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Cervical spinal nerve 7 (C7)

The cervical spinal nerve 7 (C7) is one of the major nerves emerging from the cervical region of the spinal cord. It plays a critical role in motor and sensory functions of the upper limb, particularly the triceps, and is a key landmark in clinical neurology and radiology. The C7 nerve exits the spinal canal above the C7 vertebra and is often implicated in cervical radiculopathy due to its unique anatomical position and distribution.

Synonyms

  • C7 nerve root

  • Seventh cervical spinal nerve

  • Cervical nerve 7

  • Cervical root C7

Function

  • Provides motor innervation to the triceps brachii, extensor muscles of the forearm, and some hand muscles.

  • Supplies sensory innervation to the skin over the posterior aspect of the arm, forearm, and the middle finger.

  • Key in the triceps reflex (deep tendon reflex).

  • Participates in the brachial plexus, particularly in the formation of the middle trunk.

MRI Appearance

T1-weighted Imaging (T1)

  • C7 nerve root appears as a small, linear, low to intermediate signal structure exiting the spinal canal.

  • Surrounded by high signal epidural fat, aiding its identification.

  • Pathological changes such as edema or nerve compression may alter the normal low-intermediate signal.

T2-weighted Imaging (T2)

  • C7 nerve root is isointense  to adjacent muscle.

  • Edematous or inflamed nerves may appear brighter (hyperintense).

  • Useful for detecting nerve root swelling, compression, or signal changes due to pathology.

STIR (Short Tau Inversion Recovery)

  • C7 nerve root demonstrates low signal under normal conditions.

  • Markedly increased signal intensity in cases of nerve edema, inflammation, or compression.

  • Highly sensitive for detecting subtle nerve pathology and surrounding soft tissue changes.

CT Appearance

  • The C7 nerve root is not directly visualized on standard CT due to low soft tissue contrast.

  • Indirect evidence: enlargement of the neural foramen, foraminal narrowing, or bone changes at the C6-C7 level may suggest nerve impingement.

  • CT myelography can outline the nerve root by showing contrast filling defects or nerve root sleeves.

MRI images

Cervical spinal nerve 7 (C7) MRI axial t2 image