A 43-year-old man is admitted to the hospital, having suffered a whiplash injury when his compact auto was struck from behind by a sports utility vehicle. MRI examination reveals some herniation of a disk in the cervical region. Physical examination reveals that the patient has lost elbow extension; there is absence of his triceps reflex and loss of extension of the metacarpophalangeal joints on the ipsilateral side. Which of the following spinal nerves is most likely affected?: (A) C5, (B) C6, (C) C7, (D) C8
Answer is C. C7 is the main spinal nerve that contributes to the radial nerve and innervates the triceps. Absence of the triceps reflex is usually indicative of a C7 radiculopathy or injury.