Posterior cortical atrophy: a review of the literature

Practical use of DAT SPECT imaging in diagnosing dementia with Lewy bodies: a US perspective of current guidelines and future directions

Background

Diagnosing Dementia with Lewy Bodies (DLB) remains a challenge in clinical practice. The use of 123I-ioflupane (DaTscan™) SPECT imaging, which detects reduced dopamine transporter (DAT) uptake-a key biomarker in DLB diagnosis-could improve diagnostic accuracy. However, DAT imaging is underutilized despite its potential, contributing to delays and suboptimal patient management.

Methods

This review evaluates DLB diagnostic practices and challenges faced within the U.S. by synthesizing information from current literature, consensus guidelines, expert opinions, and recent updates on DaTscan FDA filings. It contrasts DAT SPECT with alternative biomarkers, provides recommendations for when DAT SPECT imaging may be indicated and discusses the potential of emerging biomarkers in enhancing diagnostic approaches.

Results

The radiopharmaceutical 123I-ioflupane for SPECT imaging was initially approved in Europe (2000) and later in the US (2011) for Parkinsonism/Essential Tremor. Its application was extended in 2022 to include the diagnosis of DLB. DaTscan's diagnostic efficacy for DLB, with its sensitivity, specificity, and predictive values, confirms its clinical utility. However, US implementation faces challenges such as insurance barriers, costs, access issues, and regional availability disparities.

Conclusion

123I-ioflupane SPECT Imaging is indicated for DLB diagnosis and differential diagnosis of Alzheimer's Disease, particularly in uncertain cases. Addressing diagnostic obstacles and enhancing physician-patient education could improve and expedite DLB diagnosis. Collaborative efforts among neurologists, geriatric psychiatrists, psychologists, and memory clinic staff are key to increasing diagnostic accuracy and care in DLB management.

Visual impairment in aging and cognitive decline: experience in a Memory Clinic

Visual impairment is common in people living with dementia and regular ophthalmological exams may improve their quality of life. We evaluated visual function in a cohort of elderly individuals and analyzed its association with their degree of cognitive impairment. Participants underwent neurological and neuropsychological exams, neuro-ophthalmological assessment (visual acuity, intraocular pressure, rates of past ophthalmological pathologies, use of ocular correction, treatments and surgeries) and optical coherence tomography (OCT) scan. We analyzed differences in ophthalmological characteristics among diagnostic groups. The final sample of 1746 study participants aged ≥ 50 comprised 229 individuals with Subjective Cognitive Decline (SCD), 695 with mild cognitive impairment (MCI) and 833 with Dementia (Alzheimer disease: n = 660; vascular dementia: n = 92, Lewy body dementia: n = 34; frontotemporal dementia: n = 19 and other: n = 28). Age, gender and education were used as covariates. Patients with Dementia, compared to those with SCD and MCI, presented worse visual acuity (p < 0.001), used less visual correction (p = 0.02 and p < 0.001, respectively) and fewer ophthalmological treatments (p = 0.004 and p < 0.001, respectively) and underwent fewer ocular surgeries (p = 0.009 and p < 0.001, respectively). OCT image quality worsened in parallel to cognitive decline (Dementia vs SCD: p = 0.008; Dementia vs MCI: p < 0.001). No group differences in past ophthalmological disorders or abnormal OCT findings were detected. Efforts should be made to ensure dementia patients undergo regular ophthalmological assessments to correct their visual function in order to improve their quality of life.

A neuropathologic diagnosis of Alzheimer's disease in an older adult with HIV-associated neurocognitive disorder

We discuss the challenges associated with diagnosing neurodegenerative disorders in older adults living with HIV, illustrated through a case report where neurologic co-diagnosis of Alzheimer's disease (AD) and HIV-associated Neurocognitive Disorder (HAND) are considered. The patient was followed and evaluated for over 4 years and underwent post-mortem neuropathologic evaluation. Further work is needed to identify diagnostic tests that can adequately distinguish HAND from early stage neurodegenerative disorders among older adults living with HIV and cognitive changes.

