Sensitivity of 14-3-3 protein test varies in subtypes of sporadic Creutzfeldt-Jakob disease

Case report: Atypical young case of MV1 Creutzfeldt-Jakob disease with unusually long survival

Creutzfeldt-Jakob disease (CJD) is a rare, fatal, rapidly progressive neurodegenerative disease resulting from an accumulation of misfolded prion proteins (PrP). CJD affects 1-2 new individuals per million each year, and the sporadic type accounts for 90% of those cases. Though the median age at onset and disease duration vary depending on the subtype of sporadic CJD (sCJD), the disease typically affects middle-aged to elderly individuals with a median survival of 4-6 months. sCJD in younger individuals is extremely rare. Here, we present a 21-year-old female who died with a sporadic prion disease. She presented with psychiatric symptoms followed by a rapidly progressive neurocognitive and motor decline. EEG was negative for periodic sharp wave complexes; however, brain MRI was suggestive of prion disease. The cerebrospinal fluid (CSF) real-time quaking-induced conversion (RT-QuIC) assay was indeterminate. Neuropathologic examination at autopsy revealed severe neuronal loss and gliosis with secondary white matter degeneration but minimal spongiform changes and PrP deposits in the cerebellum and neocortex by immunohistochemistry. Absence of pathogenic mutations and methionine/valine heterozygosity at codon 129 of the prion protein gene (PRNP), atypical type 1 protease-resistant PrP that lacks or shows underrepresentation of the diglycosylated PrP isoform by western blot analysis, and no acquired prion disease risk factors resulted in a final diagnosis of atypical sCJD. Very young onset sCJD often has atypical clinical presentations and disease progression, neuropathological examination results, and/or laboratory test results that may confound diagnosis. It is critical to perform thorough, comprehensive evaluations to make an accurate diagnosis, which includes autopsy confirmation with histology, prion protein typing and prion gene sequencing.

An autopsy case of MV 2K + C subtype of Creutzfeldt-Jakob disease

Methionine/valine (MV) 2 type of sporadic Creutzfeldt-Jakob (sCJD) is divided into three subtypes based on neuropathological criteria: MV2-kuru (MV2K), MV2-cortical (MV2C), and MV2K + C, exhibiting the co-occurrence of these two pathological features. We report an autopsy case of MV2K + C subtype of sCJD. A 46-year-old Japanese man began to make mistakes at work. Two months later, he gradually developed gait instability. The initial neurological examination revealed limb ataxia and myoclonus. Diffusion-weighted images (DWI) showed a hyperintensity in the right frontal cortex, basal ganglia, and thalamus. Ten months after the onset of disease, he fell into akinetic mutism. He died at 47 years of age, 12 months after the initial presentation. Pathological investigation revealed microvacuolation and confluent vacuoles in the cerebral cortex. In the basal ganglia and thalamus, there was severe neuronal loss and gliosis with mild spongiform change. Kuru plaques were found within the cerebellum. Prion protein (PrP) immunostaining revealed synaptic, perivacuolar, perineuronal, and plaque-like deposits in the cerebral cortex. There were synaptic and plaque-like PrP deposits in the basal ganglia, thalamus, and granular cell layer of the cerebellum. In these areas, plaque-like deposits mainly consisted of small deposits, whereas plaque-like deposits in the cerebral cortex consisted both of coarse granular and small deposits. Analysis of the PrP gene showed no pathogenic mutations, and Western blot examination revealed a mixture of type 2 and intermediate-type PrP. The progressive cognitive decline and ataxia in addition to the hyperintensity in the basal ganglia and/or thalamus on DWI are the basis for clinical diagnosis of MV2. The severe gliosis in the basal ganglia and various morphologies of plaque-like deposits that differ by the region may be characteristic of MV2K + C. Detailed neuropathological examination together with Western blot analysis is important to collect more cases for elucidating the pathogenesis of MV2K + C.

Application of real-time quaking-induced conversion in Creutzfeldt-Jakob disease surveillance

BACKGROUND

Evaluation of the application of CSF real-time quaking-induced conversion in Creutzfeldt-Jakob disease surveillance to investigate test accuracy, influencing factors, and associations with disease incidence.

METHODS

In a prospective surveillance study, CSF real-time quaking-induced conversion was performed in patients with clinical suspicion of prion disease (2014-2022). Clinically or histochemically characterized patients with sporadic Creutzfeldt-Jakob disease (n = 888) and patients with final diagnosis of non-prion disease (n = 371) were included for accuracy and association studies.

RESULTS

The overall test sensitivity for sporadic Creutzfeldt-Jakob disease was 90% and the specificity 99%. Lower sensitivity was associated with early disease stage (p = 0.029) and longer survival (p < 0.001). The frequency of false positives was significantly higher in patients with inflammatory CNS diseases (3.7%) than in other diagnoses (0.4%, p = 0.027). The incidence increased from 1.7 per million person-years (2006-2017) to 2.0 after the test was added to diagnostic the criteria (2018-2021).

CONCLUSION

We validated high diagnostic accuracy of CSF real-time quaking-induced conversion but identified inflammatory brain disease as a potential source of (rare) false-positive results, indicating thorough consideration of this condition in the differential diagnosis of Creutzfeldt-Jakob disease. The surveillance improved after amendment of the diagnostic criteria, whereas the incidence showed no suggestive alterations during the COVID-19 pandemic.

[Prognostic and diagnostic value of cerebrospinal fluid analysis in neurodegenerative dementia diseases]

Cerebrospinal fluid (CSF) analysis is an important diagnostic tool in the assessment of dementia. For the differentiation of Alzheimer's disease from other etiologies of dementia syndromes, established biological markers could be helpful to confirm a distinctive neuropathology. Whereas negative CSF findings can rule out the majority of primarily neurodegenerative disorders, overlapping biomarker profiles remain a diagnostic challenge. Therefore, it is important to interpret CSF results within a specific clinical context. Furthermore, atypical CSF data can be challenging and require profound knowledge of preanalytics, biomarker profiles and the broad spectrum of diseases associated with cognitive decline. Beyond the Alzheimer's disease clinical spectrum, current studies aim at investigating CSF biomarkers to better differentiate tauopathies, TDP43(Transactive response DNA binding protein 43 kDa)-proteinopathies and synucleinopathies.

The Use of Real-Time Quaking-Induced Conversion for the Diagnosis of Human Prion Diseases

Prion diseases are rapidly progressive, invariably fatal, transmissible neurodegenerative disorders associated with the accumulation of the amyloidogenic form of the prion protein in the central nervous system (CNS). In humans, prion diseases are highly heterogeneous both clinically and neuropathologically. Prion diseases are challenging to diagnose as many other neurologic disorders share the same symptoms, especially at clinical onset. Definitive diagnosis requires brain autopsy to identify the accumulation of the pathological prion protein, which is the only specific disease biomarker. Although brain post-mortem investigation remains the gold standard for diagnosis, antemortem clinical, instrumental, and laboratory tests showing variable sensitivities and specificity, being surrogate disease biomarkers, have been progressively introduced in clinical practice to reach a diagnosis. More recently, the ultrasensitive Real-Time Quaking-Induced Conversion (RT-QuIC) assay, exploiting, for the first time, the detection of misfolded prion protein through an amplification strategy, has highly improved the “in-vitam” diagnostic process, reaching in cerebrospinal fluid (CSF) and olfactory mucosa (OM) around 96% sensitivity and close to 100% specificity. RT-QuIC also improved the detection of the pathologic prion protein in several peripheral tissues, possibly even before the clinical onset of the disease. The latter aspect is of great interest for the early and even preclinical diagnosis in subjects at genetic risk of developing the disease, who will likely be the main target population in future clinical trials. This review presents an overview of the current knowledge and future perspectives on using RT-QuIC to diagnose human prion diseases.

