The Median Nerve


	Head and Neck

	Vagus (X)

	Spinal Accessory Nerve (XI)

	Cervical Plexus (C2-4)

	Brachial Plexus (C5-T1)

	Upper Extremity

	Musculocutaneous

	Radial

	Median

	Ulnar

	Lower Extremity

	Ilioinguinal / Iliohypogastric

	Femoral

	Sciatic

	Common Peroneal

	Tibial

	Sural

The ultrasound appearance of the median nerve has been extensively described in the carpal tunnel syndrome literature. The median nerve arises from the medial and lateral cords of the brachial plexus.

The Median Nerve in the Arm (supine with arm abducted)

The median nerve usually lies superficial to the axillary artery in the axilla. The median crosses the front of the artery from lateral to medial and can be displaced to either side of the axillary artery with transducer compression (Video 604 KB).

The Median Nerve in the Forearm (supine with arm supinated)

The median nerve lies of the medial side of the brachial artery near the antecubital fossa. The median nerve leaves the brachial artery or ulnar artery to enter the forearm.

In the forearm the median nerve lies in the fascia between the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) muscles (Video 232 KB). Around 5 cm proximal to the flexor retinaculum, the median nerve courses around the lateral edge of the FDS (Jamadar et al., 2001) and over the pronator quadratus. This is where the median nerve is usually brightest (Jamadar et al., 2001).

(Roll cursor over image to see labels.)

While the median artery normally evolutes during development, persistent median artery can be detected with high-resolution ultrasound in about 25% of asymptomatic individuals (Video 380 KB). Persistent median artery is sometimes associated with high division or bifid median nerve.

References

Gassner EM, Schocke M, Peer S, Schwabegger A, Jaschke W, Bodner G. Persistent median artery in the carpal tunnel: color Doppler ultrasonographic findings. J Ultrasound Med. 2002 Apr;21(4):455-61. PMID: 11934102

Jamadar DA, Jacobson JA, Hayes CW. Sonographic evaluation of the median nerve at the wrist. J Ultrasound Med. 2001 Sep;20(9):1011-4. PMID: 11549149

Propeck T, Quinn TJ, Jacobson JA, Paulino AF, Habra G, Darian VB. Sonography and MR imaging of bifid median nerve with anatomic and histologic correlation. AJR Am J Roentgenol. 2000 Dec;175(6):1721-5. Review. PMID: 11090410

Retzl G, Kapral S, Greher M, Mauritz W. Ultrasonographic findings of the axillary part of the brachial plexus. Anesth Analg. 2001 May;92(5):1271-5. PMID: 11323361

Iannicelli E, Chianta GA, Salvini V, Almberger M, Monacelli G, Passariello R. Evaluation of bifid median nerve with sonography and MR imaging. J Ultrasound Med. 2000 Jul;19(7):481-5. PMID: 10898302

Walker FO, Cartwright MS, Wiesler ER, Caress J. Ultrasound of nerve and muscle. Clin Neurophysiol. 2004 Mar;115(3):495-507. Review. PMID: 15036045

Bianchi S, Montet X, Martinoli C, Bonvin F, Fasel J. High-resolution sonography of compressive neuropathies of the wrist. J Clin Ultrasound. 2004 Nov-Dec;32(9):451-61. PMID: 15558623

Martinoli C, Bianchi S, Pugliese F, Bacigalupo L, Gauglio C, Valle M, Derchi LE. Sonography of entrapment neuropathies in the upper limb (wrist excluded). J Clin Ultrasound. 2004 Nov-Dec;32(9):438-50. Review. PMID: 15558622

Chen P, Maklad N, Redwine M, Zelitt D. Dynamic high-resolution sonography of the carpal tunnel. AJR Am J Roentgenol. 1997 Feb;168(2):533-7. Review. PMID: 9016242