Dementia and motor neuron disease: morphometric, biochemical, and Golgi studies

Frontotemporal dementia: from genetics to therapeutic approaches

INTRODUCTION

Frontotemporal dementia (FTD) includes a group of neurodegenerative diseases characterized clinically by behavioral disturbances and by neurodegeneration of brain anterior temporal and frontal lobes, leading to atrophy. Apart from symptomatic treatments, there is, at present, no disease-modifying cure for FTD.

AREAS COVERED

Three main mutations are known as causes of familial FTD, and large consortia have studied carriers of mutations, also in preclinical Phases. As genetic cases are the only ones in which the pathology can be predicted in life, compounds developed so far are directed toward specific proteins or mutations. Herein, recently approved clinical trials will be summarized, including molecules, mechanisms of action and pharmacological testing.

EXPERT OPINION

These studies are paving the way for the future. They will clarify whether single mutations should be addressed rather than common proteins depositing in the brain to move from genetic to sporadic FTD.

Neuronal dysfunction caused by FUSR521G promotes ALS-associated phenotypes that are attenuated by NF-κB inhibition

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are related neurodegenerative diseases that belong to a common disease spectrum based on overlapping clinical, pathological and genetic evidence. Early pathological changes to the morphology and synapses of affected neuron populations in ALS/FTD suggest a common underlying mechanism of disease that requires further investigation. Fused in sarcoma (FUS) is a DNA/RNA-binding protein with known genetic and pathological links to ALS/FTD. Expression of ALS-linked FUS mutants in mice causes cognitive and motor defects, which correlate with loss of motor neuron dendritic branching and synapses, in addition to other pathological features of ALS/FTD. The role of ALS-linked FUS mutants in causing ALS/FTD-associated disease phenotypes is well established, but there are significant gaps in our understanding of the cell-autonomous role of FUS in promoting structural changes to motor neurons, and how these changes relate to disease progression. Here we generated a neuron-specific FUS-transgenic mouse model expressing the ALS-linked human FUSR521G variant, hFUSR521G/Syn1, to investigate the cell-autonomous role of FUSR521G in causing loss of dendritic branching and synapses of motor neurons, and to understand how these changes relate to ALS-associated phenotypes. Longitudinal analysis of mice revealed that cognitive impairments in juvenile hFUSR521G/Syn1 mice coincide with reduced dendritic branching of cortical motor neurons in the absence of motor impairments or changes in the neuromorphology of spinal motor neurons. Motor impairments and dendritic attrition of spinal motor neurons developed later in aged hFUSR521G/Syn1 mice, along with FUS cytoplasmic mislocalisation, mitochondrial abnormalities and glial activation. Neuroinflammation promotes neuronal dysfunction and drives disease progression in ALS/FTD. The therapeutic effects of inhibiting the pro-inflammatory nuclear factor kappa B (NF-κB) pathway with an analog of Withaferin A, IMS-088, were assessed in symptomatic hFUSR521G/Syn1 mice and were found to improve cognitive and motor function, increase dendritic branches and synapses of motor neurons, and attenuate other ALS/FTD-associated pathological features. Treatment of primary cortical neurons expressing FUSR521G with IMS-088 promoted the restoration of dendritic mitochondrial numbers and mitochondrial activity to wild-type levels, suggesting that inhibition of NF-κB permits the restoration of mitochondrial stasis in our models. Collectively, this work demonstrates that FUSR521G has a cell-autonomous role in causing early pathological changes to dendritic and synaptic structures of motor neurons, and that these changes precede motor defects and other well-known pathological features of ALS/FTD. Finally, these findings provide further support that modulation of the NF-κB pathway in ALS/FTD is an important therapeutic approach to attenuate disease.

Synaptic dysfunction in ALS and FTD: anatomical and molecular changes provide insights into mechanisms of disease

Synaptic loss is a pathological feature of all neurodegenerative diseases including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). ALS is a disease of the cortical and spinal motor neurons resulting in fatal paralysis due to denervation of muscles. FTD is a form of dementia that primarily affects brain regions controlling cognition, language and behavior. Once classified as two distinct diseases, ALS and FTD are now considered as part of a common disease spectrum based on overlapping clinical, pathological and genetic evidence. At the cellular level, aggregation of common proteins and overlapping gene susceptibilities are shared in both ALS and FTD. Despite the convergence of these two fields of research, the underlying disease mechanisms remain elusive. However, recent discovers from ALS and FTD patient studies and models of ALS/FTD strongly suggests that synaptic dysfunction is an early event in the disease process and a unifying hallmark of these diseases. This review provides a summary of the reported anatomical and cellular changes that occur in cortical and spinal motor neurons in ALS and FTD tissues and models of disease. We also highlight studies that identify changes in the proteome and transcriptome of ALS and FTD models and provide a conceptual overview of the processes that contribute to synaptic dysfunction in these diseases. Due to space limitations and the vast number of publications in the ALS and FTD fields, many articles have not been discussed in this review. As such, this review focuses on the three most common shared mutations in ALS and FTD, the hexanucleuotide repeat expansion within intron 1 of chromosome 9 open reading frame 72 (C9ORF72), transactive response DNA binding protein 43 (TARDBP or TDP-43) and fused in sarcoma (FUS), with the intention of highlighting common pathways that promote synaptic dysfunction in the ALS-FTD disease spectrum.

