Clinical and genetic characterization of leukoencephalopathies in adults.

Leukodystrophies and genetic leukoencephalopathies are a rare group of disorders leading to progressive degeneration of cerebral white matter. They are associated with a spectrum of clinical phenotypes dominated by dementia, psychiatric changes, movement disorders and upper motor neuron signs. Mutations in at least 60 genes can lead to leukoencephalopathy with often overlapping clinical and radiological presentations. For these reasons, patients with genetic leukoencephalopathies often endure a long diagnostic odyssey before receiving a definitive diagnosis or may receive no diagnosis at all. In this study, we used focused and whole exome sequencing to evaluate a cohort of undiagnosed adult patients referred to a specialist leukoencephalopathy service. In total, 100 patients were evaluated using focused exome sequencing of 6100 genes. We detected pathogenic or likely pathogenic variants in 26 cases. The most frequently mutated genes were NOTCH3, EIF2B5, AARS2 and CSF1R. We then carried out whole exome sequencing on the remaining negative cases including four family trios, but could not identify any further potentially disease-causing mutations, confirming the equivalence of focused and whole exome sequencing in the diagnosis of genetic leukoencephalopathies. Here we provide an overview of the clinical and genetic features of these disorders in adults.

Semantic dementia: demography, familial factors and survival in a consecutive series of 100 cases.

A great deal has been written about cognitive aspects of semantic dementia but little is known about the demography or prognosis. We describe these features in a consecutive series of 100 patients seen over a 17-year period; all cases were assessed and followed up in a specialist clinic. The mean age at diagnosis was 64.2 (+/-7.1) range 40-79 years, but 46 presented after age 65 and 7 after 75; a higher proportion than the existing literature might predict. Fifteen had a first-degree relative with dementia, but in seven this was almost certainly unrelated. Only two had relatives with young-onset dementia. There were no families with more than two affected members. The familial rate was estimated at between 2% and 7% (95% confidence interval 0-12%). Kaplan-Meier analyses indicated a 50% survival of 12.8 years (95% confidence interval 11.9-13.7); a more benign course than suggested by neuropathologically based studies. We were unable to identify any factors influencing survival. Of the 100, 34 have died, with pathological confirmation in 24; 18 had frontotemporal lobar degeneration with ubiquitin-positive inclusions (13 of 13 confirmed TAR DNA binding protein-43 positive), and 3 had classic tau-positive Pick bodies and 3 had Alzheimer's pathology. The age at diagnosis or death across the pathological subgroups was equivalent. Although semantic dementia has a strong statistical association with ubiquitin-positive pathology, it does not have the signature of familial frontotemporal lobar degeneration with ubiquitin-positive inclusions, notably the presence of intranuclear lentiform TAR DNA binding protein-43 inclusions. The age of onset is older than predicted and the course more slowly progressive than suggested by earlier studies of small groups of subjects.

The evolution and pathology of frontotemporal dementia.

This is a clinicopathologic study of a prospective, clinic-based cohort of patients with frontotemporal dementia (FTD)/Pick complex, who were followed to autopsy. A total of 60 patients with the clinical syndromes of the behavioural variant of FTD (FTD-bv) (n = 32), primary progressive aphasia (PPA) (n = 22), corticobasal degeneration syndrome (CBDS) (n = 4) and progressive supranuclear palsy (PSP) (n = 2) at onset, referred to a cognitive neurology clinic who had subsequent post-mortem examination were included. The most common histological variety was motor neurone disease type inclusion (MNDI) (n = 18), followed by corticobasal degeneration (CBD) (n = 12), then Pick's disease (n = 6), dementia lacking distinctive histology (DLDH) (n = 6) and PSP (n = 3). Others fulfilled the histological criteria for Alzheimer's disease combined with glial pathology (n = 6), Alzheimer's disease only (n = 4), Lewy body variant (n = 2), prion disease (n = 1), vascular dementia (n = 1) and undetermined (n = 1). The most common first syndrome among the MNDI and DLDH (tau negative) pathologies was FTD-bv, but subsequently progressive aphasia (PA), occasionally CBDS and semantic dementia also developed. Tau positive histologies of CBD, PSP and Pick bodies were most frequently associated with PPA onset or CBDS/PSP, but behavioural symptoms were also common. Age of onset was earlier in tau negative cases, but the duration of illness and gender distribution were about the same in all histological variants. Although the tau negative and positive histologies are predicted to some extent by the clinical onset, the extent of the overlap and the convergence of the syndromes in the course of the disease argue in favour of maintaining the clinical and pathological varieties under a single umbrella.

