Mechanism of enterovirus VP0 maturation cleavage based on the structure of a stabilised assembly intermediate

Molecular details of genome packaging are little understood for the majority of viruses. In enteroviruses (EVs), cleavage of the structural protein VP0 into VP4 and VP2 is initiated by the incorporation of RNA into the assembling virion and is essential for infectivity. We have applied a combination of bioinformatic, molecular and structural approaches to generate the first high-resolution structure of an intermediate in the assembly pathway, termed a provirion, which contains RNA and intact VP0. We have demonstrated an essential role of VP0 E096 in VP0 cleavage independent of RNA encapsidation and generated a new model of capsid maturation, supported by bioinformatic analysis. This provides a molecular basis for RNA-dependence, where RNA induces conformational changes required for VP0 maturation, but that RNA packaging itself is not sufficient to induce maturation. These data have implications for understanding production of infectious virions and potential relevance for future vaccine and antiviral drug design.

Amino acid substitutions in norovirus VP1 dictate host dissemination via variations in cellular attachment

IMPORTANCE

All viruses initiate infection by utilizing receptors to attach to target host cells. These virus-receptor interactions can therefore dictate viral replication and pathogenesis. Understanding the nature of virus-receptor interactions could also be important for the development of novel therapies. Noroviruses are non-enveloped icosahedral viruses of medical importance. They are a common cause of acute gastroenteritis with no approved vaccine or therapy and are a tractable model for studying fundamental virus biology. In this study, we utilized the murine norovirus model system to show that variation in a single amino acid of the major capsid protein alone can affect viral infectivity through improved attachment to suspension cells. Modulating plasma membrane mobility reduced infectivity, suggesting an importance of membrane mobility for receptor recruitment and/or receptor conformation. Furthermore, different substitutions at this site altered viral tissue distribution in a murine model, illustrating how in-host capsid evolution could influence viral infectivity and/or immune evasion.

Production of antigenically stable enterovirus A71 virus-like particles in Pichia pastoris as a vaccine candidate

Enterovirus A71 (EVA71) causes widespread disease in young children with occasional fatal consequences. In common with other picornaviruses, both empty capsids (ECs) and infectious virions are produced during the viral lifecycle. While initially antigenically indistinguishable from virions, ECs readily convert to an expanded conformation at moderate temperatures. In the closely related poliovirus, these conformational changes result in loss of antigenic sites required to elicit protective immune responses. Whether this is true for EVA71 remains to be determined and is the subject of this investigation.We previously reported the selection of a thermally resistant EVA71 genogroup B2 population using successive rounds of heating and passage. The mutations found in the structural protein-coding region of the selected population conferred increased thermal stability to both virions and naturally produced ECs. Here, we introduced these mutations into a recombinant expression system to produce stabilized virus-like particles (VLPs) in Pichia pastoris.The stabilized VLPs retain the native virion-like antigenic conformation as determined by reactivity with a specific antibody. Structural studies suggest multiple potential mechanisms of antigenic stabilization, however, unlike poliovirus, both native and expanded EVA71 particles elicited antibodies able to directly neutralize virus in vitro. Therefore, anti-EVA71 neutralizing antibodies are elicited by sites which are not canonically associated with the native conformation, but whether antigenic sites specific to the native conformation provide additional protective responses in vivo remains unclear. VLPs are likely to provide cheaper and safer alternatives for vaccine production and these data show that VLP vaccines are comparable with inactivated virus vaccines at inducing neutralising antibodies.

Amino acid substitutions in norovirus VP1 dictate cell tropism via an attachment process dependent on membrane mobility

Viruses interact with receptors on the cell surface to initiate and co-ordinate infection. The distribution of receptors on host cells can be a key determinant of viral tropism and host infection. Unravelling the complex nature of virus-receptor interactions is, therefore, of fundamental importance to understanding viral pathogenesis. Noroviruses are non-enveloped, icosahedral, positive-sense RNA viruses of global importance to human health, with no approved vaccine or antiviral agent available. Here we use murine norovirus as a model for the study of molecular mechanisms of virus-receptor interactions. We show that variation at a single amino acid residue in the major viral capsid protein had a key impact on the interaction between virus and receptor. This variation did not affect virion production or virus growth kinetics, but a specific amino acid was rapidly selected through evolution experiments, and significantly improved cellular attachment when infecting immune cells in suspension. However, reducing plasma membrane mobility counteracted this phenotype, providing insight into for the role of membrane fluidity and receptor recruitment in norovirus cellular attachment. When the infectivity of a panel of recombinant viruses with single amino acid variations was compared in vivo, there were significant differences in the distribution of viruses in a murine model, demonstrating a role in cellular tropism in vivo. Overall, these results highlight the importance of lipid rafts and virus-induced receptor recruitment in viral infection, as well as how capsid evolution can greatly influence cellular tropism, within-host spread and pathogenicity.

Production of antigenically stable enterovirus A71 virus-like particles in Pichia pastoris as a vaccine candidate

Enterovirus A71 (EVA71) causes widespread disease in young children with occasional fatal consequences. In common with other picornaviruses, both empty capsids (ECs) and infectious virions are produced during the viral lifecycle. While initially antigenically indistinguishable from virions, ECs readily convert to an expanded conformation at moderate temperatures. In the closely related poliovirus, these conformational changes result in loss of antigenic sites required to elicit protective immune responses. Whether this is true for EVA71 remains to be determined and is the subject of this investigation. We previously reported the selection of a thermally resistant EVA71 genogroup B2 population using successive rounds of heating and passage. The mutations found in the structural protein-coding region of the selected population conferred increased thermal stability to both virions and naturally produced ECs. Here, we introduced these mutations into a recombinant expression system to produce stabilised virus-like particles (VLPs) in Pichia pastoris . The stabilised VLPs retain the native virion-like antigenic conformation as determined by reactivity with a specific antibody. Structural studies suggest multiple potential mechanisms of antigenic stabilisation, however, unlike poliovirus, both native and expanded EVA71 particles elicited antibodies able to directly neutralise virus in vitro . Therefore, the anti-EVA71 neutralising antibodies are elicited by sites which are not canonically associated with the native conformation, but whether antigenic sites specific to the native conformation provide additional protective responses in vivo remains unclear. VLPs are likely to provide cheaper and safer alternatives for vaccine production and these data show that VLP vaccines are comparable with inactivated virus vaccines at inducing neutralising antibodies.

Thermal stabilization of enterovirus A 71 and production of antigenically stabilized empty capsids

Enterovirus A71 (EVA71) infection can result in paralysis and may be fatal. In common with other picornaviruses, empty capsids are produced alongside infectious virions during the viral lifecycle. These empty capsids are antigenically indistinguishable from infectious virus, but at moderate temperatures they are converted to an expanded conformation. In the closely related poliovirus, native and expanded antigenic forms of particle have different long-term protective efficacies when used as vaccines. The native form provides long-lived protective immunity, while expanded capsids fail to generate immunological protection. Whether this is true for EVA71 remains to be determined. Here, we selected an antigenically stable EVA71 virus population using successive rounds of heating and passage and characterized the antigenic conversion of both virions and empty capsids. The mutations identified within the heated passaged virus were dispersed across the capsid, including at key sites associated with particle expansion. The data presented here indicate that the mutant sequence may be a useful resource to address the importance of antigenic conformation in EVA71 vaccines.

Structural insight into Pichia pastoris fatty acid synthase

Type I fatty acid synthases (FASs) are critical metabolic enzymes which are common targets for bioengineering in the production of biofuels and other products. Serendipitously, we identified FAS as a contaminant in a cryoEM dataset of virus-like particles (VLPs) purified from P. pastoris, an important model organism and common expression system used in protein production. From these data, we determined the structure of P. pastoris FAS to 3.1 Å resolution. While the overall organisation of the complex was typical of type I FASs, we identified several differences in both structural and enzymatic domains through comparison with the prototypical yeast FAS from S. cerevisiae. Using focussed classification, we were also able to resolve and model the mobile acyl-carrier protein (ACP) domain, which is key for function. Ultimately, the structure reported here will be a useful resource for further efforts to engineer yeast FAS for synthesis of alternate products.

