Interpretation

Clinical Interpretation Manual

ImPACT Interpretive Strategy

As with the interpretation of any neuropsychological test or test battery, test data often require analysis at multiple levels. Any program that claims to diagnose all concussions through a "yes-no" or "red light-green light" decision making process is overly simplistic and may miss subtle difficulties. This could expose the athlete to further injury.

Therefore, ImPACT does not yield one summary score, but rather a series of indicators that have been demonstrated to be sensitive to concussion (see reference section of website). Not every athlete will demonstrate impairment on all indices and the individual test performance of the athlete may depend on a number of factors that include type of blow to the head, site of the blow, and the patient's individual history. In addition, ImPACT team members have developed a symptom scale that has been adopted by most professional sports organizations as well as by the International Olympic Committee, FIFA and the International Ice Hockey Foundation. The interpretation of ImPACT© should ideally follow a multi-level path of analysis. Of course, it should be stressed that as a brief screening battery, ImPACT does not purport to represent a comprehensive evaluation of neuropsychological functioning. Some athletes may require more involved evaluation, which should always be accomplished by a qualified neuropsychologist.

As a first step in the clinical interpretation of ImPACT, an evaluation of the five composite scores is recommended. Even a cursory review of the composite scores often reveals subtle deficits in the core areas of attention/memory (as evidenced by decreased performance on the Verbal and Visual Memory composites) or cognitive speed (as evidenced by increased reaction time or a decreased score on the Visual-Motor Processing composite). The magnitude of changes from baseline testing is assessed via the use of Reliable Change Index (RCI) scores for the ImPACT composites. If an athlete demonstrates a change in scores that falls outside of the range of normal score variation, the ImPACT report notes these changes in test performance (version 3.0 and higher). However, even subtle changes in performance that fail to reach the level of the RCI score may be significant if they are different from baseline performance. If baseline performance has not been completed, a comparison of ImPACT scores to established age and gender stratified normative scores is recommended. For Versions 1.0 and 2.0, an extensive normative database is available at www.impacttest.com. For Version, 3.0 and higher, age and gender referenced percentile scores are automatically printed within the report. These scores can be very helpful in establishing the overall level of performance in comparison to the athlete's peer group for each composite score. The second step of test analysis should involve a more specific analysis of the individual scores that comprise the composite scores. This type of pattern analysis involves a thorough analysis of each of the module scores as well as an analysis of patterns or strengths and weaknesses in various areas of performance. For instance, does the athlete display relatively intact performance on tests measuring memory but deficits on tests that tap cognitive speed? In addition, it is important to evaluate the dimension of speed and memory accuracy on specific tests, examining what individual scores may have lead to the drop in overall performance measured by the composite scores. Since several of the ImPACT© modules are multi-dimensional and measure both speed and memory, the injured athlete may sacrifice performance in one dimension for performance in another. This is often seen on the Symbol Match subtest. In an apparent attempt to increase memory accuracy, an athlete may slow down considerably with regard to the speed element of the test. The astute clinician will recognize this as abnormal performance.

It is important to emphasize that not all concussed athletes demonstrate clear evidence of cognitive dysfunction on neuropsychological testing. Non-cognitive symptoms such as headache, nausea, balance problems and dizziness are common and should be thoroughly assessed. Although athletes at all levels of competition are notorious for minimizing symptoms, particularly later in the recovery process when they are being considered for return to play, the tracking of symptoms still represents an important and necessary element of the concussion management process. Although as noted earlier, every concussion may present differently, there are often symptom constellations that may suggest specific clinical syndromes. For example, migraine-type headaches are relatively common following concussion and often present with the characteristic symptoms of headache (often unilateral and described as throbbing or pulsating), dizziness, photophobia or phonophobia, and nausea. A recent study utilizing ImPACT© has demonstrated that this type of post-traumatic migraine syndrome is associated with reduced neurocognitive performance (Collins et al., 2003), although this is not always the case. Post-traumatic migraine is particularly common in individuals with a prior history or family history of headache and this history adds an additional level of complexity to the return to play decision making process. To complicate matters further, these athletes often receive pharmacologic treatment of their headaches, which may help with regard to the headache but not treat the underlying neurocognitive dysfunction. In this case, the clinician should be especially careful to assure that the athlete is indeed recovered with regard to their level of cognitive functioning, prior to consideration of return to play.

The ImPACT symptom scale has become standard throughout amateur and professional sports and promotes the quantification of the severity of symptoms. This scale also allows for the accurate tracking of recovery from each of the individual symptoms throughout the recovery process. Finally, this scale serves as an educational tool, alerting both the athlete, team staff and parent regarding potential post-concussive symptoms. See scale below.

Symptom None Minor Moderate Severe Headache 0 1 2 3 4 5 6 Nausea 0 1 2 3 4 5 6 Vomiting 0 1 2 3 4 5 6 Balance Problems 0 1 2 3 4 5 6 Dizziness 0 1 2 3 4 5 6 Fatigue 0 1 2 3 4 5 6 Trouble Falling Asleep 0 1 2 3 4 5 6 Sleeping More Than Usual    0 1 2 3 4 5 6 Sleeping Less Than Usual 0 1 2 3 4 5 6 Drowsiness 0 1 2 3 4 5 6 Sensitivity to Light 0 1 2 3 4 5 6 Sensitivity to Noise 0 1 2 3 4 5 6 Irritability 0 1 2 3 4 5 6 Sadness 0 1 2 3 4 5 6 Nervousness 0 1 2 3 4 5 6 Feeling More Emotional 0 1 2 3 4 5 6 Numbness or Tingling 0 1 2 3 4 5 6 Feeling Slowed Down 0 1 2 3 4 5 6 Feeling Mentally "Foggy" 0 1 2 3 4 5 6 Difficulty Concentrating 0 1 2 3 4 5 6 Difficulty Remembering 0 1 2 3 4 5 6 Visual Problems 0 1 2 3 4 5 6

Adapted from Lovell and Collins, Journal of Head Trauma and Rehabilitation 1998;13:9-26.

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