MRI and clinical syndrome in dura mater-related Creutzfeldt-Jakob disease

Syntaxin-6 delays prion protein fibril formation and prolongs the presence of toxic aggregation intermediates

Prions replicate via the autocatalytic conversion of cellular prion protein (PrPC) into fibrillar assemblies of misfolded PrP. While this process has been extensively studied in vivo and in vitro, non-physiological reaction conditions of fibril formation in vitro have precluded the identification and mechanistic analysis of cellular proteins, which may alter PrP self-assembly and prion replication. Here, we have developed a fibril formation assay for recombinant murine and human PrP (23-231) under near-native conditions (NAA) to study the effect of cellular proteins, which may be risk factors or potential therapeutic targets in prion disease. Genetic screening suggests that variants that increase syntaxin-6 expression in the brain (gene: STX6) are risk factors for sporadic Creutzfeldt-Jakob disease. Analysis of the protein in NAA revealed, counterintuitively, that syntaxin-6 is a potent inhibitor of PrP fibril formation. It significantly delayed the lag phase of fibril formation at highly sub-stoichiometric molar ratios. However, when assessing toxicity of different aggregation time points to primary neurons, syntaxin-6 prolonged the presence of neurotoxic PrP species. Electron microscopy and super-resolution fluorescence microscopy revealed that, instead of highly ordered fibrils, in the presence of syntaxin-6 PrP formed less-ordered aggregates containing syntaxin-6. These data strongly suggest that the protein can directly alter the initial phase of PrP self-assembly and, uniquely, can act as an 'anti-chaperone', which promotes toxic aggregation intermediates by inhibiting fibril formation.

Prion therapeutics: Lessons from the past

Prion diseases are a group of incurable zoonotic neurodegenerative diseases (NDDs) in humans and other animals caused by the prion proteins. The abnormal folding and aggregation of the soluble cellular prion proteins (PrPC) into scrapie isoform (PrPSc) in the Central nervous system (CNS) resulted in brain damage and other neurological symptoms. Different therapeutic approaches, including stalling PrPC to PrPSc conversion, increasing PrPSc removal, and PrPC stabilization, for which a spectrum of compounds, ranging from organic compounds to antibodies, have been explored. Additionally, a non-PrP targeted drug strategy using serpin inhibitors has been discussed. Despite numerous scaffolds being screened for anti-prion activity in vitro, only a few were effective in vivo and unfortunately, almost none of them proved effective in the clinical studies, most likely due to toxicity and lack of permeability. Recently, encouraging results from a prion-protein monoclonal antibody, PRN100, were presented in the first human trial on CJD patients, which gives a hope for better future for the discovery of other new molecules to treat prion diseases. In this comprehensive review, we have re-visited the history and discussed various classes of anti-prion agents, their structure, mode of action, and toxicity. Understanding pathogenesis would be vital for developing future treatments for prion diseases. Based on the outcomes of existing therapies, new anti-prion agents could be identified/synthesized/designed with reduced toxicity and increased bioavailability, which could probably be effective in treating prion diseases.

Characterization of Sporadic Creutzfeldt-Jakob Disease and History of Neurosurgery to Identify Potential Iatrogenic Cases

We previously reported a phenotype of Creutzfeldt-Jakob disease (CJD), CJD-MMiK, that could help identify iatrogenic CJD. To find cases mimicking CJD-MMiK, we investigated clinical features and pathology of 1,155 patients with diagnosed sporadic CJD or unclassified CJD with and without history of neurosurgery. Patients with history of neurosurgery more frequently had an absence of periodic sharp-wave complexes on electroencephalogram than patients without a history of neurosurgery. Among 27 patients with history of neurosurgery, 5 had no periodic sharp-wave complexes on electroencephalogram. We confirmed 1 case of CJD-MMiK and suspected another. Both had methionine homozygosity at codon 129 of the prion protein gene and hyperintensity lesions in the thalamus on magnetic resonance images of the brain, which might be a clinical marker of CJD-MMiK. A subgroup with a history of neurosurgery and clinical features mimicking dura mater graft-associated CJD might have been infected during neurosurgery and had symptoms develop after many years.

