Diagnosis of ulnar neuropathy in the elbow: value of ultrasonography and MRI

Transcription

1 Diagnosis of ulnar neuropathy in the elbow: value of ultrasonography and MRI Poster No.: C-2216 Congress: ECR 2013 Type: Educational Exhibit Authors: P. L. Pegado, C. A. Santos Ruano, J. Raposo, P. Alves, R. M R. Mateus Marques, L. Vieira ; Lisboa/PT, Lisbon/PT Keywords: Neuroradiology peripheral nerve, Musculoskeletal soft tissue, Ultrasound, MR, Diagnostic procedure, Education, Education and training DOI: /ecr2013/C-2216 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 19

2 Learning objectives To demonstrate the use of ultrasound (US) and magnetic resonance imaging (MRI) in the diagnosis of ulnar neuropathy in the elbow (UNE). To illustrate the imaging protocol and findings in UNE and its main etiologies. To describe the advantages and limitations of US and MRI in the diagnosis of UNE. Images for this section: Fig. 1: Sites of potencial ulnar nerve compression and the causes of compression at each site in the elbow. In site 1, compression is caused by Arcade of Struthers. In site 2, compression is caused by medial epicondyle. In site 3, compression is caused by the entrance or within the cubital tunnel. In site 4, compression is caused by thickened Page 2 of 19

3 aponeurosis of deep flexorpronator. (Adapted from Grant's Atlas of Anatomy, 11th ed. Philadelphia: Lippincott Williams & Wilkins) Page 3 of 19

4 Background Neuropathy is a broad term referring to the clinical presentation of sensory abnormalities or motor weakness, and it can be caused by metabolic or structural anomalies (1). Here we focus on the main etiologies of UNE in the elbow determining structural anomalies identified by imaging techniques. Ulnar nerve compression at the elbow is the second most common nerve entrapment of the upper extremity, after carpal tunnel syndrome, with an estimated annual incidence of cases per population (8). Patients with UNE complain of pain, usually worsens with elbow flexion, paresthesias and weakness in 5th finger and ulnar side of the 4th finger and numbness in the dorsal ulnar aspect of hand and fingers. Physical labor that involves repetitive elbow flexion is one of the most important risk factors, reported in the literature (6). The possible structural causes of UNE include overuse, subluxation of the ulnar nerve, trauma with or without humeral fracture, an anconeus epitrochlearis muscle, osteophytes, ganglia, synovitis, infection and nerve intrinsic causes such as tumors. Entrapment syndromes refer to a group of neuropathies due to a structural abnormality at a specific location. Compression of the ulnar nerve may occur at four different anatomical sites along its course at the elbow from proximal to distal: at the intermuscular septum due to the arcade of Struthers; at the medial epicondyle just before the entrance of the cubital tunnel; within the cubital tunnel; and at the flexorpronator aponeurosis between the heads of the flexor carpi ulnaris where the nerve enters the forearm. The cubital tunnel is the most common location of ulnar nerve compression (Fig.1). Page 4 of 19

5 Fig. 1: Sites of potencial ulnar nerve compression and the causes of compression at each site in the elbow. In site 1, compression is caused by Arcade of Struthers. In site 2, compression is caused by medial epicondyle. In site 3, compression is caused by the entrance or within the cubital tunnel. In site 4, compression is caused by thickened aponeurosis of deep flexorpronator. (Adapted from Grant's Atlas of Anatomy, 11th ed. Philadelphia: Lippincott Williams & Wilkins) References: (Adapted from Grant's Atlas of Anatomy, 11th ed. Philadelphia: Lippincott Williams & Wilkins) The diagnosis is suspected clinically, and electrophysiological studies play an important role in the assessment of suspected UNE. The role of imaging is to identify the structural abnormality causing the entrapment, such as masses, anomalous muscles, fibrous bands, and osseous deformities, or to show secondary findings that confirm or support the diagnosis. In several cases electromyographic findings are non-localizing, and US and MRI are used for assessment of the nerve to determine the site and also the etiology of compression. This information has a value in the surgical planning as it may change the choice of the surgery approach (7). Page 5 of 19

