Assessment of Mendelian and risk-factor genes in Alzheimer disease: A prospective nationwide clinical utility study and recommendations for genetic screening

PURPOSE

To assess the likely pathogenic/pathogenic (LP/P) variants rates in Mendelian dementia genes and the moderate-to-strong risk factors rates in patients with Alzheimer disease (AD).

METHODS

We included 700 patients in a prospective study and performed exome sequencing. A panel of 28 Mendelian and 6 risk-factor genes was interpreted and returned to patients. We built a framework for risk variant interpretation and risk gradation and assessed the detection rates among early-onset AD (EOAD, age of onset (AOO) ≤65 years, n = 608) depending on AOO and pedigree structure and late-onset AD (66 < AOO < 75, n = 92).

RESULTS

Twenty-one patients carried a LP/P variant in a Mendelian gene (all with EOAD, 3.4%), 20 of 21 affected APP, PSEN1, or PSEN2. LP/P variant detection rates in EOAD ranged from 1.7% to 11.6% based on AOO and pedigree structure. Risk factors were found in 69.5% of the remaining 679 patients, including 83 (12.2%) being heterozygotes for rare risk variants, in decreasing order of frequency, in TREM2, ABCA7, ATP8B4, SORL1, and ABCA1, including 5 heterozygotes for multiple rare risk variants, suggesting non-monogenic inheritance, even in some autosomal-dominant-like pedigrees.

CONCLUSION

We suggest that genetic screening should be proposed to all EOAD patients and should no longer be prioritized based on pedigree structure.

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.

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.

Distinct effects of dopamine vs STN stimulation therapies in associative learning and retention in Parkinson disease

Evidence has been provided in Parkinson's disease patients of cognitive impairments including visual memory and learning which can be partially compensated by dopamine medication or subthalamic nucleus stimulation. The effects of these two therapies can differ according to the learning processes involving the dorsal vs ventral part of the striatum. Here we aimed to investigate and compare the outcomes of dopamine vs stimulation treatment in Parkinson patient's ability to acquire and maintain over successive days their performance in visual working memory. Parkinson patients performed conditional associative learning embedded in visual (spatial and non spatial) working memory tasks over two consecutive days either ON or OFF dopaminergic drugs or STN stimulation depending on the group of patients studied. While Parkinson patients were more accurate and faster in memory tasks ON vs OFF stimulation independent of the day of testing, performance in medicated patients differed depending on the medication status during the initial task acquisition. Patients who learnt the task ON medication the first day were able to maintain or even improve their memory performance both OFF and ON medication on the second day after consolidation. These effects were observed only in patients with dopamine replacement with or without motor fluctuations. This enhancement in memory performance after having learnt under dopamine medication and not under STN stimulation was mostly significant in visuo-spatial working memory tasks suggesting that dopamine replacement in the depleted dorsal striatum is essential for retention and consolidation of learnt skill.

Dissociable dorsal and ventral frontostriatal working memory circuits: evidence from subthalamic stimulation in Parkinson's disease

In this study, we investigated the neural substrates involved in visual working memory (WM) and the resulting effects of subthalamic nucleus (STN) stimulation in Parkinson's disease (PD). Cerebral activation revealed by positron emission tomography was compared among Parkinson patients with (PD-ON) or without (PD-OFF) STN stimulation, and a group of control subjects (CT) in two visual WM tasks with spatial (SP) and nonspatial (NSP) components. PD-OFF patients displayed significant reaction time (RT) deficits for both memory tasks. Although there were no significant differences in RT between patients with PD-ON and -OFF stimulation, patients with PD-ON stimulation performed comparably to controls. The memory tasks were executed with normal error rates in PD-ON and -OFF stimulation. In contrast to these behavioral results, whether the corresponding prefrontal activation was differentially affected by deep brain stimulation status in patients depended on whether the WM modality was SP versus NSP. Thus, SP WM was associated with (1) abnormal reduction in dorsolateral prefrontal activity in PD-OFF and -ON stimulation and (2) abnormal overactivation in parieto-temporal cortex in PD-OFF and in limbic circuits in PD-ON stimulation. In NSP WM, normal activation of the ventral prefrontal cortex was restored in PD-ON stimulation. In both visual modalities the posterior cerebral regions including fusiform cortex and cerebellum, displayed abnormally reduced activity in PD. These results indicate that PD induces a prefrontal hypoactivation that STN stimulation can partially restore in a modality selective manner by additional recruitment of limbic structures in SP WM or by recovery of the ventral prefrontal activation in NSP WM.