Altered mRNA and Protein Expression of Monocarboxylate Transporter MCT1 in the Cerebral Cortex and Cerebellum of Prion Protein Knockout Mice

The effect of a cellular prion protein (PrP^c) deficiency on neuroenergetics was primarily analyzed via surveying the expression of genes specifically involved in lactate/pyruvate metabolism, such as monocarboxylate transporters (MCT1, MCT2, MCT4). The aim of the present study was to elucidate a potential involvement of PrP^c in the regulation of energy metabolism in different brain regions. By using quantitative real-time polymerase chain reaction (qRT-PCR), we observed a marked reduction in MCT1 mRNA expression in the cortex of symptomatic Zürich I Prnp^−/− mice, as compared to their wild-type (WT) counterparts. MCT1 downregulation in the cortex was accompanied with significantly decreased expression of the MCT1 functional interplayer, the Na⁺/K⁺ ATPase α2 subunit. Conversely, the MCT1 mRNA level was significantly raised in the cerebellum of Prnp^−/− vs. WT control group, without a substantial change in the Na⁺/K⁺ ATPase α2 subunit expression. To validate the observed mRNA findings, we confirmed the observed change in MCT1 mRNA expression level in the cortex at the protein level. MCT4, highly expressed in tissues that rely on glycolysis as an energy source, exhibited a significant reduction in the hippocampus of Prnp^−/− vs. WT mice. The present study demonstrates that a lack of PrP^c leads to altered MCT1 and MCT4 mRNA/protein expression in different brain regions of Prnp^−/− vs. WT mice. Our findings provide evidence that PrP^c might affect the monocarboxylate intercellular transport, which needs to be confirmed in further studies.

Epilepsy and prion diseases: A narrative review

Epileptic seizures have been described as one feature of prion diseases, but are an unusual clinical presentation. The aim of this narrative Review was to summarize current knowledge of epileptic seizures in the various forms of prion diseases, from a clinical perspective. Examination of the published literature identified no systematic studies; the evidence base is largely anecdotal, consisting mainly of case studies and small case series. Hence, uncertainty prevails as to seizure frequency, semiology, treatment, and pathogenesis in prion diseases. Seizures probably occur in around 10% of sporadic cases but less frequently in iatrogenic and familial forms, with the possible exception of the E200K mutation. The literature suggests a predominance of focal motor and nonconvulsive status epilepticus. Electroencephalographic accompaniments include periodic lateralized or generalized periodic epileptiform discharges (PLEDs, GPEDs), sometimes predating the more typical periodic sharp wave complexes. There are no convincing accounts of successful antiepileptic drug therapy. The underlying mechanisms of epileptogenesis in prion diseases may include loss of cellular prion protein function (PrP^c) and aggregation of abnormally folded prion protein (PrP^Sc). The need for systematic studies and clinical trials to expand the evidence base surrounding epilepsy and prion diseases is evident.

Diffusion-weighted magnetic resonance imaging in dura mater graft-associated Creutzfeldt-Jakob disease

PURPOSE

To elucidate the extension patterns of the hyperintense areas on diffusion-weighted magnetic resonance imaging (DW-MRI) in patients with dura mater graft-associated Creutzfeldt-Jakob disease (dCJD).

METHODS

We collected the DW-MRI of dCJD cases identified by the CJD Surveillance Committee in Japan, between April 1999 and February 2018. The dCJD cases were classified into non-plaque and plaque-types. The relationship among the abnormal signals, the pathological classification, and the sites of grafting were analyzed.

RESULTS

We collected DW-MRI of 11 patients with dCJD, all of whom were methionine homozygous at codon 129 of the prion protein gene. The age at onset was 41 (26-76) [median (range)] years, the age at dural grafting was 19 (10-53) years, and the incubation period was 22 (16-29) years. Eight dCJD cases were classified as non-plaque-type and three cases were plaque-type. Five of the non-plaque-type cases and all the plaque-type cases were pathologically confirmed. Brain DW-MRI was performed 3 (1-22) months after the onset. Most of the non-plaque-type cases showed brighter hyperintensity in the cerebral cortex and basal ganglia on the side of dural grafting. Subsequent DW-MRI showed widespread hyperintense lesions in the brain. Regarding the plaque-type cases, initial scans showed hyperintensity in the basal ganglia and the thalamus in one patient. Another patient's lesion was confined to the basal ganglia. The third patient showed no abnormalities seven months post-onset; however, serial images showed a hyperintensity confined to the thalamus.

CONCLUSIONS

Non-plaque and plaque-types demonstrated different patterns of propagation of distinct prion strains.

Identification of novel risk loci and causal insights for sporadic Creutzfeldt-Jakob disease: a genome-wide association study

BACKGROUND

Human prion diseases are rare and usually rapidly fatal neurodegenerative disorders, the most common being sporadic Creutzfeldt-Jakob disease (sCJD). Variants in the PRNP gene that encodes prion protein are strong risk factors for sCJD but, although the condition has similar heritability to other neurodegenerative disorders, no other genetic risk loci have been confirmed. We aimed to discover new genetic risk factors for sCJD, and their causal mechanisms.