6 Imaging findings OR Procedure details Due to false negative or non-localizing results of the electrophysiological studies, US of the ulnar nerve has been recently recommended as an accurate noninvasive tool (2). On the other hand, MRI is being increasingly used in the evaluation of UNE. To the best of our knowledge, the diagnostic value of both ultrasonography and MRI in UNE has not been entirely investigated (2). The selection of the imaging modality to be used for UNE depends on the anatomic location of the abnormality, the clinician's preference, local technique availability, and the individual experience of radiologist with each modality (1). High-resolution US using 15 MHZ transducers is a quick, low cost, noninvasive imaging technique with specific advantages, including dynamic evaluation, high spatial resolution, and the capacity to help explore all the ulnar nerve traject. Limitations include operator dependence and confined use for the assessment of the superficial part of the ulnar nerve. MRI offers better depiction of deeper parts of the ulnar nerve and higher contrast resolution (6). Ulnar nerve entrapment despite the location in the elbow, follows a similar pattern of morphological change, which is well depicted by US. In the context of entrapment, the nerve is flattened; additionally, just proximal to the site of entrapment, the nerve increases in cross sectional area (CSA) giving the appearance of a "pseudoneuroma". Most investigators found an upper limit of normal CSA of the ulnar nerve at the level of the 2 medial epicondyle of 8-10 mm (3). During measurements, the transducer should be held perpendicular to the nerve to avoid measurement errors. Most investigators measure nerve size within the hyperechoic rim surrounding the nerve. It is important to note that, 0 with elbow flexion > 90, the shape of the ulnar nerve changes and the CSA decreases (3). Another US morphological feature of nerve entrapments is the change in nerve echotexture: the ulnar nerve become more hypoecogenic and, along with the increase in syndrome's severity, it culminates in loss of fascicular pattern (Fig. 2,3,4,5,6 and 7). Page 6 of 19

7 Fig. 2: UNE in 32 year old women. Transverse US image with hypoechogenicity and swelling of ulnar nerve (UN). Color sonography may also be used to differentiate the ulnar nerve from a vascular structure: in patients with UNE the latter has typically a smaller diameter when compared with the ulnar nerve, as in the case we ilustrate. Page 7 of 19

8 Fig. 3: UNE in a woman with Paget disease. Transverse ultrasound image, proximal to the ulnar tunnel, shows a CSA enlargement of the ulnar nerve (UN), about 11 mm2, that appears swollen and hypoechoic with an absent fascicular pattern. ME (medial epicondyle). Page 8 of 19

9 Fig. 4: UNE in a man with psoriartric arthritis. Longitudinal ultrasound compound image adjacent to the ulnar nerve, with apparently focal compression (small white arrow) and proximal nerve swelling and hypoechogenicity (large white arrow) Page 9 of 19

10 Fig. 5: A rare case of UNE in a man with leprosy. A transverse (A) and longitudinal (B) ultrasound image show CSA enlargement of the ulnar nerve and the characteristic macro- fascicular pattern. Page 10 of 19

11 Fig. 6: A post-surgery neuroma in 15 year old boy who have been involved in an accident with a glass which resulted in transection of the ulnar nerve followed by surgical repair. Because the patient kept motor symptoms 6 months after surgery, US imaging was requested.(a) Transverse ultrasound image at the level of the medial epicondyle (ME) shows a severe enlarged CSA of the ulnar nerve, about 52 mm2 (normal < 10 mm2) and an heterogeneous, hyperecoic nerve (arrows) in relation to the surgery performed. (B) Longitudinal image at the same level shows the heterogeneous focal enlargement of the ulnar nerve. Findings are consistent with a post-surgery neuroma. Page 11 of 19

12 Fig. 7: UNE in a woman with motor multifocal motor polineuropathy. Transverse ultrasound image shows an increase in the sectional area of the ulnar nerve (white arrow), without loose of the fascicular pattern. MRI of the symptomatic ulnar nerve may show signal hiperintensity on T2-weighted images and nerve swelling (Fig. 8 and 9). However signal hyperintensity is not a specific finding because it has been shown in 60% of asymptomatic elbows (8). Page 12 of 19

13 Fig. 8: UNE in a man. Axial Fat Sat T2-weighted MRI image reveals swollen and edematous ulnar nerve (white arrow) at the level of proximal cubital tunnel. Page 13 of 19

14 Fig. 9: UNE in a woman, with complain of pain, tenderness and paresthesias in the forearm, no structural etiology has been depicted by MRI. (A) Axial STIR MRI shows swollen and increased signal intensity of the ulnar nerve (white arrow). (B) Coronal reconstruction DESS MRI from the same patient also shows slight intensity signal increase of the ulnar nerve (white arrow), note the wavy shape of the ulnar nerve due to extension position during the acquisition of the image. Indirect MRI findings of ulnar nerve entrapment may be identified, including denervation muscle edema or muscle atrophy. The characteristic MRI signal intensity patterns of acute and subacute muscle denervation include high signal intensity in flexor carpi ulnaris or in the ulnar half of the flexor digitorum profundus muscles on images obtained with fluid-sensitive sequences, such as T2-weighted or STIR images, and normal signal intensity on T1-weighted images. With regard to denervated muscle, MRI is more sensitive to signal intensity changes of the muscle than US is to changes in the echo pattern (5). It is also a technique that better characterizes some specific structural conditions but is less accessible for dynamic evaluation when compared with US, as shown on the following examples. Page 14 of 19