Role of Biomarkers for the Diagnosis of Prion Diseases: A Narrative Review

Prion diseases are progressive and irreversible neurodegenerative disorders with a low incidence (1.5–2 cases per million per year). Genetic (10–15%), acquired (anecdotal) and sporadic (85%) forms of the disease have been described. The clinical spectrum of prion diseases is very varied, although the most common symptoms are rapidly progressive dementia, cerebellar ataxia and myoclonus. Mean life expectancy from the onset of symptoms is 6 months. There are currently diagnostic criteria based on clinical phenotype, as well as neuroimaging biomarkers (magnetic resonance imaging), neurophysiological tests (electroencephalogram and polysomnogram), and cerebrospinal fluid biomarkers (14-3-3 protein and real-time quaking-induced conversion (RT-QuIC)). The sensitivity and specificity of some of these tests (electroencephalogram and 14-3-3 protein) is under debate and the applicability of other tests, such as RT-QuIC, is not universal. However, the usefulness of these biomarkers beyond the most frequent prion disease, sporadic Creutzfeldt–Jakob disease, remains unclear. Therefore, research is being carried out on new, more efficient cerebrospinal fluid biomarkers (total tau, ratio total tau/phosphorylated tau and neurofilament light chain) and potential blood biomarkers (neurofilament light chain, among others) to try to universalize access to early diagnosis in the case of prion diseases.

Clinical Use of Improved Diagnostic Testing for Detection of Prion Disease

Prion diseases are difficult to recognize as many symptoms are shared among other neurologic pathologies and the full spectra of symptoms usually do not appear until late in the disease course. Additionally, many commonly used laboratory markers are non-specific to prion disease. The recent introduction of second-generation real time quaking induced conversion (RT-QuIC) has revolutionized pre-mortem diagnosis of prion disease due to its extremely high sensitivity and specificity. However, RT-QuIC does not provide prognostic data and has decreased diagnostic accuracy in some rarer, atypical prion diseases. The objective of this review is to provide an overview of the current clinical utility of fluid-based biomarkers, neurodiagnostic testing, and brain imaging in the diagnosis of prion disease and to suggest guidelines for their clinical use, with a focus on rarer prion diseases with atypical features. Recent advancements in laboratory-based testing and imaging criteria have shown improved diagnostic accuracy and prognostic potential in prion disease, but because these diagnostic tests are not sensitive in some prion disease subtypes and diagnostic test sensitivities are unknown in the event that CWD transmits to humans, it is important to continue investigations into the clinical utility of various testing modalities.

MM2-type sporadic Creutzfeldt-Jakob disease: new diagnostic criteria for MM2-cortical type

OBJECTIVE

To clinically diagnose MM2-cortical (MM2C) and MM2-thalamic (MM2T)-type sporadic Creutzfeldt-Jakob disease (sCJD) at early stage with high sensitivity and specificity.

METHODS

We reviewed the results of Creutzfeldt-Jakob disease Surveillance Study in Japan between April 1999 and September 2019, which included 254 patients with pathologically confirmed prion diseases, including 9 with MM2C-type sCJD (MM2C-sCJD) and 10 with MM2T-type sCJD (MM2T-sCJD), and 607 with non-prion diseases.

RESULTS

According to the conventional criteria of sCJD, 4 of 9 patients with MM2C- and 7 of 10 patients with MM2T-sCJD could not be diagnosed with probable sCJD until their death. Compared with other types of sCJD, patients with MM2C-sCJD showed slower progression of the disease and cortical distribution of hyperintensity lesions on diffusion-weighted images of brain MRI. Patients with MM2T-sCJD also showed relatively slow progression and negative results for most of currently established investigations for diagnosis of sCJD. To clinically diagnose MM2C-sCJD, we propose the new criteria; diagnostic sensitivity and specificity to distinguish 'probable' MM2C-sCJD from other subtypes of sCJD, genetic or acquired prion diseases and non-prion disease controls were 77.8% and 98.5%, respectively. As for MM2T-sCJD, clinical and laboratory features are not characterised enough to develop its diagnostic criteria.

CONCLUSIONS

MM2C-sCJD can be diagnosed at earlier stage using the new criteria with high sensitivity and specificity, although it is still difficult to diagnose MM2T-sCJD clinically.

Focal sharp waves are a specific early-stage marker of the MM2-cortical form of sporadic Creutzfeldt-Jakob disease

Periodic sharp wave complexes (PSWCs), identified using electroencephalography, are observed in less than half of patients with the methionine homozygosity type 2 cortical (MM2c) form of sporadic Creutzfeldt-Jakob disease (sCJD), and only at a later stage of the disease. In this study, we identified early and specific markers on the electroencephalograms (EEGs) of patients with MM2c-sCJD. We retrospectively investigated the clinical records, EEGs, and magnetic resonance imaging (MRI) scans of patients diagnosed with sCJD and compared the EEG findings of MM2c-sCJD and MM1/classic sCJD groups. The records of six patients with MM2c-sCJD and eight with MM1/classic sCJD were included. The median ages of onset in the MM2c- and MM1/classic sCJD groups were 75.0 (range, 60–83) and 72.5 (range, 51–74) years, respectively, and the average durations between disease onset and the first EEG were 9.17 (range, 4–15) and 1.88 (range, 1–4) months, respectively. Focal sharp waves and/or focal spike-and-wave complexes in the brain regions corresponding with cortical hyperintensities on MRI scans were identified on the EEGs of patients with MM2c-sCJD in the early stages of disease progression. In contrast, EEGs of patients in the early stages of MM1/classic sCJD showed lateralized or generalized diffuse sharp waves and spike-and-wave complexes, which were not limited to cortical hyperintensities identified with MRI scans. Our findings indicate that focal sharp waves and/or focal spike-and-wave complexes on the EEGs of patients in the early phase of MM2c-sCJD are characteristic of the disease, suggesting the possible usefulness of this characteristic for early diagnosis.

A case of MV2K subtype of sporadic Creutzfeldt-Jakob disease with florid-like plaques: Similarities and differences to variant Creutzfeldt-Jakob disease

Variant Creutzfeldt-Jakob disease (vCJD) is traditionally regarded as having a distinct clinical course, imaging study findings and neuropathological features, which in combination should allow a clear distinction from the six currently well-defined subtypes of sporadic Creutzfeldt-Jakob disease (sCJD). This is of major importance, especially from the standpoint of epidemiology. As we would like to demonstrate through this case report, the MV2K subtype of sCJD, being rare and heterogeneous in both clinical and neuropathological presentations, might challenge this concept by virtue of partial overlapping, both clinically and neuropathologically, with the characteristic phenotype of vCJD. Chiefly, we observed prolonged isolated psychiatric prodrome, new onset limb pain and late cognitive decline clinically, while florid-like plaques were present on routine histology, albeit in scarce and regionally restricted distribution when compared to vCJD. However, the issue is further complicated by the fact that a case of vCJD in a heterozygous (i.e. methionine - M and valine - V) allelic state with regard to the polymorphic codon 129 of the prion protein gene (PRNP) has recently been described in the UK, which deviated from the otherwise well-defined and constant clinicopathological phenotype that vCJD had thus far demonstrated. Taking both the facts into account, we would like to emphasize the use of complementary diagnostic methods to the established and otherwise reliable histological type-based model, particularly when confronted with a rare or atypical phenotype such as ours.

