Ultrasonography evaluation of the normal ulnar nerve in adult: Comparison of the cross-sectional area at elbow extension and flexion

Diagnostic efficiency of conventional ultrasound, shear wave elastography, and superb microvascular imaging in evaluating ulnar neuropathy at the elbow

INTRODUCTION/AIMS

The current diagnosis of ulnar neuropathy at the elbow (UNE) relies mainly on the clinical presentation and nerve electrodiagnostic (EDX) testing, which can be uncomfortable and yield false negatives. The aim of this study was to investigate the diagnostic value of conventional ultrasound, shear wave elastography (SWE), and superb microvascular imaging (SMI) in diagnosing UNE.

METHODS

We enrolled 40 patients (48 elbows) with UNE and 48 healthy volunteers (48 elbows). The patients were categorized as having mild, moderate or severe UNE based on the findings of EDX testing. The cross-sectional area (CSA) was measured using conventional ultrasound. Ulnar nerve (UN) shear wave velocity (SWV) and SMI were performed in a longitudinal plane.

RESULTS

Based on the EDX findings, UNE severity was graded as mild in 4, moderate in 10, and severe in 34. The patient group showed increased ulnar nerve CSA and stiffness at the site of maximal enlargement (CSA mean at the site of max enlargement [CSAmax] and SWV mean at the site of max enlargement [SWVmax]), ulnar nerve CSA ratio, and stiffness ratio (elbow-to-upper arm), compared with the control group (p < .001). Furthermore, the severe UNE group showed higher ulnar nerve CSAmax and SWVmax compared with the mild and moderate UNE groups (p < .001). The cutoff values for diagnosis of UNE were 9.5 mm2 for CSAmax, 3.06 m/s for SWVmax, 2.00 for CSA ratio, 1.36 for stiffness ratio, and grade 1 for SMI.

DISCUSSION

Our findings suggest that SWE and SMI are valuable diagnostic tools for the diagnosis and assessment of severity of UNE.

Assessment of the ulnar nerve stiffness during valgus stress of the elbow using shear wave elastography: an observational cross-sectional study

BACKGROUND

Identification of the relationship between valgus stress in the medial elbow and ulnar nerve strain during maximum external rotation of the shoulder is pivotal for the prevention and management of ulnar neuropathies. In this observational cross-sectional study, we aimed to determine the changes in ulnar nerve stiffness under valgus stress at different nerve entrapment sites.

METHODS

Twenty healthy baseball players participated in the study. The stiffness of the ulnar nerve on the throwing side was assessed at two sites, the arcade of Struthers and the Osborne's ligament, at 0°, 60°, and 90° flexion by shear wave elastography using a 10-MHz linear transducer. The arcade of Struthers was defined as the proximal site and the Osborne's ligament as the distal site. Valgus stress was applied to the medial elbow at 0, 30, 50, and 70 N using a Telos stress device, and the stiffness caused by valgus stress was measured.

RESULTS

At all elbow flexion angles, the stiffness of the ulnar nerve under 70 N valgus stress was higher than that under 30 N stress. The stiffness of the ulnar nerve at the proximal site was significantly higher than that at the distal site.

CONCLUSION

Valgus stress increases ulnar nerve stiffness. In addition, the stiffness of the proximal site increases.

Characteristics of ulnar neuropathy in baseball players: Focusing on the entrapment point of the ulnar nerve and valgus instability

Background

The region where the ulnar nerve (UN) is swollen in baseball players with ulnar neuropathy is not apparent. This study investigated the UN's cross-sectional area (CSA) at each entrapment point in baseball players. We also aimed to clarify the relationship between valgus instability and the CSA of the UN.

Methods

Forty baseball players were separated into healthy and ulnar neuropathy groups. The CSA and valgus instability were measured using ultrasonography (US). Relative to the medial epicondyle (MEC), the arcade of Struthers (SA) was 5 cm proximal, the cubital tunnel was the posterior part, and Osborne's ligament was defined as 3 cm distal. The ulnohumeral joint space was imaged as a low-echo space between the distal-medial corner of the trochlea and the proximal edge of the sublime tubercle.