Cognitive Rehabilitation and Transcranial Direct Current Stimulation in a Patient with Posterior Cortical Atrophy: An fMRI Study

BACKGROUND Posterior cortical atrophy (PCA) is a neurodegenerative syndrome that accounts for 5% of the atypical presentation of Alzheimer disease (AD). To date, only a few studies have explored the effect of non-pharmacological treatment in PCA patients and no studies have evaluated the efficacy of transcranial direct current stimulation (tDCS) in this disorder. CASE REPORT A 58-year-old PCA patient underwent a cognitive rehabilitation treatment followed by 2 cycles of tDCS stimulation. The effects of both treatments were monitored over time with a standardized task-based fMRI protocol and with a neuropsychological assessment. Improvements in cognitive abilities, increased fMRI activation in the dorsolateral prefrontal cortex, and deactivation of the default mode network during the Stroop test performance were detected after each session treatment. CONCLUSIONS This combined approach lead to both cognitive improvements and neurophysiological adaptive changes, however, further studies on a larger cohort are needed to confirm these preliminary results.

Alzheimer's Disease: Past, Present, and Future

Although dementia has been described in ancient texts over many centuries (e.g., "Be kind to your father, even if his mind fail him." - Old Testament: Sirach 3:12), our knowledge of its underlying causes is little more than a century old. Alzheimer published his now famous case study only 110 years ago, and our modern understanding of the disease that bears his name, and its neuropsychological consequences, really only began to accelerate in the 1980s. Since then we have witnessed an explosion of basic and translational research into the causes, characterizations, and possible treatments for Alzheimer's disease (AD) and other dementias. We review this lineage of work beginning with Alzheimer's own writings and drawings, then jump to the modern era beginning in the 1970s and early 1980s and provide a sampling of neuropsychological and other contextual work from each ensuing decade. During the 1980s our field began its foundational studies of profiling the neuropsychological deficits associated with AD and its differentiation from other dementias (e.g., cortical vs. subcortical dementias). The 1990s continued these efforts and began to identify the specific cognitive mechanisms affected by various neuropathologic substrates. The 2000s ushered in a focus on the study of prodromal stages of neurodegenerative disease before the full-blown dementia syndrome (i.e., mild cognitive impairment). The current decade has seen the rise of imaging and other biomarkers to characterize preclinical disease before the development of significant cognitive decline. Finally, we suggest future directions and predictions for dementia-related research and potential therapeutic interventions. (JINS, 2017, 23, 818-831).

Semantic word category processing in semantic dementia and posterior cortical atrophy

There is general agreement that perisylvian language cortex plays a major role in lexical and semantic processing; but the contribution of additional, more widespread, brain areas in the processing of different semantic word categories remains controversial. We investigated word processing in two groups of patients whose neurodegenerative diseases preferentially affect specific parts of the brain, to determine whether their performance would vary as a function of semantic categories proposed to recruit those brain regions. Cohorts with (i) Semantic Dementia (SD), who have anterior temporal-lobe atrophy, and (ii) Posterior Cortical Atrophy (PCA), who have predominantly parieto-occipital atrophy, performed a lexical decision test on words from five different lexico-semantic categories: colour (e.g., yellow), form (oval), number (seven), spatial prepositions (under) and function words (also). Sets of pseudo-word foils matched the target words in length and bi-/tri-gram frequency. Word-frequency was matched between the two visual word categories (colour and form) and across the three other categories (number, prepositions, and function words). Age-matched healthy individuals served as controls. Although broad word processing deficits were apparent in both patient groups, the deficit was strongest for colour words in SD and for spatial prepositions in PCA. The patterns of performance on the lexical decision task demonstrate (a) general lexicosemantic processing deficits in both groups, though more prominent in SD than in PCA, and (b) differential involvement of anterior-temporal and posterior-parietal cortex in the processing of specific semantic categories of words.