Functional advantages of triplication of the 3B coding region of the FMDV genome

For gene duplication to be maintained, particularly in the small genomes of RNA viruses, this should offer some advantages. We have investigated the functions of a small protein termed VPg or 3B, which acts as a primer in the replication of foot-and-mouth disease virus (FMDV). Many related picornaviruses encode a single copy but uniquely the FMDV genome includes three (nonidentical) copies of the 3B coding region. Using sub-genomic replicons incorporating nonfunctional 3Bs and 3B fusion products in competition and complementation assays, we investigated the contributions of individual 3Bs to replication and the structural requirements for functionality. We showed that a free N-terminus is required for 3B to function as a primer and although a single 3B can support genome replication, additional copies provide a competitive advantage. However, a fourth copy confers no further advantage. Furthermore, we find that a minimum of two 3Bs is necessary for trans replication of FMDV replicons, which is unlike other picornaviruses where a single 3B can be used for both cis and trans replication. Our data are consistent with a model in which 3B copy number expansion within the FMDV genome has allowed evolution of separate cis and trans acting functions, providing selective pressure to maintain multiple copies of 3B.

Histone deacetylase 4 promotes type I interferon signaling, restricts DNA viruses, and is degraded via vaccinia virus protein C6

Interferons (IFNs) represent an important host defense against viruses. Type I IFNs induce JAK-STAT signaling and expression of IFN-stimulated genes (ISGs), which mediate antiviral activity. Histone deacetylases (HDACs) perform multiple functions in regulating gene expression and some class I HDACs and the class IV HDAC, HDAC11, influence type I IFN signaling. Here, HDAC4, a class II HDAC, is shown to promote type I IFN signaling and coprecipitate with STAT2. Pharmacological inhibition of class II HDAC activity, or knockout of HDAC4 from HEK-293T and HeLa cells, caused a defective response to IFN-α. This defect in HDAC4-/- cells was rescued by reintroduction of HDAC4 or catalytically inactive HDAC4, but not HDAC1 or HDAC5. ChIP analysis showed HDAC4 was recruited to ISG promoters following IFN stimulation and was needed for binding of STAT2 to these promoters. The biological importance of HDAC4 as a virus restriction factor was illustrated by the observations that (i) the replication and spread of vaccinia virus (VACV) and herpes simplex virus type 1 (HSV-1) were enhanced in HDAC4-/- cells and inhibited by overexpression of HDAC4; and (ii) HDAC4 is targeted for proteasomal degradation during VACV infection by VACV protein C6, a multifunctional IFN antagonist that coprecipitates with HDAC4 and is necessary and sufficient for HDAC4 degradation.

The Structure of an Infectious Human Polyomavirus and Its Interactions with Cellular Receptors

BK polyomavirus (BKV) causes polyomavirus-associated nephropathy and hemorrhagic cystitis in immunosuppressed patients. These are diseases for which we currently have limited treatment options, but potential therapies could include pre-transplant vaccination with a multivalent BKV vaccine or therapeutics which inhibit capsid assembly or block attachment and entry into target cells. A useful tool in such efforts would be a high-resolution structure of the infectious BKV virion and how this interacts with its full repertoire of cellular receptors. We present the 3.4-Å cryoelectron microscopy structure of native, infectious BKV in complex with the receptor fragment of GT1b ganglioside. We also present structural evidence that BKV can utilize glycosaminoglycans as attachment receptors. This work highlights features that underpin capsid stability and provides a platform for rational design and development of urgently needed pharmacological interventions for BKV-associated diseases.

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Present the cryo-EM structure of native, infectious BKV virion at 3.4 Å resolution

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Reveal interpentamer interactions that mediate capsid assembly

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Determine the interaction of BKV with a receptor fragment of GT1b ganglioside

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Identify possible sites for glycosaminoglycan binding on the virion surface

Vaccinia Virus Protein C6 Inhibits Type I IFN Signalling in the Nucleus and Binds to the Transactivation Domain of STAT2

The type I interferon (IFN) response is a crucial innate immune signalling pathway required for defense against viral infection. Accordingly, the great majority of mammalian viruses possess means to inhibit this important host immune response. Here we show that vaccinia virus (VACV) strain Western Reserve protein C6, is a dual function protein that inhibits the cellular response to type I IFNs in addition to its published function as an inhibitor of IRF-3 activation, thereby restricting type I IFN production from infected cells. Ectopic expression of C6 inhibits the induction of interferon stimulated genes (ISGs) in response to IFNα treatment at both the mRNA and protein level. C6 inhibits the IFNα-induced Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathway at a late stage, downstream of STAT1 and STAT2 phosphorylation, nuclear translocation and binding of the interferon stimulated gene factor 3 (ISGF3) complex to the interferon stimulated response element (ISRE). Mechanistically, C6 associates with the transactivation domain of STAT2 and this might explain how C6 inhibits the type I IFN signalling very late in the pathway. During virus infection C6 reduces ISRE-dependent gene expression despite the presence of the viral protein phosphatase VH1 that dephosphorylates STAT1 and STAT2. The ability of a cytoplasmic replicating virus to dampen the immune response within the nucleus, and the ability of viral immunomodulators such as C6 to inhibit multiple stages of the innate immune response by distinct mechanisms, emphasizes the intricacies of host-pathogen interactions and viral immune evasion.

In response to a viral infection, infected host cells mount an early, innate immune response to limit viral replication and spread. Type I interferons (IFNs) are produced by a cell when a viral infection is detected and are a crucial aspect of this early immune response. IFNs are released from the infected cell and can act on the infected cell itself or neighbouring cells to initiate a signalling pathway that results in the production of hundreds of anti-viral proteins. In this work we investigated a vaccinia virus protein called C6, a known inhibitor of type I IFN production. Here we show that C6 also inhibits signalling initiated in response to type I IFNs, therefore providing a dual defence against this essential immune response. The results show that, unlike the majority of viral inhibitors of IFN signalling, C6 inhibits the signalling pathway at a late stage once the proteins required for IFN-stimulated gene transcription have reached the nucleus and bound to the DNA. This work illustrates the complex relationship between infecting viruses and the host immune response and further investigation of the mechanism by which C6 inhibits this important immune pathway will likely increase our knowledge of the pathway itself.

Neurodegeneration in frontotemporal lobar degeneration and motor neurone disease associated with expansions in C9orf72 is linked to TDP-43 pathology and not associated with aggregated forms of dipeptide repeat proteins

Aims

A hexanucleotide expansion in C9orf72 is the major genetic cause of inherited behavioural variant Frontotemporal dementia (bvFTD) and motor neurone disease (MND), although the pathological mechanism(s) underlying disease remains uncertain.

Methods

Using antibodies to poly‐GA, poly‐GP, poly‐GR, poly‐AP and poly‐PR proteins, we examined sections of cerebral cortex, hippocampus, thalamus, cerebellum and spinal cord, from 20 patients with bvFTD and/or MND bearing an expansion in C9orf72 for aggregated deposits of dipeptide repeat proteins (DPR).

Results

Antibodies to poly‐GA, poly‐GP and poly‐GR detected numerous rounded cytoplasmic inclusions (NCI) within granule cells of hippocampal dentate gyrus and those of the cerebellum, as well as ‘star‐burst’ shaped NCI in pyramidal neurones of CA3/4 region of hippocampus. NCI were uncommon in Purkinje cells, and only very rarely seen in anterior horn cells. Poly‐PA antibody detected occasional NCI within CA3/4 neurones alone, whereas poly‐PR antibody did not identify any NCI but immunostained the nucleus of anterior horn cells, CA3/4 neurones and Purkinje cells, in patients with or without expansion in C9orf72, as well as in normal controls. Poly‐GA antibody generally detected more DPR than poly‐GP, which in turn was greater than poly‐GR. All patients with bvFTD + MND or MND showed plentiful p62/TDP‐43 positive inclusions in remaining anterior horn cells.

