Diagnostic sonography of peripheral nerves: indications, examination techniques and pathological findings

[Ultrasound examination of nerves of the upper extremities]

The ultrasound examination of peripheral nerves has been further developed in recent years and is recognized as an independent discipline by the German Society of Ultrasound in Medicine (DEGUM). A systematic ultrasound examination of the musculoskeletal system is not limited to the joints, muscles and bones but should also include the examination of nerves and blood vessels. Therefore, in the practice of ultrasound examination every rheumatologist should have at least a basic knowledge of the ultrasound examination of the peripheral nerves. In this article the authors present a landmark-based concept in which the three large nerves of the upper extremities can be completely visualized from proximal to distal and evaluated.

Imaging of Anatomical Variants of the Lower Limb Nerves: Clinical and Preoperative Relevance

Anatomical variants of peripheral nerves of the lower limb are relatively frequent and vulnerable to injury if not considered by the surgeon. Surgical procedures or percutaneous injections are often performed without knowing the anatomical situation. In a patient with normal anatomy, these procedures are mostly performed smoothly without major nerve complications. But in the case of anatomical variants, surgery may be challenging as "new" anatomical prerequisites complicate the procedure. In this context, high-resolution ultrasonography as the first-line imaging modality to depict peripheral nerves, has become a helpful adjunct in the preoperative setting. It is crucial, on the one hand, to gain knowledge of anatomical nerve variants and, on the other hand, to depict the anatomical situation preoperatively, to minimize the risk of surgical trauma to a nerve and make surgeries safer.

Diagnostic value of shear wave ultrasound elastography of tibial nerve in patients with diabetic peripheral neuropathy

Background

Diabetic peripheral neuropathy (DPN) is a major complication of Diabetes mellitus. So this study aimed at investigation of the value of tibial nerve stiffness measured by shear wave ultrasound elastography (SWE) for detection of DPN. This case–control study involved 50 patients with DPN, 50 patients with diabetes mellitus but without DPN, and 50 healthy controls. Clinical examination, nerve conduction study of both tibial nerves, high resolution ultrasound and SWE to assess cross sectional area "CSA" of tibial nerves, and tibial nerves mean stiffness, respectively. ROC curve analysis was also performed.

Results

Mean tibial nerve stiffness by SWE was higher in patients with DPN compared to other groups (P value < 0.001). The CSA of the tibial nerve in the DPN group was significantly larger than that in the other groups (P value = 0.01). The cutoff value by ROC curve analysis for tibial nerve stiffness to differentiate patients with DPN and control group was 70.6 kPa (P value < 0.001, 95.4% sensitivity, 94.7% specificity, AUC = 0.963), while 86.5 kPa was the optimal cutoff point to differentiate patients with DPN and other groups with a 94.6% sensitivity, 93.8% specificity, AUC of 0.975 and P value < 0.001. Higher diagnostic accuracy was found when combination of SWE and high resolution US (high resolution US + shear wave; 0.987, P value < 0.001).

Conclusions

Tibial nerve stiffness was increased in patients with DPN. SWE can be used as an effective complementary method in diagnosis of DPN with high sensitivity and accuracy.

Morphological and Mechanical Properties of Lower-Limb Muscles in Type 2 Diabetes: New Potential Imaging Indicators for Monitoring the Progress of DPN

The aim of this study was to explore changes in morphological and mechanical properties of lower-limb skeletal muscles in patients with diabetes with and without diabetic peripheral neuropathy (DPN) and seek to find a potential image indicator for monitoring the progress of DPN in patients with type 2 diabetes mellitus (T2DM). A total of 203 patients with T2DM, with and without DPN, were included in this study. Ultrasonography and ultrasound shear wave imaging (USWI) of the abductor hallux (AbH), tibialis anterior (TA), and peroneal longus (PER) muscles were performed for each subject, and the shear wave velocity (SWV) and cross-sectional area (CSA) of each AbH, TA, and PER were measured. The clinical factors influencing AbH_CSA and AbH_SWV were analyzed, and the risk factors for DPN complications were investigated. AbH_CSA and AbH_SWV in the T2DM group with DPN decreased significantly (P < 0.05), but no significant differences were found in the SWV and CSA of the TA and PER between the two groups. Toronto Clinical Scoring System (CSS) score and glycosylated hemoglobin (HbA1c) were independent predictors of AbH_CSA and AbH_SWV. As AbH_SWV and AbH_CSA decreased, Toronto CSS score and HbA1c increased and incidence of DPN increased significantly. In conclusion, the AbH muscle of T2DM patients with DPN became smaller and softer, while its morphological and mechanical properties were associated with the clinical indicators related to the progression of DPN. Thus, they could be potential imaging indicators for monitoring the progress of DPN in T2DM patients.

