Evaluation of Motor Impairment in Injuries to the Cervical Spinal Cord

The level of the cervical spinal cord affected by injury can be inferred from the pattern of muscle function shown by the patient.

Spinal Segments	Muscle	Function
C3, C4, C5	diaphragm	inspiration
C5, C6	biceps brachii, brachialis	elbow flexors
C6, C7	extensor carpi radialis longus and brevis	wrist extensors
C7, C8	triceps brachii	elbow extensors
C8, T1	interossei, thenar group	hand instrinsics

The muscles (except for the diaphragm) are innervated by 2 segments or roots.

If both segments are functional, then the muscle strength is normal.

If one segment is functional, then muscle strength is weak.

If neither segment is functional, then the muscle is paralyzed.

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