Neuropsychologists are not medical doctors, but doctors of psychology whose field of study is concentrated on the brain and its functions. Neuropsychological testing is designed to determine the brain’s capacity with respect to short and long term memory, abstract reasoning, attention, concentration, executive functioning, motor skills and other cognitive and psychological factors. By comparing the pattern of these results, against the patients pre-morbid capabilities, and correlating these results with the nature of the trauma suffered by the patient, neuropsychologists can, to a reasonable degree of certainty, opine that individuals without an acute diagnosis of brain injury, have permanent deficits as a result of brain trauma.
In many cases, medical doctors, insurance adjusters and defense attorneys will minimize the survivor’s injuries because of negative scanning tests, such as X-Ray, MRI and CT scan. The favorite defense phrase is “no objective evidence of injury”. But normal imaging studies do not rule out a brain injury. In such cases, neuropsychological assessment can be “objective evidence of injury”. In fact, neuropsychological testing is the “gold standard” against which other diagnostic tools are measured to determine the existence of pathology to the brain. Only autopsy studies are more accurate.
Neuropsychologists use batteries of tests to triangulate the brain’s functioning and through that triangulation, determine whether the brain is functioning as it should. Just like tapping a knee to check the reflexes is an objective test of how the nervous system operates, neuropsychological tests are an objective measure of how the brain is functioning. If a neuropsychologist is using what is called a “fixed battery” they will be using one of two such batteries, the Halstead-Reitan or the Luria-Nebraska battery. The advantage of using such batteries is that decades of study and thousands of test results have created an accurate profile of the pattern of deficits which correlate to specific types of brain injury.
The Halstead-Reitan Battery consists of the Category Test, Tactual Performance Test, Seashore Rhythm Tests, Speech Sounds Perception Tests, Finger Tapping Test, and Trail Making. Neuropsychologists often administer Full Scale IQ, Verbal IQ, and Performance IQ. The most commonly employed intelligence test is the Wechsler Adult Intelligence Scale-Revised (WAIS-R). The three summary IQ measures are derived from averaging individual subtest scores. An Aphasia Screening Test, a Sensory-Perceptual Examination, are also typically administered, and many neuropsychologists will also administer the MMPI as well.
A normal IQ score, or even high test scores in specific areas, do not rule out brain injury. First, if a person had a 130 IQ before the injury and a 100 IQ after, this would clearly establish injury. More significantly, many profoundly brain injured survivors, maintain an average IQ near their pre-morbid levels. It is not their average scores that are significant, but the pattern of such scores. This graph shows the typical test variability often seen in neuropsych testing, which correlates to a diagnosis of permanent brain injury. Plus, the IQ only measures certain brain functions, those primarily cognitive in nature. The neuropscyh exam is designed to evaluate a comprehensive cross section of brain function.
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