Diagnosis

The following tests are commonly used to try to determine the cause of a thunderclap headache.

• CT scan of the head. CT scans take X-rays that create slice-like, cross-sectional images of your brain and head. A computer combines these images to create a full picture of your brain. Sometimes an iodine-based dye is used to augment the picture.
• Spinal tap (lumbar puncture). The doctor removes a small amount of the fluid that surrounds your brain and spinal cord. The cerebrospinal fluid sample can be tested for signs of bleeding or infection.
• MRI. In some cases, this imaging study might be done for further assessment. A magnetic field and radio waves are used to create cross-sectional images of the structures within your brain.
• Magnetic resonance angiography. MRI machines can be used to map the blood flow inside your brain in a test called a magnetic resonance angiography (MRA).