Cerebral amyloid angiopathy in traumatic brain injury: association with apolipoprotein E genotype

Prospective memory performance in veterans with and without histories of mild traumatic brain injury: effect of the apolipoprotein E (APOE) ε4 genotype

OBJECTIVE

Identifying factors that moderate cognitive outcomes following mild traumatic brain injury (mTBI) is crucial. Prospective memory (PM) is a cognitive domain of interest in mTBI recovery as it may be especially sensitive to TBI-related changes. Since studies show that genetic status - particularly possession of the apolipoprotein E (APOE) ε4 allele - can modify PM performance, we investigated associations between mTBI status and APOE-ε4 genotype on PM performance in a well-characterized sample of Veterans with neurotrauma histories.

METHODS

59 Veterans (mTBI = 33, Military Controls [MCs] = 26; age range: 24-50; average years post-injury = 10.41) underwent a structured clinical interview, neuropsychological assessment, and genotyping. The Memory for Intentions Test (MIST) measured PM across multiple subscales. ANCOVAs, adjusting for age and posttraumatic stress symptoms, tested the effects of mTBI status (mTBI vs. MC) and ε4 status (ε4+ vs. ε4-) on MIST scores.

RESULTS

Veterans with mTBI history performed more poorly compared to MCs on the MIST 15-min delay (p=.002, ηp2 =.160), Time Cue (p = .003, ηp2 =.157), and PM Total (p = .016, ηp2 =.102). Those with at least one copy of the ε4 allele performed more poorly compared to ε4- Veterans on the MIST 15-min delay (p = .011, ηp2 =.113) and PM Total (p = .048, ηp2 = .071). No significant interactions were observed between mTBI and APOE-ε4 status on MIST outcomes (ps>.25). Within the mTBI group, APOE-ε4+ Veterans performed worse than APOE-ε4- Veterans on the MIST 15-min delay subscale (p = .031, ηp2 = .150).

CONCLUSIONS

mTBI history and APOE-ε4 genotype status were independently associated with worse PM performance compared to those without head injury histories or possession of the APOE-e4 genotype. Performance on the MIST 15-min delay was worse in Veterans with both risk factors (mTBI history and APOE-ε4 positivity). Findings suggest that genetic status may modify outcomes even in relatively young Veterans with mTBI histories. Future research examining longitudinal associations and links to neuroimaging and biomarker data are needed.

APOE-ε4 Is Associated With Reduced Verbal Memory Performance and Higher Emotional, Cognitive, and Everyday Executive Function Symptoms Two Months After Mild Traumatic Brain Injury

Background

Substantial variance exists in outcomes after mild traumatic brain injury (MTBI), and these differences are not fully explained by injury characteristics or severity. Genetic factors are likely to play a role in this variance.

Objectives

The aim of this study was to examine associations between the apolipoprotein (APOE)-ε4 allele and memory measures at two months post-MTBI and to evaluate whether subjective cognitive and affective symptoms were associated with APOE-ε4 status. Based on previous research, it was hypothesized that APOE-ε4 carriers would show poorer verbal memory performance compared to APOE-ε4 non-carriers.

Methods

Neuropsychological data at two months post-injury and blood samples that could be used to assess APOE genotype were available for 134 patients with MTBI (mean age 39.2 years, 62% males, 37% APOE-ε4 carriers). All patients underwent computed tomography at hospital admission and magnetic resonance imaging four weeks post-injury.

Results

The APOE-ε4 + status was associated with decreased immediate memory recall (p = 0.036; β = −0.10, 95% CI [−0.19, −0.01]). Emotional, cognitive, and everyday executive function symptoms at two months post-injury were significantly higher in APOE-ε4 carriers compared to non-carriers.

Conclusion

The APOE-ε4+ allele has a negative effect on verbal memory and symptom burden two months after MTBI.

Left Atrial Appendage Closure for Patients with Cerebral Amyloid Angiopathy and Atrial Fibrillation: the LAA-CAA Cohort

Anticoagulation increases the risk of intracerebral hemorrhage (ICH) in patients with cerebral amyloid angiopathy (CAA), so the management of stroke-risk in patients with both atrial fibrillation (AF) and CAA is controversial. Advances in left atrial appendage closure (LAAC) techniques provide a stroke-risk-reduction option which avoids long-term oral anticoagulation (OAC). We aimed to evaluate the safety of this intervention in patients with CAA. This is an observational cohort study of patients with severe CAA (with or without ICH) and AF who were treated with LAA closure. The Watchman™ and Amulet® LAAC devices and Lariat procedure or open surgical closure of the LAA were all considered acceptable means of closure. Patients with symptomatic ICH and those naïve to anticoagulation were placed on clopidogrel and/or aspirin for 6 weeks after the procedure; patients who previously tolerated anticoagulation remained on warfarin or a DOAC for 6 weeks post-procedure. All anticoagulation therapy was discontinued after confirmation of LAAC. All patients had aggressively optimized blood pressure and fall precautions in addition to surgical intervention. Safety, tolerability, stroke, and hemorrhage rates were documented. Twenty-six patients with a mean CHA₂DS₂-VASc score of 4.6 were treated, 13 with a history of symptomatic lobar hemorrhage and 13 without. All patients who completed LAAC tolerated the device implantation. There were no documented ischemic strokes or symptomatic ICH during the 30 days after device implantation. Patients were followed for an average of 25 months. One patient who underwent Lariat LAAC had an ischemic stroke in follow-up, but recovered well; there were no other thromboemboli in this cohort. This cohort study provides evidence that LAAC appears to be a safe and tolerable treatment to reduce stroke risk in patients with CAA. Because of the small size of the cohort and relatively short follow-up, the efficacy for stroke and ICH prevention is not conclusive, but the preliminary results are encouraging. LAA closure may be a good alternative to anticoagulation in patients with CAA and atrial fibrillation.