The cellular prion protein and its derived fragments in human prion diseases and their role as potential biomarkers

Introduction: Human prion diseases are a heterogeneous group of incurable and debilitating conditions characterized by a progressive degeneration of the central nervous system. The conformational changes of the cellular prion protein and its formation into an abnormal isoform, spongiform degeneration, neuronal loss, and neuroinflammation are central to prion disease pathogenesis. It has been postulated that truncated variants of aggregation-prone proteins are implicated in neurodegenerative mechanisms. An increasing body of evidence indicates that proteolytic fragments and truncated variants of the prion protein are formed and accumulated in the brain of prion disease patients. These prion protein variants provide a high degree of relevance to disease pathology and diagnosis. Areas covered: In the present review, we summarize the current knowledge on the occurrence of truncated prion protein species and their potential roles in pathophysiological states during prion diseases progression. In addition, we discuss their usability as a diagnostic biomarker in prion diseases. Expert opinion: Either as a primary factor in the formation of prion diseases or as a consequence from neuropathological affection, abnormal prion protein variants and fragments may provide independent information about mechanisms of prion conversion, pathological states, or disease progression.

Review: Fluid biomarkers in the human prion diseases

The human prion diseases are a diverse set of often rapidly progressive neurodegenerative conditions associated with abnormal forms of the prion protein. We review work to establish diagnostic biomarkers and assays that might fill other important roles, particularly those that could assist the planning and interpretation of clinical trials. The field now benefits from highly sensitive and specific diagnostic biomarkers using cerebrospinal fluid: detecting by-products of rapid neurodegeneration or specific functional properties of abnormal prion protein, with the second generation real time quaking induced conversion (RT-QuIC) assay being particularly promising. Blood has been a more challenging analyte, but has now also yielded valuable biomarkers. Blood-based assays have been developed with the potential to screen for variant Creutzfeldt-Jakob disease, although it remains uncertain whether these will ever be used in practice. The very rapid neurodegeneration of prion disease results in strong signals from surrogate protein markers in the blood that reflect neuronal, axonal, synaptic or glial pathology in the brain: notably the tau and neurofilament light chain proteins. We discuss early evidence that such tests, applied alongside robust diagnostic biomarkers, may have potential to add value as clinical trial outcome measures, predictors of future disease course (including for asymptomatic individuals at high risk of prion disease), and as rapidly accessible and sensitive markers to aid early diagnosis.

Sporadic Creutzfeldt-Jakob disease

Sporadic Creutzfeldt-Jakob disease (CJD), the most common human prion disease, is generally regarded as a spontaneous neurodegenerative illness, arising either from a spontaneous PRNP somatic mutation or a stochastic PrP structural change. Alternatively, the possibility of an infection from animals or other source remains to be completely ruled out. Sporadic CJD is clinically characterized by rapidly progressive dementia with ataxia, myoclonus, or other neurologic signs and, neuropathologically, by the presence of aggregates of abnormal prion protein, spongiform change, neuronal loss, and gliosis. Despite these common features the disease shows a wide phenotypic variability which was recognized since its early descriptions. In the late 1990s the identification of key molecular determinants of phenotypic expression and the availability of a large series of neuropathologically verified cases led to the characterization of definite clinicopathologic and molecular disease subtypes and to an internationally recognized disease classification. By showing that these disease subtypes correspond to specific agent strain-host genotype combinations, recent transmission studies have confirmed the biologic basis of this classification. The introduction of brain magnetic resonance imaging techniques such as fluid-attenuated inversion recovery and diffusion-weighted imaging sequences and cerebrospinal fluid biomarker assays for the detection of brain-derived proteins as well as real-time quaking-induced conversion assay, allowing the specific detection of prions in accessible biologic fluids and tissues, has significantly contributed to the improved accuracy of the clinical diagnosis of sporadic CJD in recent years.

14-3-3 and enolase abundances in the CSF of Prion diseased rats

Creutzfeldt-Jakob disease (CJD) is characterized by an extended asymptomatic preclinical phase followed by rapid neurodegeneration. There are no effective treatments. CJD diagnosis is initially suspected based upon the clinical presentation of the disease and the exclusion of other etiologies. Neurologic symptoms are assessed in combination with results from cerebrospinal fluid (CSF) biomarker abundances, electroencephalography (EEG), magnetic resonance imaging (MRI), and in some countries, real-time quaking-induced conversion (RT-QuIC). Inconsistencies in sensitivities and specificities of prion disease biomarker abundance in CSF have been described, which can affect diagnostic certainty, but the utility of biomarkers for prognosis has not been fully explored. The clinical presentation of CJD is variable, and factors such as prion protein polymorphic variants, prion strain, and other genetic or environmental contributions may affect the disease progression, confounding the appearance or abundance of biomarkers in the CSF. These same factors may also affect the appearance or abundance of biomarkers, further confounding diagnosis. In this study, we controlled for many of these variables through the analysis of serial samples of CSF from prion-infected and control rats. Prion disease in laboratory rodents follows a defined disease course as the infection route and time, prion strain, genotype, and environmental conditions are all controlled. We measured the relative abundance of 14-3-3 and neuron-specific enolase (NSE) in CSF during the course of prion infection in rats. Even when disease-related, environmental and genetic variables were controlled, CSF 14-3-3 and NSE abundances were variable. Our study emphasizes the considerable diagnostic and prognostic limitations of these prion biomarkers.

Validation and utilization of amended diagnostic criteria in Creutzfeldt-Jakob disease surveillance

Objective

To validate an amended protocol for clinical diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) including real-time quaking-induced conversion (RT-QuIC) and to observe its use in CJD surveillance.

Methods

In the framework of a prospective epidemiologic study, all neuropathologically confirmed cases with sCJD who received CSF RT-QuIC analysis during diagnostic workup (n = 65) and a control group of individuals without CJD (n = 118) were selected to investigate the accuracy of an amended diagnostic protocol. The patients had been referred to the German National Reference Center for Transmissible Spongiform Encephalopathies. The influence of the amended protocol on incidence figures was evaluated in the context of 3 years of surveillance activity (screened cases using 14-3-3 test n = 18,789, highly suspicious cases of CJD n = 704). Annual incidences were calculated with current criteria and the amended protocol.

Results

The amended protocol showed a sensitivity of 97% and a specificity of 99%. When it was applied to all suspected cases who were referred to the reference center, the assessed incidence of CJD increased from 1.7 to 2.2 per million in 2016.

Conclusion

CJD surveillance remains challenging because information from external health care institutions can be limited. RT-QuIC shows excellent diagnostic accuracy when applied in the clinical setting to symptomatic patients. Data for RT-QuIC alone when applied as a general screening test are not available yet. We propose an amended research protocol that improves early and accurate clinical diagnosis of sCJD during surveillance activities. The use of this protocol will probably lead to a significant increase of the incidence rate.

Classification of evidence

This study provides Class III evidence that for patients with suspected sCJD, criteria for clinical diagnosis plus the CSF RT-QuIC accurately identifies patients with sCJD (sensitivity 97%, specificity 99%).

Cerebrospinal fluid and blood biomarkers for neurodegenerative dementias: An update of the Consensus of the Task Force on Biological Markers in Psychiatry of the World Federation of Societies of Biological Psychiatry

In the 12 years since the publication of the first Consensus Paper of the WFSBP on biomarkers of neurodegenerative dementias, enormous advancement has taken place in the field, and the Task Force takes now the opportunity to extend and update the original paper. New concepts of Alzheimer's disease (AD) and the conceptual interactions between AD and dementia due to AD were developed, resulting in two sets for diagnostic/research criteria. Procedures for pre-analytical sample handling, biobanking, analyses and post-analytical interpretation of the results were intensively studied and optimised. A global quality control project was introduced to evaluate and monitor the inter-centre variability in measurements with the goal of harmonisation of results. Contexts of use and how to approach candidate biomarkers in biological specimens other than cerebrospinal fluid (CSF), e.g. blood, were precisely defined. Important development was achieved in neuroimaging techniques, including studies comparing amyloid-β positron emission tomography results to fluid-based modalities. Similarly, development in research laboratory technologies, such as ultra-sensitive methods, raises our hopes to further improve analytical and diagnostic accuracy of classic and novel candidate biomarkers. Synergistically, advancement in clinical trials of anti-dementia therapies energises and motivates the efforts to find and optimise the most reliable early diagnostic modalities. Finally, the first studies were published addressing the potential of cost-effectiveness of the biomarkers-based diagnosis of neurodegenerative disorders.