METHODS

We did a genome-wide association study of sCJD in European ancestry populations (patients diagnosed with probable or definite sCJD identified at national CJD referral centres) with a two-stage study design using genotyping arrays and exome sequencing. Conditional, transcriptional, and histological analyses of implicated genes and proteins in brain tissues, and tests of the effects of risk variants on clinical phenotypes, were done using deep longitudinal clinical cohort data. Control data from healthy individuals were obtained from publicly available datasets matched for country.

FINDINGS

Samples from 5208 cases were obtained between 1990 and 2014. We found 41 genome-wide significant single nucleotide polymorphisms (SNPs) and independently replicated findings at three loci associated with sCJD risk; within PRNP (rs1799990; additive model odds ratio [OR] 1·23 [95% CI 1·17-1·30], p=2·68 × 10^-15; heterozygous model p=1·01 × 10^-135), STX6 (rs3747957; OR 1·16 [1·10-1·22], p=9·74 × 10^-9), and GAL3ST1 (rs2267161; OR 1·18 [1·12-1·25], p=8·60 × 10^-10). Follow-up analyses showed that associations at PRNP and GAL3ST1 are likely to be caused by common variants that alter the protein sequence, whereas risk variants in STX6 are associated with increased expression of the major transcripts in disease-relevant brain regions.

INTERPRETATION

We present, to our knowledge, the first evidence of statistically robust genetic associations in sporadic human prion disease that implicate intracellular trafficking and sphingolipid metabolism as molecular causal mechanisms. Risk SNPs in STX6 are shared with progressive supranuclear palsy, a neurodegenerative disease associated with misfolding of protein tau, indicating that sCJD might share the same causal mechanisms as prion-like disorders.

FUNDING

Medical Research Council and the UK National Institute of Health Research in part through the Biomedical Research Centre at University College London Hospitals National Health Service Foundation Trust.

Diagnostic Accuracy of Prion Disease Biomarkers in Iatrogenic Creutzfeldt-Jakob Disease

Human prion diseases are classified into sporadic, genetic, and acquired forms. Within this last group, iatrogenic Creutzfeldt-Jakob disease (iCJD) is caused by human-to-human transmission through surgical and medical procedures. After reaching an incidence peak in the 1990s, it is believed that the iCJD historical period is probably coming to an end, thanks to lessons learnt from past infection sources that promoted new prion prevention and decontamination protocols. At this point, we sought to characterise the biomarker profile of iCJD and compare it to that of sporadic CJD (sCJD) for determining the value of available diagnostic tools in promptly recognising iCJD cases. To that end, we collected 23 iCJD samples from seven national CJD surveillance centres and analysed the electroencephalogram and neuroimaging data together with a panel of seven CSF biomarkers: 14-3-3, total tau, phosphorylated/total tau ratio, alpha-synuclein, neurofilament light, YKL-40, and real-time quaking induced conversion of prion protein. Using the cut-off values established for sCJD, we found the sensitivities of these biomarkers for iCJD to be similar to those described for sCJD. Given the limited relevant information on this issue to date, the present study validates the use of current sCJD biomarkers for the diagnosis of future iCJD cases.

Interventions to reduce the risk of surgically transmitted Creutzfeldt-Jakob disease: a cost-effective modelling review

BACKGROUND

Creutzfeldt-Jakob disease is a fatal neurological disease caused by abnormal infectious proteins called prions. Prions that are present on surgical instruments cannot be completely deactivated; therefore, patients who are subsequently operated on using these instruments may become infected. This can result in surgically transmitted Creutzfeldt-Jakob disease.

OBJECTIVE

To update literature reviews, consultation with experts and economic modelling published in 2006, and to provide the cost-effectiveness of strategies to reduce the risk of surgically transmitted Creutzfeldt-Jakob disease.

METHODS

Eight systematic reviews were undertaken for clinical parameters. One review of cost-effectiveness was undertaken. Electronic databases including MEDLINE and EMBASE were searched from 2005 to 2017. Expert elicitation sessions were undertaken. An advisory committee, convened by the National Institute for Health and Care Excellence to produce guidance, provided an additional source of information. A mathematical model was updated focusing on brain and posterior eye surgery and neuroendoscopy. The model simulated both patients and instrument sets. Assuming that there were potentially 15 cases of surgically transmitted Creutzfeldt-Jakob disease between 2005 and 2018, approximate Bayesian computation was used to obtain samples from the posterior distribution of the model parameters to generate results. Heuristics were used to improve computational efficiency. The modelling conformed to the National Institute for Health and Care Excellence reference case. The strategies evaluated included neither keeping instruments moist nor prohibiting set migration; ensuring that instruments were kept moist; prohibiting instrument migration between sets; and employing single-use instruments. Threshold analyses were undertaken to establish prices at which single-use sets or completely effective decontamination solutions would be cost-effective.

