Consider head CT (rule out intracranial hemorrhage)
Use validated decision rule to determine need
Avoid CT in patients with minor head injury who are at low risk based on validated decision rules.
Consider cervical and/or facial CT
Noncontrast CT brain is the gold standard
Acute SDH will show as a hyperdense (white) collection with a crescent-shaped appearance
Chronic SDH will show as a hypodense (dark grey/black) collection in a crescent-shape
Contrasted studies are useful in distinguishing acute, subacute, and chronic
Use validated decision rule to determine need
Avoid CT in patients with minor head injury who are at low risk based on validated decision rules.
Acute SDH will show as a hyperdense (white) collection with a crescent-shaped appearance
Chronic SDH will show as a hypodense (dark grey/black) collection in a crescent-shape
Contrasted studies are useful in distinguishing acute, subacute, and chronic
Subdural hemorrhage
Intra-axial
Subdural empyema
Hemorrhagic stroke 
Subarachnoid hemorrhage
Traumatic intracerebral hemorrhage
Epidural hemorrhage
Extra-axial