Case series of Creutzfeldt-Jakob disease in a third-level hospital in Quito

BACKGROUND

Creutzfeldt-Jakob disease is a rare and fatal neurodegenerative disorder that affects mammals and humans. The prevalence of this disease in the United States is 0.5 to 1 per million inhabitants. So far in Ecuador, we do not know what the prevalence or incidence is, and only one case report has been written.

CASE PRESENTATION

We present a case series of Creutzfeldt-Jakob disease in a third-level hospital in Quito. The average age of symptom onset in our patients was 58.8 years. The male to female ratio was 1:1. Two patients began with cognitive/behavioral symptoms, while 4 patients began with focal neurological signs; 1 case with ataxia, 2 with gait disorders and 1 with vertigo and headache. All of the patients had the clinical features established by the World Health Organization. In addition, the entire cohort was positive for the 14-3-3 protein in cerebrospinal fluid, and had high signal abnormalities in caudate and putamen nucleus in DWI and FLAIR IRM. Only in one case, did we reach a definitive diagnosis through a pathological study. All other cases had a probable diagnosis. In this series of cases, 6 out of 6 patients died. The average time from the onset of the symptoms to death in this cohort was 13 months.

CONCLUSION

This is the first report of a series of cases of Creutzfeldt-Jakob disease in Quito. Although definitive diagnosis must be histopathological, there are ancillary tests currently available that have allowed us to obtain a diagnosis of the disease.

Diagnostic Accuracy of a Combined Analysis of Cerebrospinal Fluid t-PrP, t-tau, p-tau, and Aβ42 in the Differential Diagnosis of Creutzfeldt-Jakob Disease from Alzheimer's Disease with Emphasis on Atypical Disease Variants

According to recent studies, the determination of cerebrospinal fluid (CSF) total tau (t-tau)/phosphorylated tau (p-tau) ratio and total prion protein (t-PrP) levels significantly improves the accuracy of the diagnosis of Alzheimer’s disease (AD) in atypical cases with clinical or laboratory features mimicking Creutzfeldt-Jakob disease (CJD). However, this has neither been validated nor tested in series including atypical CJD variants. Furthermore, the added diagnostic value of amyloid-β (Aβ)₄₂ remains unclear. To address these issues, we measured t-PrP, 14-3-3, t-tau, p-tau, and Aβ₄₂ CSF levels in 45 typical and 44 atypical/rapidly progressive AD patients, 54 typical and 54 atypical CJD patients, and 33 controls. CJD patients showed significantly lower CSF t-PrP levels than controls and AD patients. Furthermore, atypical CJD was associated with lower t-PrP levels in comparison to typical CJD. T-tau, 14-3-3, or t-PrP alone yielded, respectively, 80.6, 63.0, and 73.0% sensitivity and 75.3, 92.1, and 75% specificity in distinguishing AD from CJD. On receiver operating characteristic (ROC) curve analyses of biomarker combinations, the (t-tau×Aβ₄₂)/(p-tau×t-PrP) ratio achieved the best accuracy, with 98.1% sensitivity and 97.7% specificity overall, and 96.2% sensitivity and 95.5% specificity for the “atypical” disease groups. Our results show that the combined analysis of CSF t-PrP, t-tau, p-tau, and Aβ₄₂ is clinically useful in the differential diagnosis between CJD and AD. Furthermore, the finding of reduced CSF t-PrP levels in CJD patients suggest that, likewise Aβ₄₂ in AD, CSF t-PrP levels reflect the extent of PrP^c conversion into abnormal PrP (PrP^Sc) and the burden of PrP^Sc deposition in CJD.

Iatrogenic Creutzfeldt-Jakob disease

Iatrogenic transmission of Creutzfeldt-Jakob disease (CJD) has occurred through particular medical procedures. Among them, dura mater grafts and pituitary-derived growth hormone obtained from human cadavers undiagnosed as CJD are the most frequent sources of infection. Recent advances in our knowledge about dura mater graft- and human pituitary-derived growth hormone-associated CJD patients have revealed that the combination of the infected CJD strain and the PRNP genotype of the patient determines their clinical, neuropathologic, and biochemical features. In this chapter, we summarize the clinical, neuropathologic, biochemical, and diagnostic features of dura mater graft- and human pituitary-derived growth hormone-associated CJD patients for the appropriate diagnosis of iatrogenic CJD.

Clinical findings of a probable case of MM2-cortical-type sporadic Creutzfeldt-Jakob disease with antibodies to anti-N-terminus of α-enolase

We report the case of a 76-year-old woman presenting with 47-month history of progressive dementia and cortical blindness with no family history. Antibodies against thyroid glands and the N-terminus of α-enolase (NAE) were detected in her serum. Neurological examination revealed progressive dementia, frontal signs, visual disturbance, and exaggerated bilateral tendon reflexes in both legs. Diffusion MRI showed cortical hyper-intensities in the bilateral occipital and parietal, and the left frontal and temporal cortices. ^99mTc-ethyl cysteinate dimer-single photon emission computed tomography indicated decreased regional cerebral blood flow throughout the bilateral parietal lobes and partially in the left frontal and temporal lobes. PRNP gene analysis showed no mutations with methionine homozygosity at codon 129 in peripheral blood. Cerebrospinal fluid examination, including 14-3-3 and total tau protein detection, revealed normal levels; however, prion proteins were amplified by the real-time quaking-induced conversion method. Hashimoto's encephalopathy was excluded on the basis of unresponsiveness to corticosteroids. The symptoms progressed slowly. Periodic sharp-wave complexes were observed on electroencephalogram 36 months after the onset of symptoms; the patient reached a state of akinetic mutism at 47 months. This was a probable case of MM2-cortical-type sCJD with anti-NAE antibodies based on the World Health Organization (WHO) diagnostic criteria for sCJD, genetic information, and the slowly progressive course. However, this case did not meet with the probable WHO diagnostic criteria until 3 years after symptom onset, highlighting the difficulty of diagnosing a living case of the MM2-type of sCJD. Therefore, establishment of clinical diagnostic criteria for MM2-type of sCJD is required.

