A review on shared clinical and molecular mechanisms between bipolar disorder and frontotemporal dementia

Data-driven analysis of regional brain metabolism in behavioral frontotemporal dementia and late-onset primary psychiatric diseases with frontal lobe syndrome: A PET/MRI study

Late-onset primary psychiatric disease (PPD) and behavioral frontotemporal dementia (bvFTD) present with a similar frontal lobe syndrome. We compare brain glucose metabolism in bvFTD and late-onset PPD and investigate the metabolic correlates of cognitive and behavioral disturbances through FDG-PET/MRI. We studied 37 bvFTD and 20 late-onset PPD with a mean clinical follow-up of three years. At baseline evaluation, metabolism of the dorsolateral, ventrolateral, orbitofrontal regions and caudate could classify the patients with a diagnostic accuracy of 91% (95% CI: 0.81-0.98%). 45% of PPD showed low-grade hypometabolism in the anterior cingulate and/or parietal regions. Frontal lobe metabolism was normal in 32% of genetic bvFTD and bvFTD with motor neuron signs. Hypometabolism of the frontal and caudate regions could help in distinguishing bvFTD from PPD, except in cases with motor neuron signs and/or genetic bvFTD for which brain metabolism may be less informative.

TDP-43 deficiency in suprachiasmatic nucleus perturbs rhythmicity of neuroactivity in prefrontal cortex

Individuals within the amyotrophic lateral sclerosis and frontotemporal dementia disease spectrum (ALS/FTD) often experience disruptive mental behaviors and sleep-wake disturbances. The hallmark of ALS/FTD is the pathological involvement of TAR DNA-binding protein 43 (TDP-43). Understanding the role of TDP-43 in the circadian clock holds promise for addressing these behavioral abnormalities. In this study, we unveil TDP-43 as a pivotal regulator of the circadian clock. TDP-43 knockdown induces intracellular arrhythmicity, disrupts transcriptional activation regulation, and diminishes clock genes expression. Moreover, our experiments in adult mouse reveal that TDP-43 knockdown, specifically within the suprachiasmatic nucleus (SCN), induces locomotor arrhythmia, arrhythmic c-Fos expression, and depression-like behavior. This observation offers valuable insights into the substantial impact of TDP-43 on the behavioral aberrations associated with ALS/FTD. In summary, our study illuminates the significance of TDP-43 in circadian regulation, shedding light on the circadian regulatory mechanisms that may elucidate the pathological underpinnings of ALS/FTD.

Endo-Lysosomal and Autophagy Pathway and Ubiquitin-Proteasome System in Mood Disorders: A Review Article

Mood disorders are disabling conditions that cause significant functional impairment. Due to the clinical heterogeneity and complex nature of these disorders, diagnostic and treatment strategies face challenges. The etiology of mood disorders is multifactorial, involving genetic and environmental aspects that are associated with specific biological pathways including inflammation, oxidative stress, and neuroprotection. Alterations in these pathways may reduce the cell's ability to recover from stress conditions occurring during mood episodes. The endo-lysosomal and autophagy pathway (ELAP) and the ubiquitin-proteasome system (UPS) play critical roles in protein homeostasis, impacting neuroplasticity and neurodevelopment. Thus, emerging evidence has suggested a role for these pathways in mental disorders. In the case of neurodegenerative diseases (NDDs), a deeper understanding in the role of ELAP and UPS has been critical to discover new treatment targets. Since it is suggested that NDDs and mood disorders share clinical symptomatology and risk factors, it has been hypothesized that there might be common underlying molecular pathways. Here, we review the importance of the ELAP and UPS for the central nervous system and for mood disorders. Finally, we discuss potential translational strategies for the diagnosis and treatment of major depressive disorder and bipolar disorder associated with these pathways.

