Blunt Traumatic Brain Injury and Alzheimer Pathology

Introduction: Traumatic brain injury (TBI) has been associated with a greater risk of late-life dementia, including Alzheimer's disease (AD), but only a few studies examined the relationship between residuals of blunt TBI and autopsy-proven AD. The objective of the present study was to examine the incidence of fully developed AD pathology after documented blunt TBI, and the frequency of residuals of blunt TBI in a series of cases with definite AD. Methods: Among a sample of 1,750 consecutive autopsy cases of elderly demented patients, those cases with residuals of blunt (closed) TBI and definite AD pathology were assessed, and among 933 individuals with autopsy-proven AD, those with residuals of blunt TBI were selected. Results: Among 190 autopsy cases with residuals of blunt TBI, 28 (14.7%; mean age 77.2 +/- 10.6 years) revealed the pathological features of definite AD (Braak stage V or VI; ABC 3/3/3), while among 1,150 elderly controls (Braak stage < IV, mean age 77.3 +/- 9.5 years), 160 (13.6%) showed residuals of blunt TBI. The second part of the study included 933 consecutive cases with definite AD (Braak stage V or VI; ABC 3/3/3, mean age 82.3 +/- 8.4 years), in which 30 cases (3.3%; mean age 77.8 +/- 10.7 years) showed morphological residuals of blunt TBI. Conclusion: The results of this retrospective study, on the one hand, did not support the idea that blunt TBI and its morphological residuals are responsible for the development of definite AD, whereas the second part of the study, showing morphological residuals of blunt TBI among 3.3% of definite AD cases were similar to the results in a clinical series who sustained moderate to severe TBI. Considering these conflicting results, further studies on the relationship between the severity and location of morphological residuals of blunt TBI and the development of AD pathology are warranted.