Core cerebrospinal fluid biomarker profile in anti-LGI1 encephalitis.

OBJECTIVE: To compare CSF biomarkers' levels in patients suffering from anti-Leucine-rich Glioma-Inactivated 1 (LGI1) encephalitis to neurodegenerative [Alzheimer's disease (AD), Creutzfeldt-Jakob's disease (CJD)] and primary psychiatric (PSY) disorders. METHODS: Patients with LGI1 encephalitis were retrospectively selected from the French Reference Centre database between 2010 and 2019 and enrolled if CSF was available for biomarkers analysis including total tau (T-tau), phosphorylated tau (P-tau), amyloid-beta Aß1-42, and neurofilaments light chains (Nf L). Samples sent for biomarker determination as part of routine practice, and formally diagnosed as AD, CJD, and PSY, were used as comparators. RESULTS: Twenty-four patients with LGI1 encephalitis were compared to 39 AD, 20 CJD and 20 PSY. No significant difference was observed in T-tau, P-tau, and Aß1-42 levels between LGI1 encephalitis and PSY patients. T-Tau and P-Tau levels were significantly lower in LGI1 encephalitis (231 and 43 ng/L) than in AD (621 and 90 ng/L, p < 0.001) and CJD patients (4327 and 55 ng/L, p < 0.001 and p < 0.01). Nf L concentrations of LGI1 encephalitis (2039 ng/L) were similar to AD (2,765 ng/L) and significantly higher compared to PSY (1223 ng/L, p < 0.005), but significantly lower than those of CJD (13,457 ng/L, p < 0.001). Higher levels of Nf L were observed in LGI1 encephalitis presenting with epilepsy (3855 ng/L) compared to LGI1 without epilepsy (1490 ng/L, p = 0.02). No correlation between CSF biomarkers' levels and clinical outcome could be drawn. CONCLUSION: LGI encephalitis patients showed higher Nf L levels than PSY, comparable to AD, and even higher when presenting epilepsy suggesting axonal or synaptic damage linked to epileptic seizures.

Comparative diagnosis interest of NfL and pNfH in CSF and plasma in a context of FTD-ALS spectrum.

OBJECTIVE: The 'Frontotemporal dementia-Amyotrophic lateral sclerosis Spectrum' (FAS) encompasses different phenotypes, including cognitive disorders (frontotemporal dementia, FTD) and/or motor impairments (amyotrophic lateral sclerosis, ALS). The aim of this study was to apprehend the specific uses of neurofilaments light chain (NfL) and phosphorylated neurofilaments heavy chain (pNfH) in a context of FAS. METHODS: First, NfL and pNfH were measured in 39 paired cerebrospinal fluid (CSF) and plasma samples of FAS and primary psychiatric disorders (PPD) patients, considered as controls. Secondly, additional plasma samples were included to examine a larger cohort of 81 samples composed of symptomatic FAS and PPD patients, presymptomatic and non-carrier relatives individuals. The measures were performed using Simoa technology. RESULTS: There was a positive correlation between CSF and plasma values for NfL (p < 0.0001) and for pNfH (p = 0.0036). NfL values were higher for all phenotypes of symptomatic FAS patients compared to PPD patients (p = 0.0016 in CSF; p = 0.0003 in plasma). On the contrary, pNfH values were solely increased in FAS patients exhibiting motor impairment. Unlike symptomatic FAS patients, presymptomatic cases had comparable concentrations with non-carrier individuals. CONCLUSION: NfL, but not pNfH, appeared to be useful in a context of differential diagnosis between FTD and psychiatric patients. Nevertheless, pNfH seem more specific for the diagnosis and follow-up of motor impairments. In each specific indication, measures in CSF and plasma will provide identical interpretations.

Early-Onset Cerebral Amyloid Angiopathy and Alzheimer Disease Related to an APP Locus Triplication.

