Metabolic Changes Detected by 18F-FDG PET in the Preclinical Stage of Familial Creutzfeldt-Jakob Disease

Reconfigured metabolism brain network in asymptomatic Creutzfeldt-Jakob disease

BACKGROUND

Investigating brain metabolic networks is crucial for understanding the pathogenesis and functional alterations in Creutzfeldt-Jakob disease (CJD). However, studies on presymptomatic individuals remain limited. This study aimed to examine metabolic network topology reconfiguration in asymptomatic carriers of the PRNP G114V mutation.

METHODS

Seven asymptomatic PRNP G114V mutation carriers from a familial genetic CJD (gCJD) cohort, 43 CJD patients, and 35 healthy controls were included. All participants underwent neuropsychological assessments, genetic testing, and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET)/MRI scans. Voxel-based gray matter volume and FDG PET standardized uptake value ratios (SUVRs) were analyzed between asymptomatic PRNP G114V mutation carriers and healthy controls and between CJD patients and controls. Graph theory and sparse inverse covariance estimation (SICE) were used to assess the whole-brain metabolic connectomes and topological properties. Spatial independent component analysis (ICA) was used to evaluate subnetworks, including the default mode network (DMN), salience network (SN), and central executive network (CEN).

RESULTS

With respect to global properties, assortativity was significantly increased in asymptomatic carriers, which was consistent with the findings in CJD patients. We revealed lost hubs in the right anterior cingulate, left ventral prefrontal lobe, left parahippocampal gyrus, and left lingual gyrus and reconfigured hubs in prefrontal lobes, including right ventromedial prefrontal cortex, right anterior prefrontal cortex, and right middle frontal gyrus of the orbit in asymptomatic carriers compared with healthy controls, which overlapped with the comparisons between CJD patients and controls. Alterations in the local parameters and metabolic connectivity in the left parahippocampal gyrus were most pronounced. Among the subnetworks, asymptomatic carriers presented higher assortativity and lower hierarchy in the SN, whereas the global parameters of the DMN and CEN were not significantly altered. The DMN and SN showed partial hypoconnectivity and hyperconnectivity, whereas the CEN mainly showed significantly enhanced connectivity in asymptomatic PRNP carriers.

CONCLUSIONS

This study revealed altered brain metabolic topology and connectomics in asymptomatic PRNP G114V mutation carriers, which could be detected before gray matter or regional metabolic changes, suggesting that metabolism topology reconfiguration may serve as a sensitive imaging biomarker for investigating early CJD pathological changes.

Association of Glymphatic Function With Clinical Characteristics in Patients With Clinical and Asymptomatic Creutzfeldt-Jakob Disease

BACKGROUND AND OBJECTIVES

Abnormal glymphatic system-related proteins have been identified in a small-scale pathologic study of patients with Creutzfeldt-Jakob disease (CJD). However, it remains unclear whether glymphatic dysfunction occurs in vivo in patients with CJD and whether this decline begins during the preclinical stage. This study aimed to investigate the relationship between glymphatic dysfunction and clinical characteristics in patients with CJD, as well as potential glymphatic impairment in preclinical CJD.

METHODS

This prospective cohort study recruited patients with CJD and healthy controls (HCs) from the Department of Neurology at Xuanwu Hospital, Capital Medical University, Beijing, China, from 2018 to 2022. In addition, a family with preclinical genetic CJD carrying the G114V pathogenic variant was followed over 6 years with 3 evaluations. All participants underwent diffusion tensor imaging along the perivascular space (DTI-ALPS) to measure glymphatic function in vivo and 18F-fludeoxyglucose-PET to identify CJD-related metabolic patterns. Associations between the DTI-ALPS index and Medical Research Council Prion Disease Rating Scale (MRC-PDRS) score were evaluated using multiple linear regression.

RESULTS

We enrolled 35 patients with CJD (mean age 59.6 ± 10.7 years, 40% female, with the time from onset to glymphatic dysfunction assessment averaging 39% of the total disease course), 28 age-matched and sex-matched HCs, and a family with preclinical genetic CJD consisting of 7 carriers and 7 noncarriers. Patients with CJD exhibited lower DTI-ALPS values compared with HCs (p < 0.001). Partial correlation analyses revealed significant correlations between the DTI-ALPS index and MRC-PDRS score (r = 0.346, p = 0.049) and disease progression (r = -0.468, p = 0.006), but not with disease duration or cognitive severity after adjusting for age and sex. Multivariate linear analysis demonstrated that poorer MRC-PDRS scores (β = 0.702, p = 0.014) were associated with a lower DTI-ALPS index. The DTI-ALPS index of asymptomatic G114V carriers showed no significant difference compared with noncarriers. However, a preclinical CJD case exhibited an 8.2% decrease in the DTI-ALPS index 3.3 years before onset. No significant correlation was found between regional metabolic standardized uptake value ratios and DTI-ALPS index.

