C8 Nerve Root (C8)

Authors

Affiliations

Nathaniel 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

Motor Innervation

C8 Nerve Root Skeletal Muscle Innervations
Muscle	Origin	Insertion	Innervation	Action
Middle scalene	C1-C2 TP¹ Posterior tubercle of TP of C3-C7¹ C1-C2 TP [@gilroyAtlasAnatomy2020] Posterior tubercle of TP of C3-C7 [@gilroyAtlasAnatomy2020]	1st Rib (posterior to groove for subclavian a.)¹ 1st Rib (posterior to groove for subclavian a.) [@gilroyAtlasAnatomy2020]	Anterior Rami¹ C3 - C8¹ Anterior Rami [@gilroyAtlasAnatomy2020] C3 - C8 [@gilroyAtlasAnatomy2020]	Fixed ribs (bil) C/s flexion [@gilroyAtlasAnatomy2020] Cervical lateral stabilization [@finandoTriggerPointTherapy2005] Fixed ribs (unilateral) I/L C/s sidebend (unilateral) [@gilroyAtlasAnatomy2020] Mobile ribs Elevates ribs during forced inspiration [@gilroyAtlasAnatomy2020]
Pectoralis major	Clavicle (medial half)¹ Sternum¹ Costal cartilages 1-6¹ Rectus sheath (anterior layer)¹ [Clavicle (medial half)](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#origin) [@gilroyAtlasAnatomy2020] [Sternum](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#origin) [@gilroyAtlasAnatomy2020] [Costal cartilages 1-6](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#origin) [@gilroyAtlasAnatomy2020] [Rectus sheath (anterior layer)](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#origin) [@gilroyAtlasAnatomy2020]	Humerus (crest of greater tubercle)¹ [Humerus (crest of greater tubercle)](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#insertion) [@gilroyAtlasAnatomy2020]	Lateral pectoral n.¹ Medial pectoral n.¹ C5 - T1¹ [Lateral pectoral n.](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#nerve) [@gilroyAtlasAnatomy2020] [Medial pectoral n.](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#nerve) [@gilroyAtlasAnatomy2020] [C5](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#nerve) - [T1](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#nerve) [@gilroyAtlasAnatomy2020]	Clavicular & Sternocostal parts [Flexion](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#action) [@gilroyAtlasAnatomy2020] [Aids in respiration when shoulder is fixed](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#action) [@gilroyAtlasAnatomy2020] Entire muscle [Adduction](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#action) [@gilroyAtlasAnatomy2020] [IR](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_major_muscle.html#action) [@gilroyAtlasAnatomy2020]
Pectoralis minor	3-5 ribs¹ [3-5 ribs](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_minor_muscle.html#origin) [@gilroyAtlasAnatomy2020]	Coracoid process¹ [Coracoid process](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_minor_muscle.html#insertion) [@gilroyAtlasAnatomy2020]	Medial pectoral n.¹ C8 - T1¹ [Medial pectoral n.](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_minor_muscle.html#nerve) [@gilroyAtlasAnatomy2020] [C8](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_minor_muscle.html#nerve) - [T1](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_minor_muscle.html#nerve) [@gilroyAtlasAnatomy2020]	Respiration [Assists in respiration](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_minor_muscle.html#action) [@gilroyAtlasAnatomy2020] Scapula [Depression](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_minor_muscle.html#action) [@gilroyAtlasAnatomy2020] [Downward rotation](/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Axioappendicular Anterior Muscles/pectoralis_minor_muscle.html#action) [@gilroyAtlasAnatomy2020]
Posterior scalene	Posterior tubercle of TP of C5-C7¹ Posterior tubercle of TP of C5-C7 [@gilroyAtlasAnatomy2020]	2nd Rib (outer surface)¹ 2nd Rib (outer surface) [@gilroyAtlasAnatomy2020]	Anterior Rami¹ C6 - C8¹ Anterior Rami [@gilroyAtlasAnatomy2020] C6 - C8 [@gilroyAtlasAnatomy2020]	Fixed ribs (bil) C/s flexion [@gilroyAtlasAnatomy2020] Cervical lateral stabilization [@finandoTriggerPointTherapy2005] Fixed ribs (unilateral) I/L C/s sidebend (unilateral) [@gilroyAtlasAnatomy2020] Mobile ribs Elevates ribs during forced inspiration [@gilroyAtlasAnatomy2020]

DDX

Level	Root	Pain & Sensory Change	Motor Weakness	Abnormal Reflexes
C4/C5	C5	Deltoid² Lateral arm²	Deltoid² Biceps²	Bicep reflex²
C5/C6	C6	Radial forearm to thumb and index finger²	Biceps² Wrist extensor²	Bicep reflex² Brachioradialis reflex²
C6/C7	C7	Midradial forearm to index and middle finger²	Wrist Flexor² Tricep²	Triceps reflex²
C7/T1	C8	Ulnar forearm to ring and little finger²	Hand Intrinsic² Finger Flexor²	N/a²

Lesion

“This nerve root is often compressed by disc herniation at the C7/T1 vertebral level. C8 root involvement results in pain in the medial arm and forearm. With C8 lesions [40], sensory signs and symptoms occur on the medial forearm and hand and on the fifth digit. Paresis occurs predominantly and variably in the following muscles: flexor digitorum superficialis, flexor pollicis longus, flexor digitorum profundus I to IV, pronator quadratus, abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, all lumbricals, flexor carpi ulnaris, abductor digiti minimi, opponens digiti minimi, flexor digiti minimi, all interossei, adductor pollicis, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis longus and brevis, and extensor indicis (see Chapter 2 for examination methods of these muscles). The finger flexor reflex (C8 T1) may be depressed. Sympathetic fibers destined for the superior cervical ganglia are interrupted, resulting in an ipsilateral Horner syndrome (ptosis, miosis, and anhidrosis).”³

“There are frequent intradural communicating fibers between neighboring segments of the cervical posterior roots. These connections are most prominent between a specific cervical segment and the next caudal root. A lesion may therefore be falsely localized clinically to a segment one level higher than its actual location.”³

“The theoretical root syndromes discussed earlier are also related to an “idealized” brachial plexus and do not take into consideration the possibility of a prefixed or postfixed plexus (see Chapter 3 ).”³

Examination

“The patient extends the thumb just short of the full range of motion. The clinician stabilizes the patient’s wrist with one hand and applies an isometric force into thumb flexion with the other (Fig. 25-29).”⁴

References

Gilroy AM, MacPherson BR, Wikenheiser JC, Voll MM, Wesker K, Schünke M, eds. Atlas of Anatomy. 4th ed. Thieme; 2020.

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

Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology. 8th ed. Wolters Kluwer Health; 2022.

Dutton M. Dutton’s Orthopaedic Examination, Evaluation, and Intervention. 5th ed. McGraw Hill Education; 2020.

Citation

For attribution, please cite this work as:

Yomogida N, Kerstein C. C8 Nerve Root (C8). https://yomokerst.com/The Archive/Anatomy/Nerve Roots/c8_nerve_root.html