Chronic Traumatic Encephalopathy and Neuropathological Comorbidities

With age, the presence of multiple neuropathologies in a single individual becomes increasingly common. Given that traumatic brain injury and the repetitive head impacts (RHIs) that occur in contact sports have been associated with the development of many neurodegenerative diseases, including chronic traumatic encephalopathy (CTE), Alzheimer's disease, Lewy body disease, and amyotrophic lateral sclerosis, it is becoming critical to understand the relationship and interactions between these pathologies. In fact, comorbid pathology is common in CTE and likely influenced by both age and the severity and type of exposure to RHI as well as underlying genetic predisposition. Here, we review the major comorbid pathologies seen with CTE and in former contact sports athletes and discuss what is known about the associations between RHI, age, and the development of neuropathologies. In addition, we examine the distinction between CTE and age-related pathology including primary age-related tauopathy and age-related tau astrogliopathy.

Contact sport participation and chronic traumatic encephalopathy are associated with altered severity and distribution of cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) consists of beta-amyloid deposition in the walls of the cerebrovasculature and is commonly associated with Alzheimer's disease (AD). However, the association of CAA with repetitive head impacts (RHI) and with chronic traumatic encephalopathy (CTE) is unknown. We evaluated the relationship between RHI from contact sport participation, CTE, and CAA within a group of deceased contact sport athletes (n = 357), a community-based cohort (n = 209), and an AD cohort from Boston University AD Center (n = 241). Unsupervised hierarchal cluster analysis demonstrated a unique cluster (n = 11) with increased CAA in the leptomeningeal vessels compared to the intracortical vessels (p < 0.001) comprised of participants with significantly greater frequencies of CTE (7/11) and history of RHI. Overall, participants with CTE (n = 251) had more prevalent (p < 0.001) and severe (p = 0.010) CAA within the frontal leptomeningeal vessels compared to intracortical vessels. Compared to those with AD, participants with CTE had more severe CAA in frontal than parietal lobes (p < 0.001) and more severe CAA in leptomeningeal than intracortical vessels (p = 0.002). The overall frequency of CAA in participants with CTE was low, and there was no significant association between contact sport participation and the presence of CAA. However, in those with CAA, a history of contact sports was associated with increased CAA severity in the frontal leptomeningeal vessels (OR = 4.01, 95% CI 2.52-6.38, p < 0.001) adjusting for AD, APOE ε4 status, and age. Participants with CAA had increased levels of sulcal tau pathology and decreased levels of the synaptic marker PSD-95 (p's < 0.05), and CAA was a predictor of dementia (OR = 1.75, 95% CI 1.02-2.99, p = 0.043) adjusting for age, sex, and comorbid pathology. Overall, contact sport participation and CTE were associated with more severe frontal and leptomeningeal CAA, and CAA was independently associated with worse pathological and clinical outcomes.

Acquired cerebral amyloid angiopathy: An emerging concept

Cerebral amyloid angiopathy (CAA) is commonly found in older people and in patients with Alzheimer's disease (AD) accompanying cerebrovascular disorders and dementia. Early-onset CAA cases generally have been found only in rare genetic forms of CAA. Interestingly, however, CAA-related hemorrhages have been recently reported in younger people who had histories of neurosurgery with or without evidence of cadaveric dura mater grafts in childhood. It has been established in experimental settings that amyloid β-protein (Aβ) pathology can be transmitted inter-individually with Aβ seeds. Incidental Aβ pathology, predominantly Aβ-CAA, has been recognized in recipients of cadaveric dura mater grafts or cadaveric human growth hormone. These findings suggest that transmission of Aβ seeds through dura mater grafts and other contaminated materials could lead to development of CAA. In addition, neurosurgery or brain injury may contribute to cerebrovascular Aβ deposition through the disturbance of vascular Aβ drainage pathways. Thus, a novel concept, "acquired CAA," has emerged.

Apolipoprotein E Gene Polymorphisms Are Risk Factors for Spontaneous Intracerebral Hemorrhage: A Systematic Review and Meta-analysis

Intracerebral hemorrhage (ICH) is a serious clinical disease with high morbidity, whose pathogenesis might be related to apolipoprotein E (APOE) gene polymorphisms. To comprehensively evaluate the risk factors for ICH occurrence, we performed a meta-analysis. We searched online databases to identify eligible studies based on the relationship between APOE genetic polymorphisms and ICH occurrence risk. Specific and pooled odds ratios (ORs) were calculated and by assessing small study bias, we drew the relationship between APOE polymorphisms and ICH risk. We included 15 eligible studies in our study containing a total of 1642 ICH samples and 5545 normal controls. The comparison of ɛ4 and ɛ3 APOE genotypes revealed that specific and pooled ORs showed a significantly increased odds ratio in ICH patients with the ɛ4 genotype, indicating that ɛ4 gene is a risk factor for ICH occurrence, and the heterogeneity is acceptable. Similarly, it was found that the ɛ2 genotype also contributed to the incidence rate of ICH. However, after the subgroup analysis by ethnicity, this APOE genetic polymorphism acted as a harmful factor only in white populations, but did not show an effect in Asian populations. It was suggested that both ε2 and ε4 APOE alleles were risk factors for ICH in general. They were risk factors in white populations only, neither had a detectable effect in Asian populations after subgroup analysing by ethnicity.