Bipolar spectrum disorders in neurologic disorders

Psychiatric symptoms frequently predate or complicate neurological disorders, such as neurodegenerative diseases. Symptoms of bipolar spectrum disorders (BSD), like mood, behavioral, and psychotic alterations, are known to occur - individually or as a syndromic cluster - in Parkinson's disease and in the behavioral variant of frontotemporal dementia (FTD). Nonetheless, due to shared pathophysiological mechanisms, or genetic predisposition, several other neurological disorders show significant, yet neglected, clinical and biological overlaps with BSD like neuroinflammation, ion channel dysfunctions, neurotransmission imbalance, or neurodegeneration. BSD pathophysiology is still largely unclear, but large-scale network dysfunctions are known to participate in the onset of mood disorders and psychotic symptoms. Thus, functional alterations can unleash BSD symptoms years before the evidence of an organic disease of the central nervous system. The aim of our narrative review was to illustrate the numerous intersections between BSD and neurological disorders from a clinical-biological point of view and the underlying predisposing factors, to guide future diagnostic and therapeutical research in the field.

Increased levels of TAR DNA-binding protein 43 in the hippocampus of subjects with bipolar disorder: a postmortem study

Bipolar disorder shares symptoms and pathological pathways with other neurodegenerative diseases, including frontotemporal dementia (FTD). Since TAR DNA-binding protein 43 (TDP-43) is a neuropathological marker of frontotemporal dementia and it is involved in synaptic transmission, we explored the role of TDP-43 as a molecular feature of bipolar disorder (BD). Homogenates were acquired from frozen hippocampus of postmortem brains of bipolar disorder subjects. TDP-43 levels were quantified using an ELISA-sandwich method and compared between the postmortem brains of bipolar disorder subjects and age-matched control group. We found higher levels of TDP-43 protein in the hippocampus of BD (n = 15) subjects, when compared to controls (n = 15). We did not find associations of TDP-43 with age at death, postmortem interval, or age of disease onset. Our results suggest that protein TDP-43 may be potentially implicated in behavioral abnormalities seen in BD. Further investigation is needed to validate these findings and to examine the role of this protein during the disease course and mood states.

Bipolar disorder and frontotemporal dementia: A systematic review

OBJECTIVES

To detail the biological, clinical and neurocognitive characteristics differentiating bipolar disorder (BD) from frontotemporal dementia (FTD) and to investigate whether BD is a risk factor for FTD.

METHODS

A total of 16 studies were included in this systematic review. Five studies described biological and/or neurocognitive characteristics between patients with BD and FTD, and 11 studies investigated whether BD was a risk factor for FTD.

RESULTS

Individuals with FTD presented higher levels of serum neurofilament light chain, greater grey matter reduction in frontal, parietal and temporal lobes, and increased slow wave oscillations in channels F3, F4, T3, T5, T4 and T6 within an electroencephalogram (EEG), relative to individuals with BD. Patients with FTD presented greater deficits in executive function and theory of mind compared to patients with BD in a euthymic state, and more deficits in verbal fluency compared to patients with BD in a current mood episode. Patients with BD in a current mood episode showed greater impairment in attention, working memory, verbal memory and executive function relative to individuals with FTD. In addition, retrospective studies showed that 10.2%-11.6% of patients with behavioural variant FTD (bvFTD) had a preceding history of BD.

CONCLUSION

Biological and neurocognitive characteristics help to distinguish between BD and FTD, and it may help to reach a more precise diagnosis. In addition, individuals with BD are at higher risk of developing FTD. More studies are needed to identify the predictors of the conversion between BD to FTD.

Exploring Signatures of Neurodegeneration in Early-Onset Older-Age Bipolar Disorder and Behavioral Variant Frontotemporal Dementia

Introduction: Older-age bipolar disorder (OABD) may involve neurocognitive decline and behavioral disturbances that could share features with the behavioral variant of frontotemporal dementia (bvFTD), making the differential diagnosis difficult in cases of suspected dementia.

Objective: To compare the neuropsychological profile, brain morphometry, and structural connectivity patterns between patients diagnosed with bvFTD, patients classified as OABD with an early onset of the disease (EO-OABD), and healthy controls (HC).

Methods: bvFTD patients (n = 25, age: 66 ± 7, female: 64%, disease duration: 6 ± 4 years), EO-OABD patients (n = 17, age: 65 ± 9, female: 71%, disease duration: 38 ± 8 years), and HC (n = 28, age: 62 ± 7, female: 64%) were evaluated through neuropsychological tests concerning attention, memory, executive function, praxis, and language. Brain morphometry was analyzed through surface-based morphometry (SBM), while structural brain connectivity was assessed through diffusion tensor imaging (DTI).

