C6 Nerve Root

Authors
Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Figure 1: Nerve roots extending from the spinal cord
Level Root Pain & Sensory Change Motor Weakness Abnormal Reflexes
C4/C5 C5 Deltoid
Lateral arm		 Deltoid
Biceps		 Bicep reflex
C5/C6 C6 Radial forearm to thumb and index finger Biceps
Wrist extensor		 Bicep reflex
Brachioradialis reflex
C6/C7 C7 Midradial forearm to index and middle finger Wrist Flexor
Tricep		 Triceps reflex
C7/T1 C8 Ulnar forearm to ring and little finger Hand Intrinsic
Finger Flexor		 N/a

Motor Innervation

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Muscle Origin Insertion Innervation Action
Anconeus GHJ joint capsule Olecranon of Ulna (radial surface) Radial n.
C6 - C8		 Elbow: Extension, Tightens joint
Anterior deltoid Lateral third of clavicle Deltoid tuberosity of humerus Axillary n.
C5 - C6		 GHJ: Flexion, IR, Adduction
Anterior scalene Anterior tubercle of TP of C3-C6 Scalene tubercle of 1st Rib Anterior Rami
C4 - C6		 Mobile ribs: Elevates ribs during forced inspiration
Fixed ribs (unilateral): I/L C/s sidebend (unilateral)
Fixed ribs (bil): C/s flexion, Cervical lateral stabilization
Biceps brachii Long head Supraglenoid tubercle of scapula
Adjacent rim of Glenoid Labrum		 Radial tuberosity
Bicipital aponeurosis		 Musculocutaneous n.
C5 - C6		 Elbow: Flexion, Supination
GHJ: Flexion, Stabilization of humeral head during deltoid contraction, Abduction, IR
Biceps brachii Short head Coracoid process Radial tuberosity
Bicipital aponeurosis		 Musculocutaneous n.
C5 - C6		 Elbow: Flexion, Supination
GHJ: Flexion, Stabilization of humeral head during deltoid contraction, Abduction, IR
Brachialis Distal half of anterior Humerus Ulnar tuberosity Musculocutaneous n.
Radial n.
C5 - C7		 Elbow: Flexion
Brachioradialis Lateral distal humerus
Lateral intermuscular septum		 Styloid process of Radius Radial n.
C5 - C6		 Elbow: Flexion, Semipronation (to 90°)
Coracobrachialis Coracoid process Humerus (in line with crest of lesser tubercle) Musculocutaneous n.
C5 - C7		 GHJ: Flexion, Adduction, IR
Extensor carpi radialis longus Lateral supracondylar ridge
Lateral intermuscular septum		 2nd metacarpal base Radial n.
C6 - C7		 Elbow: Weak flexion
Wrist: Extension, Radial deviation
Flexor carpi radialis Medial epicondyle Base of 2nd Metacarpal
(Sometimes base of 3rd Met)		 Median n.
C6 - C7		 Wrist: Flexion, Radial deviation
Infraspinatus Infraspinous Fossa of Scapula Greater tubercle of Humerus Suprascapular n.
C4 - C6		 GHJ: ER, Stabilization
Lateral deltoid Acromion Deltoid tuberosity of humerus Axillary n.
C5 - C6		 GHJ: Abduction
Latissimus dorsi T7-T12 SP
Thoracolumbar fascia
Inferior angle of scapula
9-12 ribs
Posterior third of Iliac crest		 Floor of the intertubercular groove of the humerus Thoracodorsal n.
C6 - C8		 GHJ: IR, adduction, Extension
Respiration: "cough muscle"
Middle scalene C1-C2 TP
Posterior tubercle of TP of C3-C7		 1st Rib (posterior to groove for subclavian a.) Anterior Rami
C3 - C8		 Mobile ribs: Elevates ribs during forced inspiration
Fixed ribs (unilateral): I/L C/s sidebend (unilateral)
Fixed ribs (bil): C/s flexion, Cervical lateral stabilization
Palmaris longus Medial epicondyle Palmar aponeurosis Median n.
C6 - C7		 Elbow: Weak flexion
Wrist: Tightens aponeurosis
Pectoralis major Clavicle (medial half)
Sternum
Costal cartilages 1-6
Rectus sheath (anterior layer)		 Humerus (crest of greater tubercle) Lateral pectoral n.
Medial pectoral n.
C5 - T1		 Entire muscle: Adduction, IR
Clavicular & Sternocostal parts: Flexion, Aids in respiration when shoulder is fixed
Posterior deltoid Scapular spine Deltoid tuberosity of humerus Axillary n.
C5 - C6		 GHJ: Extension, ER, Abduction
Posterior scalene Posterior tubercle of TP of C5-C7 2nd Rib (outer surface) Anterior Rami
C6 - C8		 Mobile ribs: Elevates ribs during forced inspiration
Fixed ribs (unilateral): I/L C/s sidebend (unilateral)
Fixed ribs (bil): C/s flexion, Cervical lateral stabilization
Pronator teres Medial epicondyle
Coronoid process		 L:ateral radius distal to supinator Median n.
C6 - C7		 Elbow: Weak flexion, Pronation
Serratus anterior 1-9 Ribs Superior angle of Scapula (costal and dorsal surfaces)
Medial border of scapula (costal surface)
Medial border of scapula (costal surface)
Inferior angle of Scapula (costal & dorsal surfaces)		 Long thoracic n.
C5 - C7		 Superior part: Lowers raised arm
Entire mm.: Protraction, Rib elevation (with fixed shoulder)
Inferior part: Rotates scapula laterally forward
Splenius capitis Nuchal lig.
C7-T4 SP		 Lateral third of nuchal line
Mastoid process		 Spinal nn.
Posterior rami (lateral br.)
C1 - C6		 Bilateral: Head and neck extension
Unilateral: I/L sidebend, I/L rotation
Splenius cervicis T3-T7 SP C1-C4 SP Spinal nn.
Posterior rami (lateral br.)
C1 - C6		 Bilateral: Head and neck extension
Unilateral: I/L sidebend, I/L rotation
Subclavius 1st rib Clavicle (inferior surface) N. to subclavius
C5 - C6		 SCJ: Stabilization
Subscapularis Subscapular fossa Lesser tubercle of Humerus Upper Subscapular n.
Lower Subscapular n.
C5 - C6		 GHJ: IR, Stabilization
Supinator Olecranon
Lateral epicondyle
Radial collateral lig.
Annular lig.		 Radius (between radial tuberosity and pronator teres) Radial n.
C6 - C7		 Radioulnar joints: Supination
Supraspinatus Supraspinous Fossa of scapula Greater tubercle of Humerus Suprascapular n.
C4 - C6		 GHJ: Initiates abduction, Stabilization
Teres major Inferior angle of Scapula Crest of lesser tubercle of humerus Thoracodorsal n.
C5 - C6		 GHJ: IR, Adduction, Extension
Teres minor Greater tubercle of Humerus Axillary n.
C5 - C6		 GHJ: ER, Weak adduction
Triceps brachii lateral head Posterior humerus just *proximal* to radial groove
Lateral intermuscular septum		 Olecranon of Ulna Radial n.
C6 - C8		 Elbow: Extension
Triceps brachii Long head Infraglenoid tubercle of Scapula Olecranon of Ulna Radial n.
C6 - C8		 Elbow: Extension
GHJ: Extension, Adduction
Triceps brachii medial head Posterior humerus just distal to radial groove
Medial intermuscular septum		 Olecranon of Ulna Radial n.
C6 - C8		 Elbow: Extension