Evidence of amyloid-β cerebral amyloid angiopathy transmission through neurosurgery

Amyloid-β (Aβ) is a peptide deposited in the brain parenchyma in Alzheimer's disease and in cerebral blood vessels, causing cerebral amyloid angiopathy (CAA). Aβ pathology is transmissible experimentally in animals and through medical procedures in humans, such as contaminated growth hormone or dura mater transplantation in the context of iatrogenic prion disease. Here, we present four patients who underwent neurosurgical procedures during childhood or teenage years and presented with intracerebral haemorrhage approximately three decades later, caused by severe CAA. None of these patients carried pathogenic mutations associated with early Aβ pathology development. In addition, we identified in the literature four patients with a history of neurosurgical intervention and subsequent development of CAA. These findings raise the possibility that Aβ pathology may be transmissible, as prion disease is, through neurosurgical procedures.

Memory deficiency, cerebral amyloid angiopathy, and amyloid-β plaques in APP+PS1 double transgenic rat model of Alzheimer's disease

Transgenic rat models of Alzheimer's disease were used to examine differences in memory and brain histology. Double transgenic female rats (APP+PS1) over-expressing human amyloid precursor protein (APP) and presenilin 1 (PS1) and single transgenic rats (APP21) over-expressing human APP were compared with wild type Fischer rats (WT). The Barnes maze assessed learning and memory and showed that both APP21 and APP+PS1 rats made significantly more errors than the WT rats during the acquisition phase, signifying slower learning. Additionally, the APP+PS1 rats made significantly more errors following a retention interval, indicating impaired memory compared to both the APP21 and WT rats. Immunohistochemistry using an antibody against amyloid-β (Aβ) showed extensive and mostly diffuse Aβ plaques in the hippocampus and dense plaques that contained tau in the cortex of the brains of the APP+PS1 rats. Furthermore, the APP+PS1 rats also showed vascular changes, including cerebral amyloid angiopathy with extensive Aβ deposits in cortical and leptomeningeal blood vessel walls and venous collagenosis. In addition to the Aβ accumulation observed in arterial, venous, and capillary walls, APP+PS1 rats also displayed enlarged blood vessels and perivascular space. Overall, the brain histopathology and behavioral assessment showed that the APP+PS1 rats demonstrated behavioral characteristics and vascular changes similar to those commonly observed in patients with Alzheimer's disease.

APOE ε4 positive patients suffering severe traumatic head injury are more prone to undergo decompressive hemicraniectomy

OBJECT

In this paper we tested the hypothesis if patients with severe traumatic brain injury and presence of the apolipoprotein E (APOE) ε4 allele are more prone to undergo the surgical procedure decompressive hemicraniectomy (DC) in order to bring the intracranial pressure (ICP) under control.

METHODS

In this prospective consecutive study patients with sTBI were enrolled (n=48). Inclusion criteria were arrival to our level one trauma university hospital within 24h after trauma, patient age between 15 and 70years, Glasgow Coma Scale (GCS) score ≤8 at the time of intubation and sedation, an initial cerebral perfusion pressure >10mmHg. Venous blood was sampled for APOE genotype determination. Clinical outcome at 6months after injury was assessed with the Extended Glasgow Outcome Scale (GOSE). All surgical procedures needed for each patient were registered.

RESULTS

Patients with the APOE ε4 allele were significantly overrepresented in the DC group. In the APOE ε4+DC group, ICP_max and ICP_mean during the first 36h were significantly higher and GOSE was significantly worse at 6months.

CONCLUSION

Our data suggest that patients with the APOE ε4 allele are predisposed for the need of DC more often than patients without the APOE ε4 allele. Thus, it seems to be of importance to consider the APOE genotype in patients suffering severe traumatic brain injury in order to forecast the need for a more exquisite intensive care.

Localized cortical chronic traumatic encephalopathy pathology after single, severe axonal injury in human brain

