Ultrasound Imaging for the Cutaneous Nerves of the Extremities and Relevant Entrapment Syndromes: From Anatomy to Clinical Implications

Abstract

Cutaneous nerve entrapment plays an important role in neuropathic pain syndrome. Due to the advancement of ultrasound technology, the cutaneous nerves can be visualized by high-resolution ultrasound. As the cutaneous nerves course superficially in the subcutaneous layer, they are vulnerable to entrapment or collateral damage in traumatic insults. Scanning of the cutaneous nerves is challenging due to fewer anatomic landmarks for referencing. Therefore, the aim of the present article is to summarize the anatomy of the limb cutaneous nerves, to elaborate the scanning techniques, and also to discuss the clinical implications of pertinent entrapment syndromes of the medial brachial cutaneous nerve, intercostobrachial cutaneous nerve, medial antebrachial cutaneous nerve, lateral antebrachial cutaneous nerve, posterior antebrachial cutaneous nerve, superficial branch of the radial nerve, dorsal cutaneous branch of the ulnar nerve, palmar cutaneous branch of the median nerve, anterior femoral cutaneous nerve, posterior femoral cutaneous nerve, lateral femoral cutaneous nerve, sural nerve, and saphenous nerve.

Keywords: compression; cutaneous nerve; electromyography; pain; sonography.

Figure 1

The medial brachial cutaneous nerve (black arrowhead), intercostal brachial cutaneous nerve (yellow arrowhead), and medial antebrachial cutaneous nerve (white arrowhead) in the axillary fossa (A). The medial antebrachial cutaneous nerve at the level of the arm (B) and the forearm (C). Black arrow, median nerve; white arrow, ulnar nerve.

Figure 2

The medial brachial cutaneous nerve (black arrowhead) at the level of the proximal (A) and distal (B) arm. The intercostal brachial cutaneous nerve (yellow arrowhead) superficial to the latissimus dorsi muscle (C) and next to the nerve’s exit from the 2nd intercostal space (D). The antebrachial cutaneous nerve (white arrowhead) at the level of the axillary fossa (E), the proximal (A), and the distal (F) arm. White arrow, ulnar nerve; AA, axillary artery; AV, axillary vein; BV, basilic vein.

Figure 3

A snapped medial antebrachial cutaneous nerve (black arrow) in a woman complaining of forearm pain (A). A swollen lateral antebrachial cutaneous nerve (big white arrow) compared to the nerve of the asymptomatic side (small white arrow) in a woman with forearm pain (B). A lateral antebrachial cutaneous nerve (dotted circle) entrapped by the distal biceps tendon during elbow supination/pronation (C). A posterior antebrachial cutaneous nerve (yellow arrowhead) with peripheral hypervascularity in a male with chronic lateral epicondylitis (D). A swollen superficial radial nerve (big black arrowhead) compared to the nerve on the asymptomatic side (small black arrowhead) in a man with de Quervain’s tenosynovitis (E). A neuroma of the dorsal ulnar cutaneous nerve (big white arrowhead) and the normal contralateral nerve (small white arrowhead) in a man with a fracture of the 5th metacarpal bone (F). UN, ulnar nerve; BT, biceps tendon; CET, common extensor tendon of the wrist; ECRL, extensor carpi radialis longus muscle; APL, abductor pollicis longus tendon; EPB, extensor pollicis brevis tendon; ECU, extensor carpi ulnaris tendon.

Figure 4

The lateral antebrachial cutaneous nerve (white arrowhead) at the elbow level (A) and the posterior antebrachial cutaneous nerve (black arrowhead) at the distal forearm level (B). Orange arrow, distal biceps tendon; blue arrow, cephalic vein.

Figure 5

The lateral antebrachial cutaneous nerve (white arrowhead) at the elbow (A) and distal forearm (B) levels. The posterior antebrachial cutaneous nerve (black arrowhead) at the exit of the spiral groove (C), the distal forearm (D), and near the lateral epicondyle (E). Long axis of the posterior antebrachial cutaneous nerve (F). CV, cephalic vein; BA, brachial artery; black arrow, radial nerve.

Figure 6

The superficial radial nerve (white arrowhead) (A), the dorsal ulnar cutaneous nerve (black arrowhead) (B), and the palmar cutaneous nerve of the median nerve (yellow arrowhead) at the distal forearm level (C). ECRL, extensor carpi radialis longus muscle; APL, abductor pollicis longus tendon; EPB, extensor pollicis brevis tendon; ECU, extensor carpi ulnaris tendon; EDM, extensor digiti minimi tendon; PL, palmaris longus tendon; FCR, flexor carpi radialis tendon; black arrow, median nerve.

