRU findings matched the clinical and ENMG classifications. HRU proved to be an effective diagnostic tool for CuTS and its etiologies.

LEVEL OF EVIDENCE

IV.

Ultrasound diagnosis of ulnar neuropathy: comparison of symptomatic and asymptomatic nerve thickness

There is still no consensus on a normal value for the cross-sectional area of the ulnar nerve at the elbow. Such data would be valuable for the ultrasound diagnosis of ulnar neuropathy. Comparison of the symptomatic and contralateral asymptomatic sides has been recommended. The aim of this study was to investigate whether or not the asymptomatic ulnar nerve could be a reference value. High-resolution ultrasonic measurements of the cross-sectional areas of the ulnar nerves at the elbow were compared with 38 contralateral asymptomatic elbows of patients with unilateral ulnar neuropathy and 38 healthy controls. There were significant differences in the cross-sectional areas at all levels between the healthy control subjects and asymptomatic side of the ulnar neuropathy patients (p < 0.05). The findings of this study suggest that there is a limitation in using the asymptomatic side for obtaining reference values in ultrasonographic studies. Each ultrasonographic laboratory should determine its own reference values.

Ultrasonography of palm to elbow segment of median nerve in different degrees of diabetic polyneuropathy

OBJECTIVE

To identify the relationship between the ultrasonographic cross-sectional area (CSA) of the median nerve and electrophysiologic findings in diabetic patients.

METHODS

Sixty diabetic patients, 30 patients with carpal tunnel syndrome (CTS) and 30 healthy volunteers participated. The participants were divided into 4 groups: Control Group; Group I, diabetic patients without diabetic polyneuropathy (DPN); Group II, diabetic patients with DPN; and Group III, patients with CTS. Group II was subdivided into II-1 and II-2 according to DPN severity. The median nerve CSA was measured at 4 levels, and the wrist-to-forearm ratio (WFR) was calculated.

RESULTS

The median nerve CSAs were larger in Group II than in Group I and the Control Group. There were significant differences in the CSA between Group I and Group II-2 and between Group II-1 and II-2. There was no significant difference in the WFR among these groups. The CSAs at the wrist levels and WFR were significantly greater in Group III.

CONCLUSIONS

The median nerve CSA was greater in patients with DPN and was related to DPN severity. Diffuse increase in median nerve CSA without change in the WFR might be compatible with DPN. Ultrasonography could be applied for the diagnosis of DPN, especially in advanced cases.

SIGNIFICANCE

Ultrasonography might have value in the differential diagnosis of DPN and entrapment neuropathy.

Ultrasonography of median nerve and electrophysiologic severity in carpal tunnel syndrome

OBJECTIVE

To investigate the correlation of the ultrasonographic wrist-to-forearm median nerve area ratio (WFR) and cross sectional area of median nerve at the wrist (CSA-W) to the electrophysiologic severity in patients with carpal tunnel syndrome (CTS).

METHOD

One hundred and ten wrists electrophysiologically graded as mild, moderate, and severe CTS and 38 healthy controls underwent ultrasonography of median nerve at the distal wrist crease and mid-forearm. WFR and CSA-W were analyzed according to the severity of CTS.

RESULTS

WFR was 1.12±0.14, 1.91±0.33, 2.27±0.47 and 3.02±0.97 and the CSAs-W was 7.23±1.67 mm(2), 13.51±3.72 mm(2), 14.67±2.93 mm(2), and 18.74±6.01 mm(2) in controls, mild (n=28), moderate (n=46), and severe (n=36) CTS, respectively. CSA-W displayed significant differences between the control and the mild CTS, moderate CTS and severe CTS groups. However, there was no significant difference between mild CTS and moderate CTS groups. WFR revealed significant difference between all groups. The sensitivity and specificity of the WFR in grading the severity of CTS were higher than those of the CSA-W.

CONCLUSION

Ultrasonography is a useful complementary tool for the evaluation of CTS. Both WFR and CSA-W are highly correlated with severity grade of CTS. However, WFR is superior to CSA-W for diagnosis and grading of the severity of CTS.

Electromyography and ultrasonography in the diagnosis of a rare double-crush ulnar nerve injury

Reported here is a 46-year-old man who was seen for pain, numbness, and weakness in his left upper limb and hand. Electromyographic studies demonstrated denervation of ulnar-innervated muscle groups except for the flexor carpi ulnaris. A localized nerve conduction block could not be depicted because of severe axonal loss. Ultrasonographic evaluation showed enlargement of the ulnar nerve at 2 sites: at the level of the epicondylar groove and the inside of the flexor carpi ulnaris muscle. Herein, we would like to emphasize the complementary role of an ultrasound in peripheral nerve pathologies, not only does it confirm the entrapment but it also displays the underlying cause(s).