Conclusion

Degeneration and loss of anterior horn cells associated with expansions in C9orf72 occurs in the absence of DPR, and implies that changes involving loss of nuclear staining for and a cytoplasmic aggregation of TDP‐43 are more likely to be the cause of this.

Nuclear carrier and RNA-binding proteins in frontotemporal lobar degeneration associated with fused in sarcoma (FUS) pathological changes

AIMS

We aimed to investigate the role of the nuclear carrier and binding proteins, transportin 1 (TRN1) and transportin 2 (TRN2), TATA-binding protein-associated factor 15 (TAF15) and Ewing's sarcoma protein (EWS) in inclusion body formation in cases of frontotemporal lobar degeneration (FTLD) associated with fused in sarcoma protein (FTLD-FUS).

METHODS

Eight cases of FTLD-FUS (five cases of atypical FTLD-U, two of neuronal intermediate filament inclusion body disease and one of basophilic inclusion body disease) were immunostained for FUS, TRN1, TRN2, TAF15 and EWS. Ten cases of FTLD associated with TDP-43 inclusions served as reference cases.

RESULTS

The inclusion bodies in FTLD-FUS contained TRN1 and TAF15 and, to a lesser extent, EWS, but not TRN2. The patterns of immunostaining for TRN1 and TAF15 were very similar to that of FUS. None of these proteins was associated with tau or TDP-43 aggregations in FTLD.

CONCLUSIONS

Data suggest that FUS, TRN1 and TAF15 may participate in a functional pathway in an interdependent way, and imply that the function of TDP-43 may not necessarily be in parallel with, or complementary to, that of FUS, despite each protein sharing many similar structural elements.

Foreign accent syndrome as the initial sign of primary progressive aphasia

Foreign accent syndrome (FAS) is a rare speech disorder characterised by the emergence of a new accent, perceived by listeners as foreign. FAS has usually been described following focal brain insults, such as stroke. We describe the unusual case of a woman presenting with FAS as the earliest symptom of progressive degenerative brain disease. At presentation, she showed no language or other cognitive impairment, and functional and structural brain imaging were normal. Follow-up 1 year later revealed the emergence of mild expressive language problems. Repeat functional neuroimaging showed mild hypoperfusion of the perisylvian speech area of the left hemisphere, and structural imaging showed mild left perisylvian atrophy. We interpret the case as an unusual presentation of primary progressive non-fluent aphasia. The case provides further evidence of the variable and circumscribed nature of the clinical presentation of focal cerebral degeneration.

Accuracy of single-photon emission computed tomography in differentiating frontotemporal dementia from Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are the commonest causes of presenile dementia. In the absence of a biological marker, diagnosis is reliant on clinical evaluation. Confirmation is often sought from neuroimaging, including single-photon emission computed tomography (SPECT). Most previous SPECT studies lack pathological validation.

AIM

To examine the accuracy of SPECT in differentiating FTD from AD in patients with subsequent pathological confirmation.

METHODS

Technetium-99-labelled hexamethyl propylene amine oxime SPECT images obtained at initial evaluation in 25 pathologically confirmed cases of FTD were examined. These images were visually rated by an experienced blinded nuclear medicine consultant and compared with those of 31 patients with AD, also with pathological validation.

RESULTS

A reduction in frontal cerebral blood flow (CBF) was more common in FTD and was of diagnostic value (sensitivity 0.8, specificity 0.65 and likelihood ratio (LR) 2.25; 95% CI 1.35 to 3.77). A pattern of bilateral frontal CBF reduction without the presence of associated bilateral parietal CBF change is diagnostically more accurate (sensitivity 0.80, specificity 0.81 and +LR 4.13, 95% CI 1.96 to 8.71). Diagnostic categorisation (FTD or AD) on the basis of SPECT alone was less accurate than clinical diagnosis (based on neurology and detailed neuropsychological evaluation). One patient with FTD was initially clinically misdiagnosed as AD, owing to the lack of availability of full neuropsychological assessment. However, SPECT correctly diagnosed this patient, providing a diagnostic gain of 4%.

CONCLUSION

Technetium-99-labelled hexamethyl propylene amine oxime SPECT CBF patterns provide valuable information in the diagnosis of FTD and AD. These data can be better used as an adjunct to clinical diagnosis if pathology is to be correctly predicted in life.

Inferring thought and action in motor neurone disease

The traditional assumption that classical motor neurone disease (MND) invariably spares cognitive function is now recognised to be incorrect. Deficits have most commonly been demonstrated on executive tasks suggesting impaired function of frontal systems. Yet, crucial aspects of frontal lobe function have not hitherto been explored. The study used tests of theory of mind (ToM) (interpretation of cartoons and stories) to examine the ability of 16 patients with MND to interpret social situations and ascribe mental states to others. Only minor differences were elicited in the MND group as a whole compared to controls, and performance was not differentially affected for cartoons and stories requiring inference of another's mental state (mental) compared to control (physical) cartoons and stories. However, abnormalities were elicited on both mental and physical tasks in a subgroup of patients with bulbar signs. Moreover, examination of individual patient scores revealed a spectrum of performance ranging from normal to severely impaired. Errors were qualitatively similar to those seen in frontotemporal dementia (FTD). Performance on the ToM tasks was significantly correlated with conventional, untimed measures of executive function, suggesting that ToM deficits in MND are likely to be linked to a more general executive failure. The findings contribute to the understanding of ToM performance in neurodegenerative disease and provide further evidence of the association between MND and FTD.

Progranulin gene mutations associated with frontotemporal dementia and progressive non-fluent aphasia

Frontotemporal lobar degeneration (FTLD) refers to a focal, non-Alzheimer form of cerebral degeneration that encompasses the distinct clinical syndromes of frontotemporal dementia (FTD), progressive non-fluent aphasia (PNFA) and semantic dementia. Some patients show tau-based pathological changes and in familial cases mutations have been identified in the microtubule-associated protein tau gene (MAPT) on chromosome 17q21. However, many cases are tau-negative, showing instead ubiquitin-immunoreactive (UBQ-ir) neuronal cytoplasmic inclusions and neurites, and in some familial cases UBQ-ir neuronal intranuclear inclusions of a lentiform appearance. Very recently, mutations have been identified in familial cases in the progranulin (PGRN) gene, also on chromosome 17q21. Clinical, pathological and molecular diversity within FTLD highlights the importance of careful examination of clinical-pathological-genetic relationships. This paper reports, for the first time, a clinico-pathological investigation of two FTLD families with PGRN mutations, and compares the clinical characteristics with those of patients studied in the department with MAPT mutations. The clinical profile associated with PGRN mutations constituted, in some patients, a prototypical picture of FTD and in others one of PNFA, both profiles occurring within the same family. Patients with PGRN mutations exhibited phonological deficits, whereas in patients with MAPT mutations language abnormalities, when present in addition to the prominent behavioural disorder, take the form of semantic disturbance. The findings provide compelling evidence for the link between FTD and PNFA, while raising the possibility of identifiable clinical differences between FTLD patients with MAPT and PGRN mutations.

