Shear-wave elastography: a new potential method to diagnose ulnar neuropathy at the elbow

Abstract

ObjectivesThe primary aim of this study was to verify if shear-wave elastography (SWE) can be used to diagnose ulnar neuropathy at the elbow (UNE). The secondary objective was to compare the cross-sectional areas (CSA) of the ulnar nerve in the cubital tunnel and to determine a cut-off value for this parameter accurately identifying persons with UNE.MethodsThe study included 34 patients with UNE (mean age, 59.35 years) and 38 healthy controls (mean age, 57.42 years). Each participant was subjected to SWE of the ulnar nerve at three levels: in the cubital tunnel (CT) and at the distal arm (DA) and mid-arm (MA). The CSA of the ulnar nerve in the cubital tunnel was estimated by means of ultrasonographic imaging.ResultsPatients with UNE presented with significantly greater ulnar nerve stiffness in the cubital tunnel than the controls (mean, 96.38 kPa vs. 33.08 kPa, p < 0.001). Ulnar nerve stiffness of 61 kPa, CT to DA stiffness ratio equal 1.68, and CT to MA stiffness ratio of 1.75 provided 100% specificity, sensitivity, positive and negative predictive value in the detection of UNE. Mean CSA of the ulnar nerve in the cubital tunnel turned out to be significantly larger in patients with UNE than in healthy controls (p < 0.001). A weak positive correlation was found in the UNE group between the ulnar nerve CSA and stiffness (R = 0.31, p = 0.008).ConclusionsSWE seems to be a promising, reliable and simple quantitative adjunct test to support the diagnosis of UNE.Key Points• SWE enables reliable detection of cubital tunnel syndrome• Significant increase of entrapped ulnar nerve stiffness is observed in UNE• SWE is a perspective screening tool for early detection of compressive neuropathies

Influence of limb position on assessment of nerve mechanical properties by using shear wave ultrasound elastography

“…With elbow position held constant, we found a statistically significant difference in SW velocity between proximal and distal locations for the ulnar nerve but not for the median nerve. These results are in line with previous findings, some of which have shown localized differences in nerve SW velocity, while others have not . The reason for this disparity is likely due to nerve and location examined because nerve tension and structure are not uniform along the limb and differ with proximity to joints …”

“…We found no definitive relationship between nerve SW velocity and morphometry in unimpaired nerves such as has been found in patients with diabetic and entrapment neuropathies . Therefore, it is unlikely that differences observed in SW velocity were a result of variation in nerve morphometry.…”

“…More recently, noninvasive real‐time estimation of nerve mechanical properties, such as stiffness, has been made possible with the advent of shear wave (SW) ultrasound elastography, a technique that induces SWs and measures their velocity. Early reports of studies described finding that in vivo measurements of SW velocity in nerve tissue are greater in patients with nerve damage, including metabolic and entrapment neuropathies. This trend mirrors findings from pathological studies of other tissues including breast, liver, and passive skeletal muscle, for which greater SW velocity is largely attributed to changes in collagen content and structure.…”

Ultrasound elastography for the evaluation of peripheral nerves: A systematic review

“…There is presently only sparse data regarding the use of ultrasound elastography as a diagnostic modality in UNE. Like CTS, the studies have shown increased nerve stiffness at the site of injury but a relationship between the severity of ulnar neuropathy and ultrasound elastography values was not established . Increased nerve stiffness has also been identified in patients with ulnar neuropathy in Guyon's canal at the wrist .…”

“…Like CTS, the studies have shown increased nerve stiffness at the site of injury but a relationship between the severity of ulnar neuropathy and ultrasound elastography values was not established. 46,47 Increased nerve stiffness has also been identified in patients with ulnar neuropathy in Guyon's canal at the wrist. 48 Based on currently published data, the role of elastography in the diagnosis of ulnar neuropathy remains unclear.…”