Ultrasound assessment of the median nerve: a biomarker that can help in setting a treat to target approach tailored for carpal tunnel syndrome patients

Abstract

Ultrasonography (US) is a valuable tool for confirming the diagnosis of carpal tunnel syndrome (CTS) as it enables the detection of changes in the median nerve shape and rule out anatomic variants as well as space-occupying lesions such as ganglion cysts or tenosynovitis. This work was carried out aiming at: 1. Ultrasonography assessment of the median nerve and its neurovascular blood-flow in CTS patients before and after management. 2. Verify the possibility of using baseline US parameters as a biomarker to predict likely outcomes and frame a treatment plan for CTS patients.233 CTS subjects diagnosed based on clinical and electrophysiological (NCS) testing were included in this work. US measures at the tunnel inlet included: cross sectional area, flattening ratio and neural Power Doppler (PD) signals. Patients who had severe NCS outcomes or neurological deficit were referred for open surgical decompression; the remaining patients were given the choice of either conservative or surgical management. The main outcome variable was improvement >70% in CTS symptoms. Assessments were carried out at baseline, 1-week, 1-month and 6-months post treatment. Results revealed an inverse relation between the neural vasculature and CTS severity defined by NCS (r = − 0.648). In CTS cases treated conservatively, the US measures started to improve within 1-week, whereas in the surgically treated cohort there was an initial phase of post-operative nerve measures increase, before settling at 1-month time of follow-up. The risk of poor outcomes was significantly higher (RR 3.3) in patients with high median nerve flattening ratio. This risk was most marked in the cohort with nerve flattening associated with longer duration of illness (RR 4.3) and low PD signal (RR 4.1). The results revealed that in addition to the diagnostic value of US in CTS, the detection of increased median nerve neuro-vasculature has a good prognostic value as an indicator of early median nerve affection.

Impact of high resolution 3 tesla MR neurography (MRN) on diagnostic thinking and therapeutic patient management

“…Imaging interpretation was performed by highly trained radiologists to obtain expert readings as observer performance issues were not part of the hypothesis. Ultrasound of peripheral nerves is used in many institutions to delineate peripheral nerve anatomy and pathology owing to its lower cost and superior spatial resolution when compared to MR imaging, especially in the superficial nerves [33][34][35]. However, neuromuscular signal alterations are better seen on MRN owing to higher soft tissue contrast.…”

Cross-sectional area of the median nerve is increased in primary autoimmune hypothyroidism and decreases upon treatment with thyroxine

“…Despite some limitations, US of median nerve has not only been considered for the diagnosis of CTS, but also for the identification of the severity of median nerve damage. In comparison with NCS, US measurements from different sites were most consistent, and best sensitivity and specificity was reported for measures of cross-sectional area (CSA) of median nerve at the level of os pisiforme (17). Various studies have demonstrated that CSA of the median nerve at the carpal tunnel inlet and carpal tunnel outlet is significantly greater in CTS patients than in the normal population (15,18,19,20).…”

Diagnostic Accuracy of Ultrasound Parameters in Carpal Tunnel Syndrome: Additional Criteria for Diagnosis

“…No extraneous pressure was placed on the nerve through the transducer. It was evaluated by scores based on a study by El Miedany et al: 0, no color flow signal; 1, one single vessel within the nerve; 2, 2 or 3 single or 2 confluent vessels; and 3, more than 3 single or more than 2 confluent vessels. Palmar bowing of the flexor retinaculum was measured at the CTO. It was measured as the distance from the palmar apex of the flexor retinaculum to a straight line drawn between the apexes of the trapezium and hamate bone.…”