Non-pharmacological intervention for posterior cortical atrophy

Posterior cortical atrophy (PCA) is a rare neurodegenerative condition characterized by progressive visual-perceptual deficits. Although the neurocognitive profile of PCA is a growing and relatively well-established field, non-pharmacological care remains understudied and to be widely established in clinical practice. In the present work we review the available literature on non-pharmacological approaches for PCA, such as cognitive rehabilitation including individual cognitive exercises and compensatory techniques to improve autonomy in daily life, and psycho-education aiming to inform people with PCA about the nature of their visual deficits and limits of cognitive rehabilitation. The reviewed studies represented a total of 7 patients. There is a scarcity of the number of studies, and mostly consisting of case studies. Results suggest non-pharmacological intervention to be a potentially beneficial approach for the partial compensation of deficits, improvement of daily functionality and improvement of quality of life. Clinical implications and future directions are also highlighted for the advancement of the field, in order to clarify the possible role of non-pharmacological interventions, and its extent, in PCA.

3D Shape Perception in Posterior Cortical Atrophy: A Visual Neuroscience Perspective

Posterior cortical atrophy (PCA) is a rare focal neurodegenerative syndrome characterized by progressive visuoperceptual and visuospatial deficits, most often due to atypical Alzheimer's disease (AD). We applied insights from basic visual neuroscience to analyze 3D shape perception in humans affected by PCA. Thirteen PCA patients and 30 matched healthy controls participated, together with two patient control groups with diffuse Lewy body dementia (DLBD) and an amnestic-dominant phenotype of AD, respectively. The hierarchical study design consisted of 3D shape processing for 4 cues (shading, motion, texture, and binocular disparity) with corresponding 2D and elementary feature extraction control conditions. PCA and DLBD exhibited severe 3D shape-processing deficits and AD to a lesser degree. In PCA, deficient 3D shape-from-shading was associated with volume loss in the right posterior inferior temporal cortex. This region coincided with a region of functional activation during 3D shape-from-shading in healthy controls. In PCA patients who performed the same fMRI paradigm, response amplitude during 3D shape-from-shading was reduced in this region. Gray matter volume in this region also correlated with 3D shape-from-shading in AD. 3D shape-from-disparity in PCA was associated with volume loss slightly more anteriorly in posterior inferior temporal cortex as well as in ventral premotor cortex. The findings in right posterior inferior temporal cortex and right premotor cortex are consistent with neurophysiologically based models of the functional anatomy of 3D shape processing. However, in DLBD, 3D shape deficits rely on mechanisms distinct from inferior temporal structural integrity.

SIGNIFICANCE STATEMENT

Posterior cortical atrophy (PCA) is a neurodegenerative syndrome characterized by progressive visuoperceptual dysfunction and most often an atypical presentation of Alzheimer's disease (AD) affecting the ventral and dorsal visual streams rather than the medial temporal system. We applied insights from fundamental visual neuroscience to analyze 3D shape perception in PCA. 3D shape-processing deficits were affected beyond what could be accounted for by lower-order processing deficits. For shading and disparity, this was related to volume loss in regions previously implicated in 3D shape processing in the intact human and nonhuman primate brain. Typical amnestic-dominant AD patients also exhibited 3D shape deficits. Advanced visual neuroscience provides insight into the pathogenesis of PCA that also bears relevance for vision in typical AD.

Posterior cortical atrophy: an investigation of scan paths generated during face matching tasks

