Myotomes of the limbs

What it is

A myotome is the motor supply of one nerve root. Going through these actions one by one gives a motor level, in the same way the dermatomes give a sensory level.

• C5: shoulder abduction and external rotation; elbow flexion
• C6: wrist extension
• C7: elbow extensors and wrist flexion
• C8: thumb extension and finger flexion
• T1: finger abduction
• L1/L2: hip flexion
• L3: knee extension
• L4/L5: ankle dorsiflexion
• L5: great toe extension
• S1: ankle plantar flexion
• S4: bladder and rectum motor supply