Applied Bayesian Approaches for Research in Motor Neuron Disease

Statistical evaluation of empirical data is the basis of the modern scientific method. Available tools include various hypothesis tests for specific data structures, as well as methods that are used to quantify the uncertainty of an obtained result. Statistics are pivotal, but many misconceptions arise due to their complexity and difficult-to-acquire mathematical background. Even though most studies rely on a frequentist interpretation of statistical readouts, the application of Bayesian statistics has increased due to the availability of easy-to-use software suites and an increased outreach favouring this topic in the scientific community. Bayesian statistics take our prior knowledge together with the obtained data to express a degree of belief how likely a certain event is. Bayes factor hypothesis testing (BFHT) provides a straightforward method to evaluate multiple hypotheses at the same time and provides evidence that favors the null hypothesis or alternative hypothesis. In the present perspective, we show the merits of BFHT for three different use cases, including a clinical trial, basic research as well as a single case study. Here we show that Bayesian statistics is a viable addition of a scientist's statistical toolset, which can help to interpret data.

Frontotemporal lobar degeneration with TAR DNA-binding protein 43 (TDP-43): its journey of more than 100 years

Frontotemporal lobar degeneration (FTLD) with TDP-43-immunoreactive inclusions (FTLD-TDP) is a neurodegenerative disease associated with clinical, genetic, and neuropathological heterogeneity. An association between TDP-43, FTLD and amyotrophic lateral sclerosis (ALS) was first described in 2006. However, a century before immunohistochemistry existed, atypical dementias displaying behavioral, language and/or pyramidal symptoms and showing non-specific FTLD with superficial cortical neuronal loss, gliosis and spongiosis were often confused with Alzheimer's or Pick's disease. Initially this pathology was termed dementia lacking distinctive histopathology (DLDH), but this was later renamed when ubiquitinated inclusions originally found in ALS were also discovered in (DLDH), thus warranting a recategorization as FTLD-U (ubiquitin). Finally, the ubiquitinated protein was identified as TDP-43, which aggregates in cortical, subcortical, limbic and brainstem neurons and glial cells. The topography and morphology of TDP-43 inclusions associate with specific clinical syndromes and genetic mutations which implies different pathomechanisms that are yet to be discovered; hence, the TDP-43 journey has actually just begun. In this review, we describe how FTLD-TDP was established and defined clinically and neuropathologically throughout the past century.

Mislocalisation of TDP-43 to the cytoplasm causes cortical hyperexcitability and reduced excitatory neurotransmission in the motor cortex

Amyotrophic lateral sclerosis (ALS) is a chronic neurodegenerative disease pathologically characterised by mislocalisation of the RNA-binding protein TAR-DNA-binding protein 43 (TDP-43) from the nucleus to the cytoplasm. Changes to neuronal excitability and synapse dysfunction in the motor cortex are early pathological changes occurring in people with ALS and mouse models of disease. To investigate the effect of mislocalised TDP-43 on the function of motor cortex neurons we utilised mouse models that express either human wild-type (TDP-43^WT ) or nuclear localisation sequence-deficient TDP-43 (TDP-43^ΔNLS ) on an inducible promoter that enriches expression to forebrain neurons. Pathophysiology was investigated through immunohistochemistry and whole-cell patch-clamp electrophysiology. Thirty days expression of TDP-43^ΔNLS in adult mice did not cause any changes in the number of CTIP2-positive neurons in the motor cortex. However, at this time-point, the expression of TDP-43^ΔNLS drives intrinsic hyperexcitability in layer V excitatory neurons of the motor cortex. This hyperexcitability occurs concomitantly with a decrease in excitatory synaptic input to these cells and fluctuations in both directions of ionotropic glutamate receptors. This pathophysiology is not present with TDP-43^WT expression, demonstrating that the localisation of TDP-43 to the cytoplasm is crucial for the altered excitability phenotype. This study has important implications for the mechanisms of toxicity of one of the most notorious proteins linked to ALS, TDP-43. We provide the first evidence that TDP-43 mislocalisation causes aberrant synaptic function and a hyperexcitability phenotype in the motor cortex, linking some of the earliest dysfunctions to arise in people with ALS to mislocalisation of TDP-43.