BACKGROUND AND OBJECTIVE: To report a triplication of the amyloid-ß precursor protein (APP) locus along with relative messenger RNA (mRNA) expression in a family with autosomal dominant early-onset cerebral amyloid angiopathy (CAA) and Alzheimer disease (AD). METHODS: Four copies of the APP gene were identified by quantitative multiplex PCR of short fluorescent fragments, fluorescent in situ hybridization (FISH), and array comparative genomic hybridization. APP mRNA levels were assessed using reverse-transcription-digital droplet PCR in the proband's whole blood and compared with 10 controls and 9 APP duplication carriers. RESULTS: Beginning at age 39 years, the proband developed severe episodic memory deficits with a CSF biomarker profile typical of AD and multiple lobar microbleeds in the posterior regions on brain MRI. His father had seizures and recurrent cerebral hemorrhage since the age of 37 years. His cerebral biopsy showed abundant perivascular amyloid deposits, leading to a diagnosis of CAA. In the proband, we identified 4 copies of a 506-kb region located on chromosome 21q21.3 and encompassing the whole APP gene without any other gene. FISH suggested that the genotype of the proband was 3 copies/1 copy corresponding to an APP locus triplication, which was consistent with the presence of 2 APP copies in the healthy mother and with the paternal medical history. Analysis of the APP mRNA level showed a 2-fold increase in the proband and a 1.8 fold increase in APP duplication carriers compared with controls. DISCUSSION: Increased copy number of APP is sufficient to cause AD and CAA, with likely earlier onset in case of triplication compared with duplication.

A trial of gantenerumab or solanezumab in dominantly inherited Alzheimer's disease.

Dominantly inherited Alzheimer's disease (DIAD) causes predictable biological changes decades before the onset of clinical symptoms, enabling testing of interventions in the asymptomatic and symptomatic stages to delay or slow disease progression. We conducted a randomized, placebo-controlled, multi-arm trial of gantenerumab or solanezumab in participants with DIAD across asymptomatic and symptomatic disease stages. Mutation carriers were assigned 3:1 to either drug or placebo and received treatment for 4-7 years. The primary outcome was a cognitive end point; secondary outcomes included clinical, cognitive, imaging and fluid biomarker measures. Fifty-two participants carrying a mutation were assigned to receive gantenerumab, 52 solanezumab and 40 placebo. Both drugs engaged their Aß targets but neither demonstrated a beneficial effect on cognitive measures compared to controls. The solanezumab-treated group showed a greater cognitive decline on some measures and did not show benefits on downstream biomarkers. Gantenerumab significantly reduced amyloid plaques, cerebrospinal fluid total tau, and phospho-tau181 and attenuated increases of neurofilament light chain. Amyloid-related imaging abnormalities edema was observed in 19.2% (3 out of 11 were mildly symptomatic) of the gantenerumab group, 2.5% of the placebo group and 0% of the solanezumab group. Gantenerumab and solanezumab did not slow cognitive decline in symptomatic DIAD. The asymptomatic groups showed no cognitive decline; symptomatic participants had declined before reaching the target doses.

Improving the Diagnosis of the Frontal Variant of Alzheimer's Disease with the DAPHNE Scale.

BACKGROUND: The frontal variant of Alzheimer's disease (fAD) is poorly understood and poorly defined. The diagnosis remains challenging. The main differential diagnosis is the behavioral variant of frontotemporal degeneration (bvFTD). For fAD, there is some dissociation between the clinical frontal presentation and imaging and neuropathological studies, which do not always find a specific involvement of the frontal lobes. DAPHNE is a behavioral scale, which demonstrated excellent performance to distinguish between bvFTD and AD. OBJECTIVE: The aim of the present study was to assess the reliability of this new tool to improve the clinical diagnosis of fAD. METHODS: Twenty fAD patients and their caregivers were prospectively included and were compared with 36 bvFTD and 22 AD patients. RESULTS: The three main behavioral disorders in the fAD patients were apathy, loss of empathy, and disinhibition. Three disorders were discriminant because they were less frequent and less severe in the fAD patients than in the bvFTD patients, namely hyperorality, neglect, and perseverations. This specific pattern of behavioral disorders was corroborated by SPECT or 18FDG PET-CT scan that showed that patients with fAD could have a medial frontal hypoperfusion, whereas in bvFTD patients the orbitofrontal cortex was the main involved region, with more diffuse hypoperfusion. CONCLUSION: We demonstrated that DAPHNE had good sensitivity and good specificity to discriminate between the three groups and in particular between fAD and bvFTD patients. DAPHNE is a quick tool that could help clinicians in memory clinics not only to differentiate bvFTD from typical AD but also from fAD.