Results: Both bvFTD and EO-OABD patients showed lower performance in neuropsychological tests of attention, verbal fluency, working memory, verbal memory, and praxis than HC. Comparisons between EO-OABD and bvFTD showed differences limited to cognitive flexibility delayed recall and intrusion errors in the memory test. SBM analysis demonstrated that several frontal, temporal, and parietal regions were altered in both bvFTD and EO-OABD compared to HC. In contrast, comparisons between bvFTD and EO-OABD evidenced differences exclusively in the right temporal pole and the left entorhinal cortex. DTI analysis showed alterations in association and projection fibers in both EO-OABD and bvFTD patients compared to HC. Commissural fibers were found to be particularly affected in EO-OABD. The middle cerebellar peduncle and the pontine crossing tract were exclusively altered in bvFTD. There were no significant differences in DTI analysis between EO-OABD and bvFTD.

Discussion: EO-OABD and bvFTD may share an overlap in cognitive, brain morphometry, and structural connectivity profiles that could reflect common underlying mechanisms, even though the etiology of each disease can be different and multifactorial.

Neuropsychiatric Aspects in a Patient Diagnosed with Frontotemporal Dementia: Clinical Case of Low Incidence and Prevalence Disease in Colombia

Frontotemporal dementia (FTD) is a neuropsychiatric pathology characterized by dysfunctions in the frontal lobe of the brain, especially in planning, execution, and inhibition tasks, with an inability to make decisions and handle different sequences, also affecting the temporal lobe. The patient presents alterations to store, consolidate, and recall information. These neurocognitive deficits are accompanied by neurobehavioral disorders such as depression, anxiety, and apathy that contribute to the worsening of the quality of life, with a high impact on the individual, social, and family level. To identify the neurobehavioral disorders and neurocognitive deterioration that present a patient diagnosed with FTD: clinical case of low incidence and prevalence disease in Colombia. A 40-year-old man, with progressive deterioration of his immediate verbal memory, low verbal fluency, aberrant motor behavior, sexual impulsivity, alterations in his executive functions, especially in planning tasks, decision-making, and inhibition was found to have a lesser degree of affectation in his visuospatial functioning and visuoconstructive abilities. It was found that the patient presents a severe dysexecutive syndrome associated with a clinical picture of FTD, correlated with an inability to process and recall information, accompanied by disorders such as depression, anxiety, and apathy. It is necessary to generate a functional neurorehabilitation plan that aims to improve the quality of life in these patients. In the same way, it is necessary to create new lines of research and intervention that have the purpose to create a greater field of heuristics or new questions in this type of neurodegenerative pathologies.

Negative Air Ions in Neuropsychiatric Disorders

BACKGROUND

Air ions (AIs) are clusters of ionized particles present in the atmosphere, carrying an electrical charge of negative or positive polarity. Past speculations suggested that exposure to positive air ions may be harmful, while exposure to negative air ions (NAIs) may be associated with beneficial health effects. Increasing attention has been directed towards investigating the potential effect of NAIs on human brain activities since initial observations of their beneficial effects on some cognitive processes and mood.

AIMS

Given the paucity and scattered literature, our paper aims to review the available studies on potential positive effects of NAIs exposure on cognitive performances and depression.

DISCUSSION

The review of the literature seems to confirm the effects of NAIs on several brain functions. Indeed, a significant association between NAIs exposure and both well-being and high cognitive performances has been described. Furthermore, exposure to high concentrations of NAIs could be related to the improvement of depressive symptoms.

CONCLUSION

A growing evidence of data, although not yet conclusive, would suggest that NAIs might improve cognitive processes. These findings require specific and urgent controlled trials adopting systems based on AIs release to possibly prevent and treat cognitive dysfunctions present in a broad range of neuropsychiatric conditions.

Cognitive Trajectories in Comorbid Dementia With Schizophrenia or Bipolar Disorder: The South London and Maudsley NHS Foundation Trust Biomedical Research Centre (SLaM BRC) Case Register

OBJECTIVES

We aimed to compare trajectories of cognitive performance in individuals diagnosed with dementia with and without severe mental illness (SMI).

DESIGN

Retrospective cohort study.

SETTING

We used data from a large longitudinal mental healthcare case register, the Clinical Record Interactive Search (CRIS), at the South London and Maudsley NHS Foundation Trust (SLaM) which provides mental health services to four south London boroughs.