Phenotypic variability and its pathological basis in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized by its inherent clinicopathological variability. The concurrence of upper and lower motor neuron signs is a common feature in the majority of patients with ALS. However, some patients manifest an atypical clinical course, with only upper or lower motor neuron signs, or various extra-motor symptoms including cognitive dysfunction, parkinsonism, autonomic dysfunction, or ophthalmoparesis. This variability indicates different manifestations of ALS and is reflected by ALS pathology spreading into the central nervous system. The presence of cytoplasmic inclusions positive for transactivation response DNA-binding protein 43 kDa (TDP-43) is a key feature in ALS. Loss of TDP-43 from the nucleus and its subsequent aggregation in the cytoplasm may occur in susceptible regions and may be associated with neuronal loss. However, in some regions, there is no apparent neuronal loss while TDP-43 accumulation is evident; in contrast, in other regions, neuronal loss is apparent without any evidence of TDP-43 accumulation. Therefore, in addition to TDP-43 dysfunction, underlying region-specific cellular vulnerability may exist in the upper and lower motor neurons and frontotemporal system in patients with ALS. The microscopic discrepancy and selective vulnerability may be linked to the macroscopic propensities of the sites of onset, and may also determine the direction and rate of progression of the lesions. Thus, there may be multicentric sites of onset, region-oriented disease development, and different speeds of disease progression across patients with ALS. ALS lesions occur in motor-related areas but may spread to neighboring areas. However, since lesions may spread in a discontinuous manner, and the dynamics of disease propagation have not been able to be identified, it remains controversial whether the stepwise appearance of TDP-43-positive inclusions is based on direct cell-to-cell protein propagation. Further understanding of the phenotypic variability of ALS and its pathological basis may serve as a guide for investigating the underlying pathogenesis of ALS.

Driven to decay: Excitability and synaptic abnormalities in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron (MN) disease and is clinically characterised by the death of corticospinal motor neurons (CSMNs), spinal and brainstem MNs and the degeneration of the corticospinal tract. Degeneration of CSMNs and MNs leads inexorably to muscle wastage and weakness, progressing to eventual death within 3-5 years of diagnosis. The CSMNs, located within layer V of the primary motor cortex, project axons constituting the corticospinal tract, forming synaptic connections with brainstem and spinal cord interneurons and MNs. Clinical ALS may be divided into familial (∼10% of cases) or sporadic (∼90% of cases), based on apparent random incidence. The emergence of transgenic murine models, expressing different ALS-associated mutations has accelerated our understanding of ALS pathogenesis, although precise mechanisms remain elusive. Multiple avenues of investigation suggest that cortical electrical abnormalities have pre-eminence in the pathophysiology of ALS. In addition, glutamate-mediated functional and structural alterations in both CSMNs and MNs are present in both sporadic and familial forms of ALS. This review aims to promulgate debate in the field with regard to the common aetiology of sporadic and familial ALS. A specific focus on a nexus point in ALS pathogenesis, namely, the synaptic and intrinsic hyperexcitability of CSMNs and MNs and alterations to their structure are comprehensively detailed. The association of extramotor dysfunction with neuronal structural/functional alterations will be discussed. Finally, the implications of the latest research on the dying-forward and dying-back controversy are considered.

Motor Areas Show Altered Dendritic Structure in an Amyotrophic Lateral Sclerosis Mouse Model

Objective: Motor neurons (MNs) die in amyotrophic lateral sclerosis (ALS), a clinically heterogeneous neurodegenerative disease of unknown etiology. In human or rodent studies, MN loss is preceded by increased excitability. As increased neuronal excitability correlates with structural changes in dendritic arbors and spines, we have examined longitudinal changes in dendritic structure in vulnerable neuron populations in a mouse model of familial ALS.

Methods: We used a modified Golgi-Cox staining method to determine the progressive changes in dendritic structure of hippocampal CA1 pyramidal neurons, striatal medium spiny neurons, and resistant (trochlear, IV) or susceptible (hypoglossal, XII; lumbar) MNs from brainstem and spinal cord of mice over-expressing the human SOD1^G93A (SOD1) mutation, in comparison to wild-type (WT) mice, at four postnatal (P) ages of 8–15, 28–35, 65–75, and 120 days.

Results: In SOD1 mice, dendritic changes occur at pre-symptomatic ages in both XII and spinal cord lumbar MNs. Spine loss without dendritic changes was present in striatal neurons from disease onset. Spine density increases were present at all ages studied in SOD1 XII MNs. Spine density increased in neonatal lumbar MNs, before decreasing to control levels by P28-35 and was decreased by P120. SOD1 XII MNs and lumbar MNs, but not trochlear MNs showed vacuolization from the same time-points. Trochlear MN dendrites were unchanged.

Interpretation: Dendritic structure and spine alterations correlate with the neuro-motor phenotype in ALS and with cognitive and extra-motor symptoms seen in patients. Prominent early changes in dendritic arbors and spines occur in susceptible cranial and spinal cord MNs, but are absent in MNs resistant to loss in ALS.

Dysregulated molecular pathways in amyotrophic lateral sclerosis-frontotemporal dementia spectrum disorder

Frontotemporal dementia (FTD), the second most common form of dementia in people under 65 years of age, is characterized by progressive atrophy of the frontal and/or temporal lobes. FTD overlaps extensively with the motor neuron disease amyotrophic lateral sclerosis (ALS), especially at the genetic level. Both FTD and ALS can be caused by many mutations in the same set of genes; the most prevalent of these mutations is a GGGGCC repeat expansion in the first intron of C9ORF72 As shown by recent intensive studies, some key cellular pathways are dysregulated in the ALS-FTD spectrum disorder, including autophagy, nucleocytoplasmic transport, DNA damage repair, pre-mRNA splicing, stress granule dynamics, and others. These exciting advances reveal the complexity of the pathogenic mechanisms of FTD and ALS and suggest promising molecular targets for future therapeutic interventions in these devastating disorders.