A Spatial Decision Eye-Tracking Task in Patients with Prodromal and Mild Alzheimer's Disease.

BACKGROUND/OBJECTIVE: Performances on spatial decision eye-tracking tasks are known to be impaired in patients with moderate Alzheimer's disease (AD), but the clinical relevance of this deficit during earlier stages of AD remains unclear. METHODS: This study recruited patients with amnestic mild cognitive impairment (aMCI, prodromal AD), patients with mild AD, and age-matched controls from three French memory clinics. Participants' ability to make spatial judgments and decisions was assessed with an eye-tracking system, and cognitive performance on conventional neuropsychological tests was evaluated. RESULTS: We enrolled 26 controls, 25 aMCI patients (median Mini-Mental State Exam [MMSE] 26), and 23 mild-AD patients (median MMSE 23). Patients with mild AD had higher error rates on the spatial decision task than aMCI patients and controls (32.4% versus 23.5%; p < 0.01 and 32.4% versus 22.2%; p < 0.05, respectively), but there were no differences among the groups in anticipation rate or the percentage of express saccades. Additionally, error rates on the spatial decision task were inversely correlated with performance on visual memory tests (immediate and delayed recall on the DMS- 48: r =-0.44, p = 0.0019 and r =-0.43, p = 0.0020, respectively), semantic fluency (r =-0.44, p = 0.0016), and global cognition (MMSE: r =-0.44, p = 0.0019). Performance on the spatial decision task was not correlated with anti-saccades, processing speed, or attentional performance. CONCLUSIONS: Patients with mild AD made more errors on a spatial decision task than aMCI patients and controls. We hypothesize that impaired visuospatial judgment may explain these results and distinguish aMCI patients from mild AD patients.

Causative Mutations and Genetic Risk Factors in Sporadic Early Onset Alzheimer's Disease Before 51 Years.

BACKGROUND: Pathogenic variants in the autosomal dominant genes PSEN1, PSEN2, or APP, APOE4 alleles, and rare variants within TREM2, SORL1, and ABCA7 contribute to early-onset Alzheimer's disease (EOAD). However, sporadic EOAD patients have been insufficiently studied to define the probability of being a carrier of one of these variants. OBJECTIVE: To describe the proportion of each genetic variation among patients with very young-onset sporadic AD. METHODS: We first screened PSEN1, PSEN2, and APP in 154 EOAD patients with an onset before 51 years and a negative family history. Among 99 patients with no mutation (NMC), whole exome sequencing (WES) was performed. We analyzed the APOE genotype and rare protein-truncating or missense predicted damaging variants of TREM2, SORL1, and ABCA7. Neurological examination and cerebrospinal fluid (CSF) biomarkers were systematically retrieved. RESULTS: Nineteen (12.3%) mutation carriers (MC) harbored an APP or PSEN1 pathogenic or likely pathogenic variant. Among the NMC, 54/99 carried at least one genetic risk factor, including 9 APOE4/E4 homozygous, 37 APOE4 heterozygous, and 14 with a rare variant in another risk factor gene: 3 SORL1, 4 TREM2, and 9 ABCA7. MC presented an earlier disease onset (p < 0.0001) and associated neurologic symptoms more frequently (p < 0.002). All but one patient had at least 2 CSF biomarkers in abnormal ranges. CONCLUSION: The genetic component of very early sporadic EOAD gathers a substantial proportion of pathogenic variants in autosomal dominant genes and an even higher proportion of patients carrying genetic risk factors, suggesting an oligogenic determinism, even at this range of ages.

C9orf72 Protein Plasmatic Concentrations Are Similar between C9ORF72 Expansion Carriers and Noncarriers in Frontotemporal Dementia.