Figure 7

The superficial radial nerve (white arrowhead) at the level of the distal forearm (A) and the radial dorsal wrist (B). The dorsal ulnar cutaneous nerve (black arrowhead) at the level of the distal forearm (C) and the ulnar side of the dorsal wrist (D). The palmar branch of the median nerve (yellow arrowhead) at the level of the distal forearm (E) and emerging from the antebrachial fascia (black dashed line) (F). RA, radial artery; ECRL, extensor carpi radialis longus muscle; APL, abductor pollicis longus tendon; EPB, extensor pollicis brevis tendon; white arrow, ulnar nerve; black arrow, median nerve.

Figure 8

The anterior femoral cutaneous nerve (black arrowhead) at the inguinal region (A). The posterior femoral cutaneous nerve near the gluteal fold (white arrowhead) (B). The lateral femoral cutaneous nerve (yellow arrowhead) at the proximal thigh (C). White arrow, femoral nerve; blue arrow, great saphenous vein; GMA, gluteus maximus muscle; ST, semitendinosus muscle; BF, long head of the biceps femoris muscle; TFL, tensor fasciae latae muscle.

Figure 9

The anterior femoral cutaneous nerve (black arrowhead) at the femoral triangle in its short (A) and long (B) axes and at the mid-thigh level (C). The posterior femoral cutaneous nerve (white arrowhead) at the gluteal fold in its short axis (D) and long axis (E) and at the ischiofemoral interval (F). FN, femoral nerve; FA, femoral artery; GMA, gluteus maximus muscle; CT, hamstring conjoint tendon; ST, semitendinosus tendon; SN, sciatic nerve; QF, quadratus femoris muscle.

Figure 10

The short- (A) and long- (B) axes imaging of the anterior femoral cutaneous nerve (black arrowhead) compressed by an inguinal lymph node (dotted circle). A sural nerve (yellow arrowhead) neuroma in a male following Achilles tendon repair (C). A sural nerve schwannoma in a female with chronic calf pain (D). A swollen segment (white arrowhead) and a relatively normal portion (smaller white arrowhead) of the saphenous nerve adjacent to a hematoma (white arrow) of the distal femur (E). A thickened saphenous nerve (white arrowhead) next to serosanguinous fluid (black arrow) in a female with a degloving injury of the leg (F). FA, femoral artery; FV, femoral vein; SSV, small saphenous vein; great saphenous vein.

Figure 11

The lateral femoral cutaneous nerve (yellow arrowhead) at the level of the anterior iliac fossa (A), anterior superior iliac spine (B), and the fat compartment interposed between the sartorius and tensor fasciae latae muscles (C). The medial sural cutaneous nerve (white arrowhead) (D) and the lateral sural cutaneous nerve (black arrowhead) of the posterior leg, the sural nerve (black arrow) at the level of the distal leg (E), and the lateral foot (F). Black dashed line, fascia lata; white dashed line, fascia iliaca; MG, medial gastrocnemius; LG, lateral gastrocnemius; PL, peroneus longus; PB, peroneus brevis; CFL, calcaneofibular ligament; white arrow, lateral calcaneal branch of the sural nerve.

Figure 12

The medial sural cutaneous (white arrowhead) and the lateral sural cutaneous (black arrowhead) nerves of the posterior leg (A). The sural nerve (black arrow) and its lateral sural cutaneous branch (white arrow) (B). The infrapatellar branch (orange arrowhead) and the sartorial branches (yellow arrowhead) of the saphenous nerve crossing the knee joint (C). The saphenous nerve accompanying the great saphenous vein coursing along the distal tibia (D). MG, medial gastrocnemius muscle; LG, lateral gastrocnemius muscle; blue arrowhead, small saphenous vein; blue arrow, great saphenous vein.

Figure 13

The saphenous nerve (black arrow) proximal to the exit of the adductor canal (A). The infrapatellar (black arrowhead) and sartorial (white arrowhead) branches of the saphenous nerve at the exit of the adductor canal (B). The infrapatellar branch on the distal femur (C) and the sartorial branch on the distal tibia (D). White arrow, nerve to the vastus medialis muscle; FA, femoral artery; FV, femoral vein; GSV, great saphenous vein.