DISCUSSION

Our study indicates that glymphatic dysfunction is associated with CJD severity and disease progression. Glymphatic dysfunction may occur in the preclinical stage, but these findings should be interpreted with caution because they are based on individual findings.

The Role of PET Imaging in Patients with Prion Disease: A Literature Review

Prion diseases are rare, rapidly progressive, and fatal incurable degenerative brain disorders caused by the misfolding of a normal protein called PrPC into an abnormal protein called PrPSc. Their highly variable clinical presentation mimics various degenerative and non-degenerative brain disorders, making diagnosis a significant challenge for neurologists. Currently, definitive diagnosis relies on post-mortem examination of nervous tissue to detect the pathogenic prion protein. The current diagnostic criteria are limited. While structural magnetic resonance imaging (MRI) remains the gold standard imaging modality for Creutzfeldt-Jakob disease (CJD) diagnosis, positron emission tomography (PET) using 18fluorine-fluorodeoxyglucose (18F-FDG) and other radiotracers have demonstrated promising potential in the diagnostic assessment of prion disease. In this context, a comprehensive and updated review exclusively focused on PET imaging in prion diseases is still lacking. We review the current value of PET imaging with 18F-FDG and non-FDG tracers in the diagnostic management of prion diseases. From the collected data, 18F-FDG PET mainly reveals cortical and subcortical hypometabolic areas in prion disease, although fails to identify typical pattern or laterality abnormalities to differentiate between genetic and sporadic prion diseases. Although the rarity of prion diseases limits the establishment of a definitive hypometabolism pattern, this review reveals some more prevalent 18F-FDG patterns associated with each disease subtype. Interestingly, in both sporadic and genetic prion diseases, the hippocampus does not show significant glucose metabolism alterations, appearing as a useful sign in the differential diagnosis with other neurodegenerative disease. In genetic prion disease forms, PET abnormality precedes clinical manifestation. Discordant diagnostic value for amyloid tracers among different prion disease subtypes was observed, needing further investigation. PET has emerged as a potential valuable tool in the diagnostic armamentarium for CJD. Its ability to visualize functional and metabolic brain changes provides complementary information to structural MRI, aiding in the early detection and confirmation of CJD.

Neuroimaging in Dementia

OBJECTIVE

Neurodegenerative diseases are significant health concerns with regard to morbidity and social and economic hardship around the world. This review describes the state of the field of neuroimaging measures as biomarkers for detection and diagnosis of both slowly progressing and rapidly progressing neurodegenerative diseases, specifically Alzheimer disease, vascular cognitive impairment, dementia with Lewy bodies or Parkinson disease dementia, frontotemporal lobar degeneration spectrum disorders, and prion-related diseases. It briefly discusses findings in these diseases in studies using MRI and metabolic and molecular-based imaging (eg, positron emission tomography [PET] and single-photon emission computerized tomography [SPECT]).

LATEST DEVELOPMENTS

Neuroimaging studies with MRI and PET have demonstrated differential patterns of brain atrophy and hypometabolism in different neurodegenerative disorders, which can be useful in differential diagnoses. Advanced MRI sequences, such as diffusion-based imaging, and functional MRI (fMRI) provide important information about underlying biological changes in dementia and new directions for development of novel measures for future clinical use. Finally, advancements in molecular imaging allow clinicians and researchers to visualize dementia-related proteinopathies and neurotransmitter levels.

ESSENTIAL POINTS

Diagnosis of neurodegenerative diseases is primarily based on symptomatology, although the development of in vivo neuroimaging and fluid biomarkers is changing the scope of clinical diagnosis, as well as the research into these devastating diseases. This article will help inform the reader about the current state of neuroimaging in neurodegenerative diseases, as well as how these tools might be used for differential diagnoses.