Marked changes in dendritic structure and spine density precede significant neuronal death in vulnerable cortical pyramidal neuron populations in the SOD1(G93A) mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterised by the death of upper (corticospinal) and lower motor neurons (MNs) with progressive muscle weakness. This incurable disease is clinically heterogeneous and its aetiology remains unknown. Increased excitability of corticospinal MNs has been observed prior to symptoms in human and rodent studies. Increased excitability has been correlated with structural changes in neuronal dendritic arbors and spines for decades. Here, using a modified Golgi-Cox staining method, we have made the first longitudinal study examining the dendrites of pyramidal neurons from the motor cortex, medial pre-frontal cortex, somatosensory cortex and entorhinal cortex of hSOD1^G93A (SOD1) mice compared to wild-type (WT) littermate controls at postnatal (P) days 8–15, 28–35, 65–75 and 120. Progressive decreases in dendritic length and spine density commencing at pre-symptomatic ages (P8-15 or P28-35) were observed in layer V pyramidal neurons within the motor cortex and medial pre-frontal cortex of SOD1 mice compared to WT mice. Spine loss without concurrent dendritic pathology was present in the pyramidal neurons of the somatosensory cortex from disease-onset (P65-75). Our results from the SOD1 model suggest that dendritic and dendritic spine changes foreshadow and underpin the neuromotor phenotypes present in ALS and may contribute to the varied cognitive, executive function and extra-motor symptoms commonly seen in ALS patients. Determining if these phenomena are compensatory or maladaptive may help explain differential susceptibility of neurons to degeneration in ALS.

Psychiatric symptoms in frontotemporal dementia: epidemiology, phenotypes, and differential diagnosis

Frontotemporal dementia (FTD) is the most frequently occurring dementia in the presenile population. Despite epidemiologic data showing that patients with FTD may have experienced previous psychiatric disorders and that patients with psychotic disorders may develop dementia more often than expected in the nonaffected population, the overlap between these two conditions has been underestimated. Nevertheless, the identification in recent years of several genetic causes of FTD associated with heterogeneous and atypical presentations, including pure psychiatric symptoms, has shifted scientific interest back to obtaining a better understanding of common mechanisms between FTD and psychotic disorders. We review the current knowledge of the FTD spectrum and common features shared by FTD and some psychiatric diseases, starting from Pick's clinical description of the disease, moving toward pathogenic aspects of the disease and genetic causes and associated phenotypes, and finishing with analysis of crossing borders between FTD and psychiatric disorders (mainly represented by schizophrenia and bipolar spectrum disorders) in clinical practice in terms of overlapping symptoms, differential diagnosis, comorbidity, and treatment issues.

Amyotrophic lateral sclerosis with dementia showing clinical parkinsonism and severe degeneration of the substantia nigra: Report of an autopsy case

An autopsy case of amyotrophic lateral sclerosis with dementia (ALS-D) showing clinically overt parkinsonism and severe degeneration of the substantia nigra is reported. The patient was a 78-year-old man who died after a 2-year clinical course characterized by parkinsonism that was responsive to Levodopa (L-DOPA) treatment. Motor neuron symptoms and dementia were not apparent ante-mortem. The autopsy demonstrated the severe degeneration of the substantia nigra without alpha-synucleinopathy-related changes. Finely granular mineralization of necrotic neurons was a unique finding in the substantia nigra. The mild loss of spinal anterior horn cells, the appearance of several Bunina bodies and the degeneration of the hippocampal subiculum and temporal cortex were also noted. A small number of ubiquitinated intra-cytoplasmic inclusions were found in neurons of the dentate fascia of the hippocampus and the temporal and frontal cortices. Although the degeneration of the substantia nigra is a common finding in ALS-D, patients seldom develop clinically overt parkinsonism. This case indicates that patients with ALS-D rarely present with predominantly parkinsonian clinical features and these symptoms and signs can be improved by L-DOPA treatment.

Neuronal Ubiquitinated Intranuclear Inclusions in Familial and Non-Familial Frontotemporal Dementia of the Motor Neuron Disease Type Associated with Amyotrophic Lateral Sclerosis

Ubiquitinated cytoplasmic inclusions (Ub-CIs) in superficial frontal cortex and dentate gyrus neurons are the hallmark of frontotemporal degeneration of the motor neuron disease-type (FTD-MND-type). To date, 2 reports have described intranuclear ubiquitinated inclusions (Ub-INIs) in 9 cases of familial FTD-MND-type (without clinical or pathologic motor neuron disease, MND). In the current study we found an additional 11 cases with Ub-INIs. We have identified for the first time among these cases 2 with a negative family history and 3 that have concomitant amyotrophic lateral sclerosis (ALS). The results of the present study i) confirm a previous report of significantly lower average brain weight and longer duration in cases with Ub-INIs, ii) reveal significantly greater striatal neuronal loss and gliosis in cases with intranuclear inclusions, and iii) demonstrate that intranuclear inclusions correlate with cytoplasmic inclusions and dystrophic neurites in frontal cortex and striatum but not in dentate gyrus. In addition, the current study confirms that Ub-INIs are found in familial FTD-MND-type, but also extends the presence of Ub-INIs to familial FTD-MND (with concomitant ALS), and probably also to non-familial FTD-MND-type.

