The Behavioral Variant Frontotemporal Dementia Phenocopy Syndrome: A Review

Phenocopy behavioral variant frontotemporal dementia: A case study

Objective: Behavioral variant frontotemporal dementia (bvFTD) is a neurodegenerative condition characterized by progressive changes in behavior, cognition, and day-to-day functioning. Progression of the disease usually leads to death 3-5 years after diagnosis. However, there are reports of individuals who are initially diagnosed with bvFTD but fail to progress. These individuals are thought to have what is becoming known as phenocopy bvFTD (phFTD). Methods: This manuscript reviews a single case study of a 68-year-old male Veteran who was diagnosed with bvFTD in 2010, which has not progressed over time. Results: Review of serial neuropsychological evaluations was broadly normal with mild evidence of executive dysfunction with minimal reliable change in his performances from 2015, 2017, and 2022 evaluations. He also has not developed neuroimaging evidence of FTD. Conclusions: This case illustrates the importance of monitoring individuals over time and incorporating neuroimaging data into the diagnosis. We believe this Veteran's presentation is most consistent with what has been described as phFTD.

A systematic review of cognitive and behavioral tools to differentiate behavioral variant frontotemporal dementia from other conditions

The behavioral variant of frontotemporal dementia (bvFTD) is thought to be the commonest clinical presentation of frontotemporal lobar degeneration and is predominantly characterized by changes in behavior. In patients lacking unequivocal biomarker evidence of frontotemporal neurodegeneration, the clinical diagnosis of bvFTD is often unstable. In response, we conducted a systematic review and critical appraisal of cognitive and behavioral tools that have sought to differentiate bvFTD from other conditions. A systematic literature review of PubMed, Scopus, and Web of Science was conducted on December 31, 2023 for cognitive and behavioral tools that differentiated bvFTD from other cohorts. Ninety-six studies were included. The quality appraisal of almost all studies was low and introduced a high risk of bias. The few studies that were of high quality had a prospective study design and recruited patients suspected (but not yet confirmed) to have bvFTD. These studies reported that behavioral tools (e.g., the Frontal Behavioral Inventory) and social cognition tests (e.g., the Ekman's Faces Test) had good test performance in differentiating bvFTD from a broad range of psychiatric and neurological conditions. Importantly, the review highlighted the extreme paucity of studies that have evaluated methods where, in Bayesian terms, there is genuine clinical uncertainty regarding a diagnosis of bvFTD. Most studies used healthy controls of typical Alzheimer's disease as comparators-groups that often have negligible pretest probability of bvFTD. In response, we propose a study design checklist for studies seeking to develop diagnostic algorithms in bvFTD research.

The phenomenological experience of autobiographical memory in patients with behavioral-variant frontotemporal dementia

In this study, we offer a comprehensive assessment of the phenomenological experience of patients with behavioral-variant frontotemporal dementia (bvFTD) upon retrieval of autobiographical memory. We invited patients with bvFTD and control participants to retrieve autobiographical memories and rate, for each memory, its phenomenological characteristics. We also analyzed the retrieved memories regarding specificity (i.e., whether the memory described a general or a detailed event). Results demonstrated that, compared to control participants, patients with bvFTD attributed lower levels of reliving, back in time (feeling as if going back in time), remembering, realness, visual imagery, auditory imagery, language, emotion, rehearsal, importance, spatial recall and temporal recall to their memories. Lower autobiographical specificity was also observed in patients with bvFTD compared to control participants. Autobiographical specificity in patients with bvFTD was associated with verbal fluency and verbal episodic memory, but not with phenomenological experience. Although autobiographical memories of patients with bvFTD show low ratings of phenomenological experience, the patients may still enjoy some limited subjective experience during autobiographical retrieval.

A narrative review on mild behavioural impairment: an exploration into its scientific perspectives

In clinical practice, the admission of patients with late-onset psychological and behavioural symptoms is frequent, regardless of the presence or absence of cognitive decline. These symptoms commonly occur in the prodromal stage of dementia and can precede the onset of dementia. While the concept of Mild Cognitive Impairment (MCI) -which is defined as a level of cognitive impairment insufficient to impact daily functioning- is well established, the notion of Mild Behavioural Impairment (MBI) is not yet widely recognized. However, studies have demonstrated that the presence of MBI in both cognitively normal patients and individuals with MCI is associated with an increased risk of dementia progression. Thus, MBI may serve as a neurobehavioral indicator of pre-dementia risk states. This narrative review aims to discuss the evolution of the term, the relevant clinical aspects, and potential biomarkers that may contribute to the clinical definition of MBI. The objective is to assist clinicians in recognizing the diagnosis and differentiating it from psychiatric syndromes, as well as identifying possible etiologies of neurodegeneration.

