'Limits and current knowledge of Pick's disease: its differential diagnosis'. A translation of the 1957 Delay, Brion, Escourolle article

Cerebral atrophy as a cause of aphasia: From Pick to the modern era

In his epoch-making monograph, Wernicke (1874) claimed that atrophy of the brain cannot cause aphasia. Refuting this claim, Pick (1892, 1898, 1901, 1904a) documented in increasing detail several cases of aphasia with circumscribed atrophy of the left temporal lobe, frontal lobe, or both, which persuaded Wernicke (1906). To explain why the atrophy is circumscribed and leads to focal symptoms, Pick (1908a) advanced a functional network account. Behavioral, neuroanatomical, and histopathological studies by Dejerine and Sérieux, Fischer, Alzheimer, Altman, Gans, Onari and Spatz, and Stertz further illuminated the clinical syndromes, the exact spatial distributions of the atrophy, the underlying disease, and its laminar specificity. Unaware of these seminal studies, research from the 1970s until now has independently rediscovered all key findings, and also supports Pick's forgotten functional account of the distribution of atrophy and the focal symptoms. His frontal and temporal forms of aphasia foreshadowed what are now called the nonfluent/agrammatic and semantic variants of primary progressive aphasia. Moreover, aphasic symptoms may occur with frontal degeneration (what used to be called "Pick's disease") that yields personality changes and behavioral disturbances, now called the behavioral variant of frontotemporal dementia.

Brain PET Imaging: Frontotemporal Dementia

Brain PET adds value in diagnosing neurodegenerative disorders, especially frontotemporal dementia (FTD) due to its syndromic presentation that overlaps with a variety of other neurodegenerative and psychiatric disorders. 18F-FDG-PET has improved sensitivity and specificity compared with structural MR imaging, with optimal diagnostic results achieved when both techniques are utilized. PET demonstrates superior sensitivity compared with SPECT for FTD diagnosis that is primarily a supplement to other imaging and clinical evaluations. Tau-PET and amyloid-PET primary use in FTD diagnosis is differentiation from Alzheimer disease, although these methods are limited mainly to research settings.

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.

Evolution of neuronal and glial tau isoforms in chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) is a neurodegenerative tauopathy characterized by accumulation of hyperphosphorylated tau (p-tau) in perivascular aggregates in neurons and glia at the depths of neocortical sulci and progresses to diffuse neocortical, allocortical and brainstem structures. The strongest risk factor is exposure to repetitive head impacts acquired most commonly through contact sports and military service. Given that CTE can only be definitively diagnosed after death, a better understanding of the cellular and molecular changes in CTE brains may lead to identification of mechanisms that could be used for novel biomarkers, monitoring progression or therapeutic development. Disruption of alternative pre-mRNA splicing of tau mRNA plays a pathogenic role in tauopathy, with multiple characteristic patterns of isoform accumulation varying among tauopathies. Limited data are available on CTE, particularly at early stages. Using biochemical and histological approaches, we performed a detailed characterization of tau isoform signatures in post-mortem human brain tissue from individuals with a range of CTE stages (n = 99). In immunoblot analyses, severity was associated with decreased total monomeric tau and increased total oligomeric tau. Immunoblot with isoform-specific antisera revealed that oligomeric tau with three and four microtubule binding domain repeats (3R and 4R) also increased with CTE severity. Similarly, immunohistochemical studies revealed p-tau accumulation consisting of both 3R and 4R in perivascular lesions. When the ratio of 4R:3R was analyzed, there was mixed expression throughout CTE stages, although 4R predominated in early CTE stages (I-II), a 3R shift was observed in later stages (III-IV). While neurons were found to contain both 3R and 4R, astrocytes only contained 4R. These 4R-positive cells were exclusively neuronal at early stages. Overall, these findings demonstrate that CTE is a mixed 4R/3R tauopathy. Furthermore, histologic analysis reveals a progressive shift in tau isoforms that correlates with CTE stage and extent of neuronal pathology.

Neurodegenerative disorders of the human frontal lobes

The frontal lobes play an integral role in human socioemotional and cognitive function. Sense of self, moral decisions, empathy, and behavioral monitoring of goal-states all depend on key nodes within frontal cortex. While several neurodegenerative diseases can affect frontal function, frontotemporal dementia (FTD) has particularly serious and specific effects, which thus provide insights into the role of frontal circuits in homeostasis and adaptive behavior. FTD represents a collection of disorders with specific clinical-pathologic correlates, imaging, and genetics. Patients with FTD and initial prefrontal degeneration often present with neuropsychiatric symptoms such as loss of social decorum, new obsessions, or lack of empathy. In those patients with early anterior temporal degeneration, language (particularly in patients with left-predominant disease) and socioemotional changes (particularly in patients with right-predominant disease) precede eventual frontal dysregulation. Herein, we review a brief history of FTD, initial clinical descriptions, and the evolution of nomenclature. Next, we consider clinical features, neuropathology, imaging, and genetics in FTD-spectrum disorders in relation to the integrity of frontal circuits. In particular, we focus our discussion on behavioral variant FTD given its profound impact on cortical and subcortical frontal structures. This review highlights the clinical heterogeneity of behavioral phenotypes as well as the clinical-anatomic convergence of varying proteinopathies at the neuronal, regional, and network level. Recent neuroimaging and modeling approaches in FTD reveal varying network dysfunction centered on frontal-insular cortices, which underscores the role of the human frontal lobes in complex behaviors. We conclude the chapter reviewing the cognitive and behavioral neuroscience findings furnished from studies in FTD related to executive and socioemotional function, reward-processing, decision-making, and sense of self.

Frontotemporal Dementia

Frontotemporal dementia (FTD) is a heterogeneous disorder with distinct clinical phenotypes associated with multiple neuropathologic entities. Presently, the term FTD encompasses clinical disorders that include changes in behavior, language, executive control, and often motor symptoms. The core FTD spectrum disorders include behavioral variant FTD, nonfluent/agrammatic variant primary progressive aphasia, and semantic variant PPA. Related FTD disorders include frontotemporal dementia with motor neuron disease, progressive supranuclear palsy syndrome, and corticobasal syndrome. In this article, the authors discuss the clinical presentation, diagnostic criteria, neuropathology, genetics, and treatments of these disorders.

Frontotemporal Dementia: An Updated Clinician's Guide

Today, frontotemporal dementia (FTD) remains one of the most common forms of early-onset dementia, that is, before the age of 65, thus posing several diagnostic challenges to clinicians since symptoms are often mistaken for psychiatric or neurological diseases causing a delay in correct diagnosis, and the majority of patients with FTD present with symptoms at ages between 50 and 60. Genetic components are established risk factors for FTD, but the influence of lifestyle, comorbidity, and environmental factors on the risk of FTD is still unclear. Approximately 40% of individuals with FTD have a family history of dementia but less than 10% have a clear autosomal dominant pattern of inheritance. Lack of insight is often an early clue to FTD. A tailored treatment option at an early phase can mitigate suffering and improve patients' and caregivers' quality of life.