When viewing a face, healthy individuals focus more on the area containing the eyes and upper nose in order to retrieve important featural and configural information. In contrast, individuals with face blindness (prosopagnosia) tend to direct fixations toward individual facial features—particularly the mouth. Presented here is an examination of face perception deficits in individuals with Posterior Cortical Atrophy (PCA). PCA is a rare progressive neurodegenerative disorder that is characterized by atrophy in occipito-parietal and occipito-temporal cortices. PCA primarily affects higher visual processing, while memory, reasoning, and insight remain relatively intact. A common symptom of PCA is a decreased effective field of vision caused by the inability to “see the whole picture.” Individuals with PCA and healthy control participants completed a same/different discrimination task in which images of faces were presented as cue-target pairs. Eye-tracking equipment and a novel computer-based perceptual task—the Viewing Window paradigm—were used to investigate scan patterns when faces were presented in open view or through a restricted-view, respectively. In contrast to previous prosopagnosia research, individuals with PCA each produced unique scan paths that focused on non-diagnostically useful locations. This focus on non-diagnostically useful locations was also present when using a restricted viewing aperture, suggesting that individuals with PCA have difficulty processing the face at either the featural or configural level. In fact, it appears that the decreased effective field of view in PCA patients is so severe that it results in an extreme dependence on local processing, such that a feature-based approach is not even possible.

Posterior cortical atrophy: visuomotor deficits in reaching and grasping

Posterior Cortical Atrophy (PCA) is a rare clinical syndrome characterized by the predominance of higher-order visual disturbances such as optic ataxia, a characteristic of Balint's syndrome. Deficits result from progressive neurodegeneration of occipito-temporal and occipito-parietal cortices. The current study sought to explore the visuomotor functioning of four individuals with PCA by testing their ability to reach out and grasp real objects under various viewing conditions. Experiment 1 had participants reach out and grasp simple, rectangular blocks under visually- and memory-guided conditions. Experiment 2 explored participants' abilities to accurately reach for objects located in their visual periphery. This investigation revealed that PCA patients demonstrate many of the same deficits that have been previously reported in other individuals with optic ataxia, such as “magnetic misreaching”—a pathological reaching bias toward the point of visual fixation when grasping peripheral targets. Unlike many other individuals with optic ataxia, however, the patients in the current study also show symptoms indicative of damage to the more perceptual stream of visual processing, including abolished grip scaling during memory-guided grasping and deficits in face and object identification. These investigations are the first to perform a quantitative analysis of the visuomotor deficits exhibited by patients with PCA. Critically, this study helps characterize common symptoms of PCA, a vital first step for generating effective diagnostic criteria and therapeutic strategies for this understudied neurodegenerative disorder.

Physical medicine and rehabilitation multidisciplinary approach in a case of posterior cortical atrophy

Posterior cortical atrophy (PCA) is a degenerative syndrome heralded by progressive visual and spatial disorders, while the memory and execution capacities remain preserved for a long time. We report the clinical case of a female patient who received a global Physical and Rehabilitation Medicine (PRM) therapy. Our objective is to highlight the interest of a multidisciplinary approach in PCA. A female patient, LO, 60 years old, presented with visual and spatial difficulties of progressive worsening, while global cognitive efficiency was preserved, signing PCA, with a loss of autonomy in daily life. A six-month multidisciplinary approach (speech therapy, occupational therapy, and physiotherapy) centered on her visual disturbances and associated to the reinforcement of her preserved abilities, as well as a rehabilitation program, was proposed. At the end of this period, LO was again able to read, find efficient exploratory strategies, use the underground, visit museums, have leisure activities, and carry out everyday life activities, which she had ended up abandoning. The specific therapeutic management allowed reaching functional objectives. Our hypothesis is that the absence of other cognitive disorders allowed this type of rehabilitation "contract". The neurodegenerative pathologies responsible for specific instrumental disabilities without global cognitive alteration, and particularly PCA, should be able to benefit from a specific, or even multidisciplinary PMR therapy approach.

[Impact of drug-free care in posterior cortical atrophy: Preliminary experience with a psycho-educative program]

INTRODUCTION

Criteria for the diagnosis of posterior cortical atrophy (PCA) are well established, but little is known about the impact of drug-free care for patients and caregivers.

METHODS

We designed an adapted and specific psycho-educative program for four patients and their caregivers who participated in six sessions, one every 2 months.

RESULTS

Patients and caregivers improved their knowledge about the PCA syndrome; level of anxiety was slightly reduced among caregivers.

CONCLUSION

A specific psycho-educative program can be offered to PCA patients and their caregivers.