Dermatome

Figure 2: Dermatomal cutaneous distribution
Figure 3: Dermatomal cutaneous distribution (Posterior)

Contribution

C6 along with C5 contribute to the Superior trunk of the brachial plexus.

Lesion

“This nerve root is often compressed by disc herniation at the C5 C6 vertebral level. A monoradiculopathy affecting the C6 nerve root is the second most common level of cervical radiculopathy after lesions of the C7 level [28]. C6 root involvement results in pain in the lateral arm and dorsal forearm. Sensory signs and symptoms occur on the lateral forearm, lateral hand, and the first and second digits. Paresis occurs predominantly in the following muscles: serratus anterior, biceps, pronator teres, flexor carpi radialis, brachioradialis, extensor carpi radialis longus, supinator, and extensor carpi radialis brevis (examination of these muscles is described in Chapter 2 ). The biceps reflex (segments C5 C6) and the brachioradialis reflex (segments C5 C6) may be depressed. An “inverted radial reflex” occurs when the lesion causes compression of the spinal cord at the C5 C6 level. A central disc prolapse or a horizontal bar due to degenerative disc disease is often responsible for this clinical finding. Damage of the corticospinal tract at the level of C5 C6 results in hyperreflexia at lower levels. Therefore, tapping the tendon of the brachioradialis muscle elicits no response by the brachioradialis but a brisk contraction of the finger flexors innervated by the C8 T1 segments.”

References

1.
Gray H. Anatomy of the Human Body. 20th ed. (Lewis WH, ed.). Lea & Febiger; 1918. https://www.bartleby.com/107/
2.
Hong CG, Nam WD. Reliability and Diagnostic Accuracy of Standard Dermatomes and Myotomes for Determining the Pathologic Level in Surgically Verified Patients With Cervical Radiculopathy. Neurospine. 2022;19(4):1006-1012. doi:10.14245/ns.2244194.097
3.
Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 8th ed. Wolters Kluwer Health; 2022.

Citation

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