• Clinical science

Median nerve neuropathy

Abstract

The median nerve is a peripheral nerve originating in the cervical roots C5–T1 of the brachial plexus. It supplies motor innervation to the anterior forearm flexors, the thenar muscles, and the two lateral lumbricals as well as sensory innervation to the lateral palm and anterior, lateral three and a half fingers. Motor and sensory deficits depend on whether the lesion is proximal (above the elbow) or distal (below the elbow). While proximal lesions present with the “hand of benediction,” distal lesions present with either the “pinch sign” (anterior interosseous nerve syndrome) or, in the case of carpal tunnel syndrome, with mildly impaired thumb and index finger motion. Both proximal lesions and carpal tunnel syndrome result in reduced sensation in the area of the thumb, index and middle finger. Anterior interosseus nerve syndrome does not cause any sensory deficits. Treatment is mostly conservative and focuses on rest and immobilization.

Etiology

References:[1][2]

Clinical features

Anatomical principles

The median nerve runs from the axilla to the elbow, in the medial side of the arm in the medial bicipital groove. It enters the forearm through the two heads of the pronator teres muscle. After branching off into a motor nerve (anterior interosseous nerve), it courses distally between the superficial and deep layers of the forearm's flexor compartment to reach the wrist, where it branches off into a sensory nerve (the palmar cutaneous branch of the median nerve) before entering the hand through the carpal tunnel. In the hand, it branches off into several sensory nerves (innervating the three radial fingers) and motor branches (innervating the thenar muscles).

Location Motor deficit Sensory deficit
Proximal (above elbow)
  • Hand of benediction
    • Thumb opposition and abduction
    • Wrist pronation and flexion
    • Flexion of index and middle finger
    • Thenar muscle atrophy (chronic injury)
  • Thumb
  • Index and middle finger
  • Radial side of ring finger
Distal (below elbow)
  • none
Distal (within wrist)
  • Carpal tunnel syndrome:
    • Mild impairment of flexion of index finger, long finger, and thumb (less severe than in other median nerve lesions!)
    • Thenar muscle atrophy (chronic injury)
  • Recurrent branch of median nerve:
    • Innervates muscles of the thenar eminence
    • Damaged with lacerations of the radial-sided wrist and proximal palm
    • Results in loss of thumb flexion, opposition, and abduction without sensory or other motor deficits
  • Palmar cutaneous nerve:
    • Purely sensory nerve arising from median nerve proximal to the carpal tunnel
    • Provides sensation to the palm
  • Thumb
  • Index and middle finger
  • Radial side of ring finger

A high/proximal lesion of the median nerve manifests in the hand of benediction, while a low/distal lesion does not!

References:[3][2]

Diagnostics

References:[2][4]

Treatment

References:[3][2]

  • 1. Rezaee A, Soltany Hosn S. Pronator Teres Syndrome. https://radiopaedia.org/articles/pronator-teres-syndrome-2. Updated June 13, 2017. Accessed June 13, 2017.
  • 2. Amirlak B, Gellman H. Median Nerve Entrapment. In: Median Nerve Entrapment. New York, NY: WebMD. http://emedicine.medscape.com/article/1242387. Updated February 24, 2016. Accessed August 16, 2017.
  • 3. Andreoli TE, Carpenter CCJ. Cecil Essentials of Medicine. Elsevier; 2010.
  • 4. Joshi J, Kotwal PP. Essentials of Orthopaedics & Applied Physiotherapy - E-Book. Elsevier Health Sciences; 2016.
last updated 08/21/2018
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