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with repetitive mild impact traumatic brain injury from contact sports. Recently, a consensus panel defined the pathognomonic lesion for CTE as accumulations of abnormally hyperphosphorylated tau (p-tau) in neurons (neurofibrillary tangles), astrocytes and cell processes distributed around small blood vessels at sulcal depths in irregular patterns within the cortex. The pathophysiological mechanism for this lesion is unknown. Moreover, a subset of CTE cases harbors cortical β-amyloid plaques. In this study, we analyzed postmortem brain tissues from five institutionalized patients with schizophrenia and history of surgical leucotomy with subsequent survival of at least another 40 years. Because leucotomy involves severing axons bilaterally in prefrontal cortex, this surgical procedure represents a human model of single traumatic brain injury with severe axonal damage and no external impact. We examined cortical tissues at the leucotomy site and at both prefrontal cortex rostral and frontal cortex caudal to the leucotomy site. For comparison, we analyzed brain tissues at equivalent neuroanatomical sites from non-leucotomized patients with schizophrenia, matched in age and gender. All five leucotomy cases revealed severe white matter damage with dense astrogliosis at the axotomy site and also neurofibrillary tangles and p-tau immunoreactive neurites in the overlying gray matter. Four cases displayed p-tau immunoreactivity in neurons, astrocytes and cell processes encompassing blood vessels at cortical sulcal depths in irregular patterns, similar to CTE. The three cases with apolipoprotein E ε4 haplotype showed scattered β-amyloid plaques in the overlying gray matter, but not the two cases with apolipoprotein E ε3/3 genotype. Brain tissue samples from prefrontal cortex rostral and frontal cortex caudal to the leucotomy site, and all cortical samples from the non-leucotomized patients, showed minimal p-tau and β-amyloid pathology. These findings suggest that chronic axonal damage contributes to the unique pathology of CTE over time.

The Effect of the APOE4 Gene on Accumulation of Aβ40 After Brain Injury Cannot Be Reversed by Increasing apoE4 Protein

The apolipoprotein E (apoE) protein is involved in clearance of β-amyloid (Aβ) from the brain; and the APOE4 gene is associated with Aβ plaque formation in humans following traumatic brain injury (TBI). Here, we examined the association between apoE and Aβ₄₀ after experimental TBI and the effects of APOE alleles on this relationship. We report a biphasic response of soluble apoE protein after TBI with an acute reduction at 1 day postinjury followed by an increase at 7 days postinjury. TBI-induced Aβ₄₀ levels decreased as soluble apoE levels increased. In APOE4 mice there was a diminished apoE response to TBI that corresponded to prolonged accumulation of TBI-induced Aβ₄₀ versus that in APOE3 mice. Amyloid precursor protein processing was similar in APOE3 and APOE4 mice suggesting that impaired clearance was responsible for the abnormal accumulation of Aβ₄₀ in the latter. Treatment of APOE4 mice with bexarotene for 7 days increased apoE4 protein levels but was not sufficient to reduce TBI-induced Aβ₄₀ Thus, rapid clearance of TBI-induced Aβ₄₀ occurs in mice but these pathways are impaired in APOE4 carriers. These data may help explain the deposition of Aβ in APOE4 carriers and the increased incidence of brain Aβ plaques following TBI.

Dura mater is a potential source of Aβ seeds

Deposition of amyloid-β (Aβ) in the brain parenchyma and vessels is one of the hallmarks of Alzheimer disease (AD). Recent observations of Aβ deposition in iatrogenic Creutzfeldt-Jakob disease (iCJD) after dural grafting or treatment with pituitary extracts raised concerns whether Aβ is capable of transmitting disease as seen in prion diseases by the disease-associated prion protein. To address this issue, we re-sampled and re-evaluated archival material, including the grafted dura mater of two cases with iCJD (28 and 33-years-old) without mutations in the AβPP, PSEN1 and PSEN2 genes, and carrying ε3/ε3 alleles of the APOE gene. In addition, we evaluated 84 dura mater samples obtained at autopsy (mean age 84.9 ± 0.3) in the community-based VITA study for the presence of Aβ deposition. We show that the dura mater may harbor Aβ deposits (13 %) in the form of cerebral amyloid angiopathy or amorphous aggregates. In both iCJD cases, the grafted dura mater had accumulated Aβ. The morphology and distribution pattern of cerebral Aβ deposition together with the lack of tau pathology distinguishes the Aβ proteinopathy in iCJD from AD, from that seen in young individuals without cognitive decline carrying one or two APOE4 alleles, and from that related to traumatic brain injury. Our novel findings of Aβ deposits in the dura mater, including the grafted dura, and the distinct cerebral Aβ distribution in iCJD support the seeding properties of Aβ. However, in contrast to prion diseases, our study suggests that such Aβ seeding is unable to reproduce the full clinicopathological phenotype of AD.

Intracerebral hemorrhage due to cerebral amyloid angiopathy after head injury: Report of a case and review of the literature

Cerebral amyloid angiopathy (CAA) is an important cause of spontaneous intracerebral hemorrhage in the elderly. A few case reports of CAA-related intracerebral hemorrhage after head injury, usually following a fall, have been published. More rarely, it may occur in the setting of a traffic accident, with only four cases having been reported. We describe a case of CAA-related intracerebral hemorrhage in an 88-year-old man injured in a road traffic accident. The patient died 14 h after the accident. Autopsy examination revealed a left frontoparietal hematoma and CAA of most of the small leptomeningeal and cortical arteries, as well as several capillaries, predominantly in the parietal and occipital lobes. Except for bruises in the frontal and zygomatic regions, elbow and forearm, to the left, there were no skull fractures or traumatic lesions in other parts of the body. We review the literature on CAA-related intracerebral hemorrhage associated with head injury. CAA-related intracerebral hemorrhage after head injury may occur due to a minor trauma, minor and severe falls, or in the setting of a traffic accident. However, even in this last condition, it seems to happen mostly in patients who had a mild to moderate head injury. These facts show that replacement of the contractile components of the arterial tunica media by amyloid renders the affected cerebral blood vessels more vulnerable to head injury associated with acceleration and deceleration, independently of the severity of the dynamic loading acting on the head.