Prion-specific and surrogate CSF biomarkers in Creutzfeldt-Jakob disease: diagnostic accuracy in relation to molecular subtypes and analysis of neuropathological correlates of p-tau and Aβ42 levels

The differential diagnosis of Creutzfeldt-Jakob disease (CJD) from other, sometimes treatable, neurological disorders is challenging, owing to the wide phenotypic heterogeneity of the disease. Real-time quaking-induced prion conversion (RT-QuIC) is a novel ultrasensitive in vitro assay, which, at variance with surrogate neurodegenerative biomarker assays, specifically targets the pathological prion protein (PrP^Sc). In the studies conducted to date in CJD, cerebrospinal fluid (CSF) RT-QuIC showed good diagnostic sensitivity (82–96%) and virtually full specificity. In the present study, we investigated the diagnostic value of both prion RT-QuIC and surrogate protein markers in a large patient population with suspected CJD and then evaluated the influence on CSF findings of the CJD type, and the associated amyloid-β (Aβ) and tau neuropathology. RT-QuIC showed an overall diagnostic sensitivity of 82.1% and a specificity of 99.4%. However, sensitivity was lower in CJD types linked to abnormal prion protein (PrP^Sc) type 2 (VV2, MV2K and MM2C) than in typical CJD (MM1). Among surrogate proteins markers (14-3-3, total (t)-tau, and t-tau/phosphorylated (p)-tau ratio) t-tau performed best in terms of both specificity and sensitivity for all sCJD types. Sporadic CJD VV2 and MV2K types demonstrated higher CSF levels of p-tau when compared to other sCJD types and this positively correlated with the amount of tiny tau deposits in brain areas showing spongiform change. CJD patients showed moderately reduced median Aβ42 CSF levels, with 38% of cases having significantly decreased protein levels in the absence of Aβ brain deposits. Our results: (1) support the use of both RT-QuIC and t-tau assays as first line laboratory investigations for the clinical diagnosis of CJD; (2) demonstrate a secondary tauopathy in CJD subtypes VV2 and MV2K, correlating with increased p-tau levels in the CSF and (3) provide novel insight into the issue of the accuracy of CSF p-tau and Aβ42 as markers of brain tauopathy and β-amyloidosis.

Revisiting the Heidenhain Variant of Creutzfeldt-Jakob Disease: Evidence for Prion Type Variability Influencing Clinical Course and Laboratory Findings

The Heidenhain variant defines a peculiar clinical presentation of sporadic Creutzfeldt-Jakob disease (sCJD) characterized by isolated visual disturbances at disease onset and reflecting the early targeting of prions to the occipital cortex. Molecular and histopathological typing, thus far performed in 23 cases, has linked the Heidenhain variant to the MM1 sCJD type. To contribute a comprehensive characterization of cases with the Heidenhain variant, we reviewed a series of 370 definite sCJD cases. Eighteen patients (4.9%) fulfilled the selection criteria. Fourteen of them belonging to sCJD types MM1 or MM1+2C had a short duration of isolated visual symptoms and overall clinical disease, a high prevalence of periodic sharp-wave complexes in EEG, and a marked increase of cerebrospinal fluid proteins t-tau and 14-3-3 levels. In contrast, three cases of the MM 2C or MM 2+1C types showed a longer duration of isolated visual symptoms and overall clinical disease, non-specific EEG findings, and cerebrospinal fluid concentration below threshold for the diagnosis of "probable" CJD of both 14-3-3 and t-tau. However, a brain DWI-MRI disclosed an occipital cortical hyperintensity in the majority of examined cases of both groups. While confirming the strong linkage with the methionine genotype at the polymorphic codon 129 of the prion protein gene, our results definitely establish that the Heidenhain variant can also be associated with the MM 2C sCJD type in addition to the more common MM1 type. Likewise, our results highlight the significant differences in clinical evolution and laboratory findings between cases according to the dominant PrPSc type (type 1 versus type 2).

Creutzfeldt-Jakob disease: updated diagnostic criteria, treatment algorithm, and the utility of brain biopsy

Creutzfeldt-Jakob disease (CJD) is a rare neurodegenerative condition with a rapid disease course and a mortality rate of 100%. Several forms of the disease have been described, and the most common is the sporadic type. The most challenging aspect of this disease is its diagnosis—the gold standard for definitive diagnosis is considered to be histopatho-logical confirmation—but newer tests are providing means for an antemortem diagnosis in ways less invasive than brain biopsy. Imaging studies, electroencephalography, and biomarkers are used in conjunction with the clinical picture to try to make the diagnosis of CJD without brain tissue samples, and all of these are reviewed in this article. The current diagnostic criteria are limited; test sensitivity and specificity varies with the genetics of the disease as well as the clinical stage. Physicians may be unsure of all diagnostic testing available, and may order outdated tests or prematurely request a brain biopsy when the diagnostic workup is incomplete. The authors review CJD, discuss the role of brain biopsy in this patient population, provide a diagnostic pathway for the patient presenting with rapidly progressive dementia, and propose newer diagnostic criteria.

Alternative application of Tau protein in Creutzfeldt-Jakob disease diagnosis: Improvement for weakly positive 14-3-3 protein in the laboratory

The 14-3-3 protein has been used as a biomarker for the diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD). However, weakly positive 14-3-3 leads to false positive results and an incorrect diagnosis. We attempted to use quantitative data for tau protein to provide an accurate diagnosis based on weak 14-3-3 protein. Sixty-two patients with sCJD, including pathologically confirmed, clinically definite, and probable cases, and 89 non-CJD patients were investigated based on a Korean population. Among them, 20 sCJD and 14 non-CJD showed weakly positive 14-3-3. The total tau (t-tau) and phosphorylated tau (p-tau) protein levels were measured by ELISA, and the p-tau to t-tau ratio (p/t ratio) was calculated. The combined use of the 14-3-3 protein assay, t-tau levels, and p/t ratio improved the specificity of diagnosis compared with the use of the 14-3-3 protein assay alone (47% for 14-3-3 alone; 85.94% for 14-3-3 combined with t-tau; 90.62% for 14-3-3 combined with the p/t ratio). In addition, 18 of 20 sCJD and 12 of 14 non-CJD who were weakly positive for 14-3-3 were positive for the p/t ratio and negative for the p/t ratio, respectively. When used in combination with the 14-3-3 protein, the tau protein is useful as a biomarker for the precise diagnosis of sCJD.

[Creutzfeldt-Jakob disease: clinical and diagnostic aspects]

In this article, authors analyzed a modern approach to the diagnosis of Creutzfeldt-Jakob disease (CJD) based on the clinical signs, cerebrospinal fluid markers, electroencephalography and magnetic resonance imaging. It was demonstrated for the first time that patients with late-onset CJD differed from younger CJD patients with respect to MRI profiles and initial clinical presentation. To date, cerebrospinal fluid (CSF) analysis, particularly protein 14-3-3 testing, presents an important approach to the identification of disease cases. A spectrum of differential diagnosis of rapid progressive dementia varied from neurodegenerative dementias to dementia due to acute neurological conditions. Real-time quaking-induced conversion (RT-QuIC) allows the amplification of miniscule amounts of scrapie prion protein. Recent studies applied the RT-QuIC methodology to CSF for the diagnosis of human prion diseases.

Evidence-based guideline: diagnostic accuracy of CSF 14-3-3 protein in sporadic Creutzfeldt-Jakob disease: report of the guideline development subcommittee of the American Academy of Neurology

OBJECTIVE

To assess the available evidence for the diagnostic accuracy of CSF testing for protein 14-3-3 in patients with suspected sporadic Creutzfeldt-Jakob disease (sCJD).

METHODS

The authors performed a systematic review of the available literature from 1995 to January 1, 2011, to identify articles involving patients who were suspected of having sCJD and who had CSF analysis for protein 14-3-3. Studies were rated according to the American Academy of Neurology classification of evidence scheme for diagnostic studies, and recommendations were linked to the strength of the evidence. A pooled estimate of sensitivity and specificity was obtained for all studies rated Class II or higher. The question asked is "Does CSF 14-3-3 protein accurately identify Creutzfeldt-Jakob disease (CJD) in patients with sCJD?"

RESULTS

The analysis was conducted on the basis of samples of 1,849 patients with suspected sCJD from 9 Class II studies. Assays for CSF 14-3-3 protein are probably moderately accurate in diagnosing sCJD: sensitivity 92% (95% confidence interval [CI] 89.8-93.6), specificity 80% (95% CI 77.4-83.0), likelihood ratio of 4.7, and negative likelihood ratio of 0.10.

