Trauma radiology: Part IV. Imaging of acute craniocerebral trauma

Diagnostic imaging has a key role in diagnosis and management of patients sustaining craniocerebral injuries from trauma. We review the current role of skull radiography, computed tomography (CT), and magnetic resonance (MR) in imaging patients sustaining craniocerebral trauma, and we describe the appearance of major forms of pathology as depicted by each modality. CT scan is used to assess quickly the extent of injury and to triage patients to observation, medical, or neurosurgical management. CT findings can be divided into primary craniocerebral injuries, including skull fractures; extraaxial hematomas (subdural and epidural); intraparenchymal injury, such as hematoma, contusion, and diffuse axonal shearing; and intraventricular or subarachnoid hemorrhage. Secondary manifestations of injury, such as cerebral edema and herniation, are also identified, and their course can be followed by serial CT. CT is crucial in assessing the outcome of surgical intervention and in identifying potential delayed complications of either head trauma or surgical intervention, including infection, delayed hemorrhage, cerebral infarction, and tension pneumocephalus. In recent years, MRI has been shown to be valuable in diagnosing cerebral injury. MRI has generally been shown to have greater overall accuracy than CT in identifying and characterizing most forms of traumatic cerebral pathology, but it is less accurate at demonstrating subarachnoid hemorrhage acutely, pneumocephalus, and calvarial fractures, particularly those involving the skull base. Moreover, MRI is still more difficult to perform than CT in critically ill patients, and it is generally far more time-consuming. However, MRI is unequivocally more accurate than CT at revealing certain lesions, particularly brainstem contusion, diffuse axonal shearing, predominantly nonhemorrhagic contusions, and thin collections of blood adjacent to bone, and it should be used selectively when these injuries are suspected.