Extrapyramidal syndromes in frontotemporal degeneration.

Descriptions of extrapyramidal (EP) involvement in Pick's disease (renamed recently as FTD) appeared 80 years ago. CBD pathology was confirmed as a common substrate for primary progressive aphasia (PPA). We suggested that CBD and PPA should be included with frontal lobe dementia as Pick complex. PSP was prototype for "subcortical dementia", and aphasia and apraxia, considered unusual for PSP, are now seen as a rule. The overlap of PSP and CBD is considerable. We recently reviewed our cohort with EPS in FTD and identified 22 patients with the movement disorder as a first syndrome and another larger group of 48 patients who developed EPS after an initial onset with a cognitive disorder: aphasic, behavioral or both. All cognitive onset CBD/PSP patients and all but two with motor onset developed aphasia during the course of their illness. General cognitive and behavioral measures are similar for each presentation, but language scores are worse in cognitive onset cases, reflecting the frequency of aphasic presentations. Anomic patients become non-fluent, logopenic, agrammatic and mute. Using the Frontal Behavioral Inventory (FBI), a questionnaire specifically designed for the spectrum of apathy and disinhibition displayed by patients with FTD, we have documented the behavior change in CBD/PSP with motor and cognitive onsets. The significant personality changes consisted of apathy, disinhibition, perseveration and inattention, some of the core symptoms of FTD. In 18 autopsied cases, 15 had tau pathology. The overlap of CBD/PSP with PPA and bvFTD suggests a spectrum of related entities and predicts tau-positive pathology. Cross-sectional studies without significant follow-up may not observe the subsequent development language or behavior deficit, or the evolution from PPA and/or FTD-bv to CBD/PSP.

Behavior and cognition in corticobasal degeneration and progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), previously described as Parkinsonian syndromes are also cognitive disorders, and biologically related to the frontotemporal dementia or Pick's disease. PSP and CBD overlap clinically, pathologically and genetically, sharing tau haplotypes and mutations. In our series of CBD/PSP patients with cognitive presentation (n=36), primary progressive aphasia (PPA) was particularly common, but behavioral onset occurred also. CBD or PSP as motor presentations developed significant language disorder in 17/19. The underlying pathology is predictably tau positive in these clinical combinations, regardless of the presentation. Other cognitive features of CBDS include apraxia, alien hand and apathy, but often frontal lobe dementia with disinhibition develops also. CBDS also has visuospatial deficit, because of the parietal involvement. PSP was considered the prototype of subcortical dementia, with bradyphrenia, poor recall and executive deficit, but cortical features were recognized to be important also. Language testing and a behavioral inventory should be part of neuropsychological tests to facilitate diagnosis and to quantify the deficit. The clinical, genetic and pathological relationship is strong between CBD /PSP and the aphasic and behavioral components of the Pick complex.

What is semantic dementia?: a cohort study of diagnostic features and clinical boundaries.