[Diagnostic profile of young-onset dementia before 65 years. Experience of a French Memory Referral Center]

OBJECTIVE

The aim of the study was to compare the profiles of patients with young (age≤65 years) and late (age>65 years) onset of dementia in a memory clinic of a Memory Referral Center in Lyons (France), for the year 2008.

METHODS

A total of 746 demented patients were evaluated using clinical, neuropsychological and imaging information. For each patient, diagnoses of the dementing disorder used clinical criteria at the first visit. We examined the distribution of patients diagnosis and differences in sex and education between the young-onset dementia (YOD) and the late-onset dementia (LOD) groups.

RESULTS

From a total of 746 registered demented patients (300 men, 446 women), there were 91 patients (12.2%) with YOD (from 36.5 to 65 years) and 655 patients with LOD (from 66 to 92 years). Among the 91 YOD patients, the most frequent causes were Mild Cognitive Impairment (MCI) (18.7%), then Alzheimer's disease (AD), frontotemporal dementia and posterior cortical atrophy (14.3% each), followed by progressive aphasia (11.0%), dementia with Lewy bodies (DLD) (9.9%), semantic dementia (8.8%), other causes (3.3%), vascular dementia (2.2%), undetermined dementia (2.2%), AD+cerebrovascular disease (1.1%). Among the 655 LOD patients, AD was the most frequent cause of dementia (57.4%). Referred cases by a specialist doctor were 50.5% in the YOD group and 12.7% in the LOD group (P<0.0001). In the ACP group, 68.4% patients began before 65 years.

CONCLUSION

The number of YOD in our memory clinic was four-fold the number of expected patients in France. The characteristics of the Referral Center explain the high frequency of rare dementia such as progressive aphasia (5.2% of overall number), semantic dementia (3.6%) and posterior cortical atrophy (2.5%).

CSF biomarkers in posterior cortical atrophy

OBJECTIVE

To describe CSF biomarker profiles in posterior cortical atrophy (PCA), which induces high-order visual deficits often associated with Alzheimer disease (AD) pathology, and relate these findings to clinical and neuropsychological assessment.

METHODS

This prospective observational study included 22 patients with PCA who underwent CSF biomarker analysis of total tau (t-tau), phosphorylated tau on amino acid 181 (p-tau181), and amyloid β (Aβ(42)). At group level, the CSF profiles of patients with PCA were compared to those of patients with typical AD and patients with other dementia (OD). Individually, the clinical presentation of patients with PCA was correlated to their CSF profile to assess the predictability of clinical features for diagnosis of underlying AD pathology.

RESULTS

At group level, the PCA biomarker profile was not different from that of the AD group, but very different from that of the OD group (p < 0.001). More than 90% of patients with PCA had CSF profiles consistent with AD. All patients with PCA with either isolated higher-order visual deficit (n = 8) or visual deficit associated with memory impairment (n = 11) had CSF profiles consistent with AD. Only one of the 3 patients with PCA with asymmetric motor signs fulfilled biological CSF criteria for AD.

CONCLUSIONS

PCA syndrome is usually associated with CSF biomarkers suggestive of AD, as shown by previous neuropathologic studies. This does not apply in case of motor signs suggesting associated corticobasal syndrome. CSF biomarkers help to discriminate AD from non-AD processes associated with this condition.

[The 5-word test in 37 depressed patients compared with 36 normal controls and 35 patients with mild Alzheimer's disease]

OBJECTIVES

Patients with major depression (MD) express frequent memory complaints leading to consultations in memory clinics. The 5-word test (5WT) is a verbal memory test with semantic cueing, which has shown its sensitivity and its specificity in identifying patients with Alzheimer's disease (AD). Our objective was to evaluate memory performances of aged patients with MD compared with controls and AD patients.

