A method of diagnosing TBI-induced tauopathy/chronic traumatic encephalopathy (CTE) by obtaining control samples from a control patients that have not been exposed to TBI and recording a normal range of tissue non-specific alkaline phosphatase (TNAP) or total alkaline phosphatase (AP) activity. Then obtaining samples from object patients that have been exposed to TBI. Comparing the biomarker, TNAP/AP, levels of said object patients to the controls. Then determining if the object patient has been exposed to TBI if the TNAP/AP levels are decreased below the normal range. Treating the patient by increasing the level of TNAP enzyme in the brain to within a normal range or modifying the TNAP enzyme activity so that it regains normal activity.