Cerebral amyloid angiopathy: emerging concepts

Cerebral amyloid angiopathy (CAA) involves cerebrovascular amyloid deposition and is classified into several types according to the amyloid protein involved. Of these, sporadic amyloid β-protein (Aβ)-type CAA is most commonly found in older individuals and in patients with Alzheimer's disease (AD). Cerebrovascular Aβ deposits accompany functional and pathological changes in cerebral blood vessels (CAA-associated vasculopathies). CAA-associated vasculopathies lead to development of hemorrhagic lesions [lobar intracerebral macrohemorrhage, cortical microhemorrhage, and cortical superficial siderosis (cSS)/focal convexity subarachnoid hemorrhage (SAH)], ischemic lesions (cortical infarction and ischemic changes of the white matter), and encephalopathies that include subacute leukoencephalopathy caused by CAA-associated inflammation/angiitis. Thus, CAA is related to dementia, stroke, and encephalopathies. Recent advances in diagnostic procedures, particularly neuroimaging, have enabled us to establish a clinical diagnosis of CAA without brain biopsies. Sensitive magnetic resonance imaging (MRI) methods, such as gradient-echo T2^* imaging and susceptibility-weighted imaging, are useful for detecting cortical microhemorrhages and cSS. Amyloid imaging with amyloid-binding positron emission tomography (PET) ligands, such as Pittsburgh Compound B, can detect CAA, although they cannot discriminate vascular from parenchymal amyloid deposits. In addition, cerebrospinal fluid markers may be useful, including levels of Aβ40 for CAA and anti-Aβ antibody for CAA-related inflammation. Moreover, cSS is closely associated with transient focal neurological episodes (TFNE). CAA-related inflammation/angiitis shares pathophysiology with amyloid-related imaging abnormalities (ARIA) induced by Aβ immunotherapies in AD patients. This article reviews CAA and CAA-related disorders with respect to their epidemiology, pathology, pathophysiology, clinical features, biomarkers, diagnosis, treatment, risk factors, and future perspectives.

Predicting cerebral amyloid angiopathy-related intracerebral hemorrhages and other cerebrovascular disorders in Alzheimer's disease

Cerebral amyloid angiopathy (CAA) of amyloid β-protein (Aβ) type is common in Alzheimer's disease (AD). Aβ immunotherapies have been reported to induce CAA-related intracerebral hemorrhages (ICH) or vasogenic edema. For the purpose of developing a method to predict CAA-related ICH and other cerebrovascular disorders in AD, the biomarkers, and risk factors are reviewed. The biomarkers include (1) greater occipital uptake on amyloid positron emission tomography imaging and a decrease of cerebrospinal fluid Aβ40 levels as markers suggestive of CAA, and (2) symptomatic lobar ICH, lobar microhemorrhages, focal subarachnoidal hemorrhages/superficial siderosis, cortical microinfarcts, and subacute encephalopathy (caused by CAA-related inflammation or angiitis) as imaging findings of CAA-related ICH and other disorders. The risk factors include (1) old age and AD, (2) CAA-related gene mutations and apolipoprotein E genotype as genetic factors, (3) thrombolytic, anti-coagulation, and anti-platelet therapies, hypertension, and minor head trauma as hemorrhage-inducing factors, and (4) anti-amyloid therapies. Positive findings for one or more biomarkers plus one or more risk factors would be associated with a significant risk of CAA-related ICH and other cerebrovascular disorders. To establish a method to predict future occurrence of CAA-related ICH and other cerebrovascular disorders in AD, prospective studies with a large number of AD patients are necessary, which will allow us to statistically evaluate to what extent each biomarker or risk factor would increase the risk. In addition, further studies with progress of technologies are necessary to more precisely detect CAA and CAA-related cerebrovascular disorders.

The release of S-100B and NSE in severe traumatic head injury is associated with APOE ε4

OBJECT

In this article we tested the hypothesis that the level of two biochemical markers of brain injury may be associated with the apolipoprotein E (APOE) ε4 allele.

METHODS

In this prospective consecutive study patients with sTBI were included (n = 48). Inclusion criteria were Glasgow Coma Scale (GCS) score ≤ 8 at the time of intubation and sedation, patient age between 15 and 70 years, an initial cerebral perfusion pressure > 10 mmHg, and arrival to our level-one trauma university hospital within 24 h after trauma. Blood samples for neuron-specific enolase (NSE) and S-100B were collected as soon as possibly after arrival, and then twice daily (12-h intervals) for 5 consecutive days. Venous blood was used for APOE genotype determination. Clinical outcome at 3 months after injury was assessed with the Extended Glasgow Outcome Scale (GOSE).

RESULTS

Significantly higher levels of the maximal S-100B (S-100B(max)) and area under the curve (S-100B(AUC)) were found in subjects with the APOE ε4 allele compared to those with non-ε4. A similar tendency was observed for NSE(max) and NSE(AUC), though not statistically significant.

CONCLUSION

Our data indicate that there might be a gene-induced susceptibility to severe traumatic brain injury and that patients with the APOE ε4 allele may be more predisposed to brain cellular damage measured as S-100B and NSE. Thus, it seems to be of importance to consider the APOE genotype in interpreting the levels of the biomarkers.