BACKGROUND/AIMS: The aim of the study was to assess the theory of haploinsufficiency in C9ORF72 expansion carriers, the most frequent causative gene of frontotemporal dementia. METHODS: Plasmatic concentrations of C9orf72 protein were measured in 33 patients suspected of familial frontotemporal dementia using an enzyme-linked immunosorbent assay. RESULTS: No difference was observed between C9ORF72 expansion carriers (21.2% of patients) and noncarriers (78.8% of patients). C9orf72 protein determination is not a suitable biomarker for screening C9ORF72 expansion carriers. CONCLUSION: Our results provide new evidence against the hypothesis of haploinsufficiency leading to frontotemporal dementia in C9ORF72 expansion carriers.

Prodromal Alzheimer's Disease Demonstrates Increased Errors at a Simple and Automated Anti-Saccade Task.

Saccade alterations are potential early signs of Alzheimer's disease. However, uncertainty persists in how early and reliably automated saccade recording systems detect impairments. This multicenter pathophysiological case-control transversal study explored saccade execution in carefully diagnosed amnestic mild cognitive impairment patients fulfilling research criteria for prodromal Alzheimer's disease (n = 29), as compared to both aged-matched mild Alzheimer's disease patients (n = 23) and controls (n = 27). Auto-coded saccades from horizontal (gap) vertical (step) stimulus elicited pro-saccades, and anti-saccade (gap) tasks were compared across the 3 groups. Mild cognitive impairment patients committed significantly more anti-saccade errors compared to controls (46.9 versus 24.3%, p < 0.001). Conventional analyses of the auto-coded stimulus elicited saccades parameters did not distinguish the amnestic mild cognitive impairment from controls or the mild Alzheimer's disease group. However, an offline analysis of manually coded saccade latencies, using resampling statistics did reveal subtle differences among the groups. Analysis of the manually coded data revealed that the mild Alzheimer's disease group had a reliably larger self-corrected error-rate than in amnestic mild cognitive impairment and controls (p = 0.003). Analysis of the manually coded saccade latencies, using more sensitive lognormal bootstrap analysis revealed a continuum, from amnestic mild cognitive impairment to mild Alzheimer's disease, of an increased severity of impaired inhibition of stimulus elicited saccades and correct voluntary saccade initiation. Anti-saccade error rates and psychometric measures of executive and several other cognitive functions were moderately and negatively correlated. Overall, inhibitory impairments in stimulus elicited saccades, characteristic of Alzheimer's disease, may be detected early in presumed prodromal patients using a simple, automated anti-saccade task.

APP, PSEN1, and PSEN2 mutations in early-onset Alzheimer disease: A genetic screening study of familial and sporadic cases.

BACKGROUND: Amyloid protein precursor (APP), presenilin-1 (PSEN1), and presenilin-2 (PSEN2) mutations cause autosomal dominant forms of early-onset Alzheimer disease (AD-EOAD). Although these genes were identified in the 1990s, variant classification remains a challenge, highlighting the need to colligate mutations from large series. METHODS AND FINDINGS: We report here a novel update (2012-2016) of the genetic screening of the large AD-EOAD series ascertained across 28 French hospitals from 1993 onwards, bringing the total number of families with identified mutations to n = 170. Families were included when at least two first-degree relatives suffered from early-onset Alzheimer disease (EOAD) with an age of onset (AOO) ≤65 y in two generations. Furthermore, we also screened 129 sporadic cases of Alzheimer disease with an AOO below age 51 (44% males, mean AOO = 45 ± 2 y). APP, PSEN1, or PSEN2 mutations were identified in 53 novel AD-EOAD families. Of the 129 sporadic cases screened, 17 carried a PSEN1 mutation and 1 carried an APP duplication (13%). Parental DNA was available for 10 sporadic mutation carriers, allowing us to show that the mutation had occurred de novo in each case. Thirteen mutations (12 in PSEN1 and 1 in PSEN2) identified either in familial or in sporadic cases were previously unreported. Of the 53 mutation carriers with available cerebrospinal fluid (CSF) biomarkers, 46 (87%) had all three CSF biomarkers-total tau protein (Tau), phospho-tau protein (P-Tau), and amyloid ß (Aß)42-in abnormal ranges. No mutation carrier had the three biomarkers in normal ranges. One limitation of this study is the absence of functional assessment of the possibly and probably pathogenic variants, which should help their classification. CONCLUSIONS: Our findings suggest that a nonnegligible fraction of PSEN1 mutations occurs de novo, which is of high importance for genetic counseling, as PSEN1 mutational screening is currently performed in familial cases only. Among the 90 distinct mutations found in the whole sample of families and isolated cases, definite pathogenicity is currently established for only 77%, emphasizing the need to pursue the effort to classify variants.

