Ultrasound assessment of carpal tunnel in rheumatoid arthritis and idiopathic carpal tunnel syndrome

Antonella Incorvaia,Edoardo Cipolletta,Sergio Carloni,Walter Grassi,Emilio Filippucci,Andrea Di Matteo,Marco Di Carlo,Gianluca Smerilli

doi:10.1007/s10067-020-05293-z

Abstract

ObjectivesTo comparatively assess the sonographic spectrum of carpal tunnel syndrome (CTS) in patients with rheumatoid arthritis (RA) and in patients with idiopathic CTS.MethodsFifty-seven RA patients and 25 idiopathic CTS patients were consecutively enrolled. The diagnosis of CTS in RA patients was made according to clinical history and examination. The following sonographic findings were assessed at carpal tunnel level: median nerve cross-sectional area (CSA) at the carpal tunnel proximal inlet, finger flexor tendons tenosynovitis, radio-carpal synovitis and intraneural power Doppler (PD) signal.ResultsCTS was diagnosed in 15/57 RA patients (26.3%). Twenty-three RA wrists with CTS, 84 RA wrists without CTS and 34 idiopathic CTS wrists were evaluated. The average CSA of the median nerve was higher in idiopathic CTS than in RA wrists with CTS (17.7 mm2 vs 10.6 mm2, p < 0.01). A higher rate of inflammation of synovial structures (flexor tendons sheath and/or radio-carpal joint) was found in RA wrists with CTS compared with those without CTS (p = 0.04) and idiopathic CTS (p = 0.02). Intraneural PD signal was more common in CTS (in both RA and idiopathic CTS) wrists compared with wrists without CTS (p < 0.01).ConclusionThe sonographic spectrum of CTS in RA patients is characterized by an inflammatory pattern, defined by the presence of finger flexor tendons tenosynovitis and/or radio-carpal joint synovitis. Conversely, a marked median nerve swelling is the dominant feature in idiopathic CTS. Intraneural PD signal is a frequent finding in both conditions.Key Points• Carpal tunnel syndrome (CTS) associated with rheumatoid arthritis (RA) and idiopathic CTS have distinct ultrasound patterns.• The most characteristic sonographic features of CTS in RA patients are those indicative of synovial tissue inflammation at carpal tunnel level. Conversely, marked median nerve swelling is the dominant finding in idiopathic CTS.• Intraneural power Doppler signal is a frequent finding in both conditions.• In patients with CTS, differently from electrophysiology, US can provide clues prompting a rheumatology referral in case of prominent inflammatory findings at carpal tunnel level.

Highlights

Clinical assessmentCarpal tunnel syndrome (CTS) is the most common entrapment neuropathy [1]
Twenty-three CTS+ rheumatoid arthritis (RA) wrists, 84 CTS- RA wrists and 34 idiopathic CTS wrists were evaluated (Fig. 1)
The average cross-sectional area (CSA) of the median nerve was statistically different between the 3 groups (CTS+ RA wrists vs CTS- RA wrists, p = 0.02; CTS+ RA wrists vs idiopathic CTS, p < 0.01; CTS- RA wrists vs idiopathic CTS, p < 0.01) (Fig. 2)

Summary

Introduction

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy [1]. CTS can be associated with several rheumatologic disorders, most commonly rheumatoid arthritis (RA) [2, 3]. Idiopathic CTS is characterized by the absence of underlying identifiable conditions [4]. The diagnosis of CTS is based on clinical history and physical examination. Three meta-analysis confirmed that US is helpful for the diagnosis of CTS [11,12,13]. In 2012, American Association of Neuromuscular and Electrodiagnostic Medicine evidence-based guidelines affirmed that US adds value to electrodiagnosis [14]. US may identify several causes of median nerve entrapment at carpal tunnel level (e.g. flexor tendon tenosynovitis, wrist synovitis, or crystal deposits)

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