Evaluation Procedures for Stroke / Brain Attack

Technology makes it possible to examine how the brain looks, functions, and gets its blood supply. Tests can outline the affected part of the brain and help define the problem created by stroke. Most of the following tests are safe, painless and can be done as outpatient procedures.

Imaging tests of the brain:

• computerized axial tomographic scan (CT or CAT scan)

• magnetic resonance imaging scanning (MRI)

• radionuclide angiography - a nuclear brain scan in which radioactive compounds are injected into a vein in the arm, and a machine similar to a Geiger counter creates a map showing their uptake into different parts of the head. The images show how the brain functions rather than its structure. This test can often detect blocked blood vessels and areas where the brain is damaged.

Tests that show the brain's electrical activity:

• electroencephalogram (EEG) - small metal disks (electrodes) are put on a person's scalp to pick up electrical impulses transmitted and received by brain cells.

• evoked response test - measures how the brain handles different sensory stimuli. It can often detect abnormal areas of the brain.

Tests that show blood flow:

• Doppler ultrasound test - to detect blockages in the carotid artery.

• carotid phonoangiography - a sensitive microphone is put on the neck over the carotid artery and a technologist listens for a bruit -- the sound created by turbulent blood flow as it passes through a partially blocked artery.

• ocular plethysmography - anesthetizing drops are put into the eyes, and then small plastic cups (similar to contact lenses) are positioned on the eyes to detect pulses or measure pressure in the eyes.

• cerebral blood flow test (inhalation method) - measures how much oxygen dissolved in the blood supply reaches different areas of the brain. A person is told to lie flat on a table, then a cap containing detectors is secured over the head. Then, the person starts breathing through a mask containing air mixed with a small amount of radioactive xenon. This test usually lasts 30 minutes to an hour.

• digital subtraction angiography (DSA) - provides an image of the major blood vessels to the brain. It lets a doctor know if there are any blockages, how severe they are, and what can be done about them. In this test, dye is injected into a vein in the arm, and an x-ray machine quickly takes a series of pictures of the head and neck.