Ultrasound of Radial, Ulnar, Disclosures • Consultant: Bioclinica and Median Nerves • Contractor: POCUS PRO • Advisory Board: Philips Jon A. Jacobson, M.D. • Book Royalties: Elsevier • Not relevant to this lecture Professor of Radiology See www.jacobsonmskus.com for syllabus other educational material Nerve Compression Nerve Entrapment • Experimental model (rat, sciatic nv): • US findings: – Compression causes ischemia – Nerve enlargement proximal to entrapment – First pathologic change: edema • Best appreciated transverse to nerve • Correlated with severity of axonal injury – Abnormally hypoechoic – Mild compression: demyelination • Especially the connective tissue layers – Severe compression: axonal damage – Variable enlargement or flattening at entrapment site Powell, Laboratory Investigation 1986; 55:91 Atrophy Denervation Nerve Entrapment Syndromes • Edema: hyperechoic • Fatty degeneration: • Median: – Hyperechoic – Carpal tunnel syndrome – Echogenic interfaces – Pronator teres syndrome • Atrophy: Asymptomatic – Hyperechoic with • Ulnar: decreased muscle size – Ulnar tunnel syndrome • Compare to other side! – Cubital tunnel syndrome J Ultrasound Med 1993; 2:73 Extensor Muscles: leg 1 Volar Wrist Normal Peripheral Nerve • Ultrasound appearance: – Hypoechoic nerve fascicles – Hyperechoic connective tissue • Transverse: – Honeycomb appearance Silvestri et al. Radiology 1995; 197:291 Median Nerve From: Netter’s Atlas of Human Anatomy Volar Wrist: median nerve & flexors Peripheral Nerves • More coarse compared to tendon T – Fascicular not fibrillar – Less anisotropy unlike tendons Lunate • Transverse – Speckled, honeycomb Palmaris FCR Longus • Longitudinal: hypoechoic nerve T fascicles and hyperechoic fascia Radius Axial T1w Short Axis Lunate Silvestri et al. Radiology 1995; 197:291 Capitate Median Nerve vs. Flexor Tendons Volar Wrist: median nerve & flexors • Nerve: fascicular or honeycomb vs brush-like or fibrillar tendon FCR • Tendon: more anisotropy Palmaris Longus – Nerve: connective tissue layers • Move transducer proximal in axial plane Pronator Quadratus – Median nerve becomes relatively hyperechoic Radius between flexor digitorum superficialis & profundus Ulna muscles • Flexor tendons become hypoechoic muscles Short Axis: proximal Short Axis: more proximal Silvestri et al. Radiology 1995; 197:291 2 Volar Wrist: median nerve Peripheral Nerves • More coarse compared to tendon – Less anisotropy, unlike tendons • Transverse: speckled • Longitudinal: hypoechoic nerve fascicles and hyperechoic fascia Silvestri et al. Radiology 1995; 197:291 Short Axis Median Nerve Median Nerve Proximal Distal Short Axis Long Axis Carpal Tunnel: boundaries Median Nerve Ulnar Nerve • Palmar cutaneous Pisiform branch FCR Triquetrum Hamate Scaphoid Hook • Outside of carpal MN tunnel and retinaculum (white arrowheads) • Adjacent to flexor Proximal Distal carpi radialis Note: transverse carpal ligament (white arrows) Tagliafico et al. AJR 2008; 197:107 and median nerve (yellow arrows) 3 Carpal Tunnel Syndrome: Carpal Tunnel Syndrome: • Proximal median nerve swelling • Median nerve compression in carpal tunnel – Area: circumferential trace • Increase volume of tunnel – Normal: < 9 mm2 – Mass, fluid, fat, muscle hypertrophy, tendon – Borderline: 9 – 12 mm2 sheath enlargement, anatomic variants – Abnormal: > 12 mm2 • Decrease size of tunnel • 12.8 mm2 = moderate (83% sens, 95% spec) – Fracture, malalignment • 14.0 mm2 = severe (77% sens, 100% spec) Chen et al. AJR 1997; 168:533 Klauser AS et al. Sem Musculoskel Rad 2010; 14:487 Ooi et al. Skeletal Radiol 2014; 43:1387 Carpal Tunnel Syndrome Median Nerve: how to measure • Compare areas: • Short axis – Proximal: pronator quadratus PQ • Toggle transducer: defined borders – Distal: carpal tunnel Rad • Site of maximal enlargement 9 mm2 • ≥ 2 mm2 = carpal tunnel • Circumferential trace syndrome • Inner border of hyperechoic epineurium • 99% sensitivity • 100% specificity 2 Klauser AS. Radiology 2009; 250:171 21 mm Carpal Tunnel Carpal Tunnel Syndrome: US Syndrome • Close correlation between US and 8 mm2 electrophysiological studies, reflects Short Axis severity of disease1 • Median nerve area = sensitivity to nerve conduction studies2 Radius Lunate • Nerve area decreases after surgery3 Long Axis 1Bayrak IK, Muscle Nerve 2007; 35:344. 2Nakamichi K, Muscle Nerve 2002; 26:798. 3 Pronator Quadratus Abicalaf CA, Clin Radiol 2007; 62:891. 4 Carpal Tunnel Syndrome “Notch Sign” Carpal Tunnel Syndrome: proximal Radius Lunate Capitate Short Axis Axial T2w Normal Carpal Tunnel Syndrome: distal Carpal Tunnel Syndrome Flexor Tendons Radius Capitate Short Axis Axial T2w LunateLunate Long Axis Carpal Tunnel Syndrome: Carpal Tunnel Syndrome: ulnar bursa distention increased flow • Intraneural hypervascularity: 95% accuracy in diagnosis of carpal tunnel syndrome AJR 2006; 186:1240 Long Axis Short Axis 5 Carpal Tunnel Syndrome: ganglion Postoperative Carpal Tunnel • Discontinuous or thickened transverse carpal ligament Asymptomatic Thick retinaculum (white arrow) • Anterior displacement of Normal median nerve size (yellow arrow) transverse carpal ligament1 • Median nerve size: • May decrease2 Case #2 • Does not correlate with 3 Case #1 success Short Axis 1Lee CH et al. Ann Plast Surg 2005; 54:143 Residual symptoms 2Abicalaf CA et al. Clin Radiol 2007; 62:891 Thick retinaculum (white arrow) 3Naranjo A et al. Scand J Rheum 2010; 39:49 Enlarged median nerve (yellow arrow) Failed Carpal Tunnel Release Pitfall: bifid median nerve • Bilobed or two separate trunks • Interposed persistent median artery Transverse Sagittal • Incidence: 2.8% • Thickened transverse carpal ligament (white arrows) Propeck et al. AJR 2000;175:1721 • Persistent median nerve enlargement (yellow arrows) Bifid Median Nerve Bifid Median Nerve • Bilobed or two separate trunks • Interposed persistent median artery Short Axis Axial T1w • Incidence: 2.8% Propeck et al. AJR 2000;175:1721 6 Bifid Median Nerve with Aberrant Ulnar Trunk Bifid Median Nerve + CTS and Carpal Tunnel Syndrome • Carpal tunnel syndrome1 • Increase in cross-sectional area of ≥ 4 mm2 • Intraneural hypervascularity: 95% accuracy in diagnosis of CTS2 1Klauser et al. Radiology 2011; 259; 808 2Mallouhi et al. AJR 2006; 186:1240 Short Axis Persistent Median Artery MN Nerve Entrapment Syndromes • Median: MN – Carpal tunnel syndrome Case 1 Case 2 – Pronator