Review Question - QID 108882

A 30-year-old male presents to his primary care physician complaining of upper extremity numbness. He was involved in a head-on motor vehicle collision approximately four months ago. He reports that he has noticed progressive bilateral upper extremity numbness since the accident. On physical exam, he has decreased sensation to pain and temperature in his bilateral upper extremities. Strength is 5/5 in bilateral shoulder abduction, arm flexion and extension, and wrist flexion and extension. Proprioception and vibratory sense are intact. There is preservation of light touch, vibratory sense, and proprioception in the upper extremities bilaterally. An examination of his lower extremities reveals no abnormalities. An MRI of the cervicothoracic spinal cord is shown (Figure A). Compression of which of the following structures most likely led to this presentation?