MEDIAN NERVE

The Median (latin for "middle") nerve causes the Opponens pollicis muscle in the hand to contract, giving Humans the ability to oppose the thumb joint. This all-important nerve is what allows musicians (e.g., guitarists) to hold a pick and press a note down on the fretboard. This also happens to be a major function of the hand that separates Humans from animals (i.e., Apes). In fact, damage to this nerve, resulting in the inability to oppose the thumb, is commonly referred to as "Ape Hand" in the medical community. Median nerve compression is also the culprit in Carpal Tunnel Syndrome.

Legend

A: The Median nerve is derived from the lateral and medial cords of the Brachial plexus. Disk herniations in the Cervical spine (at the level of C5-C8 and T1) can cause numbness and/or decreased grip-strength in the hand.

B: The Opponens pollicis muscle is innervated exclusively by the Median nerve. The inability to firmly hold an object between the index finger and thumb is a classic sign of Median nerve pathology.

C: Shaded areas of the hand illustrate the sensory contribution of the Median nerve to the skin. Damage or trauma to the Median nerve will cause numbness to these areas of the hand.

D: Try this simple test of the Median nerve. (1) Rest your hand palm-up on a flat surface. (2) With a finger of the opposite hand, gently tap the center of the wrist joint where the palmar branch of the Median nerve crosses into the hand. You should feel a pins and needles sensation radiating out towards your fingertips that is consistent with the cutaneous innervation (C).

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