A 42-year-old man is brought to the Emergency Department after a fall from a ladder while doing home repairs. He has no significant medical history.
Upon examination, he is on a backboard with his cervical spine immobilized. His initial exam shows a slight drooping of the right eyelid with a constricted pupil. Examination of his mouth reveals a deviation of the tongue to the right. There are no other notable neurological findings. He reports a change in taste sensation.
What is the most probable cause of these symptoms?