The neuropsychological profile of Alzheimer disease

Neuropsychological assessment has featured prominently over the past 30 years in the characterization of dementia associated with Alzheimer disease (AD). Clinical neuropsychological methods have identified the earliest, most definitive cognitive and behavioral symptoms of illness, contributing to the identification, staging, and tracking of disease. With increasing public awareness of dementia, disease detection has moved to earlier stages of illness, at a time when deficits are both behaviorally and pathologically selective. For reasons that are not well understood, early AD pathology frequently targets large-scale neuroanatomical networks for episodic memory before other networks that subserve language, attention, executive functions, and visuospatial abilities. This chapter reviews the pathognomonic neuropsychological features of AD dementia and how these differ from "normal," age-related cognitive decline and from other neurodegenerative diseases that cause dementia, including cortical Lewy body disease, frontotemporal lobar degeneration, and cerebrovascular disease.

Neuropsychological features of mild cognitive impairment and preclinical Alzheimer's disease

Detectable cognitive decline occurs in patients with Alzheimer's disease (AD) well before the clinical diagnosis can be made with any certainty. Studies examining this preclinical period identify decline in episodic memory as the earliest manifestation of the disease (i.e., a condition of amnestic Mild Cognitive Impairment). The episodic memory impairment is characterized by deficits in a number of processes including delayed recall, the recollective aspect of recognition memory, associative memory necessary for "binding" representations of two or more stimuli, pattern separation necessary to distinguish between two similar memory representations, prospective memory required to remember a delayed intention to act at a certain time in the future, and autobiographical memory for specific episodes that occurred in one's past. A growing body of evidence suggests that cognitive changes in preclinical AD may be more global in nature. Deterioration of semantic knowledge is evident on demanding naming and category fluency tasks, and "executive" dysfunction is apparent on tasks that require concurrent mental manipulation of information (e.g., working memory) or cue-directed behavior (e.g., set-shifting). Asymmetric cognitive test performance may also be apparent prior to significant decline in cognitive ability. The pattern and progression of these neuropsychological changes fit well with the proposed distribution and spread of AD pathology and serve as important cognitive markers of early disease.

Abnormal visual phenomena in posterior cortical atrophy

Individuals with posterior cortical atrophy (PCA) report a host of unusual and poorly explained visual disturbances. This preliminary report describes a single patient (CRO), and documents and investigates abnormally prolonged colour afterimages (concurrent and prolonged perception of colours complimentary to the colour of an observed stimulus), perceived motion of static stimuli, and better reading of small than large letters. We also evaluate CRO's visual and vestibular functions in an effort to understand the origin of her experience of room tilt illusion, a disturbing phenomenon not previously observed in individuals with cortical degenerative disease. These visual symptoms are set in the context of a 4-year longitudinal neuropsychological and neuroimaging investigation of CRO's visual and other cognitive skills. We hypothesise that prolonged colour after-images are attributable to relative sparing of V1 inhibitory interneurons; perceived motion of static stimuli reflects weak magnocellular function; better reading of small than large letters indicates a reduced effective field of vision; and room tilt illusion effects are caused by disordered integration of visual and vestibular information. This study contributes to the growing characterisation of PCA whose atypical early visual symptoms are often heterogeneous and frequently under-recognised.

Cataract and cognitive impairment: a review of the literature

Acquired cataract and cognitive impairment are both common age-related problems, and ophthalmologists are increasingly likely to encounter patients who have both. Patients with dementia types who display early visuoperceptual impairment may present first to ophthalmology services. When these patients have coexisting cataract, it may be difficult to distinguish visual complaints due to cataract from those due to dementia. The interaction between visual impairment due to cataract and neurodegenerative disorders affecting the central visual pathways, is not fully understood. Visual impairment due to cataract may stress impaired attentional mechanisms and cataract extraction may improve cognitive performance in some patients with early cognitive impairment; however, the benefits of cataract surgery in established dementia are less clear. In this study, the literature on this subject was reviewed and the implications for practice were considered.