RECOMMENDATION

For patients who have rapidly progressive dementia and are strongly suspected of having sCJD and for whom diagnosis remains uncertain (pretest probability ∼20%-90%), clinicians should order CSF 14-3-3 assays to reduce the uncertainty of the diagnosis (Level B).

Role of magnetic resonance imaging, cerebrospinal fluid, and electroencephalogram in diagnosis of sporadic Creutzfeldt-Jakob disease

Sporadic Creutzfeldt-Jakob disease (sCJD) is a rapidly progressive dementia (RPD) that can be difficult to identify antemortem, with definitive diagnosis requiring tissue confirmation. We describe the clinical, magnetic resonance imaging (MRI), cerebrospinal fluid (CSF), and electroencephalogram (EEG) measures of a small cohort of 30 patients evaluated for RPD. Clinical and diagnostic measures were cross-sectionally obtained from 17 sCJD patients (15 definite, two probable), 13 non-prion rapidly progressive dementia patients (npRPD), and 18 unimpaired controls. In a subset of patients (nine sCJD and nine npRPD) diffusion tensor imaging (DTI) measures [fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD)] were also obtained for the caudate, corpus callosum, posterior limb of the internal capsule, pulvinar, precuneus, and frontal lobe. Differences among groups were assessed by an analysis of variance. Compared to npRPD individuals, sCJD patients had cerebellar dysfunction, significantly higher CSF tau, "positive" CSF 14-3-3, and hyperintensities on diffusion-weighted imaging (DWI) that met previously established imaging criteria for sCJD. EEG changes were similar for the two groups. In addition, sCJD patients had significant decreases in DTI measures (MD, AD, RD but not FA) within the caudate and pulvinar compared to either npRPD patients or unimpaired controls. Our results confirm that CSF abnormalities and MRI (especially DWI) can assist in distinguishing sCJD patients from npRPD patients. Future longitudinal studies using multiple measures (including CSF and MRI) are needed for evaluating pathological changes seen in sCJD patients.

14-3-3s are potential biomarkers for HIV-related neurodegeneration

Over the last decade, it has become evident that 14-3-3 proteins are essential for primary cell functions. These proteins are abundant throughout the body, including the central nervous system and interact with other proteins in both cell cycle and apoptotic pathways. Examination of cerebral spinal fluid in humans suggests that 14-3-3s including 14-3-3ε (YWHAE) are up-regulated in several neurological diseases, and loss or duplication of the YWHAE gene leads to Miller-Dieker syndrome. The goal of this review is to examine the utility of 14-3-3s as a marker of human immune deficiency virus (HIV)-dependent neurodegeneration and also as a tool to track disease progression. To that end, we describe mechanisms implicating 14-3-3s in neurological diseases and summarize evidence of its interactions with HIV accessory and co-receptor proteins.

Altered Prion protein expression pattern in CSF as a biomarker for Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is the most frequent human Prion-related disorder (PrD). The detection of 14-3-3 protein in the cerebrospinal fluid (CSF) is used as a molecular diagnostic criterion for patients clinically compatible with CJD. However, there is a pressing need for the identification of new reliable disease biomarkers. The pathological mechanisms leading to accumulation of 14-3-3 protein in CSF are not fully understood, however neuronal loss followed by cell lysis is assumed to cause the increase in 14-3-3 levels, which also occurs in conditions such as brain ischemia. Here we investigated the relation between the levels of 14-3-3 protein, Lactate dehydrogenase (LDH) activity and expression of the prion protein (PrP) in CSF of sporadic and familial CJD cases. Unexpectedly, we found normal levels of LDH activity in CJD cases with moderate levels of 14-3-3 protein. Increased LDH activity was only observed in a percentage of the CSF samples that also exhibited high 14-3-3 levels. Analysis of the PrP expression pattern in CSF revealed a reduction in PrP levels in all CJD cases, as well as marked changes in its glycosylation pattern. PrP present in CSF of CJD cases was sensitive to proteases. The alterations in PrP expression observed in CJD cases were not detected in other pathologies affecting the nervous system, including cases of dementia and tropical spastic paraparesis/HTLV-1 associated myelopathy (HAM/TSP). Time course analysis in several CJD patients revealed that 14-3-3 levels in CSF are dynamic and show a high degree of variability during the end stage of the disease. Post-mortem analysis of brain tissue also indicated that 14-3-3 protein is upregulated in neuronal cells, suggesting that its expression is modulated during the course of the disease. These results suggest that a combined analysis of 14-3-3 and PrP expression pattern in CSF is a reliable biomarker to confirm the clinical diagnosis of CJD patients and follow disease progression.

Desmoplakin as a potential candidate for cerebrospinal fluid marker to rule out 14-3-3 false positive rates in sporadic Creutzfeldt-Jakob disease differential diagnosis

BACKGROUND

The detection of a 14-3-3 elevated level in cerebrospinal fluid (CSF) is a part of the diagnostic criteria for probable sporadic Creutzfeldt-Jakob disease (sCJD), as defined by the WHO. However, some pathological conditions associated with acute neuronal damage may result in a positive 14-3-3 test and thereby reduce test specificity in sCJD.

OBJECTIVE

Desmoplakin has been previously identified as up-regulated CSF protein in sCJD and these studies aimed to investigate its diagnostic utility and compare it with two known CSF markers, 14-3-3 and tau.

METHODS AND RESULTS

We tested CSF levels of 14-3-3, tau and desmoplakin in 58 sCJD patients and 81 control patients including 45 cases with an elevated 14-3-3 level due to other disease than sCJD. We detected an elevated CSF level of desmoplakin in 78% of the sCJD patients, while 14-3-3 (88%) and tau (91%) showed a higher positive rate. However, the false positive rate of newly tested desmoplakin was significantly lower in comparison to 14-3-3 and tau, and it accounted for only 11% versus 56% and 35%, respectively. Further reduction of false positive rates was achieved by combination of elevated tau level with a positive desmoplakin test. Moreover, in the non-sCJD group, desmoplakin level did not correlate with the level of both above-mentioned CSF markers, whereas a clear correlation was observed in the sCJD group.

CONCLUSION

Desmoplakin showed a low positive rate accompanied by a very low false positive rate. Thus, we conclude that desmoplakin is a promising candidate for supportive CSF marker to rule out 14-3-3 false positive cases in sCJD differential diagnosis.

Cerebrospinal fluid markers in sporadic Creutzfeldt-Jakob disease

Sporadic Creutzfeldt-Jakob disease (sCJD) is the commonest form of human prion diseases, accounting for about 85% of all cases. Current criteria for intra vitam diagnosis include a distinct phenotype, periodic sharp and slow-wave complexes at electroencephalography (EEG), and a positive 14-3-3-protein assay in the cerebrospinal fluid (CSF). In sCJD, the disease phenotype may vary, depending upon the genotype at codon 129 of the prion protein gene (PRNP), a site of a common methionine/valine polymorphism, and two distinct conformers of the pathological prion protein. Based on the combination of these molecular determinants, six different sCJD subtypes are recognized, each with distinctive clinical and pathologic phenotypes. We analyzed CSF samples from 127 subjects with definite sCJD to assess the diagnostic value of 14-3-3 protein, total tau protein, phosphorylated₁₈₁ tau, and amyloid beta (Aβ) peptide 1-42, either alone or in combination. While the 14-3-3 assay and tau protein levels were the most sensitive indicators of sCJD, the highest sensitivity, specificity and positive predictive value were obtained when all the above markers were combined. The latter approach also allowed a reliable differential diagnosis with other neurodegenerative dementias.