RESULTS

A total of 169 papers were identified for the clinical review. The evidence from published literature was not deemed sufficiently strong to take precedence over the distributions obtained from expert elicitation. Forty-eight papers were identified in the review of cost-effectiveness. The previous modelling structure was revised to add the possibility of misclassifying surgically transmitted Creutzfeldt-Jakob disease as another neurodegenerative disease, and assuming that all patients were susceptible to infection. Keeping instruments moist was estimated to reduce the risk of surgically transmitted Creutzfeldt-Jakob disease cases and associated costs. Based on probabilistic sensitivity analyses, keeping instruments moist was estimated to on average result in 2.36 (range 0-47) surgically transmitted Creutzfeldt-Jakob disease cases (across England) caused by infection occurring between 2019 and 2023. Prohibiting set migration or employing single-use instruments reduced the estimated risk of surgically transmitted Creutzfeldt-Jakob disease cases further, but at considerable cost. The estimated costs per quality-adjusted life-year gained of these strategies in addition to keeping instruments moist were in excess of £1M. It was estimated that single-use instrument sets (currently £350-500) or completely effective cleaning solutions would need to cost approximately £12 per patient to be cost-effective using a £30,000 per quality-adjusted life-year gained value.

LIMITATIONS

As no direct published evidence to implicate surgery as a cause of Creutzfeldt-Jakob disease has been found since 2005, the estimations of potential cases from elicitation are still speculative. A particular source of uncertainty was in the number of potential surgically transmitted Creutzfeldt-Jakob disease cases that may have occurred between 2005 and 2018.

CONCLUSIONS

Keeping instruments moist is estimated to reduce the risk of surgically transmitted Creutzfeldt-Jakob disease cases and associated costs. Further surgical management strategies can reduce the risks of surgically transmitted Creutzfeldt-Jakob disease but have considerable associated costs.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42017071807.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 11. See the NIHR Journals Library website for further project information.

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.

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%).

Sporadic and Infectious Human Prion Diseases

Human prion diseases are rare neurodegenerative diseases that have become the subject of public and scientific interest because of concerns about interspecies transmission and the unusual biological properties of the causal agents: prions. These diseases are unique in that they occur in sporadic, hereditary, and infectious forms that are characterized by an extended incubation period between exposure to infection and the development of clinical illness. Silent infection can be present in peripheral tissues during the incubation period, which poses a challenge to public health, especially because prions are relatively resistant to standard decontamination procedures. Despite intense research efforts, no effective treatment has been developed for human prion diseases, which remain uniformly fatal.

Ethics in prion disease

This paper is intended to discuss some of the scientific and ethical issues that are created by increased research efforts towards earlier diagnosis, as well as to treatment of, human prion diseases (and related dementias), including the resulting consequences for individuals, their families, and society. Most patients with prion disease currently are diagnosed when they are about 2/3 of the way through their disease course (Geschwind et al., 2010a; Paterson et al., 2012b), when the disease has progressed so far that even treatments that stop the disease process would probably have little benefit. Although there are currently no treatments available for prion diseases, we and others have realized that we must diagnose patients earlier and with greater accuracy so that future treatments have hope of success. As approximately 15% of prion diseases have a autosomal dominant genetic etiology, this further adds to the complexity of ethical issues, particularly regarding when to conduct genetic testing, release of genetic results, and when or if to implement experimental therapies. Human prion diseases are both infectious and transmissible; great care is required to balance the needs of the family and individual with both public health needs and strained hospital budgets. It is essential to proactively examine and address the ethical issues involved, as well as to define and in turn provide best standards of care.

Neuroimaging biomarkers of neurodegenerative diseases and dementia

Neurodegenerative disorders leading to dementia are common diseases that affect many older and some young adults. Neuroimaging methods are important tools for assessing and monitoring pathological brain changes associated with progressive neurodegenerative conditions. In this review, the authors describe key findings from neuroimaging studies (magnetic resonance imaging and radionucleotide imaging) in neurodegenerative disorders, including Alzheimer's disease (AD) and prodromal stages, familial and atypical AD syndromes, frontotemporal dementia, amyotrophic lateral sclerosis with and without dementia, Parkinson's disease with and without dementia, dementia with Lewy bodies, Huntington's disease, multiple sclerosis, HIV-associated neurocognitive disorder, and prion protein associated diseases (i.e., Creutzfeldt-Jakob disease). The authors focus on neuroimaging findings of in vivo pathology in these disorders, as well as the potential for neuroimaging to provide useful information for differential diagnosis of neurodegenerative disorders.