The relationship between visual crowding and letter confusability: towards an understanding of dyslexia in posterior cortical atrophy

Visual crowding is a form of masking in which target identification is hindered by excessive feature integration from other stimuli in the vicinity. It has previously been suggested that excessive visual crowding constitutes one specific form of early-visual-processing deficit, which may be observed in individuals with posterior cortical atrophy (PCA). This study investigated whether excessive visual crowding plays a significant role in the acquired dyslexia of two PCA patients, whose reading was characterized by visual paralexias. The patients were administered a series of letter, flanked letter, and word recognition tasks, and the effects of letter spacing and letter confusability upon response accuracy and latency were measured. In both patients, the results showed (a) evidence of excessive visual crowding, (b) a significant interaction between letter spacing and confusability on flanked letter identification tasks, and (c) effects of letter confusability affecting flanked but not unflanked letter identification. However, only mild improvements in reading accuracy were achieved in the experimental manipulations of interletter spacing within words because these manipulations had a dual effect: Increasing spacing improved individual letter identification but damaged whole-word form and/or parallel letter processing. We consider the implications of these results for the characterization of dyslexia in PCA, the design of reading rehabilitation strategies, and the relationship between visual crowding and letter confusability. In particular, we argue that the reading deficits observed in our patients cannot be accounted for solely in terms of a very low signal-to-noise ratio for letter identification, and that an additional crowding deficit is implicated in which excessive integration of fundamental letter features leads to the formation of incorrect letter percepts.

Cognitive rehabilitation in posterior cortical atrophy

Posterior cortical atrophy (PCA) is a rare early-onset dementing syndrome presenting with visuo-perceptual deficits. Clinicopathologically, it is most commonly considered a form of Alzheimer's disease. We present the case of a 64-year-old male patient with posterior cortical atrophy who took part in a cognitive rehabilitation programme that included psychoeducation, compensatory strategies, and cognitive exercises. After the cognitive rehabilitation programme, subtle differences were found in visuoperceptual tasks and in the patient's subjective perception of difficulties. Cognitive rehabilitation may temporarily improve functioning in patients with posterior cortical atrophy.

Processing of wh-questions in a case of posterior cortical atrophy

Posterior cortical atrophy (PCA) is a type of dementia that is characterized by visuo-spatial and memory deficits, dyslexia and dysgraphia, relatively early onset and preserved insight. Language deficits have been reported in some cases of PCA. Using an off-line grammaticality judgement task, processing of wh-questions is investigated in a case of PCA. Other aspects of auditory language are also reported. It is shown that processing of wh-questions is influenced by syntactic structure, a novel finding in this condition. The results are discussed with reference to accounts of wh-questions in aphasia. An uneven profile of other language abilities is reported with deficits in digit span (forward, backward), story retelling ability, comparative questions but intact abilities in following commands, repetition, concept definition, generative naming and discourse comprehension.

Severe episodic memory impairment in a patient with clinical features compatible with corticobasal degeneration

Corticobasal degeneration (CBD) is a progressive neurodegenerative disorder characterized by asymmetric parkinsonism associated with apraxia, cortical sensory loss, and alien-limb phenomenon. Neuropsychological testing in patients with CBD typically shows deficits in executive functions, praxis, language, and visuospatial functioning, but not in memory. We report a CBD patient with severely impaired memory function but relatively mild motor symptoms. Detailed neuropsychological assessment showed significant verbal and visual memory deficits accompanied by frontal executive dysfunctions. Our observations indicate that CBD can in rare cases present with severe episodic memory impairment associated with frontal executive dysfunctions in the early stage of illness.