Ubiquitin-only intraneuronal inclusion in the substantia nigra is a characteristic feature of motor neurone disease with dementia

Two types of ubiquitinated inclusions have been described in motor neurone disease (MND). (1) Skein or globular ubiquitinated inclusions in the motor neurones (more frequently in the lower motor neurones). This is a characteristic feature of all motor neurone disease categories. (2) Dot-shape or crescentric ubiquitinated inclusions in the upper layers of cortex and dentate gyrus described in cases of motor neurone disease with dementia (DMND). We investigated the substantia nigra (SN) in MND cases; two cases of motor neurone disease inclusion body (MND-IB) dementia, six cases of DMND, 14 cases of MND (including one case from Guam and two cases of familial SOD1 mutation), four cases of Parkinson's disease (PD), and 10 cases of age-matched normal controls. SN and spinal cord sections were stained with ubiquitin (alpha-synuclein, tau, PGM1, SMI-31 and SOD1 antibodies). The neuronal density in SN was quantified by using a computer-based image analysis system. Four out of six DMND cases showed rounded ubiquitin positive inclusions with irregular frayed edges, associated with neuronal loss, reactive astrocytosis and a large number of activated microglia cells. These inclusions are negative with antibodies to (alpha-synuclein, tau, SMI-31 and SOD1). The SN in cases from MND-IB dementia and MND showed occasional neuronal loss and no inclusions. The ubiquitin-only inclusions in SN of DMND cases are similar (but not identical) to the ubiquitinated inclusions described previously in the spinal cord of MND cases and are distinct from Lewy bodies (LBs). The degeneration of SN is most likely a primary neurodegenerative process of motor neurone disease type frequently involving the DMND cases. MND disease is a spectrum and multisystem disorder with DMND located at the extreme end of a spectrum affecting the CNS more widely than just the motor system.

Other Parkinson syndromes

The etiology of parkinsonism is varied. Symptomatic parkinsonism is seen in the setting of genetic disorders, infectious processes, structural lesions, and as a result of concomitant medications. A thorough history and good examination will differentiate PD from the diverse group of conditions that can mimic it.

An overview of common non-alzheimer dementias

Approximately 20% to 40% of dementia is caused by diseases other than Alzheimer's disease. This article reviews the major categories of non-Alzheimer dementia, including dementia associated with cerebrovascular disease, dementia associated with extrapyramidal features, and the frontotemporal dementias. Dementia associated with cerebrovascular disease is a heterogeneous condition the importance of which is often misunderstood. Dementia with Lewy bodies, the most common of the dementias associated with extrapyramidal disease, is becoming better recognized for its unique management issues. At least some of the frontotemporal dementias, which in this article encompass the progressive aphasias, have mutations in the tau gene that account for some of the phenotypic variations.

Extramotor involvement in ALS: PET studies with the GABA(A) ligand [(11)C]flumazenil

We used the benzodiazepine GABA(A) marker [(11)C] flumazenil to study cerebral dysfunction in amyotrophic lateral sclerosis (ALS) with PET. Seventeen non-demented patients with clinically definite or probable ALS were scanned and statistical parametric maps were derived to localize changes in regional flumazenil volumes of distribution (FMZVD), which correlate closely with receptor density (B(max)), and the results were compared with those of 17 controls. The ALS group showed statistically significant decreases in relative FMZVD in the prefrontal cortex (areas 9 and 10 bilaterally), parietal cortex (area 7 bilaterally), visual association cortex (area 18 bilaterally) and left motor/premotor cortex (including area 4) (P < 0.001). Relative reductions in FMZVD were also seen in the left ventrolateral and dorsolateral prefrontal cortex (areas 45, 46 and 47), Broca's area and the right temporal (area 21) and right visual association cortex (area 19). These observations suggest that cerebral dysfunction in ALS involves motor/premotor and extramotor areas, particularly the prefrontal regions.

Frontotemporal dementia with motor neuron disease (amyotrophic lateral sclerosis with dementia)

Frontotemporal dementia (FTD) with motor neuron disease means amyotrophic lateral sclerosis (ALS) with dementia. In the cerebrum of this condition, the medial cortex of the rostral temporal lobe is constantly and most remarkably involved. Another constant and quite characteristic lesion is neuronal loss localized to the CA1-subiculum transitional area at the level of the pes hippocampi. The rostral portion of the parahippocampal gyrus, and the amygdaloid nucleus are also involved. Ubiquitinated intracytoplasmic inclusions are seen in the dentate granule cells and parahippocampal gyrus neurons. Some cases of ALS without dementia show the identical temporal lobe degeneration as well as the cortical ubiquitinated inclusions, thus raising the possibility of overlooked dementia or premature death of the patients. Similarly, recently proposed motor neuron disease-inclusion dementia may be a forme fruste of ALS with dementia.

