Studies of rodent models of Alzheimer’s disease (AD) and of human tissues suggest that the retinal changes that occur in AD, including the accumulation of amyloid beta (Aβ), may serve as surrogate markers of brain Aβ levels. As Aβ has a wavelength-dependent effect on light scatter, we investigate the potential for in vivo retinal hyperspectral imaging to serve as a biomarker of brain Aβ. Significant differences in the retinal reflectance spectra are found between individuals with high Aβ burden on brain PET imaging and mild cognitive impairment (n = 15), and age-matched PET-negative controls (n = 20). Retinal imaging scores are correlated with brain Aβ loads. The findings are validated in an independent cohort, using a second hyperspectral camera. A similar spectral difference is found between control and 5xFAD transgenic mice that accumulate Aβ in the brain and retina. These findings indicate that retinal hyperspectral imaging may predict brain Aβ load.

Objectives: To provide a clinical update for general psychiatrists on the assessment and diagnosis of Alzheimer’s disease (AD), highlighting current issues regarding epidemiology, risk factors and pathophysiology from recent relevant research findings. Conclusions: Psychiatrists can apply their skills and training in the diagnosis of AD, which is based upon a comprehensive assessment comprising history, investigations, and cognitive and functional assessment, guided by accepted diagnostic criteria.

Young-onset dementia comprises a heterogeneous range of dementias, with onset at less than 65 years of age. These include primary dementias such as Alzheimer disease, frontotemporal and vascular dementias; genetic/familial dementias; metabolic disorders; and secondary dementias such as those that result from alcohol use disorder, traumatic brain injury, and infections. The presentation of young-onset dementia is varied and may include cognitive, psychiatric and neurological symptoms. Diagnostic delay is common, with a frequent diagnostic conundrum being, "Is this young-onset dementia or is this psychiatric?". For assessment and accurate diagnosis, a thorough screen is recommended, such as collateral history and investigations such as neuroimaging, lumbar puncture, neuropsychology, and genetic testing. The management of young-onset dementia needs to be age-appropriate and multidisciplinary, with timely access to services and consideration of the family (including children).

Objectives:While early diagnosis of younger-onset dementia (YOD) is crucial in terms of accessing appropriate services and future planning, diagnostic delays are common. This study aims to identify predictors of delay to diagnosis in a large sample of people with YOD and to investigate the impact of a specialist YOD service on this time to diagnosis.Design:A retrospective cross-sectional study.Setting:The inpatient unit of a tertiary neuropsychiatry service in metropolitan Victoria, Australia.Participants:People diagnosed with a YOD.Measurements and methods:We investigated the following predictors using general linear modeling: demographics including sex and location, age at onset, dementia type, cognition, psychiatric diagnosis, and number of services consulted with prior to diagnosis.Results:A total of 242 inpatients were included. The mean time to diagnosis was 3.4 years. Significant predictors of delay included younger age at onset, dementia type other than Alzheimer’s disease (AD) and behavioral-variant frontotemporal dementia (bvFTD), and increased number of services consulted. These predictors individually led to an increased diagnostic delay of approximately 19 days, 5 months, and 6 months, respectively. A specialized YOD service reduced time to diagnosis by 12 months.Conclusion:We found that younger age at onset, having a dementia which was not the most commonly occurring AD or bvFTD, and increasing number of services were significant predictors of diagnostic delay. A novel result was that a specialist YOD service may decrease diagnostic delay, highlighting the importance of such as service in reducing time to diagnosis as well as providing post-diagnostic support.

Objective: Neurofilament light has shown promise as a biomarker for diagnosis, staging and prognosis in a wide range of neurological and neurodegenerative disorders. This study explored the utility of cerebrospinal fluid neurofilament light in distinguishing primary psychiatric disorders from neurodegenerative and neurological disorders, a common diagnostic dilemma for psychiatrists and neurologists. Methods: This cross-sectional retrospective pilot study assessed cerebrospinal fluid neurofilament light on patients referred to a tertiary neuropsychiatry service from 2009 to 2017 for diagnostic assessment of neuropsychiatric and neurocognitive symptoms, where a neurodegenerative disorder was a differential diagnosis, who received lumbar punctures as part of a comprehensive workup. The most recent gold-standard clinical consensus diagnosis was categorised into psychiatric disorder or neurodegenerative or neurological disorder. Data from healthy controls were available for comparison. Data extraction and diagnostic categorisation was blinded to neurofilament light results. Results: A total of 129 participants were included: 77 neurodegenerative or neurological disorder (mean age 57 years, including Alzheimer’s dementia, frontotemporal dementia), 31 psychiatric disorder (mean age 51 years, including schizophrenia, major depressive disorder) and 21 healthy controls (mean age 66 years). Neurofilament light was significantly higher in neurodegenerative or neurological disorder (M = 3560 pg/mL, 95% confidence intervals = [2918, 4601]) compared to psychiatric disorder (M = 949 pg/mL, 95% confidence intervals = [830, 1108]) and controls (M = 1036 pg/mL, 95% confidence intervals = [908, 1165]). Neurofilament light distinguished neurodegenerative or neurological disorder from psychiatric disorder with an area under the curve of 0.94 (95% confidence intervals = [0.89, 0.98]); a cut-off of 1332 pg/mL was associated with 87% sensitivity and 90% specificity. Conclusion: Cerebrospinal fluid neurofilament light shows promise as a diagnostic test to assist with the often challenging diagnostic dilemma of distinguishing psychiatric disorders from neurodegenerative and neurological disorders. Further studies are warranted to replicate and expand on these findings, including on plasma neurofilament light.