Head Injury Exposure in Veterans Presenting to Memory Disorders Clinic: An Observational Study of Clinical Characteristics and Relationship of Event-Related Potentials and Imaging Markers.

Katherine W Turk,Andrew E Budson,Andrew E Budson,Ana L Vives-Rodriguez,Anna Marin,Cheongmin Suh,Brigid Dwyer,Prayerna Uppal,Kylie A Schiloski,Rocco Palumbo,Rocco Palumbo,Rocco Palumbo

doi:10.3389/fneur.2021.626767

Abstract

Objective: Traumatic brain injury (TBI) and repetitive head impacts (RHI) related to blasts or contact sports are commonly reported among military service members. However, the clinical implications of remote TBI and RHI in veterans remains a challenge when evaluating older veterans at risk of neurodegenerative conditions including Alzheimer's disease (AD) and Chronic Traumatic Encephalopathy (CTE). This study aimed to test the hypothesis that veterans in a memory disorders clinic with remote head injury would be more likely to have neurodegenerative clinical diagnoses, increased rates of amyloid PET positivity, higher prevalence of cavum septum pellucidi/vergae, and alterations in event-related potential (ERP) middle latency auditory evoked potentials (MLAEPs) and long latency ERP responses compared to those without head injuries.Methods: Older veterans aged 50–100 were recruited from a memory disorders clinic at VA Boston Healthcare system with a history of head injury (n = 72) and without head injury history (n = 52). Patients were classified as reporting prior head injury including TBI and/or RHI exposure based on self-report and chart review. Participants underwent MRI to determine presence/absence of cavum and an ERP auditory oddball protocol.Results: The head injury group was equally likely to have a positive amyloid PET compared to the non-head injury group. Additionally, the head injury group were less likely to have a diagnosis of a neurodegenerative condition than those without head injury. P200 target amplitude and MLAEP amplitudes for standard and target tones were decreased in the head injury group compared to the non-head injury group while P3b amplitude did not differ.Conclusions: Veterans with reported remote head injury evaluated in a memory disorders clinic were not more likely to have a neurodegenerative diagnosis or imaging markers of neurodegeneration than those without head injury. Decreased P200 target and MLAEP target and standard tone amplitudes in the head injury group may be relevant as potential diagnostic markers of remote head injury.

Highlights

The relationship between head injury and subsequent dementia, two highly common and often co-occurring neurologic disorders, has gained increased attention in recent years with mounting pathological and epidemiological evidence indicating that head injury likely plays a causal role in the development of chronic traumatic encephalopathy (CTE) [1,2,3] and may act as a significant risk factor for Alzheimer’s disease (AD) [4,5,6,7,8]
While the strongest links are those between repetitive head impacts (RHI) and CTE pathological diagnosis [3], epidemiological studies have found an association between traumatic brain injury (TBI) and increased risk of dementia among both civilian [9] and veteran populations [10,11,12,13,14]
A selfreport checklist of depression (GDS) and mood lability (CNS-LS) showed higher levels of depression and mood lability symptoms, respectively, for the head injury compared to non-head injury group (p < 0.05)

Summary

Introduction

The relationship between head injury and subsequent dementia, two highly common and often co-occurring neurologic disorders, has gained increased attention in recent years with mounting pathological and epidemiological evidence indicating that head injury likely plays a causal role in the development of chronic traumatic encephalopathy (CTE) [1,2,3] and may act as a significant risk factor for Alzheimer’s disease (AD) [4,5,6,7,8]. The translation of pathological and epidemiological evidence into clinically meaningful and impactful diagnostic and prognostic information for older individuals with both cognitive complaints and TBI/RHI exposure is an active area of investigation. In many instances the existing TBI literature has failed to account for RHI exposure, which is common in civilian and military settings and may represent an independent and/or synergistic risk factor for neurodegenerative disease

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Conclusion