Review Question - QID 216509

A 17-year-old boy presents to the emergency department after a car accident. He drove his car into a pole while speeding at night. He has no past medical history and takes no medications. The patient is unable to offer a history and repetitively asks the nurses what happened. He knows his name and address and is able to remember other information about himself. He is complaining of a headache. His temperature is 97.6°F (36.4°C), blood pressure is 122/74 mmHg, pulse is 90/min, respirations are 12/min, and oxygen saturation is 98% of room air. Physical exam reveals a confused young man. Cranial nerves 2-12 are intact and the patient has normal strength and sensation. He demonstrates a stable gait. Throughout the exam, he continuously asks what happened to him. A head CT scan is ordered. Which of the following is the most likely diagnosis?