Electroencephalographic functional connectivity is altered in persons with Down syndrome and Alzheimer's disease.

BACKGROUND: Persons with Down syndrome (DS) are at increased risk of developing Alzheimer's dementia (DS-AD). Due to heterogeneity in the functioning in persons with DS, it is difficult to use cognitive testing to assess whether a person with DS has developed dementia due to AD. Electroencephalography (EEG) functional connectivity has shown promising results as a diagnostic tool for AD in persons without DS. In the current exploratory study, we investigated whether EEG functional connectivity could be used as a diagnostic marker of AD in persons with DS and the association with symptoms. METHODS: Electroencephalography from 12 persons with DS and 16 persons with DS-AD were analysed, and both coherence and weighted phase lag index were calculated. In addition, we calculated the average coherence for fronto-parietal and temporo-parietal connections. Lastly, we investigated the correlation between the informant-based Dementia Screening Questionnaire in Intellectual Disability (DSQIID) and total alpha coherence. RESULTS: Decreased alpha and increased delta coherence and weighted phase lag index were observed in DS-AD as compared with DS. The decrease in alpha coherence was more marked in the fronto-parietal connections as compared with the temporo-parietal connections. No significant correlation was found between DSQIID and total alpha coherence (P value = 0.095, rho = -0.335). CONCLUSION: The decreased alpha coherence and weighted phase lag index have previously been found in AD. The increased delta coherence and weighted phase lag index may indicate a different initial neurophysiological presentation as compared with patients with AD or may be a sign of more advanced disease. Larger studies are needed to confirm the current findings.

Associations between electroencephalography power and Alzheimer's disease in persons with Down syndrome.

BACKGROUND: It is complicated to diagnose dementia in persons with Down syndrome (DS). Older studies have, however, demonstrated low-frequency activity in electroencephalography (EEG) in persons with concurrent DS and Alzheimer's disease (DS-AD). The aim of this study was to examine whether it was possible to identify AD-associated changes (increased high-frequency power and decreased low-frequency power) in persons with DS-AD compared with DS. METHODS: We included 21 persons with DS-AD and 16 with DS without cognitive deterioration assessed by the informant-based Dementia Screening Questionnaire in Intellectual Disability. EEG was recorded for all participants. Absolute power for each electrode and global power were calculated for all frequency bands for both eyes open and eyes closed. RESULTS: For global power in the eyes closed condition, we found an increased global slow-frequency activity and a decreased global high-frequency activity in DS-AD compared with DS. In addition, we found a significant difference in the global alpha/delta ratio with the largest difference found for global alpha power in DS-AD compared with DS. CONCLUSIONS: In the current study, we found that changes known to be associated with AD could also be identified when comparing DS-AD with DS using quantitative EEG. In general, these findings suggest that EEG might be a useful tool in diagnosing AD in persons with DS, but larger studies are needed.

Subjective cognitive complaints included in diagnostic evaluation of dementia helps accurate diagnosis in a mixed memory clinic cohort.

OBJECTIVE: Our objective was to examine the quantity and profile of subjective cognitive complaints in young patients as compared with elderly patients referred to a memory clinic. METHODS: Patients were consecutively recruited from the Copenhagen University Hospital Memory Clinic at Rigshospitalet. In total, 307 patients and 149 age-matched healthy controls were included. Patients were classified in 4 diagnostic groups: dementia, mild cognitive impairment, affective disorders and no cognitive impairment. Subjective memory was assessed with subjective memory complaints (SMC) scale. Global cognitive functions were assessed with the Mini-mental state examination (MMSE) and Addenbrooke's cognitive examination (ACE), and symptoms of depression were rated with Major Depression Inventory (MDI). All interviews and the diagnostic conclusion were blinded to the SMC score. RESULTS: We found that young patients with dementia have a significantly higher level and a different profile of subjective cognitive complaints as compared with elderly patients with dementia. Furthermore, young patients, diagnosed with an affective disorder, had the highest level of subjective cognitive complaints of all patients in a memory clinic. The age of the patients and MDI score (but not MMSE or ACE) had significant impact on the level of subjective cognitive complaints. CONCLUSIONS: We have established that young patients with dementia have a different profile of subjective cognitive complaints than elderly patients, and further studies are needed to clarify possible relation to specific subtypes of dementia. Altogether, a systematic interview on subjective cognitive complaints may contribute to the diagnostic evaluation of patients referred to a memory clinic.

Overdiagnosis of dementia in young patients - a nationwide register-based study.

BACKGROUND: Little is known about the quality of the diagnostic evaluation and the validity of dementia diagnoses in young patients established in routine clinical practice. The aim of this study was to investigate the validity of the diagnosis of dementia registered in the Danish nationwide hospital registers in young patients. METHODS: Two hundred patients were randomly selected from 891 patients <65 years registered with a dementia diagnosis for the first time in 2008. The patients' medical records were reviewed to evaluate if they fulfilled ICD-10 and/or DSM-IV criteria for dementia and current clinical criteria for specific dementia subtypes. RESULTS: A registered diagnosis was found to be correct in only 59%. A misdiagnosis of dementia occurred primarily in patients with depression or alcohol abuse. CONCLUSION: Our results suggest that dementia is overregistered and overdiagnosed in young patients. This may be due to a different symptom profile of dementia in young patients, lack of knowledge among clinical physicians and the wide range of conditions which may be misinterpreted as dementia.