Cerebrospinal fluid biomarker supported diagnosis of Creutzfeldt-Jakob disease and rapid dementias: a longitudinal multicentre study over 10 years

To date, cerebrospinal fluid analysis, particularly protein 14-3-3 testing, presents an important approach in the identification of Creutzfeldt–Jakob disease cases. However, one special point of criticism of 14-3-3 testing is the specificity in the differential diagnosis of rapid dementia. The constant observation of increased cerebrospinal fluid referrals in the national surveillance centres over the last years raises the concern of declining specificity due to higher number of cerebrospinal fluid tests performed in various neurological conditions. Within the framework of a European Community supported longitudinal multicentre study (‘cerebrospinal fluid markers’) we analysed the spectrum of rapid progressive dementia diagnoses, their potential influence on 14-3-3 specificity as well as results of other dementia markers (tau, phosphorylated tau and amyloid-β_1–42) and evaluated the specificity of 14-3-3 in Creutzfeldt–Jakob disease diagnosis for the years 1998–2008. A total of 29 022 cerebrospinal fluid samples were analysed for 14-3-3 protein and other cerebrospinal fluid dementia markers in patients with rapid dementia and suspected Creutzfeldt–Jakob disease in the participating centres. In 10 731 patients a definite diagnosis could be obtained. Protein 14-3-3 specificity was analysed for Creutzfeldt–Jakob disease with respect to increasing cerebrospinal fluid tests per year and spectrum of differential diagnosis. Ring trials were performed to ensure the comparability between centres during the reported time period. Protein 14-3-3 test specificity remained high and stable in the diagnosis of Creutzfeldt–Jakob disease during the observed time period across centres (total specificity 92%; when compared with patients with definite diagnoses only: specificity 90%). However, test specificity varied with respect to differential diagnosis. A high 14-3-3 specificity was obtained in differentiation to other neurodegenerative diseases (95–97%) and non-neurological conditions (91–97%). We observed lower specificity in the differential diagnoses of acute neurological diseases (82–87%). A marked and constant increase in cerebrospinal fluid test referrals per year in all centres did not influence 14-3-3 test specificity and no change in spectrum of differential diagnosis was observed. Cerebrospinal fluid protein 14-3-3 detection remains an important test in the diagnosis of Creutzfeldt–Jakob disease. Due to a loss in specificity in acute neurological events, the interpretation of positive 14-3-3 results needs to be performed in the clinical context. The spectrum of differential diagnosis of rapid progressive dementia varied from neurodegenerative dementias to dementia due to acute neurological conditions such as inflammatory diseases and non-neurological origin.

Imaging of prion diseases

Prion diseases are caused by self-replicating proteins that induce lethal neurodegenerative disorders. In the last decade, the understanding of the different clinical, pathological, and neuroimaging phenotypes of this group of disorders has evolved paralleling the advances in prion molecular biology. From an imaging standpoint, the implementation of diffusion-weighted imaging in routine practice has markedly facilitated the detection of prion diseases, especially Creutzfeldt-Jakob. Less frequent prion-related disorders, including genetic diseases, may also benefit from progresses in the field of quantitative diffusion-weighted imaging, MR spectroscopy or molecular imaging. Herein, we present a review of the neuroimaging features of the prion disorders known to affect humans emphasizing the important contribution of MRI in the diagnosis of this group of disorders.

Dura mater graft-associated Creutzfeldt-Jakob disease: the first case in Korea

Since 1987, dura mater graft-associated iatrogenic Creutzfeldt-Jakob disease (dCJD) has been reported in many countries. We report the first case of dCJD in Korea. A 54-yr-old woman, who underwent resection of the meningioma in the left frontal region and received a dura mater graft 23 yr ago presented with dysesthesia followed by psychiatric symptoms and ataxia. Her neurological symptoms rapidly progressed to such an extent that she exhibited myoclonus, dementia, and pyramidal and extrapyramidal signs within 8 weeks. The 14-3-3 protein was detected in her cerebrospinal fluid; however, an electroencephalogram did not reveal characteristic positive sharp wave complexes. Diffusion-weighted magnetic resonance images, obtained serially over 64 days, revealed the rapid progression of areas of high signal intensity in the caudate nucleus and cingulate gyrus to widespread areas of high signal intensity in the cortex and basal ganglia. Pathological examination of brain biopsy specimens confirmed the presence of spongiform changes and deposition of prion protein in the neurons and neuropils.

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.