OBJECTIVES: To describe a large, clinically defined cohort of patients with semantic dementia (SD) that highlights important, sometimes overlooked features and to compare it with similar entities. DESIGN: Cohort study. SETTING: A cognitive neurology clinic. PATIENTS: A population of 48 patients clinically diagnosed with SD was contrasted with 52 patients with progressive nonfluent aphasia, 42 patients with a behavioral variety of frontotemporal dementia, and 105 patients with Alzheimer disease on speech output characteristics, comprehension, naming, and repetition subtests of the Western Aphasia Battery, the Frontal Behavioral Inventory, and other cognitive tests. Neuroimaging was visually analyzed, and 6 patients with SD had autopsy. RESULTS: Of 37 patients with probable SD, 48.6% had semantic jargon; 21.6%, excessive garrulous output; and 75.7%, some pragmatic disturbance. Semantic substitutions were frequent in SD (54.1%) but phonological errors were absent, in contrast to progressive nonfluent aphasia with the opposite pattern. All but 3 patients with probable SD questioned the meaning of words. Patients with SD had significantly lower naming and comprehension scores, and their fluency was between progressive nonfluent aphasia and Alzheimer disease or behavioral frontotemporal dementia. Behavior was abnormal in 94.6% of patients with probable SD. CONCLUSIONS: Semantic dementia is distinguishable from other presentations of frontotemporal dementia and Alzheimer disease, not only by fluent speech and impaired comprehension without loss of episodic memory, syntax, and phonology but also by empty, garrulous speech with thematic perseverations, semantic paraphasias, and poor category fluency. Questioning the meaning of words (eg, "What is steak?") is an important diagnostic clue not seen in other groups, and behavior change is prevalent.

The diagnosis and course of frontotemporal dementia.

The course of frontotemporal dementia (FTD) is examined in a prospective, incipient clinical cohort. Three hundred nineteen patients were followed yearly for an average of 3.6 years. The relative frequencies at presentation were Behavioral variety (FTD-bv) 37.6%, Primary Progressive Aphasia (PPA) 31.6%, possible PPA 10.6%, Corticobasal Syndrome (CBDS) and Progressive Supranuclear Palsy (PSP) 8.1%, Semantic Dementia (SD) 6.6%, and possible FTD 5.3%. The age of onset was significantly lower in the FTD-bv and SD groups than in the rest, but survival and sex distribution was similar in all groups. The evolution is characterized by the appearance of additional FTD syndromes in two-thirds of the patients. A significant association of SD with FTD-bv and CBDS/PSP with PPA was found. The Frontal Behavioral Inventory was highly sensitive and specific for FTD-bv. Visuospatial function was preserved except in CBDS/PSP. The clinical diagnosis showed a positive predictive value of 87% against autopsy in 67 patients. Multiple syndromes increase the likelihood of FTD pathology. In conclusion, the clinical associations follow the tau-negative and tau-positive pathologic dichotomy to some extent, but there is too much overlap to consider the clinical groups or their associations separate diseases.

Corticobasal degeneration and progressive aphasia.

OBJECTIVE: To describe language impairment in the corticobasal degeneration syndrome (CBDS) presenting as either a cognitive or motor disorder, to compare the evolution of aphasia in CBDS with primary progressive aphasia (PPA), and to examine whether the side of maximal cerebral atrophy or akinesia reflects the severity of aphasia. METHODS: We divided 40 patients with CBDS according to motor or cognitive onsets and conducted detailed language assessments with the Western Aphasia Battery (WAB). We analyzed scores according to the side of atrophy and motor rigidity. Longitudinal performance over three annual assessments was compared against matched patients with PPA and Alzheimer disease. RESULTS: Language at baseline was more impaired in cognitive than motor-onset CBDS but there was no correlation between the side of atrophy or motor impairment and the WAB. Serial assessment (n = 19) showed a similar evolution of aphasia in cognitive-onset CBDS and PPA and delayed aphasia in motor-onset CBDS. CONCLUSION: Aphasia is common in the corticobasal degeneration syndrome but there is little correlation with the laterality of clinical deficits. Cognitive-onset corticobasal degeneration syndrome and primary progressive aphasia are similar such that their aphasia appears identical.

