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Journal of Alzheimer's Disease : JAD 2018Despite common pathology, Alzheimer's disease (AD) can have multiple clinical presentations which pathological studies suggest result from differences in the regional...
BACKGROUND
Despite common pathology, Alzheimer's disease (AD) can have multiple clinical presentations which pathological studies suggest result from differences in the regional distribution of tau pathology. Positron emission tomography (PET) ligands are now available that can detect tau proteins in vivo and hence can be used to investigate the biological mechanisms underlying atypical AD.
OBJECTIVE
To assess regional patterns of tau uptake on PET imaging in two atypical AD variants, posterior cortical atrophy (PCA) and logopenic progressive aphasia (lvPPA).
METHODS
Eighteen PCA and 19 lvPPA subjects that showed amyloid-β deposition on PET underwent tau-PET imaging with [18F]AV-1451. Group comparisons of tau uptake in PCA and lvPPA were performed using voxel-level and regional-level analyses. We also assessed the degree of lobar tau asymmetry and correlated regional tau uptake to age and performance on clinical evaluations.
RESULTS
Both syndromes showed diffuse tau uptake throughout all cortical regions, although PCA showed greater uptake in occipital regions compared to lvPPA, and lvPPA showed greater uptake in left frontal and temporal regions compared to PCA. While lvPPA showed predominant left-asymmetric tau deposition, PCA was more bilateral. Younger subjects showed greater tau uptake bilaterally in frontal and parietal lobes than older subjects, and sentence repetition, Boston naming test, simultanagnosia, and visuoperceptual function showed specific regional tau correlates.
CONCLUSION
Tau deposition is closely related to clinical presentation in atypical AD with age playing a role in determining the degree of cortical tau deposition.
Topics: Aged; Aging; Alzheimer Disease; Aphasia; Atrophy; Brain; Brain Mapping; Carbolines; Female; Humans; Male; Middle Aged; Positron-Emission Tomography; Radiopharmaceuticals; tau Proteins
PubMed: 29614676
DOI: 10.3233/JAD-170740 -
Handbook of Clinical Neurology 2018In 1909 Rezsö Bálint published an extraordinary case study of a man with complex visuospatial deficits resulting from bilateral parietal lesions. Despite some...
In 1909 Rezsö Bálint published an extraordinary case study of a man with complex visuospatial deficits resulting from bilateral parietal lesions. Despite some controversies over the nature of reported symptoms, in 1954 Hecaen and Ajuriaguerra conceived the term "Bálint syndrome," not only to honor Bálint's influential work but to firmly conceptualize this striking neurologic disorder. Nowadays it is largely agreed that, while Bálint syndrome may result from multiple etiologies, it is principally diagnosed based on the presence of three symptoms: simultanagnosia, optic ataxia, and ocular apraxia. One of the most striking characteristics of Bálint syndrome, perfectly capturing the nature of this remarkable disorder, is that affected patients cannot perceive more than one object at a time or comprehend multiobject visual scenes due to a lack of ability to detect several objects concurrently and to grasp the spatial relationships between them. This chapter gives an overview of the cognitive mechanisms and neuroanatomy underlying Bálint syndrome, which provides key insights into our understanding of the role of parietal cortex in human attention, visual perception, and visuomotor control. This chapter also pays homage to Glyn Humphreys (1954-2016), who pioneered contributions to the knowledge about complexity of visual and spatial deficits associated with Bálint syndrome.
Topics: History, 20th Century; History, 21st Century; Humans; Perceptual Disorders; Vision Disorders
PubMed: 29519461
DOI: 10.1016/B978-0-444-63622-5.00012-7 -
Dementia & Neuropsychologia 2017A 75-year-old right-handed woman presented to the emergency department with simultanagnosia and right unilateral optic ataxia. Moreover, the patient had agraphia,...
A 75-year-old right-handed woman presented to the emergency department with simultanagnosia and right unilateral optic ataxia. Moreover, the patient had agraphia, acalculia, digital agnosia and right-left disorientation, consistent with complete Gerstmann's syndrome. This case highlights the concurrence of Gerstmann's syndrome and unilateral optic ataxia in the acute phase of a left middle cerebral artery stroke.
PubMed: 29354229
DOI: 10.1590/1980-57642016dn11-040018 -
Cognitive Neuropsychiatry Jan 2018Bálint's syndrome involves bilateral damage to the parieto-occipital area. The extent of the effect of unilateral damage on the Bálint's triad (oculomotor apraxia,...
