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Cervical spinal nerve 3 (C3)

he cervical spinal nerve 3 (C3) is the third pair of cervical nerves, emerging from the spinal cord above the third cervical vertebra. C3 plays a pivotal role in transmitting motor and sensory signals in the upper neck region. Its anatomical course, functions, and imaging characteristics are crucial for understanding cervical neuropathies and interpreting radiological images.

Synonyms

  • C3 nerve root

  • Third cervical nerve

  • C3 spinal nerve

Anatomical Location

  • Arises from the spinal cord above the C3 vertebral body.

  • Emerges through the intervertebral foramen between C2 and C3 vertebrae.

  • Travels laterally, joining the cervical plexus.

Function

  • Motor Function: Supplies motor fibers to several neck muscles, including portions of the sternocleidomastoid, levator scapulae, and trapezius (via the cervical plexus and accessory connections).

  • Sensory Function: Provides sensory innervation to the skin of the neck region, especially in the posterior and lateral areas.

  • Additional Role: Contributes fibers to the phrenic nerve (C3–C5), assisting in diaphragmatic movement (important for breathing).

MRI Appearance

  • T1-weighted images:

    • Nerve root appears as a low to intermediate signal intensity structure, contrasted against the hyperintense epidural fat and hypointense CSF.

  • T2-weighted images:

    • C3 nerve root demonstrates intermediate signal relative to the surrounding tissue.

    • CSF appears bright, making the nerve root more conspicuous.

  • STIR (Short Tau Inversion Recovery):

    • Enhances visualization of nerve inflammation or edema.

    • The C3 nerve appears as an intermediate signal; pathological changes (like neuritis) may appear hyperintense.

CT Appearance

  • Nerve roots are not directly visualized on routine CT due to low soft tissue contrast.

MRI images

Cervical spinal nerve 3 (C3) MRI axial t2 image