Diagnostic accuracy of ultrasonographic and nerve conduction studies in ulnar neuropathy at the elbow
Introduction
Traditionally ulnar neuropathy at the elbow (UNE) has been diagnosed using clinical examination, and confirmed by electrodiagnostic (EDx) testing. Of EDx techniques standard 10-cm nerve conduction studies (NCSs), demonstrating reduced conduction velocity or conduction block in the elbow segment, are still most often used (Preston and Shapiro, 2013). Although this approach has very high specificity (>95%), it has much lower sensitivity that varied in different studies from 37% to 86% (American Association of Electrodiagnostic Medicine and Campbell, 1999). Another EDx approach useful in diagnosis of focal neuropathies is short-segment NCSs (SSNCs). However, in spite of its higher diagnostic accuracy, only three studies reported diagnostic accuracy of SSNCs in UNE (Azrieli et al., 2003, Visser et al., 2005, Yuksel et al., 2009), which are also rarely used in UNE diagnosis.
In the last two decades important progress has been made in peripheral nerve imaging. Therefore, ulnar nerve can be now depicted with excellent resolution, also using advanced ultrasonographic (US) technology. US has been also recommended as a good and reliable additional test in the diagnosis of UNE (Beekman et al., 2011). However, US studies measuring ulnar nerve thickness in UNE patients, reported highly variable sensitivity of 46%–100% and specificity of 43%–97% (Ayromlou et al., 2012, Bayrak et al., 2010, Beekman et al., 2004, Gruber et al., 2010, Mondelli et al., 2008, Pompe and Beekman, 2013, Volpe et al., 2009, Yoon et al., 2008). Moreover, up to now only one prospective US study in UNE, designed in full accordance with the Standards for Reporting of Diagnostic Accuracy (STARD) recommendations (Bossuyt et al., 2003), has been published (Beekman et al., 2004). That study used standard 10-cm NCSs and not SSNCSs as a reference test. In addition, although nowadays nerve cross sectional area (CSA) is usually measured in clinical US practice, in that study ulnar nerve diameter was measured (Fig. 1).
In order to better define role of US in UNE diagnosis we performed the prospective study, designed in full accordance with STARD recommendations. We primarily aimed to estimate diagnostic accuracy of US in patients with the diagnosis of UNE established by clinical examination and SSNCSs. In US studies we measured ulnar nerve CSAs using a trace method. Furthermore, we also compared diagnostic accuracy of US to standard 10-cm NCSs and SSNCSs in patients with UNE diagnosis established by clinical examination alone.
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Patients and controls
We prospectively recruited consecutive patients with suspected UNE who were referred to the secondary referral centre (i.e., the Institute of Clinical Neurophysiology, University Medical Centre Ljubljana, Slovenia). Inclusion criteria was at least one of the following presenting symptoms typical for UNE: (1) continuous numbness or paresthesias in the 5th and in the ulnar half of the 4th finger; or (2) feeling of weakness or clumsiness of the ulnar-innervated muscles; or (3) pain on the medial
Results
Between April 2012 and October 2013, 109 patients (113 arms) with suspected UNE, and 49 controls with similar demographic characteristics (29 men, aged 47 ± 14, 23–81 years) were included. Subject’s status (symptomatic or asymptomatic) could not be hidden to 4 examiners in 21 controls recruited mainly from the hospital staff (Omejec and Podnar, 2014). In controls, 65% of non-dominant and 78% of left arms were evaluated. We found no significant difference on comparison of ulnar nerve CSAs in
Discussion
Together with the only previous prospective study designed in full accordance with the STARD protocol (Beekman et al., 2004), the present study confirmed diagnostic accuracy of US in UNE of about 80% (Table 3), which, considerably reduces variability reported previously (sensitivity: 46–100%, specificity: 43–97%) (Ayromlou et al., 2012, Bayrak et al., 2010, Beekman et al., 2004, Gruber et al., 2010, Mondelli et al., 2008, Pompe and Beekman, 2013, Volpe et al., 2009, Yoon et al., 2008). Although
Funding
Authors report grants from The Republic of Slovenia Research Agency (Grant No. P3-0338), during the conduct of the study. Study sponsor had no role in the collection, analysis and interpretation of data and in the writing of the manuscript.
Acknowledgments
The authors thank Alenka Dremelj for subject recruitment and assistance with nerve conduction studies and Dr. Dianne Jones for language review.
Conflict of interest: None of the authors have potential conflicts of interest to be disclosed.
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