Fronto-temporal dementia and motor neuron disease: a neuropsychological study

The neuropsychological follow-up study of a 58-year-old man suffering from Motor Neuron Disease (ALS/MND) and Fronto-Temporal Dementia (FTD) is reported. Neuromuscular signs first appeared at the age of 51 and slowly progressed to late bulbar involvement; behavioural symptoms of the frontal type first appeared around age 53; lastly, several neuropsychological symptoms suggestive of worsening temporal involvement supervened at age 57. Our patient died at 59 of respiratory failure with the classic clinical and neuroradiological picture of FTD. A short discussion addresses the controversial issue of the coupling of ALS/MND with Dementia and its possible interpretation as the expression of a chance association of relatively common diseases, versus that of a single multifaceted disease. The role of a detailed neuropsychological assessment is highlighted, within the context of increasingly specific diagnostic criteria for FTD.

Diagnostic dilemmas in amyotrophic lateral sclerosis

The El Escorial criteria for the diagnosis of amyotrophic lateral sclerosis (ALS) were introduced in 1990 to provide a standardised and diagnostically reliable approach to the early recognition of this disease. It is still unclear, however, whether these are the best criteria available for the early diagnosis of ALS. We applied these criteria retrospectively to clinical material available from 34 cases of autopsy proven ALS in an attempt to validate their usefulness in a pathological series. The clinical material was reviewed and specific clinical signs and anatomical levels of involvement recorded. Only signs listed in the criteria were included in the analysis. The El Escorial criteria for clinically definite ALS demonstrated high sensitivity and accuracy when validated in this clinicopathological study. Neuroimaging and electromyography were important in shortening the time in which patients were given a diagnosis of clinically definite ALS. Other diagnostic dilemmas in ALS and the role of early diagnosis of this disease are discussed.

Recognition memory deficits in amyotrophic lateral sclerosis assessed with event-related brain potentials

OBJECTIVES

Amyotrophic lateral sclerosis (ALS) has been shown to cause neuropsychological deficits. The present investigation sought to delineate memory deficits by recording cognitive event-related potentials (ERPs).

SUBJECTS AND METHODS

Eight ALS patients and 8 matched controls were subjected to a 2-phase recognition memory test. During the first phase words were presented consecutively on a video-screen with one-third of the words being repeated. The subject had to press buttons according to whether a word had been repeated or not. During the second phase (delay 1 h) a second list containing 33% old items from phase 1 and 66% new words was shown with an old/new decision required.

RESULTS

ALS patients showed less accurate recognition in the second phase. The ERPs of the controls showed a reliable difference between old and new items in both phases. This difference was nearly absent in the patients in both phases.

CONCLUSION

The ERP pattern suggests abnormal memory processes in ALS. The results are compared with data from similar experiments in Huntington's and Alzheimer's disease and are interpreted in terms of an encoding deficit in ALS.

Cognitive function in amyotrophic lateral sclerosis

Cognitive function in patients with amyotrophic lateral sclerosis (ALS) has drawn recent attention. However, the pathogenesis of cognitive dysfunction in patients with ALS remains uncertain. To explore the underlying mechanism for cognitive dysfunction further, we studied 26 patients with ALS (15 male and 11 female; age from 36 to 67 years) by using neuropsychological batteries, magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT). We also evaluated these patients and an additional 26 age- and sex-matched normal controls using neuropsychological batteries with special attention to the frontal lobe function. On the basis of neuropsychological examination, we classified patients into three groups using cluster analysis. Age, education level and severity were comparable across these subgroups. Neuropathologic examination was subsequently carried out in six patients. Patients in Group 1 and 2 had low scores on all measures compared to patients in Group 3 and normal controls. Patients in Group 1 and 2 had frontal atrophy on MRI and reduced isotope uptake in the frontal region on SPECT, which was more evident in patients in Group 1. On neuropathologic examination, patients in Group 1 showed spongy degeneration and neuronal loss in the frontal lobe. Patients in Group 3 showed no notable pathology in the frontal region. The gradient distribution of the scores for attention and executive function, as well as SPECT findings suggested the presence of a continuum of cognitive disability in patients with ALS corresponding to the pathologic process in the frontal lobe ranging from significant impairment to normality. We, therefore, believe that inattention and executive dysfunction alternatives may evolve in patients with ALS corresponding to the pathologic process in the frontal lobe.

Disinhibition-dementia-parkinsonism-amyotrophy complex (DDPAC) is a non-Alzheimer's frontotemporal dementia

DDPAC was defined based on the cardinal symptoms of the syndrome found in family Mo. Investigation of DDPAC cases in family Mo shows non-specific pathological changes in a distribution that is consistent with the cardinal features of the disease. Genetic analysis identified a locus on chromosome 17q21-22 that produces this syndrome which is inherited as an autosomal dominant trait. DDPAC overlaps clinically and pathologically with a variety of named neurodegenerative syndromes and falls within the spectrum called frontotemporal dementia. The localization of the disease locus for DDPAC allows the testing of whether other familial neurodegenerative conditions also map to the same chromosomal regions. It seems possible that ultimately these conditions that have thus far been difficult to categorize will be subject to a nosology based on genetic etiology.

