Peripheral Nerve Ultrasound Nerve Entrapment • US findings: Jon A. Jacobson, M.D. – Nerve enlargement proximal to entrapment • Best appreciated transverse to nerve Professor of Radiology – Abnormally hypoechoic Director, Division of Musculoskeletal Radiology • Especially the connective tissue layers University of Michigan – Variable enlargement or flattening at entrapment site

Atrophy Disclosures: Denervation • Edema: hyperechoic • Consultant: Bioclinica • Fatty degeneration: • Book Royalties: Elsevier – Hyperechoic • Advisory Board: Philips – Echogenic interfaces • Educational Grant: RSNA • Atrophy: Asymptomatic • None relevant to this talk – Hyperechoic with decreased muscle size • Compare to other side! Note: all images from the textbook Fundamentals of Musculoskeletal Ultrasound are copyrighted by Elsevier Inc. J Ultrasound Med 1993; 2:73 Extensor Muscles: leg

Carpal Tunnel Syndrome: Normal Peripheral Nerve • Proximal swelling • Ultrasound appearance: – Area: circumferential trace – Hypoechoic nerve – Normal: < 9 mm2 fascicles 2 – Hyperechoic connective – Borderline: 9 – 12 mm tissue – Abnormal: > 12 mm2 • Transverse: • 12.8 mm2 = moderate (83% sens, 95% spec) – Honeycomb • 14.0 mm2 = severe (77% sens, 100% spec) appearance Klauser AS et al. Sem Musculoskel Rad 2010; 14:487 Ooi et al. Skeletal Radiol 2014; 43:1387 Silvestri et al. Radiology 1995; 197:291 Median Nerve

1 Syndrome Bifid Median Nerve + CTS “Notch Sign” • Carpal tunnel syndrome1 • Increase in cross-sectional area of ≥ 4 mm2 • Intraneural hypervascularity: Radius 95% accuracy in 2 Lunate diagnosis of CTS Capitate

1Klauser et al. Radiology 2011; 259; 808 2Mallouhi et al. AJR 2006; 186:1240

Carpal Tunnel Syndrome Pronator Teres Syndrome PT-h • Compare areas: • Median nerve compression – Proximal: pronator quadratus between humeral and ulnar heads PT-u PQ – Distal: carpal tunnel Rad • Trauma, congenital, pronator teres 2 • ≥ 2 mm2 = carpal tunnel 9 mm hypertrophy syndrome • Rare • 99% sensitivity • Forearm pain, numbness, • 100% specificity weakness

2 Jacobson JA, et al. Semin Klauser AS. Radiology 2009; 250:171 21 mm Musculoskeletal Rad 2010; 14:473

Postoperative Accessory Abductor Carpal Tunnel Digiti Minimi • Normal variant: 24% A • Discontinuous or thickened • Origin: palmaris longus, flexor P transverse carpal ligament Asymptomatic retinaculum, fascia • Anterior displacement of Thick retinaculum (white arrow) Normal median nerve size (yellow arrow) • Insertion: abductor digiti minimi transverse carpal ligament1 A • Superficial to ulnar nerve: • Median nerve size: – Nerve compression • May decrease2 – Uncommonly interposed • Does not correlate with success3 Short Axis a 1Lee CH et al. Ann Plast Surg 2005; 54:143 Residual symptoms 2 Abicalaf CA et al. Clin Radiol 2007; 62:891 Thick retinaculum (white arrow) Timins et al. AJR 1999; 172:1397 3Naranjo A et al. Scand J Rheum 2010; 39:49 Enlarged median nerve (yellow arrow) Ulnar Nerve

2 Ulnar Nerve: cyclist wrist Anconeus Epitrochlearis Ulnar Nerve

Olecr

Med Epicond Hamate Hamate Transverse Hook Hook Motor Branch Longitudinal Transverse Sensory branch impingement between hook of hamate and bicycle handlebar

Courtesy of EFW Radiology, Calgary, Alberta, Canada Transverse

Isolated Ulnar Nerve Dislocation Ulnar Nerve: cubital tunnel syndrome • Hypoechoic and enlarged Ulnar Nerve – > 9 mm2 area1 – Ratio greater than 2.8 compared to proximal2 • Mild hypoechogenicity alone: may be normal Medial Epicondyle • Causes: Apex – Idiopathic, overuse, joint process – Anconeus epitrochlearis: compression • Normal variant accessory muscle Short Axis 1Thoirs K et al. J Ultrasound Med 2008; 27:737 2Yoon JS et al. Muscle Nerve 2008; 38:1231

Cubital Tunnel Syndrome Snapping Triceps Syndrome: dynamic imaging

Arcuate Ligament

FCUh Anterior Posterior

FCUu

Transverse Longitudinal Transverse

3 Supinator Syndrome Common Peroneal Nerve: entrapment

Supinator

Radius Humerus

Abnormal Normal

Supinator Syndrome Peroneal Intraneural Ganglion Brachioradialis RH • Pain: knee or peroneal nerve distribution Superficial – Possible palpable mass, fluctuating course Br. Deep Br. Abnormal • 18% of those with foot drop1 • No identifiable etiology – Weight loss, trauma, leg crossing • High body mass index2 Radial Head – Unlike other causes for peroneal neuropathy

1Visser et al. 2006; 67:1473 2 Transverse Normal Young et al. Neurology 2009; 72:447

Artificial Intelligence Failure #21: Peroneal Intraneural Ganglia Labradoodle versus Fried Chicken

From: Spinner et al. From: Spinner et al. Skeletal Radiol 2008;37:1091 Clin Anatomy 2007;20:826

4 Peroneal Intraneural Ganglion Ganglion Cyst:

Fibula

Talus

Calcaneus Long Axis Short Axis

Medial plantar nerve impingement from ganglion cyst originating from middle facet of anterior subtalar joint

Intraneural Ganglion Tarsal Tunnel Syndrome: Varices

>15 cm

Atrophy Asymptomatic

Muscle Hernia (extensor digitorum): superficial peroneal nerve entrapment Dynamic Evaluation • Compression – Between transducer and palpation – Bursae (dorsal) compress, neuromas (plantar) do not • Sonographic Mulder Sign – Scan plantar: coronal plane – Neuroma displaces: plantar – Palpable click

Torriani M et al. AJR 2003; 180:1121 Longitudinal Zanetti M et al. Radiology 1997; 203:516

5 Dynamic imaging: Mulder’s Maneuver

Take Home Points

• Entrapment neuropathies: – Hypoechoic edema and nerve enlargement at and proximal to the entrapment site • Dynamic evaluation: – Ulnar nerve: elbow – Morton neuroma – Sonopalpation

Syllabus on line and other educational material: www.jacobsonmskus.com Twitter handle: @jjacobsn

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