Characteristics in limbic encephalitis with anti-adenylate kinase 5 autoantibodies.

OBJECTIVE: To report 10 patients with limbic encephalitis (LE) and adenylate kinase 5 autoantibodies (AK5-Abs). METHODS: We conducted a retrospective study in a cohort of 50 patients with LE with uncharacterized autoantibodies and identified a specific target using immunohistochemistry, Western blotting, immunoprecipitation, mass spectrometry, and cell-based assay. RESULTS: AK5 (a known autoantigen of LE) was identified as the target of antibodies in the CSFs and sera of 10 patients with LE (median age 64 years; range 57-80), which was characterized by subacute anterograde amnesia without seizure and sometimes preceded by a prodromal phase of asthenia or mood disturbances. Anterograde amnesia can be isolated, but some patients also complained of prosopagnosia, paroxysmal anxiety, or abnormal behavior. No associated cancer was observed. All 10 patients had bilateral hippocampal hypersignal on a brain MRI. CSF analysis generally showed a mild pleiocytosis with elevated immunoglobulin G index and oligoclonal bands, as well as high levels of tau protein with normal concentration of Aß42 and phospho-tau, suggesting a process of neuronal death. Except for one patient, clinical response to immunotherapy was unfavorable, with persistence of severe anterograde amnesia. Two patients evolved to severe cognitive decline. Hippocampal atrophy was observed on control brain MRI. Using in vitro tests on hippocampal neurons, we did not identify clues suggesting a direct pathogenic role of AK5-Abs. CONCLUSIONS: AK5-Abs should be systematically considered in aged patients with subacute anterograde amnesia. Recognition of this disorder is important to develop new treatment strategies to prevent irreversible limbic damage.

Seizures in dominantly inherited Alzheimer disease.

OBJECTIVE: To assess seizure frequency in a large French cohort of autosomal dominant early-onset Alzheimer disease (ADEOAD) and to determine possible correlations with causative mutations. METHODS: A national multicentric study was performed in patients with ADEOAD harboring a pathogenic mutation within PSEN1, PSEN2, APP, or a duplication of APP, and a minimal follow-up of 5 years. Clinical, EEG, and imaging data were systematically recorded. RESULTS: We included 132 patients from 77 families: 94 PSEN1 mutation carriers (MCs), 16 APP duplication carriers, 15 APP MCs, and 7 PSEN2 MCs. Seizure frequency was 47.7% after a mean follow-up of 8.4 years (range 5-25). After 5-year follow-up and using a Cox model analysis, the percentages of patients with seizures were respectively 19.1% (10.8%-26.7%) for PSEN1, 28.6% (0%-55.3%) for PSEN2, 31.2% (4.3%-50.6%) for APP duplications, and no patient for APP mutation. APP duplication carriers showed a significantly increased seizure risk compared to both APP MCs (hazard ratio [HR] = 5.55 [95% confidence interval 1.87-16.44]) and PSEN1 MCs (HR = 4.46 [2.11-9.44]). Among all PSEN1 mutations, those within the domains of protein hydrophilic I, transmembrane II (TM-II), TM-III, TM-IV, and TM-VII were associated with a significant increase in seizure frequency compared to other domains (HR = 4.53 [1.93-10.65], p = 0.0005). CONCLUSIONS: Seizures are a common feature of ADEOAD. In this population, risk was significantly higher in the APP duplication group than in all other groups. Within PSEN1, 5 specific domains were associated with a higher seizure risk indicating specific correlations between causative mutation and seizures.

Pseudotumoral presentation of cerebral amyloid angiopathy-related inflammation.

