Miguel Tábuas-Pereira

Association between butyrylcholinesterase and cerebrospinal fluid biomarkers in Alzheimer’s disease patients

The deficit of cholinergic activity is one of the main findings in Alzheimers disease (AD), and is related to the synthesis of acetylcholine, and the hydrolysing enzymes, acetylcholinesterase and butyrylcholinesterase (BuChE). Together with the Apolipoprotein E-ε4 allele (ApoE-ε4), the BuChE-K variant has been proposed to increase AD risk in certain populations. In addition, this polymorphism has been associated with a lower capacity to attenuate β-amyloid aggregation. In the present study we explored the interaction of the BuChE-K variant with its activity in CSF, conventional AD biomarkers and ApoE genotype. 217 AD patients and 200 age-matched controls were genotyped for the ApoE and the BuChE-K variant. BuChE activity in CSF, as well as the levels of the CSF-AD biomarkers amyloid-beta 42 (Aβ42), total and hyperphosphorylated tau (t-tau and p-tau) were determined in 88 of these patients. The results showed no significant differences in the BuChE-K variant distribution between patients and controls. No influence of the BuChE-K variant was seen neither in CSF BuChE activity, nor in the levels of Aβ42, t-tau and p-tau in AD patients. ApoE genotype also did not seem to influence CSF BuChE activity. Interestingly, in AD patients, an association between high CSF BuChE activity and increased levels of CSF Aβ42 was shown, particularly in ApoE-ε4 allele carriers. In our population, the BuChE-K variant does not seem to confer risk for AD or to influence the activity of the enzyme in CSF. However, we demonstrated an association between BuChE activity, ApoE-ε4 genotype and CSF Aβ42 levels, highlighting the importance of assessing BuChE activity as a possible modulator of Aβ load in the brain.

Biparietal variant of Alzheimer's disease: a rare presentation of a common disease

Alzheimers disease (AD) is a clinically heterogeneous disease that may have atypical presentations with focal cortical syndromes and relatively preserved episodic memory. The posterior variant of AD has two subtypes: occipitotemporal, presenting with visuoperceptive impairment, and biparietal, presenting with visuospatial dysfunction and apraxia. We report a case of a 51-year-old woman with progressive limb apraxia and choreiform movements. Her neuropsychological evaluation was compatible with dementia, and revealed ideomotor and ideational limb apraxia, severe visuoconstructive ability impairment, dyscalculia and posterior aphasia. Workup excluded metabolic, infectious, inflammatory or neoplastic causes, and hereditary conditions as Huntingtons disease and familial AD. Cerebrospinal fluid biomarkers revealed β-amyloid reduction and τ protein increase. Brain imaging showed marked biparietal atrophy and hypoperfusion, and widespread cortical β-amyloid deposition. Biparietal variant of AD was diagnosed and acetylcholinesterase inhibitor treatment induced clinical stabilisation. AD may present with atypical features and a high clinical suspicion is necessary for an early diagnosis.

Addition of the Aβ42/40 ratio to the cerebrospinal fluid biomarker profile increases the predictive value for underlying Alzheimer’s disease dementia in mild cognitive impairment

