Traumatic Brain Injury (TBI)

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Diagnosis

Patients suffering TBI are typically brought to a hospital emergency room for initial diagnosis and treatment. Once vital signs are assessed and stabilized, and other life-threatening injuries are identified and treated, the process of diagnosing the extent of brain injury begins.

A complete neurological evaluation is performed to rule out conditions requiring neurosurgical attention, such as hematomas, depressed skull fractures, and elevated intracrantial pressure (ICP). X-rays, CT scans, and/or MRI scans may be performed to determine if the bones of the skull are fractured and if bone fragments have penetrated the brain tissues.

The patient may be presented with a series of questions (What is your name? Where are you? What day is it?) and given simple commands (Wiggle your toes. Hold up two fingers.) to determine if he or she can open their eyes, move, speak, and understand what is happening around them. If possible, a detailed medical history is performed to identify any previous injuries, existing seizure disorders, learning disabilities, prior psychiatric or psychological treatment, and/or substance abuse.

The patient's degree of consciousness is assessed to determine the severity of brain injury and predict his or her chances for recovery. To do this, physicians typically use the Glasgow Coma Scale (GCS), which measures the patient's ability to open their eyes, move, and speak. The more severe the injury, the lower the total score suggesting little chance for complete recovery.

Glasgow Coma Scale

Eye Opening
4 = Responds spontaneously
3 = Responds to voice
2 = Responds to pain
1 = No response

Best Motor Response
6 = Follows commands
5 = Localizes to pain
4 = Withdraws to pain
3 = Decorticate (produces an exaggerated posture of upper extremity flexion and lower extremity extension in response to pain)
2 = Decerebrate (produces an exaggerated posture of extension in response to pain)
1 = No Response

Best Verbal Response
5 = Oriented and converses
4 = Disoriented and converses
3 = Inappropriate words
2 = Incomprehensible sounds
1 = No response

Total scores of 8 or below indicate a true coma and severe brain injury. Scores of 9 to 12 suggest moderate brain injury; scores of 13 and above indicate mild brain injury. However, the severity of the brain injury is not determined by GCS alone, as treatable conditions such as infection and dehydration may lower the GCS score.

When the patient is unconscious, the duration or length of coma (LOC) may be used to assess the severity of TBI and predict outcome. The longer the length of coma, the more severe the injury is. An LOC of less than about 20 minutes reflects a mild brain injury; longer than about 6 hours after admission reflects severe injury; between 20 minutes and 6 hours suggests moderate injury.

The neurological examination may show signs indicating the severity of injury such as increased reflexes and muscle tone (spasticity), abnormal movements (tremors), difficulty swallowing, or slurring of speech, all of which may indicate a moderate to severe head injury.

Imaging
Neuroradiological tests using computer-assisted brain scans help visualize damage to the brain. The most common of these is computerized axial tomography (CAT 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:

• Angiogram–A 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 Monitor–A 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.

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