Genetic associations between cathepsin D exon 2 C-->T polymorphism and Alzheimer's disease, and pathological correlations with genotype

Genetic variations represent major risk factors for Alzheimer's disease (AD). While familial early onset AD is associated with mutations in the amyloid precursor protein and presenilin genes, only the e4 allele of the apolipoprotein E (APOE) gene has so far been established as a genetic risk factor for late onset familial and sporadic AD. It has been suggested that the C-->T (224Ala-->Val) transition within exon 2 of the cathepsin D gene (CTSD) might represent a risk factor for late onset AD. The objective of this study was to investigate whether possession of the CTSD exon 2 T allele increases the risk of developing AD, and to determine whether this modulates the amyloid pathology of the disease in conjunction with, or independent of, the APOE e4 allele. Blood samples were obtained from 412 patients with possible or probable AD and brain tissues from a further 148 patients with AD confirmed by postmortem examination. CTSD and APOE genotyping were performed by PCR on DNA extracted from blood, or from frontal cortex or cerebellum in the postmortem cases. Pathological measures of amyloid beta protein (Abeta), as plaque Abeta40 and Abeta42(3) load and degree of cerebral amyloid angiopathy were made by image analysis or semiquantitative rating, respectively. CTSD genotype frequencies in AD were not significantly different from those in control subjects, nor did these differ between cases of early or late onset AD or between younger and older controls. There was no gene interaction between the CTSD T and APOE e4 alleles. The amount of plaque Abeta40 was greater in patients carrying the CTSD T allele than in non-carriers, and in patients bearing APOE e4 allele compared with non-carriers. Possession of both these alleles acted synergistically to increase levels of plaque Abeta40, especially in those individuals who were homozygous for the APOE e4 allele. Possession of the CTSD T allele had no effect on plaque Abeta42(3) load or degree of CAA. Possession of the CTSD T allele does not increase the risk of developing AD per se, but has a modulating effect on the pathogenesis of the disorder by increasing, in concert with the APOE e4 allele, the amount of Abeta deposited as senile plaques in the brain in the form of Abeta40.

The apolipoprotein E epsilon4 allele selectively increases the risk of frontotemporal lobar degeneration in males

OBJECTIVE

To determine whether polymorphic variations in the apolipoprotein E gene (APOE) are associated with increased risk of frontotemporal lobar degeneration (FTLD) when mutation in tau gene is absent.

METHODS

The APOE gene was genotyped by polymerase chain reaction from DNA routinely extracted from blood or brain tissues. The APOE epsilon4 allele frequency in 198 patients with FTLD not associated with mutations in tau gene was compared with that of a control group of 756 normal individuals drawn from the same geographical region. Analyses were done according to clinical subtype or sex.

RESULTS

The APOE epsilon4 allele frequency (19.4%) was increased (p = 0.01) in FTLD v the whole control group (14.1%), while the APOE epsilon2 allele frequency in FTLD (6.5%) was slightly lower than in controls (8.0%) (NS). The APOE epsilon4 allele frequency in men with FTLD (22.3%) was greater (p = 0.002) than in male controls (12.3%); the frequency in women (16.3%) was similar to that in female controls (14.8%) (NS). The APOE epsilon2 allele frequency in men with FTLD was 4.9% while in male controls it was 9.5% (p = 0.06), but there was no difference in women (7.5% v 7.9%, NS). Neither the APOE epsilon2 nor APOE epsilon4 allele frequency varied significantly between any of the clinical subtypes.

CONCLUSIONS

In FTLD not associated with mutations in tau gene, possession of APOE epsilon4 allele in men roughly doubles the chances of developing disease, whereas this has no impact upon disease risk in women.

Qualitative neuropsychological performance characteristics in frontotemporal dementia and Alzheimer's disease

BACKGROUND

Frontotemporal dementia (FTD) and Alzheimer's disease are clinically distinct disorders, yet neuropsychological studies have had variable success in distinguishing them. A possible reason is that studies typically rely on overall accuracy scores, which may obscure differences in reasons for failure.

OBJECTIVES

To explore the hypothesis that analysis of qualitative performance characteristics and error types, in addition to overall numerical scores, would enhance the neuropsychological distinction between FTD and Alzheimer's disease.

METHODS

38 patients with FTD and 73 with Alzheimer's disease underwent assessment of language, visuospatial abilities, memory, and executive function, using a neuropsychological screening instrument and standard neuropsychological tests. In each of these cognitive domains, performance characteristics and error types were documented, in addition to numerical scores on tests.

RESULTS

Whereas comparison of neuropsychological test scores revealed some group differences, these did not occur consistently across tests within cognitive domains. However, analysis of performance characteristics and error types revealed qualitative differences between the two groups. In particular, FTD patients displayed features associated with frontal lobe dysfunction, such as concrete thought, perseveration, confabulation, and poor organisation, which disrupted performance across the range of neuropsychological tests.

CONCLUSIONS

Numerical scores on neuropsychological tests alone are of limited value in differentiating FTD and Alzheimer's disease, but performance characteristics and error types enhance the distinction between the two disorders. FTD is associated with a profound behavioural syndrome that affects performance on cognitive assessment, obscuring group differences. Qualitative information should be included in neuropsychological research and clinical assessments.

Autopsy proven sporadic frontotemporal dementia due to microvacuolar-type histology, with onset at 21 years of age

We describe the clinical, neuropsychological, and neuropathological features of a 21 year old woman with frontotemporal dementia (FTD). The early presentation was of florid behavioural change involving hyperactivity and disinhibition. Magnetic resonance imaging and single photon emission computed tomography of the brain revealed atrophy and severe functional abnormalities of the frontal and temporal lobes, respectively. Electroencephalogram was normal. At autopsy, there was gross frontotemporal brain atrophy and the underlying histology was of a microvacuolar-type degeneration; no tau or ubiquitin immunoreactive, intraneuronal inclusions were seen. There was no family history of dementia and no mutation in the tau gene. We believe this patient represents the youngest (so far) recorded case of FTD associated with this particular histological form of the disorder.

Frontotemporal dementia with Pick-type histology associated with Q336R mutation in the tau gene

In this report, we describe the clinical and neuropathological features of a case of familial frontotemporal dementia (FTD), with onset at 58 years of age and disease duration of 10 years, associated with a novel mutation, Q336R, in the tau gene (tau). In vitro studies concerning the properties of tau proteins bearing this mutation, with respect to microtubule assembly and tau filament aggregation, are reported. Clinically, the patient showed alterations in memory, language and executive functions and marked behavioural change consistent with FTD, although the extent of memory impairment was more than is characteristic of FTD. At autopsy, there was degeneration of the frontal and temporal lobes associated with the presence of hyperphosphorylated tau proteins in swollen (Pick) cells and intraneuronal inclusions (Pick bodies). By immunohistochemistry, the Pick bodies contained both 3-repeat and 4-repeat tau proteins although, because no fresh tissues were available for analysis, the exact isoform composition of the aggregated tau proteins could not be determined. Neurons within frontal cortex contained neurofibrillary tangle-like structures, comprising both straight and twisted tubules, or Pick bodies in which the filaments were short and randomly orientated. In vitro, and in common with other tau missense mutations, Q336R caused an increase in tau fibrillogenesis. However, in contrast to most other tau missense mutations, Q336R increased, not decreased, the ability of mutant tau to promote microtubule assembly. Nonetheless, this latter functional change may likewise be detrimental to neuronal function by inducing a compensatory phosphorylation that may yield increased intracellular hyperphosphorylated tau species that are also liable to fibrillize. We believe the mutation is indeed pathogenic and disease causing and not simply a coincidental rare and benign polymorphism. Since this mutation is segregating with the FTD clinical and neuropathological phenotype, it has not been found in unaffected individuals and it has novel functional properties in vitro which are likely to be detrimental to neuronal function in vivo.

Knowledge of famous faces and names in semantic dementia

Semantic dementia is a focal clinical syndrome, resulting from degeneration of the temporal lobes and characterized by progressive loss of conceptual knowledge about the world. Because of the highly circumscribed nature of the disorder it is a natural model for improving understanding of how semantic information is cerebrally represented. There is currently a lack of consensus. One view proposes the existence of modality specific meaning systems, in which visual and verbal information are stored separately. An opposing view assumes that information is represented by a unitary, amodal semantic system. The present study explores these alternatives in an examination of famous face and name knowledge in 15 patients with semantic dementia. The study of face recognition in patients with an established semantic disorder also permits an examination of the relationship between semantic dementia and the focal clinical syndrome of progressive prosopagnosia. The semantic dementia patients were profoundly impaired on both face and name identification and familiarity judgement tasks compared with amnesic patients with Alzheimer's disease and healthy controls. However, whereas the two reference groups performed better for names than faces, the semantic group showed the opposite pattern. This overall profile masked individual differences: semantic dementia patients with predominant left temporal lobe atrophy showed better recognition of names than faces, whereas patients with right temporal predominance showed the reverse pattern. Relative superiority for names or faces was mirrored by corresponding superiority for words or pictures on a standard semantic test. We interpret the findings as inconsistent with a unitary, amodal model of semantic memory. However, the data are not wholly compatible with a strict multiple system account. The data favour a model of semantic memory comprising a single interconnected network, with dedicated brain regions representing modality specific information. The data emphasize the importance of the anterior, inferolateral parts of the left temporal lobe for the representation of names and the corresponding parts of the right temporal lobe for faces. Dissociations between face and name knowledge provide a challenge for existing models of face processing. Moreover, they lead us to argue that the focal syndrome of progressive prosopagnosia is one of the clinical presentations of semantic dementia and not a separate clinical entity.