BackgroundCerebrospinal fluid (CSF) biomarkers have been used to increase the evidence of underlying Alzheimer’s disease (AD) pathology in mild cognitive impairment (MCI). However, CSF biomarker-based classification often results in conflicting profiles with controversial prognostic value. Normalization of the CSF Aβ42 concentration to the level of total amyloid beta (Aβ), using the Aβ42/40 ratio, has been shown to improve the distinction between AD and non-AD dementia. Therefore, we evaluated whether the Aβ42/40 ratio would improve MCI categorization and more accurately predict progression to AD.MethodsOur baseline population consisted of 197 MCI patients, of which 144 had a follow-up ≥ 2 years, and comprised the longitudinal study group. To establish our own CSF Aβ42/40 ratio reference value, a group of 168 AD-dementia patients and 66 neurological controls was also included. CSF biomarker-based classification was operationalized according to the framework of the National Institute of Aging–Alzheimer Association criteria for MCI.ResultsWhen using the core CSF biomarkers (Aβ42, total Tau and phosphorylated Tau), 30% of the patients fell into the high-AD-likelihood (HL) group (both amyloid and neurodegeneration markers positive), 30% into the low-AD-likelihood group (all biomarkers negative), 28% into the suspected non-Alzheimer pathophysiology (SNAP) group (only neurodegeneration markers positive) and 12% into the isolated amyloid pathology group (only amyloid-positive). Replacing Aβ42 by the Aβ42/40 ratio resulted in a significant increase in the percentage of patients with amyloidosis (42–59%) and in the proportion of interpretable biological profiles (61–75%), due to a reduction by half in the number of SNAP cases and an increase in the proportion of the HL subgroup. Survival analysis showed that risk of progression to AD was highest in the HL group, and increased when the Aβ42/40 ratio, instead of Aβ42, combined with total Tau and phosphorylated Tau was used for biomarker-based categorization.ConclusionsOur results confirm the usefulness of the CSF Aβ42/40 ratio in the interpretation of CSF biomarker profiles in MCI patients, by increasing the proportion of conclusive profiles and enhancing their predictive value for underlying AD.

Alzheimer’s Disease Assessment Scale - Cognitive Subscale (ADAS-Cog): Normative Data for the Portuguese Population

INTRODUCTION The Alzheimers Disease Assessment Scale - Cognitive Subscale is a brief battery developed to assess cognitive functioning in Alzheimers disease that encompasses the core characteristics of cognitive decline (e.g. memory, language, praxis, constructive ability and orientation). The early detection, as well as the monitoring of cognitive decline along disease progression, is extremely important in clinical care and interventional research. The main goals of the present study were to analyze the psychometric properties of the Portuguese version of the Alzheimers Disease Assessment Scale - Cognitive Subscale, and to establish normative values for the Portuguese population. MATERIAL AND METHODS The Portuguese version of Alzheimers Disease Assessment Scale - Cognitive Subscale was administered to 223 cognitively healthy participants according to a standard assessment protocol consisting of the Mini-Mental State Examination, the Montreal Cognitive Assessment and the Adults and Older Adults Functional Assessment Inventory. Normal performance on the assessment protocol was the inclusion criteria for the study. RESULTS The Alzheimers Disease Assessment Scale - Cognitive Subscale revealed good psychometric properties when used in the Portuguese population. Age was the main predictor of the Alzheimers Disease Assessment Scale - Cognitive Subscale total score (R2 = 0.123), whereas the influence of education level was lower (R2 = 0.027). These two variables explained 14.4% of the variance on the Alzheimers Disease Assessment Scale - Cognitive Subscale scores and were used to stratify the normative values for the Portuguese population presented here. CONCLUSION On the total sample, the average total score in the Alzheimers Disease Assessment Scale - Cognitive Subscale was 6 points. The normative data were determined according to age and educational level as these were the sociodemographic variables that significantly contributed to the prediction of the Alzheimers Disease Assessment Scale - Cognitive Subscale total scores, explaining 14.4% of their variance. The normative data are of the utmost importance to ensure proper use of this battery in Portugal.

