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Median nerve neuropathy

Last updated: June 15, 2021

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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. Chronic injuries to the nerve result in atrophy of median nerve innervated muscles while acute injuries do not have this feature. Treatment is mostly conservative and focuses on rest and immobilization.

References:[1]

Course of the median nerve

Lesions of the median nerve

Clinical features of median nerve lesions
Location of lesion Motor deficit Sensory deficit
Proximal (above elbow)
  • Hand of benediction: when asked to make a fist, the patient can only flex the ring finger and the little finger due to
    • Loss of thumb opposition and abduction
    • Loss of index and middle finger flexion
  • Impaired wrist pronation and flexion
  • Thenar muscle atrophy (chronic injury)
  • Thumb
  • Index and middle finger
  • Radial side of ring finger
Distal (below elbow)
  • Anterior interosseous nerve syndrome: loss of flexion in distal joints of the thumb and index finger, leading to an inability to pinch small objects (pinch sign) or form the “OK sign
  • None
Distal (within wrist)
  • Thumb
  • Index and middle finger
  • Radial side of ring finger

The hand of benediction only occurs in proximal median nerve injuries.

References:[1][2]

References:[3]

References:[2]

  1. Daroff RB, et al.. Bradley's Neurology in Clinical Practice. Elsevier
  2. Andreoli TE, Carpenter CCJ. Cecil Essentials of Medicine. Elsevier ; 2010
  3. Joshi J, Kotwal PP. Essentials of Orthopaedics & Applied Physiotherapy - E-Book. Elsevier Health Sciences ; 2016
  4. Pronator Teres Syndrome. https://radiopaedia.org/articles/pronator-teres-syndrome-2. Updated: June 13, 2017. Accessed: June 13, 2017.
  5. Amirlak B, Gellman H. Median Nerve Entrapment. Median Nerve Entrapment. New York, NY: WebMD. http://emedicine.medscape.com/article/1242387. Updated: February 24, 2016. Accessed: August 16, 2017.