Results

The UN in the ulnar neuropathy group had significant swelling in the cubital tunnel and Osborne's ligament. We found a weak positive correlation between the CSA and ulnohumeral joint space, and the ulnohumeral joint space at rest and valgus stress.

Conclusion

Evaluation and treatment of UN, especially cubital tunnel and Osborne's ligament, are necessary for the rehabilitation of baseball players presenting with ulnar neuropathy and valgus instability.

Early post-surgical rehabilitation and functional outcomes of a traumatic ulnar nerve injury: a pediatric case report

Background

Peripheral nerve injuries (PNIs) of the upper limb are very common events within the pediatric population, especially following soft tissue trauma and bone fractures. Symptoms of brachial plexus nerve injuries can differ considerably depending on the site and severity of injury. Compared to median and radial nerves, the ulnar nerve (UN) is the most frequently and severely injured nerve of the upper extremity. Indeed, due to its peculiar anatomical path, the UN is known to be particularly vulnerable to traumatic injuries, which result in pain and substantial motor and sensory disabilities of the forearm and hand. Therefore, timely and appropriate postoperative management of UN lesions is crucial to avoid permanent sensorymotor deficits and claw hand deformities leading to lifelong impairments. Nevertheless, the literature regarding the rehabilitation following PNIs is limited and lacks clear evidence regarding a solid treatment algorithm for the management of UN lesions that ensures full functional recovery.

Case presentation

The patient is a 11-year-old child who experienced left-hand pain, stiffness, and disability secondary to a domestic accident. The traumatic UN lesion occurred about 8 cm proximal to Guyon's canal and it was surgically treated with termino-terminal (end-to-end) neurorrhaphy. One month after surgery, the patient underwent multimodal rehabilitative protocol and both subjective and functional measurements were recorded at baseline (T0) and at 3- (T1) and 5-month (T2) follow-up. At the end of the rehabilitation protocol, the patient achieved substantial reduction in pain and improvement in quality of life. Of considerable interest, the patient regained a complete functional recovery with satisfactory handgrip and pinch functions in addition with a decrease of disability in activities of daily living.

Conclusion

A timely and intensive rehabilitative intervention done by qualified hand therapist with previous training in the rehabilitation of upper limb neuromuscular disorders is pivotal to achieve a stable and optimal functional recovery of the hand, while preventing the onset of deformities, in patients with peripheral nerve injuries of the upper limb.

Increase in conduction velocity in myelinated nerves due to stretch - An experimental verification

Background

Based on published experimental evidence, a recent publication revealed an anomalous phenomenon in nerve conduction: for myelinated nerves the nerve conduction velocity (NCV) increases with stretch, which should have been the opposite according to existing concepts and theories since the diameter decreases on stretching. To resolve the anomaly, a new conduction mechanism for myelinated nerves was proposed based on physiological changes in the nodal region, introducing a new electrical resistance at the node. The earlier experimental measurements of NCV were performed on the ulnar nerve at different angles of flexion, focusing at the elbow region, but left some uncertainty for not reporting the lengths of nerve segments involved so that the magnitudes of stretch could not be estimated.

Aims

The aim of the present study was to relate NCV of myelinated nerves with different magnitudes of stretch through careful measurements.

Method

Essentially, we duplicated the earlier published NCV measurements on ulnar nerves at different angles of flexion but recording appropriate distances between nerve stimulation points on the skin carefully and assuming that the lengths of the underlying nerve segment undergoes the same percentages of changes as that on the skin outside.

Results

We found that the percentage of nerve stretch across the elbow is directly proportional to the angle of flexion and that the percentage increase in NCV is directly proportional to the percentage increase in nerve stretch. Page's L Trend test also supported the above trends of changes through obtained p values.

Discussion

Our experimental findings on myelinated nerves agree with those of some recent publications which measured changes in CV of single fibres, both myelinated and unmyelinated, on stretch. Analyzing all the observed results, we may infer that the new conduction mechanism based on the nodal resistance and proposed by the recent publication mentioned above is the most plausible one to explain the increase in CV with nerve stretch. Furthermore, interpreting the experimental results in the light of the new mechanism, we may suggest that the ulnar nerve at the forearm is always under a mild stretch, with slightly increased NCV of the myelinated nerves.