Structural and functional neuroimaging in human prion diseases

INTRODUCTION

Prion diseases are neurodegenerative disorders resulting from the accumulation of a misfolded isoform of the cellular prion protein (PrPc). They can occur as acquired, sporadic, or hereditary forms. Although prion diseases show a wide range of phenotypic variations, pathological features and clinical evolution, they are all characterised by a common unfavourable course and a fatal outcome.

REVIEW SUMMARY

Some variants, such as kuru, have practically disappeared, while others, for example the variant Creutzfeldt-Jakob (vCJD) or those attributable to iatrogenic causes, are still in force and pose a challenge to current medicine. There are no definitive pre-mortem diagnostic tests, except for vCJD, where a tonsil biopsy detects 100% of the cases. For this reason, diagnostic criteria dependent on statistical probability have had to be created. These require complementary examinations, such as an electroencephalogram (EEG) or the detection of 14-3-3 protein in cerebrospinal fluid (CSF). Only the pulvinar sign in magnetic resonance imaging (MRI) has been included as a vCJD diagnostic criterion. The present review discusses neuroimaging findings for each type of prion disease in patients with a definitive histopathological diagnosis.

CONCLUSIONS

The aim is to define the usefulness of these complementary examinations as a tool for the diagnosis of this family of neurodegenerative diseases.

Molecular diagnosis of human prion disease

INTRODUCTION

Human prion diseases (PrDs) are transmissible fatal nervous system disorders with public health implications. They are characterized by the presence of a disease-associated form of the physiological cellular prion protein. Development of diagnostic procedures is important to avoid transmission, including through blood products. Methods used for the detection of disease-associated PrP have implications for other neurodegenerative diseases.

AREAS COVERED

In this review, the authors discuss recent progress in the understanding of the molecular background of phenotypic variability of human PrDs, and the current concepts of molecular diagnosis. Also, the authors provide a critical summary of the diagnostic methods with regard to the molecular subtypes.

EXPERT OPINION

In spite of a lack of specific tests to detect disease-associated PrP in body fluids, the constellation of clinical symptoms, detection of protein 14-3-3 in cerebrospinal fluid, electroencephalogram, cranial MRI and prion protein gene examinations, together have increased the specificity and sensitivity of in vivo diagnostics. As new forms of PrDs are reported, continuous evaluation of their incidence and the search for their etiology is crucial. Recent studies, suggesting prion-like properties of certain proteinopathies associated with Parkinson's or Alzheimer's disease, have again brought PrDs to the center of interest as a model of diseases with disordered protein processing.

Decreased CSF transferrin in sCJD: a potential pre-mortem diagnostic test for prion disorders

Sporadic Creutzfeldt-Jakob-disease (sCJD) is a fatal neurodegenerative condition that escapes detection until autopsy. Recently, brain iron dyshomeostasis accompanied by increased transferrin (Tf) was reported in sCJD cases. The consequence of this abnormality on cerebrospinal-fluid (CSF) levels of Tf is uncertain. We evaluated the accuracy of CSF Tf, a ‘new’ biomarker, as a pre-mortem diagnostic test for sCJD when used alone or in combination with the ‘current’ biomarker total-tau (T-tau). Levels of total-Tf (T-Tf), isoforms of Tf (Tf-1 and Tf-β2), and iron saturation of Tf were quantified in CSF collected 0.3–36 months before death (duration) from 99 autopsy confirmed sCJD (CJD+) and 75 confirmed cases of dementia of non-CJD origin (CJD-). Diagnostic accuracy was estimated by non-parametric tests, logistic regression, and receiver operating characteristic (ROC) analysis. Area under the ROC curve (AUC), sensitivity, specificity, positive and negative predictive values (PV), and likelihood ratios (LR) of each biomarker and biomarker combination were calculated. We report that relative to CJD-, CJD+ cases had lower median CSF T-Tf (125,7093 vs. 217,7893) and higher T-tau (11530 vs. 1266) values. AUC was 0.90 (95% confidence interval (CI), 0.85–0.94) for T-Tf, and 0.93 (95% CI, 0.89–0.97) for T-Tf combined with T-tau. With cut-offs defined to achieve a sensitivity of ∼85%, T-Tf identified CJD+ cases with a specificity of 71.6% (95% CI, 59.1–81.7), positive LR of 3.0 (95% CI, 2.1–4.5), negative LR of 0.2 (95% CI, 0.1–0.3), and accuracy of 80.1%. The effect of patient age and duration was insignificant. T-Tf combined with T-tau identified CJD+ with improved specificity of 87.5% (95%CI, 76.3–94.1), positive LR of 6.8 (95% CI, 3.5–13.1), negative LR of 0.2 (95% CI, 0.1–0.3), positive-PV of 91.0%, negative-PV of 80.0%, and accuracy of 86.2%. Thus, CSF T-Tf, a new biomarker, when combined with the current biomarker T-tau, is a reliable pre-mortem diagnostic test for sCJD.

Phenotypic variability of sporadic human prion disease and its molecular basis: past, present, and future

Human prion diseases are rare neurodegenerative disorders related to prion protein misfolding that can occur as sporadic, familial or acquired forms. In comparison to other more common neurodegenerative disorders, prion diseases show a wider range of phenotypic variation and largely transmit to experimental animals, a feature that led to the isolation and characterization of different strains of the transmissible agent or prion with distinct biological properties. Biochemically distinct PrP(Sc) types have been demonstrated which differ in their size after proteinase cleavage, glycosylation pattern, and possibly other features related to their conformation. These PrP(Sc) types, possibly enciphering the prion strains, together with the naturally occurring polymorphism at codon 129 in the prion protein gene have a major influence on the disease phenotype. In the sporadic form, the most common but perhaps least understood form of human prion disease, there are at least six major combinations of codon 129 genotype and prion protein isotype, which are significantly related to distinctive clinical-pathological subgroups of the disease. In this review, we provide an update on the current knowledge and classification of the disease subtypes of the sporadic human prion diseases as defined by molecular features and pathological changes. Furthermore, we discuss the molecular basis of phenotypic variability taking into account the results of recent transmission studies that shed light on the extent of prion strain variation in humans.

Variably protease-sensitive prionopathy: a new sporadic disease of the prion protein

OBJECTIVE

The objective of the study is to report 2 new genotypic forms of protease-sensitive prionopathy (PSPr), a novel prion disease described in 2008, in 11 subjects all homozygous for valine at codon 129 of the prion protein (PrP) gene (129VV). The 2 new PSPr forms affect individuals who are either homozygous for methionine (129MM) or heterozygous for methionine/valine (129MV).

METHODS

Fifteen affected subjects with 129MM, 129MV, and 129VV underwent comparative evaluation at the National Prion Disease Pathology Surveillance Center for clinical, histopathologic, immunohistochemical, genotypical, and PrP characteristics.

RESULTS

Disease duration (between 22 and 45 months) was significantly different in the 129VV and 129MV subjects. Most other phenotypic features along with the PrP electrophoretic profile were similar but distinguishable in the 3 129 genotypes. A major difference laid in the sensitivity to protease digestion of the disease-associated PrP, which was high in 129VV but much lower, or altogether lacking, in 129MV and 129MM. This difference prompted the substitution of the original designation with "variably protease-sensitive prionopathy" (VPSPr). None of the subjects had mutations in the PrP gene coding region.

INTERPRETATION

Because all 3 129 genotypes are involved, and are associated with distinguishable phenotypes, VPSPr becomes the second sporadic prion protein disease with this feature after Creutzfeldt-Jakob disease, originally reported in 1920. However, the characteristics of the abnormal prion protein suggest that VPSPr is different from typical prion diseases, and perhaps more akin to subtypes of Gerstmann-Sträussler-Scheinker disease.

