Q197. A 22-year-old male is brought to the emergency department following a high-speed road traffic accident. On initial assessment, he is unconscious but hemodynamically stable. A non-contrast CT scan of the head is reported as normal. However, within 3 hours of admission, the patient deteriorates rapidly and succumbs to his injuries. Autopsy reveals petechial hemorrhages in the corpus callosum, brainstem, and gray-white matter junction, along with evidence of brainstem retraction balls. What is the most likely diagnosis?