Imaging Tests to Diagnose TBI
Neuroradiological tests using computer-assisted brain scans help visualize damage to the brain. The most common of these is computerized axial tomography (CAT scan or CT scan), an x-ray technique that produces a cross-sectional image of the brain. CT scans can detect physical changes in the brain such as hematomas and swelling, which may require immediate treatment. The procedure is painless and takes 15 to 45 minutes, during which the patient must lie completely still.
Another useful diagnostic test is magnetic resonance imaging (MRI scan), which uses a large magnet and radio waves to generate computerized images of the brain without exposing the patient to x-ray radiation. MRIs produce high resolution images of brain structures and are painless, but noisy. The patient must lie on a flat table in the machine, typically shaped like a long tube. An MRI can take up to 60 minutes.
Depending on individual circumstances, a variety of other diagnostic tools and techniques may be employed. These include the following:
- AngiogramA test to examine blood vessels in the brain. It involves injecting dye into an artery supplying blood to the brain, usually by means of a catheter inserted in the groin. The test takes 1 to 3 hours.
- ICP MonitorA device used to measure intracranial pressure (pressure within the brain). It consists of a small tube, placed into or on top of the brain through a small hole in the skull, connected to a transducer that registers the pressure.
- EEG (electroencephalograph)A test to measure electrical activity in the brain. It uses electrodes, in the form of patches, applied to the head. This painless procedure can be done at bedside or in a hospital's EEG department. The duration of the test varies.
X-rays, MRIs, and CT scans can detect fractures, hemorrhages, swelling, and certain kinds of tissue damage, but they do not always detect traumatic brain injury. This is because TBI, especially in its milder forms, often involves subtle traumas scattered among neurons and supportive tissues, stretched or damaged axon membranes (diffuse axonal injury), chemical injury caused by the biochemical cascade of toxic substances in the brain tissues, and cellular dysfunction. These changes often cannot be found with standard imaging procedures.
More sophisticated imaging techniques that measure brain cell metabolism, such as single-photon emission computed tomography (SPECT) or positron emission tomography (PET), can help diagnose such injuries.