Open biopsy in patients with acute progressive neurologic decline and absence of mass lesion

OBJECTIVE

Patients with acute to subacute neurologic decline undergo a battery of imaging and laboratory tests to determine a diagnosis and treatment plan. Often, after an extensive evaluation, a brain biopsy is recommended as yet another tool to assist in determining the diagnosis. The goal of this retrospective cohort analysis is to measure the sensitivity of open brain biopsy in this patient population, compare these results with the preoperative presumed diagnosis, and evaluate if the biopsy result significantly alters treatment.

METHODS

The authors reviewed the medical records of 135 consecutive patients who underwent open brain biopsies for acute to subacute progressive neurologic decline between January 1999 and September 2008 at a single institution. All patients with mass lesions, with HIV/AIDS, and who were younger than 20 years of age were excluded from the study. Fifty-one patients met these criteria and all preoperative tests, imaging, and treatment plans were examined and compared with postbiopsy interventions to determine the impact of the biopsy on patient outcome.

RESULTS

The sensitivity of open brain biopsy at our institution was 35%. The most common preoperative presumed diagnosis was vasculitis and the most common postoperative finding was Creutzfeldt-Jakob disease, followed by amyloid angiopathy. Postbiopsy hemorrhage was a complication in 4% of patients. Treatment plans changed as a direct result of the biopsy in 8% of patients, and in only 4% did the biopsy findings make a difference in disease course.

CONCLUSION

In patients with progressive neurologic decline without a radiographic mass lesion or immunodeficiency, open brain biopsy often fails to provide a diagnosis and even more rarely does it significantly alter treatment.

Cerebrospinal fluid biomarkers in human prion diseases

Cerebrospinal fluid (CSF) is the main component of the brain extracellular space and participates in the exchange of many biochemical products in the CNS. Consequently, CSF contains a dynamic and complex mixture of proteins that reflect the physiological or pathological state of the CNS. Changes in the CSF proteome have been described in various neurodegenerative disorders. These alterations are also thought to reflect pathological changes in the brain, and thus understanding them will contribute to a better awareness of the pathophysiology that underlies these disorders. Proteomics offers a new methodology for the analysis of pathological changes and mechanisms occurring in neurodegenerative processes and provides the possibility of novel biomarker discovery in order to supplement faster, earlier and more precise diagnosis. In general, the following criteria have to be applied in order to qualify a protein or a gene as a potential biomarker: the selected parameters have to be sensitive (able to detect the abnormalities at early stage of disease), specific (to allow differential diagnosis), reproducible with a high positive predictive value, and should allow for disease monitoring as well as a potential therapeutic response. In Creutzfeldt–Jakob disease, two major approaches have been followed that aim to detect the pathological form of the prion protein (PrPSc) in various peripheral tissues, while other approaches look for surrogate parameters that are a consequence of the neurodegenerative process. While the amount of abnormal disease-related PrPSc in CSF and blood in human transmissible spongiform encephalopathies appears to be extremely low, the development of a PrPSc-based biomarker was hampered by technical problems and detection limits. However, a variety of other proteins have been investigated in the CSF, and recently a variety of potential biomarkers have been reported that contribute to clinical diagnosis. Already established markers are 14-3-3, β-amyloid, tau-protein and phosphorylated isoforms, S100b, as well as neuron-specific enolase. Since some of these markers display certain limitations, the search continues. This review summarizes current knowledge of biomarker development in prion diseases and discusses perspectives for new approaches.

Updated clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease

Several molecular subtypes of sporadic Creutzfeldt–Jakob disease have been identified and electroencephalogram and cerebrospinal fluid biomarkers have been reported to support clinical diagnosis but with variable utility according to subtype. In recent years, a series of publications have demonstrated a potentially important role for magnetic resonance imaging in the pre-mortem diagnosis of sporadic Creutzfeldt–Jakob disease. Magnetic resonance imaging signal alterations correlate with distinct sporadic Creutzfeldt–Jakob disease molecular subtypes and thus might contribute to the earlier identification of the whole spectrum of sporadic Creutzfeldt–Jakob disease cases. This multi-centre international study aimed to provide a rationale for the amendment of the clinical diagnostic criteria for sporadic Creutzfeldt–Jakob disease. Patients with sporadic Creutzfeldt–Jakob disease and fluid attenuated inversion recovery or diffusion-weight imaging were recruited from 12 countries. Patients referred as ‘suspected sporadic Creutzfeldt–Jakob disease’ but with an alternative diagnosis after thorough follow up, were analysed as controls. All magnetic resonance imaging scans were assessed for signal changes according to a standard protocol encompassing seven cortical regions, basal ganglia, thalamus and cerebellum. Magnetic resonance imaging scans were evaluated in 436 sporadic Creutzfeldt–Jakob disease patients and 141 controls. The pattern of high signal intensity with the best sensitivity and specificity in the differential diagnosis of sporadic Creutzfeldt–Jakob disease was identified. The optimum diagnostic accuracy in the differential diagnosis of rapid progressive dementia was obtained when either at least two cortical regions (temporal, parietal or occipital) or both caudate nucleus and putamen displayed a high signal in fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging. Based on our analyses, magnetic resonance imaging was positive in 83% of cases. In all definite cases, the amended criteria would cover the vast majority of suspected cases, being positive in 98%. Cerebral cortical signal increase and high signal in caudate nucleus and putamen on fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging are useful in the diagnosis of sporadic Creutzfeldt–Jakob disease. We propose an amendment to the clinical diagnostic criteria for sporadic Creutzfeldt–Jakob disease to include findings from magnetic resonance imaging scans.

Magnetic resonance diagnostic markers in clinically sporadic prion disease: a combined brain magnetic resonance imaging and spectroscopy study

The intra vitam diagnosis of prion disease is challenging and a definite diagnosis still requires neuropathological examination in non-familial cases. Magnetic resonance imaging has gained increasing importance in the diagnosis of prion disease. The aim of this study was to compare the usefulness of different magnetic resonance imaging sequences and proton magnetic resonance spectroscopy in the differential diagnosis of patients with rapidly progressive neurological signs compatible with the clinical diagnosis of sporadic prion disease. Twenty-nine consecutive patients with an initial diagnosis of possible or probable sporadic prion disease, on the basis of clinical and electroencephalography features, were recruited. The magnetic resonance protocol included axial fluid-attenuated inversion recovery-T2- and diffusion-weighted images, and proton magnetic resonance spectroscopy of the thalamus, striatum, cerebellum and occipital cortex. Based on the clinical follow-up, genetic studies and neuropathology, the final diagnosis was of prion disease in 14 patients out of 29. The percentage of correctly diagnosed cases was 86% for diffusion-weighted imaging (hyperintensity in the striatum/cerebral cortex), 86% for thalamic N-acetyl-aspartate to creatine ratio (cutoff </=1.21), 90% for thalamic N-acetyl-aspartate to myo-inositol (mI) ratio (cutoff </=1.05) and 86% for cerebral spinal fluid 14-3-3 protein. All the prion disease patients had N-acetyl-aspartate to creatine ratios </=1.21 (100% sensitivity and 100% negative predictive value) and all the non-prion patients had N-acetyl-aspartate to myo-inositol ratios >1.05 (100% specificity and 100% positive predictive value). Univariate logistic regression analysis showed that the combination of thalamic N-acetyl-aspartate to creatine ratio and diffusion-weighted imaging correctly classified 93% of the patients. The combination of thalamic proton magnetic resonance spectroscopy (10 min acquisition duration) and brain diffusion-weighted imaging (2 min acquisition duration) may increase the diagnostic accuracy of the magnetic resonance scan. Both sequences should be routinely included in the clinical work-up of patients with suspected prion disease.