OBJECTIVE: To identify the clinical and radiologic features that should raise suspicion for the pseudotumoral presentation of cerebral amyloid angiopathy-related inflammation (CAA-I). METHODS: We retrospectively reviewed the characteristics of 5 newly diagnosed and 23 previously reported patients in whom the CAA-I imaging findings were initially interpreted as CNS neoplasms. RESULTS: Most cases (85%) occurred in patients >60 years old. The clinical characteristics at presentation included subacute cognitive decline (50%), confusion (32%), focal deficits (32%), seizures (25%), and headaches (21%). Brain MRI demonstrated infiltrative white matter lesions that exhibited a loco-regional mass effect without parenchymal enhancement (93%). In general, these findings were interpreted as low-grade glioma or lymphoma. Eighteen patients (64%) underwent a biopsy, which was nondiagnostic in 4 patients (14%), and 6 patients (21%) underwent a surgical resection. The primary reason for the misinterpretation of the imaging findings was the absence of T2*-weighted gradient recalled echo (T2*-GRE) sequences on initial imaging (89%). When subsequently performed (39%), the T2*-GRE sequences demonstrated multiple characteristic cortical and subcortical microhemorrhages in all cases. Perfusion MRI and magnetic resonance spectroscopy (MRS), which were performed on a subset of patients, indicated markedly reduced relative cerebral blood flow and a normal metabolic ratio. CONCLUSION: The identification of one or several nonenhancing space-occupying lesions, especially in elderly patients presenting with cognitive impairment, should raise suspicion for the pseudotumoral presentation of CAA-I and lead to T2*-GRE sequences. Perfusion MRI and MRS appear to be useful techniques for the differential diagnosis of this entity.

Increased cerebrospinal fluid tau levels in logopenic variant of Alzheimer's disease.

BACKGROUND: Patients with logopenic variant of primary progressive aphasia (lvPPA) display neuropathological differences from typical amnestic Alzheimer's disease (AD). OBJECTIVE: The aim of the study was to compare cerebrospinal fluid (CSF) biomarker levels between patients with lvPPA due to AD (lvPPA-AD), non-logopenic forms of AD (nlAD), and amnestic mild cognitive impairment due to AD (aMCI-AD). METHODS: CSF biomarker concentrations were assessed in 124 patients divided into three groups matched for age, level of education, center, and disease duration: lvPPA-AD (n = 30), nlAD (n = 67). and aMCI-AD (n = 27). RESULTS: p-Tau181 levels were higher in the lvPPA-AD group than in the aMCI-AD group (p < 0.05). Total tau levels were higher in the lvPPA-AD group versus those in the nlAD (p < 0.05) and aMCI-AD (p < 0.001) groups. CONCLUSIONS: These results suggest a more pronounced involvement of a taupathy in lvPPA-AD compared to aMCI-AD and a more important neuronal death in lvPPA-AD than in nlAD or aMCI-AD.

In vivo demonstration of amyloid burden in posterior cortical atrophy: a case series with PET and CSF findings.

Our objective was to evaluate amyloid deposition in posterior cortical atrophy (PCA), using both cerebrospinal fluid (CSF) biomarker analysis and amyloid imaging. Five PCA patients, selected based on their neuropsychological profile and atrophic changes in posterior regions on MRI, underwent CSF analysis. CSF amyloid-beta 1-42, total tau, and phosphorylated tau at threonine 181 levels were determined. They also had positron emission tomography (PET) with Pittsburgh Compound B ([(11)C]PIB). [(11)C]PIB ratio images were assessed with visual, regional and voxel-based analyses and compared to eight typical Alzheimer's disease (AD) patients and eight controls. The biological profile in the five PCA patients, resulting from CSF and [(11)C]PIB images analysis, was consistent with AD. Individual comparisons of PCA patients' [(11)C]PIB images with the AD group with Statistical Parametric Mapping (SPM) revealed a distinctive posterior uptake in four out of the five patients showing increased amyloid deposition in occipital, temporal, and/or parietal regions. ROI group analysis showed a tendency for higher amyloid deposition in occipital and temporal regions. However, this pattern was not found with SPM group analysis when the global level of [(11)C]PIB uptake was used as a covariate. Our results indicate that amyloid burden can be demonstrated in vivo in PCA suggesting a diagnosis of AD. PCA patients may present a higher global amyloid load than AD that was not related to age at onset, disease severity, disease duration, or educational level in our study. Combined CSF and PET biomarkers seem helpful for in vivo diagnosis of this focal syndrome with underlying AD pathology.