Cycling-Related Compressive Neuropathy of the Deep Ulnar Motor Branch in the Hand: Is Sonography a Valid Tool?

Repetitive vibratory trauma in cyclists is one of the most common causes of ulnar nerve compression at the wrist. This study describes five cases of clinically suspected compression syndrome of the deep terminal branch of the ulnar nerve (DBUN) defined by high-resolution ultrasound (HRUS) with a 18-MHz linear transducer. Reliable HRUS visualization of the DBUN was feasible in all patients. The affected nerves had focally swollen and hypo-echoic changed segments. HRUS is a good imaging tool for the evaluation of a suspicious DBUN neuropathy if no electrodiagnostic testing is available or in patients with mild to moderate clinical symptoms with inconclusive electrodiagnostic results.

[Imaging of the hand : What should be considered regarding the nerves?]

BACKGROUND

Peripheral nerve disorders of the hand and wrist are most commonly caused by entrapment neuropathies, while traumatic nerve injuries and neoplasms are less common.

OBJECTIVES

The indication for additional imaging methods and different imaging options, especially in patients with atypical symptoms or remaining unclear etiology of symptoms after completion of standard diagnostics, are presented.

MATERIALS AND METHODS

The imaging methods magnetic resonance (MR) neurography and neurosonography are introduced, and typical findings as well as diagnostic pitfalls are presented.

RESULTS

The diagnostic gold standard, which comprises a past medical history, neurologic examination and electrophysiology, can often establish the diagnosis. Imaging methods, especially MR neurography and neurosonography, are gaining increasing importance in the diagnostic workup of atypical neuropathies, as well as in the determination of the exact lesion location and spatial lesion extension, especially for surgical planning. Recent technical advances allow high-resolution depiction of small distal terminal nerve branches.

CONCLUSIONS

MR neurography allows for the high-resolution depiction of peripheral nerves of the hand and wrist. It can confirm the diagnosis of neuropathy, identify the exact lesion location, and rule out any differential diagnoses. Neurosonography is a time- and cost-efficient alternative diagnostic method.

Ultrasound-Guided Minimal Invasive Carpal Tunnel Release: An Optimized Algorithm

PURPOSE

To present a safety-optimized ultrasound-guided minimal invasive carpal tunnel release (CTR) procedure.

MATERIALS AND METHODS

104 patients (67 female, 37 male; mean age 60.6 ± 14.3 years, 95% CI 57.9 to 63.4 years) with clinical and electrophysiological verified typical carpal tunnel syndrome were referred for a high-resolution ultrasound of the median nerve and were then consecutively assigned for an ultrasound-guided CTR after exclusion of possible secondary causes of carpal tunnel syndrome such as tumors, tendovaginitis, ganglia and possible contraindications (e.g., crossing collateral vessels, nerve variations). Applying a newly adapted and optimized algorithm, basing on the work proposed by Petrover et al. CTR was performed using a button tip cannula which has several safety advantages: On the one hand, the button tip cannula acts as a blunt and atraumatic guiding splint for the subsequent insertion of the hook-knife, and on the other hands, it serves as a "hydro-inflation"-tool, i.e., a fluid-based expansion of the working-space is warranted during the whole procedure whenever needed.

RESULTS

In all patients, successful releases were confirmed by the depiction of a completely transected transverse carpal ligament during and in the postoperative ultrasound-controls two weeks after intervention. All patients reported markedly reduction of symptoms promptly after this safety-optimized ultrasound-guided minimal invasive CTR and at the follow-up examination. No complications were evident.

CONCLUSION

The here proposed optimized algorithm assures a reliable and safe ultrasound-guided CTR and thus should be taken into account for this minimal invasive interventional procedure.

