Red flags defined by the ACR include:

• Increasing frequency or severity
• Fever or neurologic deficit
• History of cancer or immunocompromise
• Older age (>50 years) of onset
• Posttraumatic onset

Most appropriate imaging: MRI head C-/C+ (contrast is preferred to evaluate for neoplastic or inflammatory process)

Alternatives:

• CT head C- (particularly in the case of trauma, useful for rapidly identifying intracranial hemorrhage)

ACR appropriateness criteria