PARTICIPANTS

Our sample (N = 4718) consisted of any individual who had a primary or secondary diagnosis of dementia from 2007 to 2018, was 50 years old or over at first diagnosis of dementia and had at least 3 recorded Mini-Mental State Examination (MMSE) scores.

MEASUREMENTS

Cognitive performance was measured using MMSE. Linear mixed models were fitted to explore whether MMSE trajectories differed between individuals with or without prior/current SMI diagnoses. Models were adjusted by socio-demographics, cardiovascular risk, smoking, and medication.

RESULTS AND CONCLUSIONS

Our results showed differences in the rate of change, where individuals with comorbid SMI had a faster decline when compared with those that have dementia without comorbid SMI. However, this association was partially attenuated when adjusted by socio-demographics, smoking and cardiovascular risk factors; and more substantially attenuated when medication was included in models. Additional analyses showed that this accelerated decline might be more evident in individuals with bipolar disorders. Future research to detangle the potential biological underlying mechanisms of these associations is needed.

Degenerative dementias: Alterations of emotions and mood disorders

Degenerative dementias such as Alzheimer's disease and frontotemporal dementia result in distinct alterations in emotional processing, emotional experiences, and mood. The neuropathology of these dementias extends to structures involved in emotional processing, including the basolateral limbic network (orbitofrontal cortex, anterior temporal lobe, amygdala, and thalamus), the insula, and ventromedial frontal lobe. Depression is the most common emotion and mood disorder affecting patients with Alzheimer's disease. The onset of depression can be a prodromal sign of this dementia. Anxiety can also be present early in the course of Alzheimer's disease and especially among patients with early-onset forms of the disease. In contrast, patients with behavioral variant frontotemporal dementia demonstrate hypoemotionality, deficits in the recognition of emotion, and decreased psychophysiological reactivity to emotional stimuli. They typically have a disproportionate impairment in emotional and cognitive empathy. One other unique feature of behavioral variant frontotemporal dementia is the frequent occurrence of bipolar disorder. The management strategies for these alterations of emotion and mood in degenerative dementias primarily involve the judicious use of the psychiatric armamentarium of medications.

Frontotemporal Dementia and Late-Onset Bipolar Disorder: The Many Directions of a Busy Road

It is a common pathway for patients with the behavioral variant of frontotemporal dementia (bvFTD) to be first misdiagnosed with a primary psychiatric disorder, a considerable proportion of them being diagnosed with bipolar disorder (BD). Conversely, not rarely patients presenting in late life with a first episode of mania or atypically severe depression are initially considered to have dementia before the diagnosis of late-onset BD is reached. Beyond some shared features that make these conditions particularly prone to confusion, especially in the elderly, the relationship between bvFTD and BD is far from simple. Patients with BD often have cognitive complaints as part of their psychiatric disorder but are at an increased risk of developing dementia, including FTD. Likewise, apathy and disinhibition, common features of depression and mania, respectively, are among the core features of the bvFTD syndrome, not to mention that depression may coexist with dementia. In this article, we take advantage of the current knowledge on the neurobiology of these two nosologic entities to review their historical and conceptual interplay, highlighting the clinical, genetic and neuroimaging features that may be shared by both disorders or unique to each of them.

Bipolar Disorder Among Patients Diagnosed With Frontotemporal Dementia

OBJECTIVE

Previous studies have documented manic and hypomanic symptoms in behavioral variant frontotemporal dementia (bvFTD), suggesting a relationship between bipolar disorder and bvFTD.

METHODS

The investigators conducted a literature review as well as a review of the psychiatric histories of 137 patients with bvFTD, and patients with a prior diagnosis of bipolar disorder were identified. The clinical characteristics of patients' bipolar disorder diagnosis, family history, features of bvFTD, and results from fluorodeoxyglucose positron emission tomography (FDG-PET), as well as autopsy findings, were evaluated.