teres syndrome • Ulnar: – Ulnar tunnel syndrome – Cubital tunnel syndrome • Incidence: 10 – 20%: most with bifid median nerve Gassner EM et al. JUM 2002; 21:455c Median Nerve: pronator teres Pronator Teres Syndrome PT-h A • Median nerve compression BT between humeral and ulnar heads PT-u • Trauma, congenital, pronator teres Lateral Medial hypertrophy • Rare • Forearm pain, numbness, weakness Jacobson JA, et al. Semin Pronator Teres: Musculoskeletal Rad 2010; 14:473 Humeral and Ulnar Heads 7 Pronator Teres Syndrome Anterior Interosseous Nerve Syndrome Pronator Pronator Quadratus Quadratus Denervation Flexor Pollicis Longus changes Flexor Digitorum Profundus (lateral aspect) Volar Wrist Nerve Entrapment Syndromes • Median: – Carpal tunnel syndrome – Pronator teres syndrome • Ulnar: – Ulnar tunnel syndrome – Cubital tunnel syndrome From: Netter’s Atlas of Human Anatomy Technique: volar Volar Wrist: Guyon’s canal • Median nerve • Flexor tendons Pisiform • Volar joint recesses Ulnar • Guyon canal Artery – Ulnar artery and nerve Axial T1w Short Axis 8 Volar Wrist: ulnar nerve Ulnar Nerve • At hook of hamate • Sensory branch: – Superficial to hook – One or two trunks Hamate – White arrows Hook Hamate • Motor branch: Hook – Ulnar side of hook – Yellow arrow Sagittal T1w Long Axis Silvestri et al. Radiology 1995; 197:291 Ulnar Nerve: DCBUN Guyon’s Canal: • Dorsal cutaneous branch • Ulnar tunnel syndrome of the ulnar nerve FCU – Ulnar nerve compression • Distal 1/3 of forearm a – Accessory Abductor Digiti Minimi1 • Courses volar to dorsal: Ulnar • Variant: up to 24% of wrists Ulna deep to flexor carpi Nerve • Hypothenar hammer syndrome2 ulnaris (FCU) – Trauma • Sensory: dorsal 5th – Ulnar artery thrombosis + distal emboli finger, dorsolateral 4th finger and hand 1AJR 1999; 172:1397 2J Vasc Surg 1987; 5:838 Le Corroller et al. Eur Radiol 2013; 23:2246 Accessory Abductor Ulnar Nerve: cyclist wrist Digiti Minimi • Normal variant: 24% A • Origin: palmaris longus, flexor P retinaculum, fascia Ulnar Nerve • Insertion: abductor digiti minimiA • Superficial to ulnar nerve: Hamate Hamate – Nerve compression Hook Hook – Uncommonly interposed Motor Branch Longitudinal Transverse a Sensory branch impingement between hook of hamate and bicycle handlebar Timins et al. AJR 1999; 172:1397 Ulnar Nerve Courtesy of EFW Radiology, Calgary, Alberta, Canada 9 Ulnar Artery Aneurysm Nerve Entrapment Syndromes • Median: – Carpal tunnel syndrome – Pronator teres syndrome • Ulnar: – Ulnar tunnel syndrome – Cubital tunnel syndrome Longitudinal Ulnar Nerve: anatomy • Behind medial epicondyle Ulnar Nerve of humerus: Osborne fascia – Cubital tunnel retinaculum or Osborne fascia Arcuate ligament • Distal to epicondyle: – True cubital tunnel – Between ulnar and humeral heads: flexor carpi ulnaris – Under arcuate ligament Martinoli, C. et al. Radiographics 2000;20:S199-S217 Ulnar Nerve Cubital Tunnel Syndrome: Proximal to Cubital Tunnel: Medial • Ulnar nerve entrapment at elbow Olecranon Epicondyle • Space between medial Apex • 2nd most common upper extremity epicondyle and entrapment neuropathy olecranon process • Etiologies: • Contains ulnar nerve – Trauma, valgus deformity, Flexor