Most brain aneurysms go unnoticed until they rupture or are detected during medical imaging tests for another condition. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Cerebral-Aneurysms-Fact-Sheet#5

If you have experienced a severe headache or have any other symptoms related to a ruptured aneurysm your doctor will order tests to determine if blood has leaked into the space between the skull bone and brain. 

Several tests are available to diagnose brain aneurysms and determine the best treatment. These include: 

• Computed tomography (CT).  This fast and painless scan is often the first test a physician will order to determine if blood has leaked into the brain.  CT uses x-rays to create two-dimensional images, or “slices,” of the brain and skull.  Occasionally a contrast dye is injected into the bloodstream prior to scanning to assess the arteries, and look for a possible aneurysm.  This process, called CT angiography (CTA), produces sharper, more detailed images of blood flow in the brain arteries.  CTA can show the size, location, and shape of an unruptured or a ruptured aneurysm. 
• Magnetic resonance imaging (MRI).   An MRI uses computer-generated radio waves and a magnetic field to create two- and three-dimensional detailed images of the brain and can determine if there has been bleeding into the brain.  Magnetic resonance angiography (MRA) produces detailed images of the brain arteries and can show the size, location, and shape of an aneurysm. 
• Cerebral angiography.  This imaging technique can find blockages in arteries in the brain or neck.  It also can identify weak spots in an artery, like an aneurysm.  The test is used to determine the cause of the bleeding in the brain and the exact location, size, and shape of an aneurysm.  Your doctor will pass a catheter (long, flexible tube) typically from the groin arteries to inject a small amount of contrast dye into your neck and brain arteries.  The contrast dye helps the X-ray create a detailed picture of the appearance of an aneurysm and a clear picture of any blockage in the arteries. 
• Cerebrospinal fluid (CSF) analysis.  This test measures the chemicals in the fluid that cushions and protects the brain and spinal cord (cerebrospinal fluid).  Most often a doctor will collect the CSF by performing a spinal tap (lumbar puncture), in which a thin needle is inserted into the lower back (lumbar spine) and a small amount of fluid is removed and tested.   The results will help detect any bleeding around the brain.  If bleeding is detected, additional tests would be needed to identify the exact cause of the bleeding. 

In the next segment, I will talk about treatment.

Most brain aneurysms go unnoticed until they rupture or are detected during medical imaging tests for another condition. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Cerebral-Aneurysms-Fact-Sheet#5

If you have experienced a severe headache or have any other symptoms related to a ruptured aneurysm your doctor will order tests to determine if blood has leaked into the space between the skull bone and brain. 

Several tests are available to diagnose brain aneurysms and determine the best treatment. These include: 

• Computed tomography (CT).  This fast and painless scan is often the first test a physician will order to determine if blood has leaked into the brain.  CT uses x-rays to create two-dimensional images, or “slices,” of the brain and skull.  Occasionally a contrast dye is injected into the bloodstream prior to scanning to assess the arteries, and look for a possible aneurysm.  This process, called CT angiography (CTA), produces sharper, more detailed images of blood flow in the brain arteries.  CTA can show the size, location, and shape of an unruptured or a ruptured aneurysm. 
• Magnetic resonance imaging (MRI).   An MRI uses computer-generated radio waves and a magnetic field to create two- and three-dimensional detailed images of the brain and can determine if there has been bleeding into the brain.  Magnetic resonance angiography (MRA) produces detailed images of the brain arteries and can show the size, location, and shape of an aneurysm. 
• Cerebral angiography.  This imaging technique can find blockages in arteries in the brain or neck.  It also can identify weak spots in an artery, like an aneurysm.  The test is used to determine the cause of the bleeding in the brain and the exact location, size, and shape of an aneurysm.  Your doctor will pass a catheter (long, flexible tube) typically from the groin arteries to inject a small amount of contrast dye into your neck and brain arteries.  The contrast dye helps the X-ray create a detailed picture of the appearance of an aneurysm and a clear picture of any blockage in the arteries. 
• Cerebrospinal fluid (CSF) analysis.  This test measures the chemicals in the fluid that cushions and protects the brain and spinal cord (cerebrospinal fluid).  Most often a doctor will collect the CSF by performing a spinal tap (lumbar puncture), in which a thin needle is inserted into the lower back (lumbar spine) and a small amount of fluid is removed and tested.   The results will help detect any bleeding around the brain.  If bleeding is detected, additional tests would be needed to identify the exact cause of the bleeding. 

In the next segment, I will talk about treatment.