RESULTS

Among the 137 patients, 14 (10.2%) had a psychiatric diagnosis of bipolar disorder, eight of whom met criteria for bipolar disorder (type I, N=6; type II, N=2) 6-12 years preceding onset of classic symptoms of progressive bvFTD. Seven of the eight patients with bipolar disorder had a family history of mood disorders, four had bitemporal predominant hypometabolism on FDG-PET, and two had a tauopathy involving temporal lobes on autopsy. Three additional patients with late-onset bipolar I disorder proved to have a nonprogressive disorder mimicking bvFTD. The remaining three patients with bvFTD had prior psychiatric symptoms that did not meet criteria for a diagnosis of bipolar disorder. The literature review and the findings for one patient further suggested a shared genetic mutation in some patients.

CONCLUSIONS

Manic or hypomanic episodes years before other symptoms of bvFTD may be a prodrome of this dementia, possibly indicating anterior temporal involvement in bvFTD. Other patients with late-onset bipolar disorder exhibit the nonprogressive frontotemporal dementia phenocopy syndrome. Finally, a few patients with bvFTD have a genetic predisposition for both disorders.

Crossing Borders Between Frontotemporal Dementia and Psychiatric Disorders: An Updated Overview

Frontotemporal dementia (FTD) includes a group of neurocognitive syndromes, clinically characterized by altered behaviors, impairment of language proficiency, and altered executive functioning. FTD is one of the most frequently observed forms of dementia in the elderly population and the most common in presenile age. As for other subtypes of dementia, FTD incidence is constantly on the rise due to the steadily increasing age of the population, and its recognition is now becoming a determinant for clinicians. FTD and psychiatric disorders can overlap in terms of clinical presentations by sharing a common genetic predisposition and neuropathological mechanism in some cases. Nonetheless, this association is often unclear and underestimated. Since its first reports, research into FTD has constantly grown, with the identification of recent findings related to its neuropathology, genetic, clinical, and therapeutic issues. Literature is thriving on this topic, with numerous research articles published in recent years. In the present review, we aimed to provide an updated description of the clinical manifestations that link and potentially confound the diagnosis of FTD and psychiatric disorders in order to improve their differential diagnosis and early detection. In particular, we systematically reviewed the literature, considering articles specifically focused on the behavioral variant FTD, published after 2015 on the PubMed database.

The path to biomarker-based diagnostic criteria for the spectrum of neurodegenerative diseases

Introduction: The postmortem examination still represents the reference standard for detecting the pathological nature of chronic neurodegenerative diseases (NDD). This approach displays intrinsic conceptual limitations since NDD represent a dynamic spectrum of partially overlapping phenotypes, shared pathomechanistic alterations that often give rise to mixed pathologies.Areas covered: We scrutinized the international clinical diagnostic criteria of NDD and the literature to provide a roadmap toward a biomarker-based classification of the NDD spectrum. A few pathophysiological biomarkers have been established for NDD. These are time-consuming, invasive, and not suitable for preclinical detection. Candidate screening biomarkers are gaining momentum. Blood neurofilament light-chain represents a robust first-line tool to detect neurodegeneration tout court and serum progranulin helps detect genetic frontotemporal dementia. Ultrasensitive assays and retinal scans may identify Aβ pathology early, in blood and the eye, respectively. Ultrasound also represents a minimally invasive option to investigate the substantia nigra. Protein misfolding amplification assays may accurately detect α-synuclein in biofluids.Expert opinion: Data-driven strategies using quantitative rather than categorical variables may be more reliable for quantification of contributions from pathophysiological mechanisms and their spatial-temporal evolution. A systems biology approach is suitable to untangle the dynamics triggering loss of proteostasis, driving neurodegeneration and clinical evolution.

Dementia associated with disorders of the basal ganglia

Dementia is now the leading cause of death in the United Kingdom, accounting for over 12% of all deaths and is the fifth most common cause of death worldwide. As treatments for heart disease and cancers improve and the population ages, the number of sufferers will only increase, with the chance of developing dementia doubling every 5 years after the age of 65. Finding an effective treatment is ever more critical to avert this pandemic health (and economic) crisis. To date, most dementia-related research has focused on the cortex and the hippocampus; however, with dementia becoming more fully recognized as aspects of diseases historically categorized as motor disorders (e.g., Parkinson's and Huntington's diseases), the role of the basal ganglia in dementia is coming to the fore. Conversely, it is highly likely that neuronal pathways in these structures traditionally considered as spared in Alzheimer's disease are also affected, particularly in later stages of the disease. In this review, we examine some of the limited evidence linking the basal ganglia to dementia.