Apolipoprotein E in Alzheimer's disease and other neurological disorders

Apolipoprotein E (APOE) is a 299-aminoacid protein encoded by the APOE gene. Three common polymorphisms in the APOE gene, ɛ2, ɛ3, and ɛ4, result in a single aminoacid change in the APOE protein. APOE ɛ2, ɛ3, and ɛ4 alleles strongly alter, in a dose-dependent manner, the likelihood of developing Alzheimer's disease and cerebral amyloid angiopathy. In particular, APOE ɛ4 is associated with increased risk for Alzheimer's disease whereas APOE ɛ2 is associated with decreased risk. The effects of APOE genotype on risk of these diseases are likely to be mediated by differential effects of APOE on amyloid-β accumulation in the brain and its vasculature. Response to treatment for Alzheimer's disease might differ according to APOE genotype. Because convincing evidence ties the APOE genotype to risk of Alzheimer's disease and cerebral amyloid angiopathy, APOE has been studied in other neurological diseases. APOE ɛ4 is associated with poor outcome after traumatic brain injury and brain haemorrhage, although the mechanisms underlying these associations are unclear. The possibility that APOE has a role in these and other neurological diseases has been of great interest, but convincing associations have not yet emerged.

Apolipoprotein E genotype and concussion in college athletes

OBJECTIVE

To evaluate the association between apolipoprotein E (APOE) polymorphisms (E2, C/T Arg158Cys; E4, T/C Cys112Arg; and promoter, g-219t) and the history of concussion in college athletes. We hypothesized that carrying 1 or more APOE rare (or minor) allele assessed in this study would be associated with having a history of 1 or more concussions.

DESIGN

Multicenter cross-sectional study.

SETTING

University athletic facilities.

PARTICIPANTS

One hundred ninety-six male football (n = 163) and female soccer (n = 33) college athletes volunteered.

INTERVENTIONS

Written concussion history questionnaire and saliva samples for genotyping.

MAIN OUTCOME MEASURES

Self-reported history of a documented concussion and rare APOE genotype (E2, E4, promoter).

RESULTS

There was a significant association (Wald χ² = 3.82; P = 0.05; odds ratio = 9.8) between carrying all APOE rare alleles and the history of a previous concussion. There was also a significant association (Wald χ² = 3.96, P = 0.04, odds ratio = 8.4) between carrying the APOE promoter minor allele and experiencing 2 or more concussions.

CONCLUSIONS

Carriers of all 3 APOE rare (or minor) alleles assessed in this study were nearly 10 times more likely to report a previous concussion and may be at a greater risk of concussion versus noncarriers. Promoter minor allele carriers were 8.4 times more likely to report multiple concussions and may be at a greater risk of multiple concussions versus noncarriers. Research involving larger samples of individuals with multiple concussions and carriers of multiple APOE rare alleles is warranted.

Genetic association studies in patients with traumatic brain injury

Traumatic brain injury (TBI) constitutes a major cause of mortality and disability worldwide, especially among young individuals. It is estimated that despite all the recent advances in the management of TBI, approximately half of the patients suffering head injuries still have unfavorable outcomes, which represents a substantial health care, social, and economic burden to societies.

Considerable variability exists in the clinical outcome after TBI, which is only partially explained by known factors. Accumulating evidence has implicated various genetic elements in the pathophysiology of brain trauma. The extent of brain injury after TBI seems to be modulated to some degree by genetic variants.

The authors' current review focuses on the up-to-date state of knowledge regarding genetic association studies in patients sustaining TBI, with particular emphasis on the mechanisms underlying the implication of genes in the pathophysiology of TBI.

Apolipoprotein E genotype and traumatic brain injury in children--association with neurological outcome

OBJECTIVE

To determine whether the presence of Apolipoprotein E epsilon4 genotype (ApoE epsilon4) is associated with outcomes of traumatic brain injury in children.

MATERIALS AND METHODS

The ApoE genotype was examined in the group of 70 pediatric patients who suffered from traumatic brain injury. The group consists of 48 boys and 22 girls, and the most frequent was the E3 isoform of ApoE. Polymerase chain reaction/restriction fragment length polymorphism method was used for the ApoE genotype assessment. The severity of trauma was assessed by Glasgow Coma Scale and graded into three categories. The presence of focal neurology signs, comparing the admission and dimission status, and duration of hospital care were observed. The neurological outcome after 1 year was assessed by Glasgow Outcome Scale. Trauma severity was compared with the neurological outcome, according to different ApoE genotypes. For statistical processing, t test, nonparametric Wilcoxon test, Fisher, and chi(2) tests were used.

CONCLUSION

Our results suggest the association between the ApoE genotype and outcome of traumatic brain injury in children. Patients with ApoE epsilon4 genotype were more likely to have severe clinical symptomatology and unfavorable neurological outcome after traumatic brain injury compared to significantly better outcome with other ApoE genotype.

Apolipoprotein E genotype and traumatic brain injury in children--association with neurological outcome

OBJECTIVE

To determine whether the presence of Apolipoprotein E epsilon4 genotype (ApoE epsilon4) is associated with outcomes of traumatic brain injury in children.

