Upper Extremity Dermatomes and Myotomes

Motor Function

Shoulder:

 • Abduction - C5,C6 (axillary)

 • Adduction - C6, C7, C8

Elbow:

 • Flexion - C5,C6 (musculocutaneous)

 • Extension C6, C7, C8 (radial)

Supination - C6

Pronation - C7, C8

Wrist:

 • Flexion - C6, C7 (median)

 • Extension - C7, C8 (radial)

Finger:

 • Mexion - C8 (median)

 • Extension - C7, C8 (radial)

 • Abduction - C8-T1 (ulnar)

 • Adduction - C7-T1 (ulnar)

 • Thumb opp - C8, T1 (median)

Reflexes: 

 • Triceps Jerk - C7, C8

 • Biceps Jerk - C5, C6

 • Supinator - C5, C6

 • Finger Jerk - C8

Important Conditions

Erb's Palsy is caused by damage to the upper trunk and results in characteristic "waiter's tip" position.

Klumpke's Ralsy - Damage to C8 and T1 leading toc aracteristic "claw hand" ± Horner Syndrome

Wrist drop - Occurs after damage to the radial nerve in the radial groove. Triceps power is characteristically spared in this injury. "Saturday night palsy" is a common cause.

Carpal Tunnel Syndrome - Causes paraesthesia in the median nerve distribution with atrophy of the thenar eminence.

Anterior Shoulder Dislocation - May cause axillary nerve damage resulting in "regimental badge" anesthesia and deltoid weakness.



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