Nonverbal visual attention, but not recognition memory of learning, processes are impaired in motor neurone disease

Pathology outside the motor system is being increasingly recognised in motor neurone disease (MND) and up to 3% of patients may have overt dementia of frontal lobe type; it is not clear whether milder cognitive disturbance is a more frequent feature of the disease. Standard neuropsychological testing can be difficult in MND and we therefore used the microcomputer-controlled Cambridge Neuropsychological Test Automated Battery (CANTAB), which allows accurate assessment in the presence of motor and bulbar dysfunction. The results of subtests evaluating nonverbal visual attention, recognition memory and learning from a large (n = 50) group of patients with MND compared to normal (n = 27) and neurological disease (n = 23) control groups are presented in this report. The MND group showed significant impairment in a focal attention (visual search) task, but no deficits in memory or learning. Inspection of the visual search data showed that up to a quarter of the MND patients scored two or more standard deviations below the mean control score. It is suggested that this reflects pathology in fronto-striatal circuitry.

Mouse inoculation studies reveal no transmissible agent in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) resembles the spongiform encephalopathies in its dual pattern of inherited and sporadic cases, its uniform prevalence in different populations, its late onset (suggestive of a long incubation period) and its pathological picture of neuronal degeneration without inflammation. There is a well-established protocol for primary transmission of scrapie and related diseases to mice. Using this, we inoculated four longlived, inbred, mouse strains with cord material fresh-frozen within three hours of death, from a case of ALS or a control case. No motor neuron loss, gliosis or tract demyelination was found in the experimental group. Fifty per cent of each group were observed for more than 600 days. Two types of lesions were found in these animals at death: widespread foci of white matter vacuolation and bilateral thalamic mineral deposits. They were present in the control group at the same incidence and severity as in the experimental group and were thus considered to represent an age-related change. Attention is drawn to them because they have been claimed as significant when found in a transgenic model of spongiform encephalopathy. The results of our carefully-controlled experiment suggest that it is unlikely that ALS is caused by a scrapie-like agent capable of transmission to mice.

Corticobasal degeneration with neither argyrophilic inclusions nor tau abnormalities: a new subgroup?

In corticobasal degeneration (CBD), cerebral cortical neuronal loss with achromasia and degeneration of the subcortical nuclei, particularly the substantia nigra, are common. Recent studies have suggested that the occurrence of argyrophilic nigral inclusions, resembling the neurofibrillary tangles found in progressive supranuclear palsy, and widespread tau abnormalities may be features of CBD. We studied brain tissues from two patients in whom CBD was suspected clinically. From the distribution of their cortical and subcortical lesions, the patients were diagnosed as having CBD. However, Gallyas/tau-positive neuronal and glial structures were not found, which suggests there may be a subgroup of CBD with neither argyrophilic inclusions nor tau abnormalities.

Clinical, neuroimaging, and pathologic features of progressive nonfluent aphasia

We report the clinical, neuroimaging, and neuropathologic features of progressive nonfluent aphasia (PNFA), a rare neurodegenerative syndrome most notable for its distinct language disturbance. Longitudinal observations of 3 patients revealed progressively telegraphic speech and writing, followed by gradual deterioration of sentence comprehension, and finally, preterminal mutism and dementia. Magnetic resonance imaging revealed cortical atrophy most pronounced in anterior regions of the left hemisphere. Functional neuroimaging demonstrated reduced cerebral activity most prominently in left frontal and temporal regions. At necropsy, microscopic pathology of brain was most consistent with the diagnosis of "dementia lacking distinctive histology" (DLDH). A review of published primary progressive aphasia cases with adequate clinical and histopathological descriptions reveals that the most common pathology underlying PNFA is DLDH. PNFA is one example of a family of clinical syndromes with similar underlying histopathology that affects different regions of the frontal lobe.

The neurochemistry of Alzheimer type, vascular type and mixed type dementias compared

We present the results of a meta-analysis of neurochemical changes in human post mortem brains of Alzheimer type (AD), vascular type (VD) and mixed type (MF) dementias, and matched controls based on 275 articles published between January 1980 and February 1994. Severity of degeneration between the different neurochemical systems is as follows, although ranking is difficult with regard to limited numbers of investigations in some neurochemical systems: Cholinergic system > serotonergic system > excitatory amino acids > GABAergic system > energy metabolism > NA > oxidative stress parameters > neuropeptides > DA. But, within a neurochemical system, degeneration is not evenly distributed. Spared parameters, e.g. muscarinic receptors and MAO-B, allow to make some suggestions for future therapeutic strategies.

Hypertension and neuropsychological function: a lifespan perspective

This article explores the relationship of hypertension to neuropsychological performance from a lifespan perspective. First, I examine cross-sectional and longitudinal studies of neuropsychological performance in cohorts of young to middle-aged hypertensive patients (ages 20-60); older hypertensive patients (ages 60-80+); and the young, normotensive offspring of hypertensive parents (ages 18-25). The pattern of performance deficits associated with hypertension is generally found to differ from that related to hypertension risk. Next, I discuss potential mechanisms underlying hypertension-performance relationships in the aforementioned cohorts. I suggest that lowered levels of performance in the offspring of hypertensives reflect genetic risk for hypertension. Compromised neuropsychological function in young and middle-aged hypertensives may occur secondary to alterations in neurophysiological function that result from elevated blood pressure. Such neurophysiological changes may predispose to neuroanatomical changes in older hypertensive patients.

