Patients with progranulin mutations overlap with the progressive dysexecutive syndrome: towards the definition of a frontoparietal dementia phenotype

Three cases of Creutzfeldt-Jakob disease presenting with a predominant dysexecutive syndrome

Creutzfeldt-Jakob disease (CJD) is a rare, uniformly fatal prion disease. Although CJD commonly presents with rapidly progressive dementia, ataxia, and myoclonus, substantial clinicopathological heterogeneity is observed in clinical practice. Unusual and predominantly cognitive clinical manifestations of CJD mimicking common dementia syndromes are known to pose as an obstacle to early diagnosis and prognosis. We report a series of three patients with probable or definite CJD (one male and two females, ages 52, 58 and 68) who presented to our tertiary behavioral neurology clinic at Mayo Clinic Rochester that met criteria for a newly defined progressive dysexecutive syndrome. Glucose hypometabolism patterns assessed by ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) strongly resembled those of dysexecutive variant of Alzheimer's disease (dAD). However, magnetic resonance imaging (MRI) demonstrated restricted diffusion in neocortical areas and deep nuclei, while cerebrospinal fluid biomarkers indicated abnormal levels of 14-3-3, total-tau, and prion seeding activity (RT-QuIC), establishing the diagnosis of CJD. Electroencephalogram (EEG) additionally revealed features previously documented in atypical cases of CJD. This series of clinical cases demonstrates that CJD can present with a predominantly dysexecutive syndrome and FDG-PET hypometabolism typically seen in dAD. This prompts for the need to integrate information on clinical course with multimodal imaging and fluid biomarkers to provide a precise etiology for dementia syndromes. This has important clinical implications for the diagnosis and prognosis of CJD in the context of emerging clinical characterization of progressive dysexecutive syndromes in neurodegenerative diseases like dAD.

Serum neurofilament light chain as a surrogate of cognitive decline in sporadic and familial frontotemporal dementia

BACKGROUND AND PURPOSE

Neurofilament light chain (NfL) has recently been proposed as a promising biomarker in frontotemporal dementia (FTD). We investigated the correlation of both cerebrospinal fluid (CSF) and serum NfL with detailed neuropsychological data and cognitive decline in a cohort of sporadic and familial FTD.

METHODS

CSF and serum NfL, as well as conventional CSF Alzheimer's disease (AD) biomarkers (Aβ42, t-Tau, p-Tau181), were determined in 63 FTD patients (30 sporadic-FTD, 20 with progranulin (GRN) mutations [FTD-GRN], 13 with chromosome 9 open reading frame 72 [C9orf72] expansions [C9orf72-FTD]), 37 AD patients, and 31 neurologic controls. Serum NfL was also quantified in 37 healthy individuals. Correlations between baseline CSF and serum NfL levels, standardized neuropsychological tests, and the rate of cognitive decline in FTD patients were assessed.

RESULTS

CSF and serum NfL presented with significantly higher levels in FTD than in AD patients and both control groups. Within FTD subtypes, genetic cases, and particularly FTD-GRN, had higher CSF and serum NfL levels. Significant correlations between NfL levels and overall cognitive function, abstract reasoning (CSF and serum), executive functions, memory, and language (serum) were found. A relationship between increased baseline CSF and serum NfL and a decay in cognitive performance over time was also observed.

CONCLUSIONS

Our findings highlight the potential of serum NfL as a useful surrogate end point of disease severity in upcoming targeted treatments.