A Five-Year Clinical Course of Potential Phenocopy Syndrome of Behavioral Variant Frontotemporal Dementia: A Case Report and Literature Review

Frontotemporal dementia is a neurocognitive disorder that affects language, behavior, or executive functioning. This disease includes a spectrum of presentations that includes multiple variants. The phenocopy syndrome of the behavioral variant of frontotemporal dementia mimics the behavioral variant of frontotemporal dementia. Patients with this condition show a decline in personality, social conduct, and cognitive ability but often display no signs of neurological imaging and exhibit slow progression. This case focuses on a now 70-year-old male who has shown signs of behavioral changes with a slowly progressive clinical course and minimal findings on positron emission tomography (PET) scan, but moderate changes seen on MRI. This report details a clinical presentation of an individual potentially with phenocopy syndrome of behavioral variant frontotemporal dementia and provides context to how symptoms can be managed to better help assist patients and their caregivers.

Cerebrospinal fluid neurofilament light chain differentiates behavioural variant frontotemporal dementia progressors from non-progressors

BACKGROUND

Distinguishing behavioural variant frontotemporal dementia (bvFTD) from non-neurodegenerative 'non-progressor' mimics of frontal lobe dysfunction, can be one of the most challenging clinical dilemmas. A biomarker of neuronal injury, neurofilament light chain (NfL), could reduce misdiagnosis and delay.

METHODS

Cerebrospinal fluid (CSF) NfL, amyloid beta 1-42 (AB42), total and phosphorylated tau (T-tau, P-tau) levels were examined in patients with an initial diagnosis of bvFTD. Based on follow-up information, patients were categorised as Progressors or Non-Progressors: further subtyped into Non-Progressor Revised (non-neurological/neurodegenerative final diagnosis), and Non-Progressor Static (static deficits, not fully explained by non-neurological/neurodegenerative causes).

RESULTS

Forty-three patients were included: 20 Progressors, 23 Non-Progressors (15 Non-Progressor Revised, 8 Non-Progressor Static), and 20 controls. NfL concentrations were lower in Non-Progressors (Non-Progressors Mean, M = 554 pg/mL, 95%CI:[461, 675], Non-Progressor Revised M = 459 pg/mL, 95%CI:[385, 539], and Non-Progressor Static M = 730 pg/mL, 95%CI:[516, 940]), compared to Progressors (M = 2397 pg/mL, 95%CI:[1607, 3332]). NfL distinguished Progressors from Non-Progressors with the highest accuracy (area under the curve 0.92, 90%/87% sensitivity/specificity, 86%/91% positive/negative predictive value, 88% accuracy). Non-Progressor Static tended to have higher T-tau and P-tau levels compared to Non-Progressor Revised Diagnoses.

CONCLUSION

This study demonstrated strong diagnostic utility of CSF NfL to distinguish bvFTD from non-progressor variants, at baseline, with high accuracy, in a real-world clinical setting. This has important clinical implications, to improve outcomes for patients and clinicians facing this challenging clinical dilemma, healthcare services, and clinical trials. Further research is required to investigate heterogeneity within the non-progressor group and potential diagnostic algorithms, and prospective studies are underway assessing plasma NfL.

Pupillometry as an index for cognitive processing in behavioral variant FrontoTemporal Dementia: a series of case studies

We investigated whether pupil size can variate with the intensity of cognitive processing in patients with behavioral-variant-Frontotemporal-Dementia (bvFTD). We invited five bvFTD participants and 21 controls to perform forward spans and backward spans, and, in a control condition, to count aloud. We recorded pupil activity using eye-tracking-glasses during the spans and control condition. Analysis demonstrated larger pupil sizes during backward spans than during forward spans, and larger pupil sizes during forward spans than during counting in both bvFTD and control participants. These findings demonstrate how increased cognitive load triggers increased pupil size and how this connection is maintained in bvFTD.

Sustained Long-term Improvement in Neuropsychiatric Symptoms of an Individual With Initial bvFTD Diagnosis: A Case Report

The behavioral variant of frontotemporal dementia (bvFTD) is a neurodegenerative disease that is diagnosed by progressive neuropsychiatric changes and supportive neuroimaging. Making an accurate diagnosis of bvFTD is a challenging process that can be complicated by the presence of a subset of nonprogressive, or phenocopy, cases whose symptoms remain stable. Our patient, who presented with neuropsychiatric symptoms that are characteristic of bvFTD, improved and stabilized after thorough neuropsychiatric and neuropsychological evaluation and treatment. Our case illustrates that, despite diagnostic uncertainties, appropriate evaluation and treatment can lead to improvement and stabilization of neuropsychiatric symptoms in individuals presumed to have bvFTD.