Ultrasonography in ulnar neuropathy at the elbow: A critical review

TLDR: Ultrasonography of the ulnar nerve has been recommended as a useful additional test in ulnar neuropathy at the elbow (UNE).

Abstract: Introduction: Ultrasonography of the ulnar nerve has been recommended as a useful additional test in ulnar neuropathy at the elbow (UNE). Methods: We searched the literature and systemically reviewed all clinical trials in UNE. We also looked for articles about the normal sonoanatomy and spe- cific causes of UNE. Results: Seven of 14 clinical trials in UNE were suitable for further analysis. Ultrasonographic ulnar nerve size measurement appears to be a test with good diag- nostic accuracy. The most frequently reported abnormality was an increased cross-sectional area of the ulnar nerve at the elbow. However, several studies had methodological flaws. In addition, the ultrasonographic techniques and study designs dif- fered among the studies. There were a few other uncontrolled studies about the underlying causes of UNE. Discussion: The role of ultrasonography in UNE seems promising but could not be firmly established. More prospective studies are needed, and we make several recommendations for further research. Muscle Nerve 43: 627-635, 2011 The diagnosis of ulnar neuropathy at the elbow (UNE) may seem straightforward in the majority of cases. Clinicians will usually suspect an ulnar neu- ropathy when the characteristic symptoms and signs are present, and electrophysiological studies will eventually confirm the diagnosis. However, UNE has to be distinguished from other disorders and from ulnar neuropathy at other levels. Clinical signs indicating a lesion of the ulnar nerve above the level of the wrist (e.g., paresis of the flexor carpi ulnaris or flexor digitorum profundus muscles) are absent in many cases 1,2 and provocative clinical tests have a low diagnostic accuracy. 3 In addition, electrophysio- logical studies may be false negative or non-localiz- ing with sensitivities ranging from 37% to 86%. 4 Fur- thermore, the reliability of electrophysiological studies is undermined by a broad 95% confidence interval of the conduction velocity across the elbow owing to the accumulation of measurement errors. 5,6 Therefore, new laboratory tests are needed to improve the reliability of the diagnosis of UNE. 4 Ultrasonography of the ulnar nerve has been rec- ommended by several investigators as a good and reliable additional test in UNE. Using advanced ultrasonographic techniques, the ulnar nerve can be depicted with excellent resolution, and thickening may be revealed in patients with UNE. However, to our best knowledge, ultrasonography still has no de- finitive role in guidelines or practice parameters. As new and promising tests often become widely applied before they are critically appraised 7 we aimed to perform a more close and systematic review of the studies published so far. Ultrasonography in UNE requires detailed knowledge of the normal (sono-)anatomy, dynam- ics, and variations of the ulnar nerve and related structures. Therefore, we will first provide a synop- sis of the normal sonographic anatomy of the ul- nar nerve and then review ultrasonographic studies in the diagnosis of UNE and studies about underly- ing abnormalities in UNE.