16/09/2024
*Weakness of wrist extension* ✅
C5-C6 (C6 nerve root): Pain, tingling, and/or numbness may be felt in the thumb side of the hand. Weakness may also be experienced in the biceps (muscles in the front of the upper arms) and wrist extensor muscles in the forearms. The C5-C6 disc is one of the most common to herniate.
*Myotome*
A myotome (greek: myo=muscle, tome = a section, volume) is defined as a group of muscles which is innervated by a single spinal nerve root. Myotome testing is an essential part of neurological examination when suspecting radiculopathy. Myotomes are much more complex to test then dermatomes, since each skeletal muscle is innervated by nerves derived from more than one spinal cord level.
Myotomes are a part of the somatic nervous system and the somatic nervous system is a part of the peripheral nervous system.
*There are 31 spinal nerves, each vertebrae has a spinal nerve. The nerves are categorized by the vertebra which house them. There are 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, 5 sacral nerves,1 coccygeal nerve. 16 of these 31 nerves has a specific myotome that controls voluntary muscle movement.*
*Upper Extremity Myotomes*
C5 : Shoulder Abduction
C6 : Elbow Flexion
Wrist Extension
C7 : Elbow Extension
C8 : Thumb Extension
Ulnar Deviation
T1 : Finger Abduction
*Lower Extremity Myotomes*
L2 : Hip Flexion
L3 : Knee Extension
L4 : Ankle Dorsiflexion
L5 : Big Toe Extension
S1 :Ankle Plantarflexion
S2 : Knee Flexion
*Purpose*
Testing of myotomes, in the form of isometric resisted muscle testing, gives information about the level in the spine where a lesion may be present. During myotome testing, you are looking for muscle weakness of a particular group of muscles. Results may indicate lesion to the spinal cord nerve root, or intervertebral disc herniation pressing on the spinal nerve roots. The muscle strength grading scale, which assigns a rating to the degree of muscle weakness, is often used.
