This patient should have CT of the head without contrast. The American College of Emergency Physicians and the Centers for Disease Control and Prevention have published guidelines for management of mild traumatic brain injury (TBI). Their recommendation is to consider a noncontrast head CT in patients with TBI who have had no loss of consciousness or posttraumatic amnesia but have a focal neurologic deficit, vomiting, severe headache, physical signs of a basilar skull fracture, Glasgow Coma Scale score less than 15, coagulopathy, or a dangerous mechanism of injury, such as ejection from a motor vehicle or a falling from a height of more than 3 feet. This patient sustained a TBI with a dangerous mechanism of injury several hours ago and has developed symptoms (worsening headache and vomiting) mentioned in the guideline. Therefore, noncontrast CT of the head is indicated. A finding of parenchymal, subdural, or epidural hemorrhage requires emergent neurosurgical evaluation and consideration of possible hematoma evacuation.

In the setting of acute head trauma, head CT without contrast is preferable to head CT with contrast and brain MRI because of its lower cost and wider availability. Contrast administration aids in the assessment of certain malignant and vascular lesions of the brain but adds nothing to the evaluation of acute head trauma. Head CT without contrast is also very sensitive for detecting skull fracture or acute hemorrhage, and a CT scan generally requires shorter examination times than a brain MRI requires, both important factors in the evaluation of a patient with acute head injury and symptoms of potential deterioration.

Hospital observation without first ruling out intracranial hemorrhage is inappropriate management of TBI. Untreated intracranial hemorrhage can lead to an accumulation of blood and edema within the skull, which can cause compression or destruction of brain tissue, increased intracranial pressure, and even herniation and death.