15 Accessory muscles An accessory anconeus epitrochlearis muscle has been described as one of the most common structural abnormality of the nerve in the cubital tunnel. Located along the posterior aspect of the cubital tunnel, the anconeus epitrochlearis muscle may compress the ulnar nerve against the medial epicondyle or olecranon (Fig.10). Fig. 10: UNE in a man with anconeus epitrochlearis muscle. Axial T1-weighted MRI shows ulnar nerve (white arrowhead) with high signal intensity compressed against medial epicondyle (E) by anconeus epitrochlearis muscle (arrow). (O- olecranon process) Subluxation of the Ulnar Nerve Another group at risk for dynamic UNE is people with recurrent anterior subluxation of the ulnar nerve. Ulnar nerve subluxation represents abnormal movement of the ulnar nerve out of the cubital tunnel and over the medial epicondyle during elbow flexion (Fig.11). This Page 15 of 19

16 abnormal nerve translation, however, has been reported in 16% to 20% of asymptomatic people (4). The repetitive translation of the nerve over the bony prominence of the epicondyle as it dislocates in flexion and reduces in extension can cause frictional neuritis. Fig. 11: UNE in a man with subluxation of the ulnar nerve. US transverse image with elbow flexion shows, proximal to cubital tunnel, anterior dislocation of ulnar nerve (arrowheads). Note subluxation of triceps medial head (T) over de medial epicondyle (E). The ulnar nerve is enlarged and hypoecogenic, consistent with UNE. Risk factors for ulnar nerve anterior dislocation include cubitus varus deformity, a hypertrophic medial head of the triceps, or an accessory head of the triceps. Sonographic imaging during flexion and extension is a practical and real-time method to evaluate this nerve dislocation. On routine MRI, which is performed with the elbow Page 16 of 19

17 extended, the nerve dislocation will not be seen, the elbow must be imaged in the flexed position (8). Tumors There were a few case reports about tumors of the ulnar nerve at the elbow, including intraneural hemangioma, lymphoma, infiltration of myeloma cells and capillary hemangioma (3) (Fig. 12). Fig. 12: UNE in a man with pain in the forearm. Axial T2 - weighted fat satured MRI (A) and corresponding axial T1 - weighted fat satured (B) - An hemangioma compressing the ulnar nerve (black arrow) at the cubital tunnel. Increased signal intensity in the ulnar nerve (A) is indicating of focal neuritis. Angio RM coronal reconstruction (C) where we can depict the hemangioma (white circle). Page 17 of 19

18 Conclusion As a complementary tool, ultrasonography of the ulnar nerve using CSA is both sensitive and specific in UNE. Ulnar nerve MRI targeted to the increased signal of the ulnar nerve can be a useful diagnostic test for evaluation of UNE, particularly in conjunction with clinical and electrophysiological data. MRI has an added value in early stage diagnosis, as muscle atrophy may be the single modification in the imaging studies, and US has little accuracy to this, sometimes initial, subtle feature. Both US and MRI may provide useful information with regard to the exact anatomic location of the entrapment or may aid in narrowing the differential diagnosis. References Andreisek G, Crook D, Burg D, Marincek B, Weishaupt D Peripheral Neuropathies of the Median, Radial, and Ulnar Nerves: MRInaging Features. RadioGraphics 2006; 26: Ayromlou H, Tarzammi M, Daghighi M Diagnostic Value of Ultrasonography and Magnetic Resonance Imaging in Ulnar Neuropathy at the Elbow. Neurology 2012;2012: Beekman R, Visser LH, Verhagen Ultrsonography in ulnar neuropathy at elbow: A critical review. Muscle & Nerve 2011; Jacobson J, Jebson P, Jeffers A, Fessell D, Hayes C Ulnar Nerve Dislocation and Snapping Triceps Syndrome: Diagnois with Dynamic Sonography - Report of Three Cases. Radiology 2011; 220: Kim SJ, Hong SH, Jun WS, et al. MR Imaging Mapping of Skeletal Muscle Denervation in Entrapment and Compressive Neuro pathies. RadioGraphics 2011; 32: Linda DD, Harish S, Stewart BG, et al. Multimodality Imaging of Peripheral Neuropathies of the Upper Limb and Brachial Plexus. RadioGraphics 2010; 30: Martinoli C, Bianchi S, Gandolfo N, et al. US of Nerve. Entrapment in Osteofibrous Tunnels of the upper and Lower Limbs. RadioGraphics 2000; 20:S199-S217. Miller T, Reinus W Nerve entrapment Syndromes of the Elbow, Forearm, and Wrist AJR 2010; 195: Page 18 of 19

19 Personal Information Pedro Luís Pegado, is Resident of Radiology at "Serviço de Radiologia do Hospital de São José - Centro Hospitalar de Lisboa Central (CHLC)" Carina Alexandra Ruano is Resident of Radiology at "Serviço de Radiologia do Hospital de Santo António dos Capuchos - Centro Hospitalar de Lisboa Central (CHLC)". Joana Raposo and Pedro Alves are Radiology Consultants and Rui Mateus Marques is a Senior Consultant of Radiology (Chief of Department) at "Serviço de Radiologia do Hospital de São José - CHLC". Luís Vieira is Radiology Consultant at "Serviço de Radiologia do Hospital de Santo António dos Capuchos - Centro Hospitalar de Lisboa Central (CHLC)". Page 19 of 19