METHODS

Characteristics of the 5WT were investigated in a sample of 37 patients with MD (66.8±7.5 years) compared with 36 normal controls (67.3±6.8 years) and 35 mild AD patients (67.5±6.1 years).

RESULTS

Duration of depression was 15.3±11.5 years. Memory complaints of MD patients were ancient (4.6±5.5 years) and severe (McNair memory questionnaire=47.6±20.7). The Total score of MD patients did not differ from controls but was greater than those of AD patients. Learning and Memory scores of MD patients were significantly lower than those of controls and significantly greater than those of AD patients. Forgetting rate between Learning and Memory scores was more important in AD (72.4%) than in controls (2.8%) and MD (13.6%). No intrusions were recorded in controls, three MD patients each made one intrusion, whereas 80% of AD patients made between one to six intrusions (mainly during cued delayed recall). Receiver operating characteristic curves determined the most significant cut-off scores of the Total score. It appeared easy to discriminate AD patients from controls (cut-off=9, sensitivity=94.3%, specificity=100%) or MD patients (cut-off=8, sensitivity=88.5%, specificity=89.2%) whereas it was more difficult to discriminate MD patients from controls (cut-off=10, specificity=88.9%, sensitivity=37.8%).

DISCUSSION

MD patients had significant difficulties with the 5WT as compared to controls, without being of the magnitude of those observed in AD patients.

CONCLUSION

The 5WT allows a reliable evaluation of memory in MD patients. The presence of true memory deficits with the 5WT could not be ascribed to depression but to other pathological conditions. Consequently, further memory testing should be conducted.

[The 5-word test in 85 patients with generalized anxiety disorder]

OBJECTIVES

Patients with generalized anxiety disorder (GAD) expressed frequent memory complaints leading to consultations in memory clinics. The 5-word test (5WT) is a serial verbal memory test with semantic cuing. It is proposed to rapidly evaluate memory of people with memory complaints. It has previously shown its sensitivity and its specificity in identifying patients with Alzheimer's disease (AD). The objective was to evaluate memory performances of patients with GAD.

METHODS

Characteristics of the 5WT were investigated in a sample of 85 patients with GAD compared with 183 normal controls aged from 40 to 70 years.

RESULTS

For each score of the 5WT, GAD patients significantly differed from controls. Forgetting rate was twice more important in GAD patients than in controls. However, for any score of the 5WT, Receiver Operating Characteristic (ROC) curves found no significant cut-off scores combining reliable sensitivity, specificity and correct classification of the subjects.

DISCUSSION

In spite of ancient and severe mnestic complaints, GAD patients have significant difficulties with the 5WT as compared to controls without being of the magnitude of those observed in AD patients.

CONCLUSION

The 5WT is an easy and rapid test allowing a reliable evaluation of memory in GAD patients. Results could usually confort patients. The presence of true memory deficits with the 5WT could not be ascribed to anxiety but to other pathological conditions. Consequently, further memory testing should be done.

Bilateral subthalamic nucleus stimulation in advanced Parkinson's disease: three years follow-up

OBJECTIVE

To assess the long-term efficacy and safety of chronic bilateral stimulation of the subthalamic nucleus (STN) in patients with advanced Parkinson's disease (PD).

METHODS

36 consecutive patients with idiopathic Parkinson's disease treated with bilateral stimulation of the STN were studied. Parkinsonian status was assessed preoperatively and at 1 and 3 years postoperatively using the Unified Parkinson's Disease Rating Scale (UPDRS) and neuropsychological evaluation in on and off-medication / on and off stimulation conditions.

RESULTS

At 3 years follow-up, STN stimulation reduced the UPDRS motor score by 54.2 % compared to baseline in the off-medication conditions. Tremor, rigidity, bradykinesia, postural stability, and gait improved by 72.2 %, 62.4 %, 56.8 %, 40.5 % and 45.3 %, respectively. UPDRS part II scores were reduced by 41.4 %. The overall dopaminergic drugs dose was reduced by 48.6 % after surgery and four patients were no longer taking antiparkinsonian medication at three years. However, axial dopa-unresponsive signs worsened in some patients. The most frequent transient adverse event consisted in mood disorders in 23 patients.