Social cognition in frontotemporal dementia and Huntington's disease

Frontotemporal dementia (FTD) and Huntington's disease (HD) are degenerative disorders, with predominant involvement, respectively of frontal neocortex and striatum. Both conditions give rise to altered social conduct and breakdown in interpersonal relationships, although the factors underlying these changes remain poorly defined. The study used tests of theory of mind (interpretation of cartoons and stories and judgement of preference based on eye gaze) to explore the ability of patients with FTD and HD to interpret social situations and ascribe mental states to others. Performance in the FTD group was severely impaired on all tasks, regardless of whether the test condition required attribution of a mental state. The HD group showed a milder impairment in cartoon and story interpretation, and normal preference judgements. Qualitative differences in performance were demonstrated between groups. FTD patients made more concrete, literal interpretations, whereas HD patients were more likely to misconstrue situations. The findings are interpreted as demonstrating impaired theory of mind in FTD, as one component of widespread executive deficits. In HD the evidence does not suggest a fundamental loss of theory of mind, but rather a tendency to draw faulty inferences from social situations. It is concluded that social breakdown in FTD and HD may have a different underlying basis and that the frontal neocortex and striatum have distinct contributions to social behaviour.

Distinct neuropsychological characteristics in Creutzfeldt-Jakob disease

OBJECTIVES

To characterise the nature of cognitive change in Creutzfeldt-Jakob disease (CJD).

METHODS

Case histories are reported of four patients with sporadic (sCJD) and two with familial CJD (fCJD), with postmortem pathological findings in four cases. The data derived from cognitive examination are examined with respect to the presence or absence of a variety of characteristics to elicit performance profiles across cognitive domains.

RESULTS

Three patients with sCJD exhibited clear focal cortical deficits. One patient had visual impairment leading to cortical blindness, associated with posterior hemisphere abnormalities on single photon emission computed tomography (SPECT) imaging; two others had impairments in language, mirrored by left hemisphere SPECT abnormalities. The remaining three patients showed no specific cortical symptomatology. Despite these differences all six patients shared common qualitative characteristics: episodic unresponsiveness, interference effects, and profound verbal and motor perseveration. These common features are interpreted in terms of impaired activation and regulation of neocortex from subcortical structures. Findings from postmortem pathological examination and from the published literature provide converging evidence to implicate a critical role of the thalamus.

CONCLUSION

These preliminary findings suggest that sCJD and fCJD may be associated with distinct neuropsychological characteristics.

Qualitative performance characteristics differentiate dementia with Lewy bodies and Alzheimer's disease

OBJECTIVES

To determine whether dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) can be differentiated on the basis of qualitative performance characteristics during neuropsychological evaluation.

METHODS

Forty one patients with clinically defined DLB were matched with 26 patients with AD for age, illness duration, nature and severity of cognitive deficits, and regional blood flow distribution on SPECT. The presence or absence of a set of qualitative performance characteristics, observed and recorded during the patients' initial cognitive evaluation, was identified by retrospective analysis of patients' records and the groups compared.

RESULTS

Inattention, visual distractibility, impairments in establishing and shifting mental set, incoherence, confabulatory responses, perseveration, and intrusions were significantly more common in DLB than AD. Intrusions were particularly common in DLB, occurring in 78% of the group. They included externally cued intrusions arising from the visual environment, a feature never seen in AD. In a stepwise logistic regression analysis impaired mental set shifting, perseveration, and the presence of intrusions correctly classified 79% of patients.

CONCLUSION

It is possible to differentiate DLB and AD on the basis of qualitative features of performance. As many features are amenable to detection at clinical interview, they ought to contribute to clinicians' diagnostic armoury, leading to improved clinical recognition of DLB.

Diagnostic value of high signal abnormalities on T2 weighted MRI in the differentiation of Alzheimer's, frontotemporal and vascular dementias

OBJECTIVE

The occurrence of high signal abnormalities on T2 weighted images is strongly age related. The diagnostic value of these changes in a younger population with dementia is not currently known. We studied the potential of high signal changes on magnetic resonance imaging (MRI) in differentiating Alzheimer's disease (AD), frontotemporal dementia (FTD) and vascular dementia (VaD) in younger patients.

METHODS

High signal abnormalities were rated, using a previously validated scale, from hard copies of T2 weighted axial images of 102 patients with AD (n=49), VaD (n=31), FTD (n=22) (mean ages 63-65 years).

RESULTS

High signal abnormalities were widespread across AD, VaD and FTD. Although they were most frequent and most severe in the VaD group only lacunes and grade III deep white matter hyperintensities (DWMH) were specific for these patients.

CONCLUSIONS

High signal changes on T2 weighted images on MRI are common across degenerative (AD and FTD) and vascular dementias. Although lacunes and grade III DWMH are specific for VaD, the low sensitivities (sensitivities: for lacunes, 0.32; for grade III DWMH, 0.16) limit their use as diagnostic markers for VaD. High signal changes on MRI should be interpreted with caution in dementias. Their presence, even in younger patients, should not deter one from diagnosing AD or FTD.

Inherited frontotemporal dementia in nine British families associated with intronic mutations in the tau gene

Genetic screening of 171 patients with frontotemporal lobar degeneration disclosed 14 patients, across nine pedigrees, with mutations in the intron to exon 10 in the tau gene, a region regulating the splicing of exon 10 via a stem loop mechanism. Thirteen of these patients had the +16 splice site mutation and one had the +13 splice site mutation. Affected members of all nine families presented with changes in behaviour and social conduct that were prototypical of frontotemporal dementia (FTD). In all patients with the +16 splice site mutation, the behavioural profile was characterized by disinhibition, restless overactivity, a fatuous affect, puerile behaviour and verbal and motor stereotypies. The single patient with the +13 mutation presented a contrasting picture of apathy and inertia. In addition, all patients had evidence of semantic loss. Pathologically, five of the six patients so far autopsied shared frontotemporal atrophy with involvement of the substantia nigra. The underlying histology was that of microvacuolar-type cortical degeneration with a few swollen cells. Tau pathology was widespread throughout the brain and present in neurones and glial cells, mostly in the frontal and temporal cortical regions. This was in the form of neurofibrillary tangles and amorphous tau deposits (pre-tangles); Pick bodies were not observed. Ultrastructurally, the tau filaments had a twisted, ribbon-like morphology distinct from the paired helical filaments of Alzheimer's disease. One patient died from an unrelated illness whilst in the early clinical stages of FTD. In this patient, cortical microvacuolar and astrocytic changes were absent, though there were scattered neurones and glial cells, immunoreactive to tau, throughout the cortical and subcortical regions. The disease process underlying the neurodegeneration within these inherited forms of FTD may therefore stem directly from early, primary alterations in the function of tau. All eight families with the +16 mutation seem to be part of a common extended pedigree, possibly originating from a founder member residing within the North Wales region of Great Britain.

Diagnostic patterns of regional atrophy on MRI and regional cerebral blood flow change on SPECT in young onset patients with Alzheimer's disease, frontotemporal dementia and vascular dementia

OBJECTIVES

Alzheimer's disease (AD), frontotemporal dementia (FTD) and vascular dementia (VaD) are the three most common causes of young onset dementias. Most neuroimaging studies of these disorders have involved comparisons with normal controls. The aims of this study were to examine the clinical diagnostic value of magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) (in combination and in isolation) in the differentiation of one form of dementia from another from amongst a group of AD, FTD and VaD.

