Is a Computed Tomography (CT) scan indicated for diagnosing headaches?

From the Guidelines

A CT scan for headaches is generally not recommended as a first-line approach unless there are specific warning signs, such as sudden severe headache ("thunderclap"), headaches with fever, or headaches with neurological symptoms, as indicated by the most recent guideline from the American Heart Association/American Stroke Association 1.

Key Considerations

• The Ottawa SAH Rule can be used to screen out individuals with a low likelihood of aneurysmal subarachnoid hemorrhage (aSAH), but it is essential to note that many analyses do not apply to patients with atypical presentations 1.
• High-quality CT scanners can detect SAH with a high sensitivity, especially when the images are interpreted by fellowship-trained, board-certified neuroradiologists, and a negative head CT performed within 6 hours of symptom onset is likely sufficient to exclude aSAH 1.
• MRI scans are often preferred for headache evaluation when imaging is necessary, though they take longer and may not be immediately available, and CT scans should be used judiciously due to radiation exposure 1.

Warning Signs for CT Scan

• Sudden severe headache ("thunderclap")
• Headaches with fever
• Headaches that wake you from sleep
• New headaches after age 50
• Headaches with neurological symptoms (vision changes, weakness, numbness)
• Headaches that worsen with coughing or movement

Imaging Modalities

• CT scans: quick to perform, but use radiation and should be used judiciously
• MRI scans: do not use radiation, often preferred for headache evaluation, but take longer and may not be immediately available
• CTA: widely available and often used as the next diagnostic test when SAH is diagnosed with noncontrast CT
• DSA: considered the gold-standard modality for the evaluation of cerebrovascular anatomy and aneurysm geometry, and can aid in decision-making on the choice of optimal treatment modality 1.

From the Research

CT Scan for Headaches

• A CT scan may be recommended for patients presenting with headaches in the setting of "red flags" such as head trauma, cancer, immunocompromised state, pregnancy, patients 50 years or older, related to activity or position, or with a corresponding neurological deficit 2.
• The American College of Radiology Appropriateness Criteria suggest that imaging is not required for many types of headaches, but may be beneficial in certain cases to identify a treatable cause 2.
• Studies have shown that approximately 90% of people in the US experience headache during their lifetime, and migraine is the second leading cause of years lived with disability worldwide 3.
• Patients presenting with headache should be evaluated to determine whether their headache is most likely a primary or a secondary headache disorder, and should be evaluated for symptoms or signs that suggest an urgent medical problem 3.

Indications for CT Scan

• Severe and sudden onset of headache 2
• Optic disc edema 2
• "Red flags" such as head trauma, cancer, immunocompromised state, pregnancy, patients 50 years or older, related to activity or position, or with a corresponding neurological deficit 2
• Migraine or tension-type headache 2
• Trigeminal autonomic origin 2
• Chronic headaches with and without new or progressive features 2

Diagnostic Yield of CT Scan

• A study found that CT angiography (CTA) may increase diagnostic yield in patients with acute severe headache, with a high percentage of vascular abnormalities found in patients with normal neurological examination and no abnormalities at standard CT and CSF analysis 4.
• Another study found that most head CT scans in children with medical emergency with acute neurological illness were normal, but patients with ventriculoperitoneal shunt (VPS) constituted the majority of patients with abnormal CT scans that required subsequent neurosurgical intervention 5.

Prognostic Value of CT Scan

• A study found that early signs of elevated intracranial pressure on computed tomography correlate with measured intracranial pressure in the intensive care unit and six-month outcome after moderate to severe traumatic brain injury 6.
• The study suggested that radiographic signs of elevated ICP, such as sulcal obliteration and third ventricular compression, may be useful in triage and prognostication for patients after moderate-severe TBI 6.