CONCLUSIONS

Our data demonstrate that: 1) bilateral STN stimulation is relatively safe, improves the motor symptoms and drug-related motor complications of PD, and reduces the daily dosage of medication; 2) this benefit is sustained over time despite the occurrence of axial doparesistant signs in some patients.

Double dissociation in neural correlates of visual working memory: A PET study

Using positron emission tomography (PET), we investigated the organisation of spatial versus object-based visual working memory in 11 normal human subjects. The paradigm involved a conditional colour-response association task embedded within two visual working memory tasks. The subject had to remember a position (spatial) or shape (object-based) and then use this to recover the colour of the matching element for the conditional association. Activation of the nucleus accumbens and the anterior cingulate cortex was observed during the conditional associative task, indicating a possible role of these limbic structures in associative memory. When the 2 memory tasks were contrasted, we observed activation of 2 distinct cortical networks: (1) The spatial task activated a dorsal stream network distributed in the right hemisphere in the parieto-occipital cortex and the dorsal prefrontal cortex, and (2) The non spatial task activated a ventral stream network distributed in the left hemisphere in the temporo- occipital cortex, the ventral prefrontal cortex and the striatum. These results support the existence of a domain-specific dissociation with dorsal and ventral cortical systems involved respectively in spatial and non spatial working memory functions.

Role of Dopaminergic Treatment in Dopamine Receptor Down-regulation in Advanced Parkinson Disease

BACKGROUND

In patients with advanced Parkinson disease (PD) who are undergoing long-term treatment with a dopaminergic medication, a down-regulation of striatal dopamine D2 receptor expression has been demonstrated and interpreted as a consequence of either the disease itself or dopaminergic drug administration.

OBJECTIVE

To compare, using positron emission tomography, the striatal binding of raclopride carbon C 11, a dopamine D2 receptor ligand, in PD patients who completely discontinued dopaminergic therapy (off drug) with that in PD patients who continued receiving dopaminergic therapy (on drug) after undergoing subthalamic nucleus stimulation.

MAIN OUTCOME MEASURES

The positron emission tomographic data were acquired in off-stimulation and, for 12 hours, off-medication conditions. Five off-drug PD patients, 7 on-drug PD patients, and 8 healthy subjects participated.

RESULTS

In off-drug PD patients, the putaminal raclopride C 11 binding was 24% higher than in on-drug PD patients. The same tendency was noted for the caudate nucleus, but was not significant (P=.07). Compared with control subjects, the putaminal raclopride C 11 binding was increased by 21% in off-drug and was normal in on-drug PD patients. Compared with controls, the caudate raclopride C 11 binding was reduced by 23% in on-drug and was normal in off-drug PD patients. Further analysis using statistical parametric mapping showed a significant increase of binding bilaterally in the caudate nucleus and putamen in off-drug compared with on-drug PD patients (P=.002 at cluster level).

CONCLUSIONS

The down-regulation of dopamine D2 receptors probably relates to the long-term and intermittent administration of dopaminergic treatments rather than to disease progression. This phenomenon is reversed by the complete withdrawal of dopaminergic drugs. Furthermore, an up-regulation of putaminal dopamine D2 receptors is demonstrated in late-stage PD after dopaminergic drug withdrawal.

Dissociable effects of dopaminergic therapy on spatial versus non-spatial working memory in Parkinson's disease

There is now evidence for definite and early cognitive deficits in Parkinson's disease (PD), involving, in particular, executive functions and working memory. However, the distinction between visuo-spatial and non-spatial working memory deficits and the impact of dopamine on these deficits are still open to debate. The aim of this study was therefore to investigate cognitive and motor performance in PD patients in two conditional associative learning tasks requiring either spatial or non-spatial visual working memory. The subject had to point to visual targets according to the visual characteristics of memorised visual cues (colour, position and form). To assess the effect of L-dopa therapy, PD patients were studied over two consecutive days: one ON/OFF group of nine PD patients with treatment (ON condition) on the first day and without treatment (OFF condition) on the second day; and another OFF/ON group of nine PD patients tested on reverse. The PD groups were compared to a control group of nine age-matched healthy subjects. Our main data demonstrate that: (1) in PD patients with OFF treatment, the response time of manual pointing is increased mainly in the non-spatial working memory task; and (2) in PD patients with ON treatment, either the response time is normal (on the first day) or is increased in both visuo-spatial and non-spatial tasks. We suggest that this dissociation between spatial versus non-spatial working memory deficits in non-medicated PD might be related to compensatory mechanisms that occur following fronto-striatal dysfunction.

