OBJECTIVES To determine the frequency of neurobehavioral signs and symptoms reported in every published case of traumatic encephalopathy with a view toward the development of clinical diagnostic criteria with predictive validity.    INTRODUCTION Cases of persistent or progressive neurological or neurobehavioral change following exposure to one or more head injuries have been reported since 1928. This condition is often referred to as traumatic encephalopathy (TE). To date, however, no diagnostic criteria have been advanced or accepted for the clinical diagnosis of TE. Provisional research diagnostic criteria are required not only for meaningful diagnosis but also to facilitate research to determine the epidemiology, etiology, course, prognosis, imaging and biomarkers, neuropathological features and potentially effective treatments of TE.   
 METHODS All 436 published cases of TE in all languages were reviewed. All symptoms and signs reported in these cases were classified and enumerated.   
 RESULTS Ninety-seven cases met inclusion criteria based on sufficient documentation of the history and neurobehavioral examination. Provisional research diagnostic criteria for clinically probable and clinically possible TE were developed based on the most frequently reported clinical features.   
 CONCLUSION The provisional diagnostic criteria for TE presented here are the first published criteria for this condition based upon a systematic analysis of its clinical characteristics. This is the first a step toward scientifically derived consensus criteria, which are essential to accelerate progress in the investigation of this important condition.
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