Quantitative and qualitative analyses of clock drawing in frontotemporal dementia and Alzheimer's disease.

The clock drawing test (CDT) is a widely used cognitive screening test. It is useful in identifying focal lesions and cognitive deficits in dementia groups. Lately, several studies attempted its use to differentiate between dementia subtypes. Although many studies have examined the CDT in dementia populations, research into the use of clock drawing in frontotemporal dementia (FTD) is limited. We examined quantitative (global) and qualitative (specific error type) differences on the CDT between FTD (n = 36) and Alzheimer's disease (AD; n = 25) patients and controls without dementia (n = 25). Results showed significantly lower overall scores in the dementia groups compared to the control group, whereas FTD patients scored significantly higher than the AD group. On qualitative analysis, the FTD group had fewer stimulus bound responses, conceptual deficits, and spatial or planning errors compared to the AD group. In conclusion, both global and error analysis of the CDT helped discriminate the FTD group from controls and AD patients.

The cognitive profile of posterior cortical atrophy.

BACKGROUND: Posterior cortical atrophy (PCA) is a progressive dementia characterized by prominent disorders of higher visual processing, affecting both dorsal and ventral streams to cause Balint's syndrome, alexia, and visual agnosia. OBJECTIVE: To define the cognitive profile of PCA and compare to the typical, primary amnestic dementia of the Alzheimer's type (DAT). METHODS: The authors used standard cognitive tests and a novel battery designed to reflect dysfunction in both ventral (Object, Face & Color Agnosia Screen [OFCAS]) and dorsal (complex pictures and compound stimuli) visual streams. The authors identified 19 patients with PCA and compared their performance to a matched group of patients with DAT and normal controls. RESULTS: Patients with PCA were younger with marked impairment in visuospatial tasks, reading, and writing but relative preservation of memory compared to DAT using standard tests. Dorsal stream signs were most prevalent among the patients with PCA with no pure ventral stream syndromes found. All novel tests distinguished reliably between subjects with complex picture descriptions and processing of compound stimuli showing the most significant differences compared to DAT. CONCLUSIONS: PCA is predominantly a dorsal stream syndrome, distinct from typical DAT, which involves occipitotemporal regions over time.

Further evidence of dementia in SPG4-linked autosomal dominant hereditary spastic paraplegia.

OBJECTIVE: To investigate the progression of cognitive impairment and its behavioral aspects in patients with SPG4-linked autosomal dominant hereditary spastic paraplegia (SPG4-ADHSP). METHODS: Sixteen patients, 45 years or older, from five families with SPG4-ADHSP were prospectively assessed. Eleven of these, from three families, were followed and 10 had two cognitive examinations using the Cambridge Cognitive Assessment (CAMCOG) 2.9 years apart. The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE), the Neuropsychiatric Inventory (NPI), and the Nurses' Observation Scale for Geriatric Patients (NOSGER) were completed by close relatives of the 11 patients at the second assessment. Eleven matched control subjects had CAMCOG examinations 3.1 years apart. RESULTS: The mean CAMCOG score at the initial assessment was lower for the 10 HSP patients (73.5/107) than for 10 control subjects (91.7/107, p = 0.005). After 2.9 years, the HSP patients experienced a fall in the mean CAMCOG by 9.1 points to 64.4/107 (p = 0.008). The mean CAMCOG score for the control subjects (90.8/107) fell by only 0.9 points after 3.1 years (p = 0.36). The CAMCOG scores of two HSP patients moved from the mild (60 to 80) into the moderate dementia category (35 to 59) and in three other patients into the mild dementia range from borderline normal scores (81 to 85). IQCODE scores were abnormal in 9/11 HSP patients and 1/11 controls (p = 0.001). Seven of the 11 HSP patients were considered as having dementia. CONCLUSION: This study indicates an active progression of cognitive deterioration and dementia in older patients with SPG4-ADHSP.