METHODS

T1 weighted MRI images and 99mTc-HMPAO SPECT images were obtained from consecutive patients with FTD (n=21), AD (n=23) and VaD (n=20) and rated visually by experienced neuroradiologists and nuclear medicine physicians.

RESULTS

Asymmetrical atrophy was seen only in FTD. Frontotemporal dementia patients were the most atrophic whereas severe atrophy was rarely observed in VaD. Severe frontal atrophy (unilaterally or bilaterally) and/or asymmetrical atrophy on MRI is highly diagnostic (sensitivity 0.71, specificity 0.93, LR 10.24) of FTD from within a group of FTD and non-FTD (AD, VaD) patients. Mild or severe parietal atrophy with severe reduction in parietal regional cerebral blood flow on SPECT is diagnostic (sensitivity 0.71, specificity 0.76, LR 3.02) of AD from within a group of AD and non-AD (VaD, FTD) patients.

CONCLUSION

Anatomical (MRI) and functional (SPECT) imaging provide different information and a combination of these modalities improves diagnostic specificity.

Psychomotor, executive, and memory function in preclinical Huntington's disease

The earliest changes in the development of Huntington's disease (HD) remain controversial. Studies of cognitive function in preclinical individuals who have the HD mutation have yielded contradictory results. This study compared cognitive and motor performance in 51 people with the HD mutation who had no clinical signs of HD, 85 at-risk individuals without the HD mutation and 43 individuals in the early stages of HD. Whereas highly significant differences were detected between the preclinical and early-HD groups, only subtle impairments were present in at-risk individuals with the HD mutation compared to those with normal HD alleles, principally for low-demand psychomotor tasks. Complementing these observations, longitudinal investigation showed that performance on psychomotor tasks in people with the mutation who were close to clinical onset of HD was intermediate between that of individuals many years from onset and those in the early stages of HD, suggesting a slowly insidious evolution of deficit. In contrast, memory performance showed a more precipitous decline around the time of clinical onset of HD. The findings, which suggest that HD patients' functional deficits do not evolve uniformly, help to resolve some of the disparities in the literature on preclinical HD.

Behavioral changes in Huntington Disease

OBJECTIVES

This study aimed to gain a better understanding of behavioral abnormalities in Huntington disease (HD) and to develop a method for reliably assessing these changes.

BACKGROUND

Behavioral changes are a central feature of HD and often cause considerable distress and difficulty to patients and their relatives. However, they have received little attention from research despite their prevalence and clinical significance.

METHODS

One hundred thirty-four patients with HD were assessed using the Problem Behaviors Assessment for Huntington Disease (PBA-HD), an instrument for rating the presence, severity and frequency of behavioral abnormalities in HD.

RESULTS

The findings confirm that behavioral problems are common among patients with HD. The most common symptoms were loss of energy and initiative, poor perseverance and quality of work, impaired judgment, poor self-care and emotional blunting. Affective symptoms such as depression, anxiety and irritability occurred in around half the patients studied. Psychotic symptoms (hallucinations and delusions) were rarely reported. Factor analysis distinguished three clusters of behavioral symptoms, which were interpreted respectively as reflecting Apathy, Depression and Irritability. The 'Apathy' factor was highly correlated with duration of illness, whereas no such relationship was observed for the 'Depression' and 'Irritability' factors.

CONCLUSIONS

The results suggest that certain behavioral changes are fundamental to the progression of HD, whereas others have a more complex relationship to the disease process. The findings have implications for the choice of behavioral measures used to evaluate efficacy of therapeutic interventions.

Behaviour in frontotemporal dementia, Alzheimer's disease and vascular dementia

OBJECTIVES

The study aimed to increase understanding of behavioural changes in frontotemporal dementia (FTD) and identify features that best differentiate FTD from Alzheimer's disease (AD) and cerebrovascular dementia (CvD).

METHODS

A semi-structured questionnaire was administered to carers of 30 FTD, 75 AD and 34 CvD patients.

RESULTS

Behavioural changes that strongly discriminated FTD from AD and to a lesser extent CvD were loss of emotions and insight, selfishness, disinhibition, personal neglect, gluttony and sweet food preference, wandering, motor and verbal stereotypies, loss of pain, echolalia and mutism. Irritability, hyposexuality and hypersomnia did not discriminate. Emotional, eating and stereotyped behaviours correctly classified 95% of patients using regression analysis.

CONCLUSIONS

Behavioural characteristics accurately differentiate FTD from AD and CvD. The findings highlight the particular importance of affective change in FTD, and underline the role of the frontotemporal lobes in emotion.

Classification and description of frontotemporal dementias

A number of distinct clinical syndromes have been described that are associated with focal degeneration of the frontal and temporal lobes and have a non-Alzheimer pathology. The nosological status of frontotemporal lobar degeneration (FTLD) has been a matter of controversy, in view of the diversity of clinical manifestations and distribution and nature of histopathological change. This paper describes the major clinical syndromes of frontotemporal dementia, progressive aphasia, and semantic dementia; it discusses their underlying pathologies and considers their molecular status. Common histopathological changes are demonstrated across the three clinical syndromes, highlighting the link between these clinical disorders. It has been suggested that these disorders should be regarded as tauopathies on the basis of the tau pathology seen in a number of cases and the mutations in the tau gene in some familial cases. However, in a series of 47 consecutive autopsy series of FTLD, only 36% had tau pathology and 10% mutations in the tau gene, suggesting that FTLD does not constitute a unitary etiological disorder and that its characterization as a tauopathy may be potentially misleading.

Distinct behavioural profiles in frontotemporal dementia and semantic dementia

OBJECTIVE

To test predictions that frontotemporal dementia and semantic dementia give rise to distinct patterns of behavioural change.

METHODS

An informant based semistructured behavioural interview, covering the domains of basic and social emotions, social and personal behaviour, sensory behaviour, eating and oral behaviour, repetitive behaviours, rituals, and compulsions, was administered to carers of 41 patients with semantic dementia and with apathetic (FTD-A) and disinhibited (FTD-D) forms of frontotemporal dementia.

RESULTS

Consistent with prediction, emotional changes differentiated FTD from semantic dementia. Whereas lack of emotional response was pervasive in FTD, it was more selective in semantic dementia, affecting particularly the capacity to show fear. Social avoidance occurred more often in FTD and social seeking in semantic dementia. Patients with FTD showed reduced response to pain, whereas patients with semantic dementia more often showed exaggerated reactions to sensory stimuli. Gluttony and indiscriminate eating were characteristic of FTD, whereas patients with semantic dementia were more likely to exhibit food fads. Hyperorality, involving inedible objects, was unrelated to gluttony, indicating different underlying mechanisms. Repetitive behaviours were common in both FTD and semantic dementia, but had a more compulsive quality in semantic dementia. Behavioural differences were greater between semantic dementia and FTD-A than FTD-D. A logistic regression analysis indicated that emotional and repetitive, compulsive behaviours discriminated FTD from semantic dementia with 97% accuracy.

CONCLUSION

The findings confirm predictions regarding behavioural differences in frontotemporal and semantic dementia and point to differential roles of the frontal and temporal lobes in affect, social functioning, eating, and compulsive behaviour.

Cognitive change in motor neurone disease/amyotrophic lateral sclerosis (MND/ALS)

A motor neuronopathy complicating frontotemporal dementia (FTD) has been recognised and designated FTD/motor neurone disease (MND). FTD is characterised by profound character change and altered social conduct, and executive deficits, reflecting focal degeneration of the frontal and temporal neocortex. The motor neuronopathy comprises bulbar palsy and limb amyotrophy. The major histological change is typically of microvacuolation of the cerebral cortex, with atrophy of the bulbar neurones and anterior horn cells of the spinal cord. Ubiquitinated inclusion bodies occur in large pyramidal cortical neurones and in surviving cranial nerve nuclei and anterior horn cells. Evidence is emerging that some patients with classical MND/amyotrophic lateral sclerosis (ALS), who are thought not to be demented, develop cognitive deficits in the realm of frontal executive functions. Moreover, frontal lobe abnormalities have been demonstrated by neuroimaging. The findings point to a link between FTD/MND and cMND/ALS and suggest that a proportion of patients with cMND/ALS go on to develop FTD. Patients with cMND/ALS may not be equally vulnerable. The hypothesis is that patients who present with bulbar palsy and amyotrophy, rather than corticospinal and corticobulbar features, may be most susceptible to the development of FTD.