Prognosis of Early-Onset vs. Late-Onset Mild Cognitive Impairment: Comparison of Conversion Rates and Its Predictors

Background: Despite having the same histopathological characteristics, early-onset and late-onset Alzheimer’s disease (AD) patients show some distinct clinical and neuropsychological profiles. Early Onset Mild Cognitive Impairment (EOMCI) is a less characterized group. The aim of this study is to characterize MCI probably due to AD in terms of the clinical, genetic, Cerebrospinal fluid (CSF) biomarkers profile and conversion rate of EOMCI, compared to the late-onset form (LOMCI). Methods: 159 MCI patients were divided in two groups: 52 EOMCI (onset < 65 years) and 107 LOMCI (onset ≥ 65 years). We investigated differences in neuropsychological scores, clinical variables, ApoE genotype, CSF biomarkers (Aβ42, t-Tau and p-Tau) in both groups. Conversion was ascertained during follow-up. Results: EOMCI showed a longer duration of symptoms prior to the first evaluation (EOMCI = 4.57 vs. LOMCI = 3.31, p = 0.008) and scored higher on the subjective memory complaints scale (9.91 vs. 7.85, p = 0.008), but performed better in brief cognitive tests (27.81 vs. 26.51, p < 0.001 in Mini-Mental State Examination; 19.84 vs. 18.67, p = 0.005 in Montreal Cognitive Assessment) than LOMCI. ApoE genotype distribution and CSF biomarker profile were similar in both groups, as was the conversion risk. Lower Aβ42 (Hazard ratio (HR): 0.998, 95% Confidence Interval (CI) = [0.996–1.000], p = 0.042), higher t-Tau levels (HR: 1.003, 95%CI = [1.000–1.005], p = 0.039) and higher scores in the Alzheimer Disease Assessment Scale-Cognitive (HR: 1.186, 95%CI = [1.083–1.299], p = 0.002) increased the risk of conversion. Discussion: Despite differences in memory performance and memory complaints, EOMCI and LOMCI seem to represent indistinct biological groups that do not have a higher risk of conversion to AD or differ in risk factors for conversion.

Prosopagnosia as the Presenting Symptom of Whipple Disease.

Whipple disease is a rare, chronic multisystem infectious disease. The central nervous system (CNS) is secondarily involved in 43% of patients; 5% of patients have isolated or primary CNS involvement. The most frequent CNS symptoms are cognitive changes. Prosopagnosia is an inability to recognize familiar faces, in a person who does not have vision impairments or cognitive alterations. This relatively rare condition is usually related to vascular, traumatic, degenerative, or infectious lesions. We report a 54-year-old woman who presented subacutely with fever, headache, and seizures that led to a diagnosis of infectious meningoencephalitis. She improved temporarily on broad-spectrum antibiotics, but then developed a chronically evolving cognitive impairment with associative prosopagnosia as the major complaint. She had a history of sporadic abdominal pain and mild sacroiliac arthralgia. After a negative duodenal biopsy, we confirmed primary CNS Whipple disease by polymerase chain reaction and brain biopsy. We treated the patient with ceftriaxone for 15 days and then co-trimoxazole for 2 years. At 8-year follow-up, she had no further impairments, but continuing prosopagnosia. To our knowledge, this is the first description of isolated prosopagnosia in a patient with primary CNS Whipple disease. Because CNS Whipple disease can lead to serious, irreversible lesions if not promptly treated, clinicians must suspect the diagnosis, treat with long-term antibiotics, and follow patients carefully to prevent recurrence.

Validity and Clinical Utility of Different Clock Drawing Test Scoring Systems in Multiple Forms of Dementia

The Clock Drawing Test (CDT) has a known potential for the detection of cognitive impairment in populations with dementia, especially Alzheimer disease (AD). Our aim was to compare the clinical utility of 3 CDT scoring systems (Rouleau, Cahn, and Babins) in several pathologies with cognitive compromise from a tertiary center memory clinic. We selected patients with a clinical diagnosis of mild stage AD, behavioral variant frontotemporal dementia (FTD), vascular dementia (VaD), dementia with Lewy bodies (DLB), and Parkinson disease with dementia (PDD). The results showed significant differences between the several diagnoses with the following pattern of results: AD, DLB < FTD, VaD, PDD. Qualitative analysis of clock drawing errors confirmed the stimulus-bound response as a hallmark of AD, while conceptual deficit was significantly more prevalent in patients with AD and DLB. Our results supported the CDT potential as a cognitive screening measure for mild dementia, particularly sensitive to AD and DLB, especially when we used the Cahn scoring system and its analysis of qualitative errors.