What's new in the diagnosis and treatment of peripheral nerve entrapment neuropathies

Entrapment neuropathies can be common conditions with the potential to cause significant disability. Correct diagnosis is essential for proper management. This article is a review of recent developments related to diagnosis and treatment of various common and uncommon nerve entrapment disorders. When combined with classical peripheral nerve examination techniques, innovations in imaging modalities have led to more reliable diagnoses. Moreover, innovations in conservative and surgical techniques have been controversial as to their effects on patient outcome, but randomized controlled trials have provided important information regarding common operative techniques. Treatment strategies for painful peripheral neuropathies are also reviewed.

Ultrasonography in patients with ulnar neuropathy at the elbow: comparison of cross-sectional area and swelling ratio with electrophysiological severity

The aim of this study was to determine the diagnostic value of ultrasonographic measurements in ulnar neuropathy at the elbow (UNE) and to assess the relationship between the measurements and the electrophysiological severity. The largest anteroposterior diameter (LAPD) and cross-sectional area (CSA) measurements of the ulnar nerve were noted at multiple levels along the arm, and the distal-to-proximal ratios were calculated. Almost all of the measurements and swelling ratios between patients and controls showed statistically significant differences. The largest CSA, distal/largest CSA ratio, CSA at the epicondyle, and proximal LAPD had larger areas under the curve than other measurements. The sensitivity and specificity in diagnosing UNE were 95% and 71% for the largest CSA, 83% and 85% for the distal/largest CSA ratio, 83% and 81% for the CSA at the epicondyle, and 93% and 43% for the proximal LAPD, respectively. There was a statistically significant correlation between the electrophysiological severity scale score (ESSS) and the largest CSA, the CSA at the epicondyle and 2 cm proximal to the epicondyle, and the LAPD at the level of the epicondyle (P < 0.05). None of the swelling ratios showed a significant correlation with the ESSS. The largest CSA measurement is the most valuable ultrasonographic measurement both for diagnosis and determining the severity of UNE.

The validity of ultrasonographic assessment in cubital tunnel syndrome: the value of a cubital-to-humeral nerve area ratio (CHR) combined with morphologic features

Diagnosis of a typical idiopathic cubital tunnel syndrome (CuTS) is straight forward but the work-up of mild forms is clinically challenging. The diagnostic value of high-resolution ultrasound (HRUS) relying solely on nerve measurements is doubtful. Additional textural analysis of the nerve may possibly overcome this drawback. Thirty-eight prospectively enrolled patients with idiopathic CuTS and 23 healthy volunteers underwent standardized HRUS. A cubital-to-humeral nerve area ratio (CHR) was calculated and the texture of the most swollen nerve segment assessed. CHR was significantly different among patients and volunteers (p<0.001) but with a marked overlap. Combination of at least partial inner fascicular masking plus a CHR>1.4 showed a positive linear coherence with idiopathic CuTS at a specificity>95% and a PPV>90%. Thus, the combined textural analysis and CHR calculation seems a powerful tool for the sonographic diagnosis of idiopathic CuTS.

Ultrasonographic swelling ratio in the diagnosis of ulnar neuropathy at the elbow

High-resolution ultrasound can demonstrate focal nerve enlargement in entrapment neuropathies. We hypothesized that a ratio between the nerve cross-sectional area at the site of maximal enlargement and at an unaffected site may improve diagnostic accuracy in ulnar neuropathy at the elbow (UNE), when compared to a single measurement at the site of maximal enlargement. Ultrasound was used to measure the cross-sectional area of the ulnar nerve at three sites in 30 normal, healthy controls and 26 individuals with UNE. In individuals with UNE, the ratio was 2.9:1 when the site of maximal swelling was compared with a distal ulnar nerve site and 2.8:1 when compared with a proximal site. This represented a significant increase compared with the ratio of 1.1:1 for both comparisons in controls (P < 0.0001). This type of ratio may be particularly useful for assessing entrapment in those with polyneuropathy or obesity, both of which can cause diffuse nerve enlargement.

Ulnar nerve and cubital tunnel ultrasound in ulnar neuropathy at the elbow

OBJECTIVE

To determine the accuracy of the ultrasonographic measurement of ulnar nerve to cubital tunnel area for diagnosis of ulnar neuropathy at the elbow.

DESIGN

Patients with confirmed ulnar neuropathy at the elbow and normative, healthy volunteers were evaluated with high-resolution ultrasound. The cross-sectional areas (CSAs) of the ulnar nerve and cubital tunnel were measured with the elbow extended and flexed, and results from the 2 groups were compared.

SETTING

Electromyography laboratory and radiology department of a tertiary care center.

PARTICIPANTS

Twenty-seven patients with ulnar neuropathy at the elbow and 20 controls.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The ratio of ulnar nerve to cubital tunnel CSA with the elbow flexed.

RESULTS

The ulnar nerve, with the elbow flexed, was larger in those with ulnar neuropathy at the elbow, and this group also had larger cubital tunnels than did controls. In those with ulnar neuropathy at the elbow, the ratio of the ulnar nerve to cubital tunnel was .31, and in the controls it was .32, which was not significantly different (P=.89).

CONCLUSIONS

The ratio of ulnar nerve to cubital tunnel did not differentiate those with ulnar neuropathy at the elbow from controls.