The electroencephalogram in dementia with Lewy bodies

OBJECTIVES

Dementia with Lewy bodies (DLB) is the second commonest neurodegenerative cause of dementia. While there is consensus on the clinical diagnostic criteria for DLB, the use of EEG to increase the diagnostic sensitivity has not been substantiated.

MATERIAL AND METHODS

We studied the resting EEG findings in 18 consecutive patients with DLB and compared them with a control group of 20 patients with "probable" Alzheimer's disease (AD). We aimed to evaluate the use of EEG in a representative sample of patients with DLB.

RESULTS

All patients with DLB fulfilled accepted clinical criteria for DLB. The DLB group had a more severe dementia than the AD group, as measured by the Mini-Mental State Examination (MMSE) test (DLB mean MMSE 9.4 and AD mean MMSE 17.2) despite a similar duration of overall severity of illness. The EEG was slow in both groups, predominantly in the 4-7 Hz range. Although there was no statistically significant difference in the EEG findings between the DLB and AD groups, there was a correlation between the EEG score and MMSE score (Spearman Rank correlation rs = -0.61, P < 0.001).

CONCLUSION

These findings suggest that although patients with DLB have a more aggressive course than AD, EEG abnormalities do not differ in the 2 groups. However, we believe the EEG provides important supporting diagnostic information in DLB.

[Diagnostic criteria for fronto-temporal lobe degeneration]

Circumscribed atrophy of the frontal and temporal lobes (frontotemporal lobar degeneration) accounts for about one fifth of cases of primary degenerative dementia occurring before the age of 65. It produces three prototypical clinical syndromes. The most common is frontotemporal dementia, characterized by personality change and profound alteration in social conduct and associated with bilateral atrophy of the frontal and anterior temporal lobes. Progressive non-fluent aphasia is characterized by difficulty in verbal expression, anomia and phonemic errors in the presence of relative preservation of comprehension and associated with atrophy predominantly of the left hemisphere. In semantic dementia there is fluent speech with semantic errors and severely impaired comprehension and naming, together with a visual associative agnosia, resulting from bilateral atrophy of the inferior and middle temporal gyri. The clinical syndromes occur with either of two main histological types: prominent microvacuolar change, without specific histological features (frontal lobe degeneration-type), severe astrocytic gliosis with or without ballooned cells and inclusion bodies (Pick-type). To improve clinical recognition and advance understanding of this relatively common form of cerebral degeneration, members of an international workshop on Frontotemporal Lobar Degeneration developed consensus criteria, building upon earlier published clinical diagnostic guidelines for frontotemporal dementia. The consensus criteria reported here specify core and supportive features for each of the prototypical clinical syndromes: frontotemporal dementia, progressive aphasia and semantic dementia, as well as providing broad inclusion and exclusion criteria for the generic entity of frontotemporal lobar degeneration.

Memory dysfunction in multiple sclerosis corresponds to juxtacortical lesion load on fast fluid-attenuated inversion-recovery MR images

BACKGROUND AND PURPOSE

MR imaging is a sensitive diagnostic tool and paraclinical marker of disease activity and prognosis in multiple sclerosis (MS), yet the role of MR imaging of MS is controversial. The aim of this study was to describe the relationship between cognitive function and MS lesion size and position, as shown on comparative images from conventional spin-echo (CSE) and fast fluid-attenuated inversion-recovery (fast FLAIR) MR studies.

METHODS

CSE and fast FLAIR sequences consisted of 40 noncontiguous, 3-mm-thick axial sections matched for geometric position in 18 patients with relapsing-remitting MS. Lesions were scored for size, anatomic position, and their comparative appearance on CSE and fast FLAIR images. The neuropsychological assessment tested general psychological performance, memory, and frontal lobe executive function.

RESULTS

Fast FLAIR images showed significantly more small (146 versus six) and medium-sized (18 versus four) juxtacortical lesions than did CSE sequences. Small juxtacortical lesions displayed only on fast FLAIR images had a distinctive appearance, suggestive of small areas of perivascular inflammation. The number of these lesions corresponded to reduced performance on the fifth and delayed trials of the Rey Auditory Verbal Learning memory function test.

CONCLUSION

Fast FLAIR images show small lesions at the juxtacortical boundary that are not seen on CSE studies. The presence of such lesions correlates with impaired retention of information in memory tasks, which is characteristic of cognitive problems in patients with MS.

Neuropsychiatric aspects of frontotemporal dementias

Frontotemporal dementia (FTD) is a clinically distinct disorder that is under-recognized. A primary focus of recent research has been to delineate neuropsychiatric features that best discriminate FTD from other dementias, and to identify test instruments that elicit differentiating characteristics most effectively. Additional studies have taken advantage of the clinical and anatomic selectivity that is the hallmark of FTD to explore the functions of different regions of the frontal and temporal lobes. Symptomatic treatments for FTD have shown some promise, raising the potential for improved management in the future.

Semantic dysfunction in frontotemporal lobar degeneration

Semantic dementia, characterized by loss of word meaning and impaired face and object recognition, is one of the clinical manifestations of frontotemporal lobar degeneration and is associated with atrophy of the inferior and middle temporal gyri. Patients may present predominantly with problems in naming and understanding words, or in face and object recognition, the verbal or nonverbal predominance reflecting the accent of atrophy on the left or right temporal lobe. Behavioural changes may occur, although these have a more obsessional quality than is typically seen in frontotemporal dementia (FTD). However, overlap in clinical symptomatology of semantic dementia and FTD may occur with disease progression reinforcing the link between these clinical syndromes. Semantic dysfunction is poorly recognized and may be mistaken for the amnesia of Alzheimer's disease, yet may be important in explaining some of the behavioural characteristics seen in focal cerebral degeneration.

Evaluation of the NINCDS-ADRDA criteria in the differentiation of Alzheimer's disease and frontotemporal dementia

OBJECTIVES

The diagnosis of Alzheimer's disease (AD) is now reliant on the use of NINCDS-ADRDA criteria. Other diseases causing dementia are being increasingly recognised--for example, frontotemporal dementia (FTD). Historically, these disorders have not been clearly demarcated from AD. This study assesses the capability of the NINCDS-ADRDA criteria to accurately distinguish AD from FTD in a series of pathologically proved cases.

METHODS

The case records of 56 patients (30 with AD, 26 with FTD) who had undergone neuropsychological evaluation, brain imaging, and ultimately postmortem, were assessed in terms of whether at initial diagnosis the NINCDS-ADRDA criteria were successful in diagnosing those patients who had AD and excluding those who did not.

RESULTS

(1) The overall sensitivity of the NINCDS-ADRDA criteria in diagnosing "probable" AD from 56 patients with cortical dementia (AD and FTD) was 0.93. However, the specificity was only 0.23; most patients with FTD also fulfilled NINCDS-ADRDA criteria for AD. (2) Cognitive deficits in the realms of orientation and praxis significantly increased the odds of a patient having AD compared with FTD, whereas deficits in problem solving significantly decreased the odds. Neuropsychological impairments in the domains of attention, language, perception, and memory as defined in the NINCDS-ADRDA statement did not contribute to the clinical differentiation of AD and FTD.

CONCLUSION

NINCDS-ADRDA criteria fail accurately to differentiate AD from FTD. Suggestions to improve the diagnostic specificity of the current criteria are made.

Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria

OBJECTIVE

To improve clinical recognition and provide research diagnostic criteria for three clinical syndromes associated with frontotemporal lobar degeneration.