INTRODUCTION
Bálint's syndrome involves bilateral damage to the parieto-occipital area. The extent of the effect of unilateral damage on the Bálint's triad (oculomotor apraxia, optic ataxia, and simultanagnosia) remains unknown.
METHODS
We examined a 63-year-old, right-handed woman who developed right hemianopia, oculomotor apraxia, optic ataxia, simultanagnosia, and hemispatial neglect (HSN) for the right after a cerebral infarction, with detailed neuropsychological tests, magnetic resonance imaging, and single photon emission computed tomography (SPECT).
RESULTS
Neuropsychological examination showed that oculomotor apraxia, optic ataxia, and simultanagnosia were more pronounced in the right hemi-space, probably due to the limited eye movement in the right visual field, whereas HSN was restricted to the right hemi-space. Diffusion-weighted MR images revealed hyperintensity in the left parieto-temporo-occipital region, and several spotty areas of the bilateral frontal and parietal subcortical regions. SPECT revealed hypoperfusion in the left parieto-occipital region and frontal operculum and small areas of the right superior parietal lobule.
CONCLUSIONS
The case suggests that asymmetric (more pronounced in the right hemi-space) oculomotor apraxia, optic ataxia, and simultanagnosia occur in an extensive lesion of the left parieto-occipital cortices. Although HSN is not a prerequisite for simultanagnosia, the coexistence of HSN aggravates simultanagnosia in the hemi-space opposite the lesion.
Topics: Agnosia; Apraxias; Ataxia; Cogan Syndrome; Fatal Outcome; Female; Humans; Magnetic Resonance Imaging; Middle Aged; Neuropsychological Tests; Occipital Lobe; Parietal Lobe; Perceptual Disorders
PubMed: 29199507
DOI: 10.1080/13546805.2017.1407304 -
Journal of Neuro-ophthalmology : the... Sep 2018There are many disorders of higher visual processing that result from damage to specific areas of the cerebral cortex that have a specific role in processing certain... (Review)
Review
BACKGROUND
There are many disorders of higher visual processing that result from damage to specific areas of the cerebral cortex that have a specific role in processing certain aspects (modalities) of vision. These can be grouped into those that affect the ventral, or "what?", pathway (e.g., object agnosia, cerebral achromatopsia, prosopagnosia, topographagnosia, and pure alexia), and those that affect the dorsal, or "where?", pathway (e.g., akinetopsia, simultanagnosia, and optic ataxia).
EVIDENCE ACQUISITION
This article reviews pertinent literature, concentrating on recent developments in basic science research and studies of individual patients.
RESULTS
An overview of the current understanding of higher cerebral visual processing is followed by a discussion of the various disorders listed above.
CONCLUSIONS
There has been considerable progress in the understanding of how the extrastriate visual cortex is organized, specifically in relation to functionally specialized visual areas. This permits a better understanding of the individual visual agnosias resulting from damage to these areas.
Topics: Agnosia; Humans; Visual Cortex; Visual Perception
PubMed: 28945627
DOI: 10.1097/WNO.0000000000000556 -
PM & R : the Journal of Injury,... Jan 2018The constellation of ocular symptoms known as Balint syndrome is a rare disorder seen in bilateral parieto-occipital lesions and is most frequently due to arterial...
UNLABELLED
The constellation of ocular symptoms known as Balint syndrome is a rare disorder seen in bilateral parieto-occipital lesions and is most frequently due to arterial occlusive disease or acute hypertension. Here we present the case of a patient with tacrolimus-induced posterior reversible encephalopathy syndrome (PRES) who presented with optic ataxia, simultanagnosia, and ocular apraxia. These ocular findings, consistent with Balint syndrome, are rarely the initial presentation of PRES. This case highlights the importance of early recognition of this unusual phenomenon, as well as the importance of an individualized rehabilitation plan to maximize functional independence in these patients.
LEVEL OF EVIDENCE
V.