Intracranial Internal Carotid Artery Wall Calcification in Ischemic Strokes Treated with Thrombolysis

Background: Calcifications are an important element of atherosclerotic plaques and have been used as a marker of atherosclerosis and clinical outcome predictor in different vascular territories. CT-scan, performed in the acute ischemic stroke setting, can reliably detect intracranial arterial calcifications. Objectives: To investigate the association between intracranial internal carotid artery calcification and functional outcome, symptomatic intracerebral hemorrhage (sICH), recanalization, and death. Methods: We included 396 consecutive ischemic stroke patients submitted to recombinant tissue plasminogen activator treatment between January 2011 and September 2014. Admission CT-scans were reviewed to calculate the Total Carotid Syphon Calcification score. Patients were followed for up to at least 6 months post-stroke or until death. Outcome measures included evaluation of recanalization on the first 24 h (transcranial color coded Doppler or angio-CT), sICH, and assessment of functional outcome at 3 months after stroke (using modified Rankin scale). Results: Carotid artery wall calcification did not predict sICH, recanalization or any good outcome. However, it was a statistically significant predictor of death (OR 1.102, 95% CI [1.004–1.211], p = 0.042). Discussion: Intracranial carotid artery calcification does not increase the risk of thrombolysis-induced sICH. Patients with higher grade of carotid artery wall calcification may have a higher mortality rate.

The Head Turning Sign in Dementia and Mild Cognitive Impairment: Its Relationship to Cognition, Behavior, and Cerebrospinal Fluid Biomarkers

Background/Aims: The head turning sign (HTS) is frequently noticed in clinical practice, but few studies have investigated its etiological and neuropsychological correlates. Methods: The presence and frequency of the HTS was operationalized and prospectively evaluated in patients with Alzheimer’s disease (AD), amnestic mild cognitive impairment (MCI), and behavioral-variant frontotemporal dementia (bvFTD). Cerebrospinal fluid (CSF) samples for AD biomarkers were collected. Mini-Mental State Examination, Montreal Cognitive Assessment, Geriatric Depression Scale (GDS), and insight scale scores were ascertained. Results: A total of 84 patients were included. The HTS was more prevalent in AD than in MCI or bvFTD. It correlated negatively with cognitive measures and depression. It also had a positive correlation with CSF total tau and hyperphosphorylated tau proteins. Total tau protein and GDS score were the only variables independently associated with the HTS. Conclusions: The presence of the HTS in a cognitively impaired individual suggests a diagnosis of AD. A higher HTS frequency correlates with higher CSF total tau levels, a smaller GDS score, and worse cognitive measures. In the MCI subgroup, the HTS may suggest a higher risk of progression.

Clinical Reasoning: A 55-year-old man with rapidly progressive dementia and parkinsonism

A 55-year-old right-handed man presented with a history of rapidly progressive apathy and behavior changes, speech loss, bladder and bowel incontinence, and gait loss in the previous month. He had been diagnosed with depression 7 months before and tried to commit suicide with carbon monoxide poisoning 2 months before, needing treatment in a hyperbaric chamber, with a good recovery. He had no history of other comorbidities and an unremarkable family history. At the first neurologic evaluation at our department, he presented with marked apathy and mutism, pseudobulbar affect, marked frontal release signs, generalized rigidity with hypomimia, global hyperreflexia with a left extensor plantar reflex, infrequent generalized myoclonus, and gait apraxia. Basic laboratory tests including electrolytes, complete blood count, carboxyhemoglobin, and liver function tests and CT scan had normal results. He had been medicated with lorazepam and mirtazapine but abandoned medication 2 weeks after the suicide attempt. He denied drug use or substantial alcohol consumption.