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Cervical spinal nerve 5 (C5)

The Cervical spinal nerve 5 (C5) is one of eight cervical nerves located in the cervical segment of the spinal cord. Arising from the C4-C5 intervertebral foramen, it plays a critical role in motor and sensory innervation to the upper limb, particularly the shoulder and upper arm. Due to its anatomical position and functions, C5 is essential for upper limb mobility, sensation, and reflexes. Clinical evaluation and imaging of the C5 nerve are vital in diagnosing cervical radiculopathy, trauma, or degenerative disease affecting the cervical spine.

Synonyms

  • Fifth cervical spinal nerve

  • C5 nerve root

  • C5 nerve

Function

  • Motor Innervation: Supplies the deltoid, supraspinatus, infraspinatus, and partially the biceps brachii and brachialis muscles (shoulder abduction, external rotation, elbow flexion).

  • Sensory Innervation: Provides sensation to the lateral (outer) aspect of the upper arm, over the deltoid region.

  • Reflexes: Involved in the biceps reflex and contributes to the brachioradialis reflex.

MRI Appearance

  • T2-Weighted Imaging:

  • The C5 nerve root appears as a small, round or oval structure with intermediate signal intensity .

  • Hyperintensity may be observed in cases of nerve edema, inflammation, or compression.

  • T1-Weighted Imaging:

  • C5 nerve root is isointense to muscle, and usually hypointense compared to the bright epidural and foraminal fat.

  • Good for anatomical localization, but less sensitive to pathological changes.

STIR (Short Tau Inversion Recovery):

  • C5 nerve appears with low to intermediate signal intensity.

  • Edema or inflammation in or around the nerve will show as marked hyperintensity due to fluid sensitivity of STIR.

  • CT Appearance

  • The C5 nerve root itself is not clearly visible on standard CT, but the neural foramen and bony boundaries (C4/5 and C5/6 intervertebral foramina) can be assessed for narrowing or impingement.

  • CT myelography can better delineate the nerve root, especially in cases of foraminal stenosis or nerve root avulsion.

MRI images

Cervical spinal nerve 5 (C5) MRI axial t2 image