MATERIALS AND METHODS

The ApoE genotype was examined in the group of 70 pediatric patients who suffered from traumatic brain injury. The group consists of 48 boys and 22 girls, and the most frequent was the E3 isoform of ApoE. Polymerase chain reaction/restriction fragment length polymorphism method was used for the ApoE genotype assessment. The severity of trauma was assessed by Glasgow Coma Scale and graded into three categories. The presence of focal neurology signs, comparing the admission and dimission status, and duration of hospital care were observed. The neurological outcome after 1 year was assessed by Glasgow Outcome Scale. Trauma severity was compared with the neurological outcome, according to different ApoE genotypes. For statistical processing, t test, nonparametric Wilcoxon test, Fisher, and chi(2) tests were used.

CONCLUSION

Our results suggest the association between the ApoE genotype and outcome of traumatic brain injury in children. Patients with ApoE epsilon4 genotype were more likely to have severe clinical symptomatology and unfavorable neurological outcome after traumatic brain injury compared to significantly better outcome with other ApoE genotype.

Apolipoprotein E4 allele presence and functional outcome after severe traumatic brain injury

Presence of the apolipoprotein E (APOE) 4 allele has been associated with increased incidence and faster progression of neurodegenerative diseases, poorer recovery from neurologic insult, and decreased cognitive function in the well-elderly. The specific association between APOE genotype and recovery from severe traumatic brain injury (TBI) is conflicting with many groups finding the APOE 4 allele to be associated with poorer outcome while others have found no association. The purpose of this study was to investigate the association between APOE 4 allele presence and recovery during the two years after injury from severe TBI in light of other potential covariates, such as age, race, gender, hypotension or hypoxia before hospital admission and severity of injury. APOE genotype was determined for 123 subjects with severe TBI. Glasgow outcome score (GOS) and mortality were collected at 3, 6, 12, and 24 months after injury. Results showed individuals improved over the two year period following injury and those with the 4 allele had a slower recovery rate than those without the APOE 4 allele over the two year period. We did not however find significant differences in GOS at individual time points when controlling for other covariates. Our findings suggest that APOE 4 allele presence influences recovery rate from severe TBI independent of other covariates. The findings of this study are unique in that they address not only the relationship between APOE 4 allele presence and outcome from severe TBI, but also describe differences in trajectory of recovery by APOE 4 allele presence.

Impact of genetic factors on outcome from brain injury

Most human phenotypic characteristics are determined by the interplay of environmental factors (whether external, or related to the internal milieu) with the unique genetic attributes of the individual. The same is true for predisposition to and outcome from most disease states, with acute brain injury being no exception. A greater understanding of this interplay is likely to allow improved risk stratification of patients, the development of new preventative and therapeutic modalities, and the possibility of 'individualizing' patient management based upon their genetic inheritance.

Apolipoprotein E alleles can contribute to the pathogenesis of numerous clinical conditions including HSV-1 corneal disease

Apolipoprotein E (ApoE) alleles have been reported to affect the clinical outcome of numerous cardiovascular, neurodegenerative, and viral infectious diseases, including atherosclerosis, Alzheimer's disease (AD), hepatitis C, and HIV. The major alleles of ApoE are 2, 3, and 4. ApoE genotypes have been hypothesized to regulate many biological functions, resulting in significant changes in the onset and/or outcome (severity and duration) of several clinical conditions. Based on genetic analyses in human and animal studies using knockout (ApoE -/-) mice and mice transgenic for human 3 and 4, we present evidence that strongly suggests that the ApoE alleles can regulate the pathogenesis of ocular herpes simplex virus type 1 (HSV-1) infections. This review will summarize the major studies that support this hypothesis. Significant gender based differences in HSV-1 pathogenesis have also been reported, suggesting that hormonal regulation combined with ApoE genotype plays a significant role in HSV-1 pathogenesis. Identification of specific mechanisms in ocular HSV-1 infections related to the ApoE alleles and gender could lead to therapeutic intervention based on the properties of the apoE isoforms. While many clinical investigations have been reported and, to a lesser extent, transgenic mouse studies have been conducted, no specific mechanisms of how ApoE induces or alters clinical disease are known.

Association of APOE e4 and cerebrovascular pathology in traumatic brain injury

BACKGROUND

Previous studies have found the e4 allele of the apolipoprotein E gene (APOE e4) is associated with an unfavourable outcome after head injury, but this has not been related to specific pathological features.

OBJECTIVES

This study tested the postulate that head injured patients with APOE e4, amounting to approximately a third of the population, are selectively predisposed to one or more of the different pathological features that constitute the response to traumatic brain injury (TBI), and that this underlies the association of APOE e4 with poor clinical outcome.

METHODS

Included in the study were 239 fatal cases of TBI (1987-1999) for which APOE genotypes were determined from archival tissue. For each case, specific pathological features of trauma were recorded by researchers blinded to the APOE e4 status. Of the 239 cases examined, 83 (35%) were APOE e4 carriers and 156 (65%) were non-carriers.

RESULTS

Possession of APOE e4 was associated with a greater incidence of moderate or severe contusions (42% v 30% for carriers versus e4 non-carriers; p = 0.05) and there was a trend towards a greater incidence of severe ischaemic brain damage (54% v 42%; p = 0.08). Significant differences were not noted between the other pathological features examined.