METHODS

Consensus criteria for the three prototypic syndromes-frontotemporal dementia, progressive nonfluent aphasia, and semantic dementia-were developed by members of an international workshop on frontotemporal lobar degeneration. These criteria build on earlier published clinical diagnostic guidelines for frontotemporal dementia produced by some of the workshop members.

RESULTS

The consensus criteria specify core and supportive features for each of the three prototypic clinical syndromes and provide broad inclusion and exclusion criteria for the generic entity of frontotemporal lobar degeneration. The criteria are presented in lists, and operational definitions for features are provided in the text.

CONCLUSIONS

The criteria ought to provide the foundation for research work into the neuropsychology, neuropathology, genetics, molecular biology, and epidemiology of these important clinical disorders that account for a substantial proportion of cases of primary degenerative dementia occurring before the age of 65 years.

Awareness of involuntary movements in Huntington disease

OBJECTIVE

To determine why patients with Huntington disease are apparently unaware of their involuntary movements.

DESIGN

Correlative study using a subjective report questionnaire of physical symptoms and objective measures of neurologic and cognitive dysfunction.

PATIENTS

Forty patients with Huntington disease attending a regional Huntington disease clinic.

RESULTS

Patients were poor at reporting experiential symptoms of involuntary movements. There was no relationship between self-report of these symptoms and objective indices of motor dysfunction or severity of cognitive impairment. Patients could, however, report secondary consequences of their movement disorder, which correlated highly with nonchoreic indices of motor dysfunction.

CONCLUSIONS

Patients with Huntington disease have impaired subjective experience of chorea. Denial of symptoms is likely to have a physiological basis and is not a secondary consequence of patients' cognitive impairment or a psychological defense against a debilitating disease.

A clinical role for 99mTc-HMPAO SPECT in the investigation of dementia?

OBJECTIVES

To provide the clinician with a guide to the clinical utility of 99mTc-HMPAO single photon emission computed tomography (SPECT) and to the interpretation of specific test results in the differential diagnosis of dementia.

METHODS

Three hundred and sixty three patients with dementia were studied prospectively for a median three (range 1-6) years and classified into disease groups on the basis of established clinical criteria. The degree to which different patterns of cerebral blood flow (CBF) abnormality found on 99mTc-HMPAO SPECT imaging at the time of initial patient presentation modified clinical diagnoses was determined by calculating the likelihood ratios for pairwise disease group comparisons. The optimal clinical usage of 99mTc-HMPAO SPECT was determined by calculating the percentage of significant test results for each pairwise disease group comparison.

RESULTS

Bilateral posterior CBF abnormality was found to significantly increase the odds of a patient having Alzheimer's disease as opposed to vascular dementia or frontotemporal dementia. Bilateral anterior CBF abnormality significantly increased the odds of a patient having frontotemporal dementia as opposed to Alzheimer's disease, vascular dementia, or Lewy body disease. "Patchy" CBF changes significantly increased the odds of a patient having vascular dementia as opposed to Alzheimer's disease. Unilateral anterior, unilateral anterior plus unilateral posterior, and generalised CBF abnormality failed to contribute to the differentiation of any of these forms of dementia.

CONCLUSIONS

99mTc-HMPAO SPECT was found to be most useful in distinguishing Alzheimer's disease from vascular dementia and fronto temporal dementia, and least useful in differentiating between Alzheimer's disease and Lewy body disease, and between vascular dementia, frontotemporal dementia, and progressive aphasia. It is suggested that CBF SPECT should be used selectively and as an adjunct to clinical evaluation and CT.

A 99mTc-HMPAO single-photon emission computed tomography study of Lewy body disease

The purpose of this study was to investigate patterns of 99mTc-HMPAO single-photon emission computed tomography (SPECT) abnormality in Lewy body disease (LBD) and to compare findings with those encountered in Alzheimer's disease (AD). The study group comprised 20 consecutive patient referrals fulfilling clinical criteria for LBD. All patients had fluctuating cognitive impairment and 'subcortical' dysfunction with or without perceptuospatial and/or linguistic impairment. Six patients had asymmetrical signs of parkinsonism (three left-sided and three right-sided), and 14 patients had symmetrical features of extrapyramidal involvement. 99mTc-HMPAO SPECT imaging was performed on LBD patients and findings compared with those of 57 patients with 'probable' AD and 11 normal age-matched controls. Within the LBD and AD groups, patterns of cortical and subcortical blood-flow abnormality were compared with patterns of cognitive and neurological breakdown. LBD was associated with bilateral posterior cortical blood flow abnormality, a pattern strikingly similar to that found in AD. Within the LBD group, cortical blood-flow abnormality was found to reflect patterns of neurological dysfunction (parkinsonism) indicative of subcortical involvement. In contrast, cortical blood-flow changes did not reflect patterns of neuropsychological impairment suggestive of cortical dysfunction. Within the AD group, cortical blood-flow changes were mirrored by the pattern of neuropsychological impairment. Findings support the notion that cortical blood-flow abnormality in LBD might reflect a combination of direct cortical pathology and cortical deafferentation secondary to subcortical Lewy body pathology. It would appear that 99mTc-HMPAO SPECT imaging is of limited value in the clinical differentiation of LBD and AD.

Atypical amyloid (A beta) deposition in the cerebellum in Alzheimer's disease: an immunohistochemical study using end-specific A beta monoclonal antibodies

We have used the end-specific monoclonal antibodies to amyloid beta-protein (A beta), BC05 and BA27, to investigate the molecular characteristics of the cored or stellate type of amyloid plaque that is sometimes present, along with the more common diffuse type of plaque, in the cerebellar cortex in (usually younger) cases of Alzheimer's disease. In five such cases of Alzheimer's disease the (many) cored plaques were strongly BA27, but less strongly BC05, immunopositive, indicating the presence of (much) A beta 40 and A beta 42(43), respectively. Diffuse plaques were only BC05 positive, except on rare occasions where a litter BA27 reactivity was present. Cerebellar cored plaques, like the diffuse plaques, were not associated with tau or astrocytic (glial fibrillary acid protein) immunoreactivity, though in contrast to cerebellar diffuse plaques, but like the cored plaques in the cerebral cortex, microglial cells were usually present. The cause of this form of A beta deposition in the cerebellum is not known. Although congophilic angiopathy was severe in two patients, this was only mild in the other. Similar plaques were also seen in the cerebellum of most, but not all, of five other younger patients with chromosome 14-linked Alzheimer's disease and again, although congophilic angiopathy was severe in one such case with many cored plaques, this was not so in the others. At present the relationship (if any) between this pathological change and the possession of the chromosome 14 mutation of Alzheimer's disease or the occurrence of congophilic angiopathy remains uncertain.

Autobiographical experience and word meaning

The role of current personal experience in understanding of word meaning was investigated in a patient, WM, who suffers from semantic dementia. The study was prompted by the observation that WM, despite being severely impaired on formal tests of word comprehension and naming, retained a range of vocabulary pertaining to her daily life. If autobiographical experience has a general facilitatory effect, then this should affect which concepts are retained and which lost, but not influence the quality of that conceptual knowledge. Conversely, if personal autobiography has a direct role in investing concepts with meaning, then WM's understanding of nominal terms that she uses spontaneously in conversation ought not to be normal, but should be constrained by the autobiographical context in which she uses those terms. WM could define nouns and noun phrases drawn from her conversational vocabulary, but her definitions had a markedly autobiographical quality. Moreover, WM was extremely impaired in her ability to define new noun phrases, constructed by combining words from her conversational vocabulary (e.g. "dog licence", constructed from "driving licence" and "dog"; "oil field" constructed from "oil" and "field"). It was concluded that WM does not have normal conceptual understanding of nouns and noun phrases that she uses appropriately in conversation. Her understanding is narrow and autobiographically constrained. The findings, which suggest an interactive relationship between autobiographical and semantic memory, have implications for understanding of the progressive breakdown of semantic knowledge.