The timing of antiparkinsonian treatment reduction after subthalamic nucleus stimulation

The objective of this work was to precisely analyse the reduction of the antiparkinsonian treatment in 18 consecutive patients with Parkinson's disease (PD) operated on for bilateral subthalamic nucleus (STN) stimulation, first after 1 month of follow-up, then at 1 year postoperatively. Trihexyphenidyle, selegiline, entacapone, apomorphine and lisuride could be withdrawn shortly after starting STN electrical stimulation. The levodopa mean daily dose was reduced by 57% at 1 month after surgery and remained stable at 1 year. The mean ropinirole and bromocriptine daily dose decrements after surgery corresponded to 54 and 63%, respectively, at 1 month and to 77 and 40% at 1 year. At 12 months postoperatively, one third of the patients no longer received any antiparkinsonian drugs and the others were on monotherapy of either levodopa or dopamine agonists or received a combined treatment of a dopaminergic agonist and levodopa. In conclusion, STN stimulation allows a major reduction and simplification of antiparkinsonian treatment which can usually be achieved during the early postoperative period.

Subthalamic nucleus stimulation in Parkinson's disease: clinical evaluation of 18 patients

The aim of the present study was to assess the efficacy and safety of chronic subthalamic nucleus deep-brain stimulation (STN-DBS) in patients with Parkinson's disease (PD). 18 consecutive severely affected PD patients were included (mean age, SD: 56.9+/-6 years; mean disease duration: 13.5+/-4.4 years). All the patients were evaluated clinically before and 6 months after the surgical procedure using the Unified Parkinson's Disease Rating Scale (UPDRS). Additionally, a 12 months follow-up was available in 14 patients. The target coordinates were determined by ventriculography under stereotactic conditions, followed by electrophysiology and intraoperative stimulation. After surgery, continuous monopolar stimulation was applied bilaterally in 17 patients at 2.9+/-0.4 V through 1 (n = 31) or 2 contacts (n = 3). One patient had bilateral bipolar stimulation. The mean frequency of stimulation was 140+/-16 Hz and pulse width 68+/-13 micros. Off medication, the UPDRS part III score (max = 108) was reduced by 55 % during on stimulation (score before surgery: 44.9+/-13.4 vs at 6 months: 20.2+/-10; p < 0.001). In the on medication state, no difference was noted between the preoperative and the postoperative off stimulation conditions (scores were respectively: 17.9+/-9.2 and 23+/-12.6). The severity of motor fluctuations and dyskinesias assessed by UPDRS IV was reduced by 76 % at 6 months (scores were respectively: 10.3+/-3 and 2.5+/-3; p < 0.001). Off medication, the UPDRS II or ADL score was reduced by 52.8 % during on stimulation (26.9+/-6.5 preop versus 12.7+/-7 at 6 months). The daily dose of antiparkinsonian treatment was diminished by 65.5 % (levodopa equivalent dose -- mg/D -- was 1045 +/- 435 before surgery and 360 +/- 377 at 6 months; p < 0.01). These results remained stable at 12 months for the 14 patients studied. Side effects comprised lower limb phlebitis (n = 2), pulmonary embolism (n = 1), depression (n = 6), dysarthria and freezing (n = 1), sialorrhea and drooling (n = 1), postural imbalance (n = 1), transient paresthesias and dyskinesias. This study confirms the great value of subthalamic nucleus stimulation in the treatment of intractable PD. Some adverse events such as depression may be taken into account in the inclusion criteria and also in the post-operative outcome.