Foveal crowding in posterior cortical atrophy: a specific early-visual-processing deficit affecting word reading

Visual crowding is a form of masking in which single-letter identification is compromised by the presence of additional letters or other simple visual forms in close proximity. This behavioural phenomenon has been studied most frequently in the context of amblyopic and normal peripheral vision. In the current study, we investigate this phenomenon in the context of two patients with peripheral dyslexia and a third with visual disorientation consequent to bilateral posterior cortical atrophy. In one case, reading showed the effects of word length typical of letter-by-letter reading, whereas the second case was unable to read any whole words. In a series of letter identification tasks, recognition accuracy was shown to decrease significantly in the presence of a range of flanking stimuli (e.g., letters, digits, letter fragments). Compatible with previous reports of the crowding phenomenon, the flanking effect was strengthened by increasing flanker proximity but was unaffected by target or flank size, flank contrast, target-flank lexicality, or flank category. One patient also showed amelioration of the flanking effect when the target and flankers were of opposite contrast polarity. To the best of our knowledge, this is the first demonstration of visual crowding in individuals with posterior cortical atrophy. We consider the relevance of these empirical findings to accounts of the letter-by-letter reading form of peripheral dyslexia. In particular, we suggest that crowding constitutes one specific form of early-visual-processing deficit, which impairs the reading process.

Alexia without agraphia in Creutzfeldt–Jakob disease

Progressive dementia uncommonly presents with focal deficits referable to posterior cortical dysfunction. We describe a 62 year-old man who presented with progressive visual disturbance in whom detailed cognitive testing documented alexia without agraphia. The only finding from diagnostic investigations was hypoperfusion of the posterior left temporoparietal region on brain SPECT scan. He rapidly progressed and Creutzfeldt-Jakob disease (CJD) was confirmed at autopsy. Although reading disorders may develop in association with posterior cortical atrophy due to CJD, this is the first reported autopsy-confirmed case presenting as alexia without agraphia.

Insight in frontotemporal dementia: Conceptual analysis and empirical evaluation of the consensus criterion “loss of insight” in frontotemporal dementia

The objective of this study was to suggest a new formulation of the core research diagnostic consensus criterion "loss of insight" in frontotemporal dementia (FTD). Eight patients with FTD (diagnoses made by interviews, medical and neuropsychological examination, CT scan, and regional cerebral glucose metabolism measured by positron emission tomography (PET) participated in the study). The results indicated that insight was present in three out of eight patients, and that insight appears to be a heterogeneous concept. Two types of insight emerged: Emotional insight associated with frontotemporal functions, and cognitive insight, related to posterior cognitive functions. These results suggest that loss of insight should not serve as a core criterion on FTD, but serves well as a supportive criterion of the disease.

Les marqueurs neuropsychologiques du diagnostic de la maladie d’Alzheimer

Better knowledge of the preclinical phase of Alzheimer's disease and of the symptomatic pre-dementia stage designated "mild cognitive impairment" will require considerable progress in our understanding of neuropsychological processes. The results of studies suggest that impaired performance in memory tests may serve as a marker for Alzheimer's disease. The best current predictors include stringent tests of episodic memory and recognition tests. The early stages of Alzheimer's disease also seem to involve subtle deficits in semantic memory and attentional processes. Face recognition and denomination seem to be useful tools. Greater accuracy and precision in the transitional zone between healthy aging and the first manifestations of Alzheimer's disease will require work combining data on neuropsychological profiles and neuroimaging.

Das klinische Syndrom der posterioren kortikalen Atrophie

Posterior cortical atrophy (PCA) is a syndrome that involves distinct neuropsychological deficits. This paper presents the clinical and neuropsychological findings recorded in four patients with PCA and reviews the characteristics of the syndrome and other conditions that need to be considered in the differential diagnosis. The cardinal symptoms of PCA are deficits of higher visual and spatial functions (mostly taking the form of Balint's syndrome), variably associated with disorders of visual perception, topographical disorientation, visual object agnosia and prosopagnosia, and deficits affecting reading, copying, drawing, and calculation. PCA is mostly associated with histopathological changes similar to those found in dementia of Alzheimer type (DAT), which are located predominantly in posterior brain regions. Memory and language functions tend to be preserved better and for a longer time in PCA than in the normal variant of DAT. SPECT and PET show deficits of perfusion and metabolism in both parietal and occipital lobes. The diagnosis of PCA is based on neuropsychological and imaging findings.