Topographic involvement of the striatal efferents in basal ganglia of patients with adult-onset motor neuron disease with basophilic inclusions

This report concerns the topographic immunohistochemical analysis of the putamen, globus pallidus (GP) and substantia nigra (SN) of two patients with adult-onset motor neuron disease with basophilic inclusions (MND/BIs), seven patients with sporadic classic amyotrophic lateral sclerosis (sporadic ALS) and five neurologically normal individuals. The striatal efferent terminals of the GP and SN were visualized immunohistochemically using antibodies to met-enkephalin (MEnk) and substance P (SP). In specimens from patients with sporadic ALS and normal subjects there was intense immunostaining for MEnk and SP throughout the external and internal segments of the GP, respectively. By contrast, a marked reduction of MEnk- and SP-positive striatal efferents was seen in the ventrocaudal portions of both GP segments from the MND/BIs patients. Moreover, while MEnk-positive striosomes was readily detected in the putamen of normals and sporadic ALS patients, there was significant reduction in MEnk immunoreactivity, and no evidence of striosomal organization in the putamen of MND/BIs patients. In addition, whereas the SN of patients with sporadic ALS expressed SP, the ventrolateral SN portion of the MND/BIs patient tested had reduced immunoreactivity. The present findings on patients with MND/BIs may represent a reflection of the topographic striatum degeneration in this disease and appear to provide additional evidence for the heterogeneity of MND.

Unusual case of corticobasal degeneration with tau/Gallyas-positive neuronal and glial tangles

A 74-year-old woman with corticobasal degeneration (CBD) had a 9-year history of progressive loss of strength and rigidity of her right hand and then arm, followed by speech difficulties, dyskinesia, rigidity, spasticity and weakness of the ipsilateral lower limb, ultimately also involving the opposite side. She later developed supranuclear gaze palsy. Her memory remained intact during most of the duration of her disease. Laboratory tests and anti-Parkinsonian medications were not helpful. At autopsy, frontal lobe atrophy, discoloration of putamen (Pt) and pallor of substantia nigra (Sn) were observed. Neuronal loss and gliosis were extensive in motor cortex and milder in frontal cortex, abruptly ending at the central sulcus and junction of cingulate gyrus. "Achromatic" neurons were present. Neuronal loss and gliosis were seen in Pt and Sn and corticobasal inclusions in Sn. Numerous Gallyas/tau-positive, Bielschowsky/ubiquitin-negative coil, sickle, or coma-shaped tangles and thread-like processes were found in affected cortex, Pt and Sn. Some of the tangles were in neurons, but most occurred in astroglia, and their processes. The presence of Gallyas/tau-positive glia in CBD may have the same diagnostic significance as in progressive supranuclear palsy, analogous to the argyrophilic ubiquinated inclusions in oligodendroglia in multisystem atrophy. We suggest that in CBD: (1) cytoskeletal protein metabolism in neurons and glia can simultaneously be perturbed in certain neurodegenerative diseases, and (2) the astrocytosis in CBD may not be simply a reactive process but an integral part of the disease.

Participation of the limbic system and its associated areas in the dementia of amyotrophic lateral sclerosis

The topographic distribution of degenerative changes in large brain sections from five sporadic amyotrophic lateral sclerosis (ALS) patients with dementia and three without dementia was examined. The dementia characteristics were impaired shifting from one line of thinking to another, perseveration, and emotional disinhibition as well as impairment of cognition, and judgment. Neuropathological examinations showed definite ALS changes in all the patients studied. In addition, the five patients with dementia showed neuronal loss, gliosis, and sponginess of the superficial layers throughout the cerebral cortices, predominantly in the dorsomedial cortex of the temporal tip and the parahippocampal, ambiens, anterior cingulate, rectal, orbital, and insular gyri as well as neuronal loss in the basolateral nucleus of the amygdala, nucleus accumbens, and subiculum of the hippocampus. Ubiquitin-immunoreactive inclusions were present in some neurons in the granular cell layers of the hippocampus. Fibrous gliosis was extensive in the subcortical and deep white matter of the frontotemporal lobes. The affected regions take in the limbic system and its associated areas which are the sources of the psychological problems, including emotional disturbance, experienced by these ALS patients. The psychological problems of ALS need to be investigated in relation to the involvement of the limbic system.

New pathological findings in amyotrophic lateral sclerosis

There have been recent developments in the pathology of sporadic ALS. A new filamentous neuronal inclusion body in ALS detected by immunohistochemical localisation of the protein ubiquitin has been characterised at the light microscopic and ultrastructural level and appears specific for the disease. The molecular composition of underlying filaments remains unresolved but the quest for this is a major aim in ALS research. Despite being a progressive degenerative process which primarily affects motor systems, ALS is now recognised to involve several non-motor systems and in long survivors affects many subcortical structures. There is also accumulating evidence that the neurodegenerative process underlying ALS may present as a non-motor clinical syndrome, particularly as a frontal lobe dementia with characteristic inclusions present in the non-motor cortex. Considering ALS as a multisystem disease rather than simply a disease of motor neurones has major implications for research into pathogenesis.