Shear wave elastography evaluation of the median and tibial nerve in diabetic peripheral neuropathy

Background

To evaluate the value of shear wave elastography (SWE) in the detection of diabetic peripheral neuropathy (DPN) of the median and tibial nerves.

Methods

The study included 40 DPN patients, 40 diabetic mellitus (DM) patients without DPN, and 40 healthy subjects. High-resolution ultrasonography (US) and SWE were performed on the median nerve (MN) and tibial nerve (TN), and cross-sectional area (CSA) and nerve stiffness were measured. ROC analysis was also performed.

Results

The patients with DPN demonstrated higher stiffness of the median and tibial nerve compared with that of healthy volunteers and DM patients (P<0.001). Bilateral analysis showed that there was no significant difference in nerve stiffness between the left and right median nerves and tibial nerves in DPN patients (P>0.05). The stiffness of median nerve and tibial nerve in each one side also had no significant difference in patients with DPN (P>0.05). The CSA of the tibial nerve in the DPN group was significantly larger than that in the other groups (P<0.001), while there was no significant difference of median nerve CSA among the three groups (P>0.05). The area under curve (AUC) of SWE (MN: 0.899, TN: 0.927) to diagnose DPN was significantly greater than that of CSA (TN: 0.798). The optimal cut-off value in SWE of the tibial nerve and median nerve for diagnosis of DPN was 4.11 and 4.06 m/s, respectively, with a good sensitivity and specificity.

Conclusions

Median and tibial nerve stiffness was significantly higher in patients with DPN. These findings suggest that SWE-based stiffness measurement of the nerve was a better method than CSA, and it can be used as another effective assistant method in the diagnosis of DPN.

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.

A rare case of a punched nerve syndrome of the deep motor branch of the ulnar nerve

INTRODUCTION

Peripheral compression neuropathy of the ulnar nerve is a frequent condition, most likely encountered at the ulnar sulcus or the Guyon's canal. High-resolution ultrasound (HRUS) can often identify the site of injury. Primarily idiopathic, compression neuropathy can stem from a punched nerve syndrome, in which direct contact between an arterial branch and the nerve leads to compression.

MATERIALS AND METHODS

A 42-year-old male patient was examined by means of HRUS using a 17-5 MHz linear transducer on a Philips iU22(®) (Philips, Bothell, Washington, USA).

RESULTS

After reporting a punched nerve syndrome of the deep motor branch of the ulnar nerve distal to the Guyon's canal, the patient underwent surgery and showed electrophysiological and clinical improvement 6 months after decompression.

CONCLUSION

HRUS is a viable method to demonstrate a punched nerve syndrome. In conjunction with clinical presentation, even unlikely sites of compression such as the deep motor branch of the ulnar nerve can be identified.

Can ultrasound of the tibial nerve detect diabetic peripheral neuropathy? A cross-sectional study

OBJECTIVE

Peripheral nerve imaging by portable ultrasound (US) may serve as a noninvasive and lower-cost alternative to nerve conduction studies (NCS) for diagnosis and staging of diabetic sensorimotor polyneuropathy (DSP). We aimed to examine the association between the size of the posterior tibial nerve (PTN) and the presence and severity of DSP.

RESEARCH DESIGN AND METHODS

We performed a cross-sectional study of 98 consecutive diabetic patients classified by NCS as subjects with DSP or control subjects. Severity was determined using the Toronto Clinical Neuropathy Score. A masked expert sonographer measured the cross-sectional area (CSA) of the PTN at 1, 3, and 5 cm proximal to the medial malleolus.

RESULTS

Fifty-five patients had DSP. The mean CSA of the PTN in DSP compared with control subjects at distances of 1 (23.03 vs. 17.72 mm(2); P = 0.004), 3 (22.59 vs. 17.69 mm(2); P < 0.0001), and 5 cm (22.05 vs. 17.25 mm(2); P = 0.0005) proximal to the medial malleolus was significantly larger. Although the area under the curve (AUC) for CSA measurements at all three anatomical levels was similar, the CSA measured at 3 cm above the medial malleolus had an optimal threshold value for identification of DSP (19.01 mm(2)) with a sensitivity of 0.69 and a specificity of 0.77 by AUC analysis.

CONCLUSIONS

This large study of diabetic patients confirms that the CSA of the PTN is larger in patients with DSP than in control subjects, and US is a promising point-of-care screening tool for DSP.