Prion Mutations in Republic of Republic of Korea, China, and Japan

Prion gene (PRNP) mutations are associated with diverse disease phenotypes, including familiar Creutzfeldt-Jakob Disease (CJD), Gerstmann-Sträussler-Scheinker disease (GSS), and fatal familial insomnia (FFI). Interestingly, PRNP mutations have been reported in patients diagnosed with Alzheimer's disease, dementia with Lewy bodies, Parkinson's disease, and frontotemporal dementia. In this review, we describe prion mutations in Asian countries, including Republic of Republic of Korea, China, and Japan. Clinical phenotypes and imaging data related to these mutations have also been introduced in detail. Several prion mutations are specific to Asians and have rarely been reported in countries outside Asia. For example, PRNP V180I and M232R, which are rare in other countries, are frequently detected in Republic of Korea and Japan. PRNP T188K is common in China, and E200K is significantly more common among Libyan Jews in Israel. The A117V mutation has not been detected in any Asian population, although it is commonly reported among European GSS patients. In addition, V210I or octapeptide insertion is common among European CJD patients, but relatively rare among Asian patients. The reason for these differences may be geographical or ethical isolation. In terms of clinical phenotypes, V180I, P102L, and E200K present diverse clinical symptoms with disease duration, which could be due to other genetic and environmental influences. For example, rs189305274 in the ACO1 gene may be associated with neuroprotective effects in cases of V180I mutation, leading to longer disease survival. Additional neuroprotective variants may be possible in cases featuring the E200K mutation, such as KLKB1, KARS, NRXN2, LAMA3, or CYP4X1. E219K has been suggested to modify the disease course in cases featuring the P102L mutation, as it may result in the absence of prion protein-positive plaques in tissue stained with Congo red. However, these studies analyzed only a few patients and may be too preliminary. The findings need to be verified in studies with larger sample sizes or in other populations. It would be interesting to probe additional genetic factors that cause disease progression or act as neuroprotective factors. Further studies are needed on genetic modifiers working with prions and alterations from mutations.

A longitudinal 18F-FDG PET/MRI study in asymptomatic stage of genetic Creutzfeldt-Jakob disease linked to G114V mutation

BACKGROUND

Pathogenic prion protein may start to deposit in some brain regions and cause functional alterations in the asymptomatic stage in Creutzfeldt-Jakob disease. The study aims to determine the trajectory of the brain metabolic changes for prion protein diseases at the preclinical stage.

METHODS

At baseline, we enrolled five asymptomatic PRNP G114V mutation carriers, six affected genetic PRNP E200K CJD patients and 23 normal controls. All participants completed clinical, diffusion-weighted imaging (DWI) and 18F fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) examinations. Longitudinal follow-up was completed in five asymptomatic mutation carriers. We set three-time points to identify the changing trajectory in the asymptomatic carriers group including baseline, 2-year and 4-year follow-up.

RESULTS

At baseline, DWI signals, the cerebral glucose standardized uptake value rate ratio (SUVR) and clinical status in 5 asymptomatic cases were normal. At the follow-up period, mild hypometabolism on PET images was found in asymptomatic carriers without any DWI abnormal signal. Further group quantitatively analysis showed hypometabolic brain regions in the asymptomatic genetic CJD group were in the insula, frontal, parietal, and temporal lobes in 4-year follow-up. The SUVR changing trajectories of all asymptomatic cases were within the range between the normal controls and affected patients. Notably, the SUVR of one asymptomatic individual whose baseline age was older showed a rapid decline at the last follow-up.

CONCLUSIONS

Our study illustrates that the neurodegenerative process associated with genetic CJD may initiate before the clinical presentation of the disease.

White Matter Integrity Involvement in the Preclinical Stage of Familial Creutzfeldt-Jakob Disease: A Diffusion Tensor Imaging Study

Objective

The objective of the study was to explore patterns of white matter (WM) alteration in preclinical stage familial Creutzfeldt–Jakob disease (fCJD) using diffusion tensor imaging (DTI).

Methods

Seven asymptomatic carriers of the PRNP G114V mutation and six non-carriers were recruited from the same fCJD kindred and follow-up obtained from all asymptomatic carriers and two non-carriers 2 years later. Overlapping WM patterns were also explored in asymptomatic carriers and symptomatic CJD patients. All participants underwent clinical and neuropsychological assessments and DTI at baseline and follow-up. DTI data were subjected to whole-brain voxel-wise analysis of fractional anisotropy (FA) and mean diffusivity (MD) in WM using tract-based spatial statistics. Three comparisons were conducted: baseline carriers against non-carriers (baseline analysis), changes after 2 years in carriers (follow-up analysis), and differences between patients with symptomatic CJD and healthy controls (CJD patient analysis).

Results

Neither carriers nor non-carriers developed any neurological symptoms during 2 years of follow-up. Baseline analysis showed no differences between the carrier and non-carrier groups in MD and FA. Follow-up analysis showed significantly increased MD in multiple WM tracts, among which increased MD in the bilateral superior longitudinal fasciculus, bilateral anterior thalamic radiation, bilateral cingulate gyrus, and left uncinate fasciculus overlapped the patterns observed in patients with symptomatic CJD.

Conclusion

Changes in integrity within multiple WM tracts can be detected during the preclinical stage of fCJD.