CONCLUSIONS

Possession of APOE e4 is associated with a greater incidence of moderate/severe contusional injury and severe ischaemic brain damage in fatal cases of TBI. This may be relevant to the relatively poor outcome from traumatic brain injury in patients with APOE e4 identified in clinical studies.

In search of genes involved in neurodegenerative disorders

Dissecting the genetics of Alzheimer's disease (AD) and Parkinson's disease (PD) has contributed significantly to our understanding of the pathogenesis of neurodegeneration in these two complex disorders. For AD, three highly penetrant genes (amyloid precursor protein (APP, PSEN1 and PSEN2) and one susceptibility gene (APOE) have been identified. For PD, seven genes (SNCA, Parkin, UCHL1, NR4A2, DJ1, PINK1 and LRRK2) have been found. These genes explain only a small proportion of AD and PD patients and are mostly associated with an early onset presentation of the disease. APOE remains the only common gene, which increases the risk of both rare early and late onset AD. The ongoing challenge is to unravel the genetics of the most frequent forms of these complex disorders. In the present paper, we briefly review the state of the art in the genetics of AD and PD. We also discuss the prospects of finding new genes associated with common forms of these diseases in light of two hypotheses concerning the genetic variation of complex diseases: common disease/common variants and common disease/rare variants.

Sporadic cerebral amyloid angiopathy: pathology, clinical implications, and possible pathomechanisms

Cerebral amyloid angiopathy (CAA) was observed for the first time nearly 100 years ago and systematically described in 1938. It is a common finding in elderly individuals, defined by beta-amyloid peptide (Abeta) depositions in cerebral blood vessels, and associated with Alzheimer's disease (AD). A variety of genetic mutations cause hereditary forms of CAA; in this review, however, only the sporadic variant of CAA is considered. In CAA, Abeta depositions primarily occur in the abluminal portion of the tunica media, and with increasing severity all layers of the blood vessel wall are infiltrated and an additional spread of Abeta into the surrounding neuropil may be seen (i.e., dyshoric changes). CAA is most pronounced in the occipital lobe and its distribution is usually patchy. The relationship between CAA and AD is poorly understood; however, low positive correlations between the severity of both CAA and AD pathology have been observed. CAA is a frequent cause of (warfarin-associated) intracerebral hemorrhage, and the diagnosis of probable CAA-related hemorrhage can be made during life with high accuracy. Both APOE-epsilon4 and APOE-epsilon2 are risk factors for CAA, while only APOE-epsilon2 increases the risk for hemorrhage in CAA. Although the role of CAA as an independent risk factor for cognitive decline is unclear, severe CAA is likely to lower the threshold for clinically overt dementia in neurodegenerative diseases. As for the origin of Abeta in CAA, it may be both produced by smooth muscle cells (vessel wall) and derived from neurons in the course of perivascular drainage.

Alzheimer's disease pathology influences severity and topographical distribution of cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is defined by beta-amyloid peptide (Abeta) depositions in cerebral vessels and is associated with Alzheimer's disease (AD). The relationship between sporadic CAA and AD, and the origin of Abeta in CAA are poorly understood. The aim of our study was to investigate the relationship between CAA and AD. Autopsy brains (n=113, 61.1% female, 55.8% clinically demented, age range 54-102 years, mean +/- SE 83.5+/-0.93 years) underwent standardized neuropathological assessment. CAA was evaluated in frontal, frontobasal, hippocampal, and occipital regions. Using immunohistochemistry, the severity of Abeta deposition in vessels was assessed semiquantitatively for each region separately. Evaluation of APOE genotype in 53 cases using real-time PCR showed significant correlations with severe AD pathology and CAA. CAA was present in 77 cases (68.1%), with the occipital region being affected significantly more often and more severely than other regions (P<0.01). Of brains without AD pathology 23.5% revealed CAA, whereas 24% with AD pathology showed no CAA. In concordance with other studies, the severity of both AD pathology and CAA showed a low, but significant correlation. This correlation, however, was only caused by the significant increase of occipital CAA with increasing AD pathology (P<0.01), and was independent of APOE genotype. Our results suggest that progressing AD pathology not only increases the severity of CAA, but also shifts its topographical distribution towards the occipital cortex.

The association between APOE ε4, age and outcome after head injury: a prospective cohort study

Previous preliminary studies have suggested that possession of the APOE epsilon4 allele is associated with a poor outcome after head injury. This study was designed to confirm and extend those observations in a larger study with examination of additional variables. We prospectively identified admissions to a Neurosurgical Unit for head injury, collected demographic and clinical data, determined APOE genotypes and obtained follow-up information at 6 months. A total of 1094 subjects were enrolled (age range: 0-93 years, mean 37 years). Outcome was assessed using the Glasgow Outcome Scale. There was no overall association between APOE genotype and outcome, with 36% of APOE epsilon4 carriers having an unfavourable outcome compared with 33% of non-carriers of APOE epsilon4. However, there was evidence of an interaction between age and APOE genotype on outcome (P = 0.007) such that possession of APOE epsilon4 reduced the prospect of a favourable outcome in children and young adults. The influence of APOE genotype in younger patients after head injury can be expressed as, at age <15 years, carriage of APOE epsilon4 being equivalent to ageing by 25 years. This finding is consistent with experimental data suggesting that the effect of APOE genotype on outcome after head injury may be expressed through the processes of repair and recovery.