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BrainRecovery: Brain Injury

Background on Evaluation Techniques

Since the early 1990s, a diagnostic test called a quantitative electro-encephalogram (qEEG) has been used in the diagnosis of minimal traumatic brain injury. This test is based on work by Robert Thatcher, Ph.D. (Bay Pines VA Medical Center, Medical Research Service and Department of Neurology and Radiology, University of South Florida College of Medicine, Tampa, Florida) The test involves comparison of a patient's EEG signature with that of a database of normal EEG signatures.

The difference in the signatures is expressed in terms of Z score, or degree of deviation from the normal, and is very helpful in distinguishing subtle changes in the anatomy as well as the processing function of the human brain. The signature is submitted to a multi-variant regression analysis, which can discriminate for mechanical head injury, as well as diffuse axonal injury, (which may occur with the twisting and shearing forces of traumatic head injury). The discriminant analysis has a sensitivity and specificity of over 95%.

Three classes of variables are attributed to mechanical head injury.

1. Increased coherence and decreased phase in the frontal and frontal-temporal region. 
  • Frontal region is concerned with executive function, organization and planning ahead. 
  • Temporal region is concerned with hearing and processing of emotion.
  • Increased coherence means that we cannot get out of a thought loop, thus our mental processes are slowed or become obsessive.
  • Decreased phase means that signals transverse the brain too slowly, because of injury to the myelin sheath of nerves, so that clinically we lose focus, we are not able to remember things for very long, and our short memory is poor.
2. Decreased power differences between anterior and posterior cortical regions, which is interpreted as changes in the long nerve cells connecting the two regions.

3. Reduced alpha power in posterior cortical regions, which would indicate "contra-coup" injury in this posterior region, resulting in an inability to relax, so that the brain is always going full speed ahead, with consequent anxiety and insomnia.