Topics: Adult; Apraxias; Cogan Syndrome; Diagnosis, Differential; Female; Humans; Immunosuppressive Agents; Magnetic Resonance Imaging; Occipital Lobe; Parietal Lobe; Posterior Leukoencephalopathy Syndrome; Tacrolimus
PubMed: 28911995
DOI: 10.1016/j.pmrj.2017.07.079 -
Frontiers in Neurology 2017Posterior cortical atrophy (PCA) is a syndromic diagnosis. It is characterized by progressive impairment of higher (cortical) visual function with imaging evidence of... (Review)
Review
Posterior cortical atrophy (PCA) is a syndromic diagnosis. It is characterized by progressive impairment of higher (cortical) visual function with imaging evidence of degeneration affecting the occipital, parietal, and posterior temporal lobes bilaterally. Most cases will prove to have Alzheimer pathology. The aim of this review is to summarize the development of the concept of this disorder since it was first introduced. A critical discussion of the evolving diagnostic criteria is presented and the differential diagnosis with regard to the underlying pathology is reviewed. Emphasis is given to the visual dysfunction that defines the disorder, and the classical deficits, such as simultanagnosia and visual agnosia, as well as the more recently recognized visual field defects, are reviewed, along with the evidence on their neural correlates. The latest developments on the imaging of PCA are summarized, with special attention to its role on the differential diagnosis with related conditions.
PubMed: 28861031
DOI: 10.3389/fneur.2017.00389 -
Cognitive Neuropsychology 2017Simultanagnosic patients have difficulty in perceiving multiple objects when presented simultaneously. In this review article, I discuss how neuropsychological research... (Review)
Review
Simultanagnosic patients have difficulty in perceiving multiple objects when presented simultaneously. In this review article, I discuss how neuropsychological research on simultanagnosia has been inspirational for two interconnected lines of research related to the core mechanisms by which the visual system processes cluttered scenes. First, I review previous studies on enumeration tasks indicating that, despite their inability to identify multiple objects, simultanagnosic patients can enumerate up to 2-3 elements as efficiently as healthy individuals (the so-called "subitizing" phenomenon). This intriguing observation is one of the first results to support the existence of an "object individuation" mechanism that can spatially tag a limited set of objects simultaneously, and resonates with recent research on the brain dynamics of enumeration in healthy individuals. Second, I further develop the implications of the dissociation between object identification and object enumeration in simultanagnosia specifically for the distinction between object identification and individuation. The latter distinction has been the subject of recent neuroimaging research that has provided fine-grained information on the spatial as well as temporal aspects of object individuation and recognition. The lessons learned from neuropsychological research on exact enumeration in simultanagnosia can be generalized to the normal functioning of the human mind, and have provided insightful clues for cognitive neuroscience.
Topics: Agnosia; Brain; Female; Humans; Individuation; Male; Pattern Recognition, Visual
PubMed: 28632043
DOI: 10.1080/02643294.2017.1331212 -
Internal Medicine (Tokyo, Japan) 2017We herein report a 65-year-old man demonstrating dementia with Lewy bodies who first presented with Bálint's syndrome. Two years later, a mild cognitive impairment was...
We herein report a 65-year-old man demonstrating dementia with Lewy bodies who first presented with Bálint's syndrome. Two years later, a mild cognitive impairment was noted. From three years after onset, he developed progressive parkinsonism, visual hallucination, and autonomic dysfunction, in line with the deterioration of the cognitive function. Single photon emission computed tomography with a Tc-ethylcysteinate dimer performed two years after onset revealed hypoperfusion in the restricted area of the bilateral superior parietal lobule, which extended to the lateral occipital cortices within two years. It is suggested that the pathological process can extend from the parietal to occipital lobes.
Topics: Aged; Cognition; Disease Progression; Humans; Lewy Body Disease; Male; Nervous System Diseases; Syndrome; Tomography, Emission-Computed, Single-Photon
PubMed: 28566609
DOI: 10.2169/internalmedicine.56.7005 -
Cortex; a Journal Devoted To the Study... Jan 2018The 'two visual systems' account proposed by Milner and Goodale (1992) argued that visual perception and the visual control of action depend upon functionally distinct...
The 'two visual systems' account proposed by Milner and Goodale (1992) argued that visual perception and the visual control of action depend upon functionally distinct and anatomically separable brain systems: a ventral stream of visual processing that mediates visual perception (object identification and recognition) and a dorsal stream of visual processing mediating visually guided action. Compelling evidence for this proposal was provided by the neuropsychological studies of brain injured patients, in particular the contrasting pattern of impaired and preserved visual processing abilities of the visual object agnostic patient [DF] and optic ataxic patients who it was argued presented with impaired dorsal stream function. Optic ataxia [OA] has thus become a cornerstone of this 'two visual system' account (Pisella et al., 2009). In the current study we re-examine this assumption by investigating how several individuals presenting with OA performed on a bimanual haptic matching task performed without vision, when the bar to be matched was presented haptically or visually. We demonstrate that, unlike neurologically healthy controls who perform the task with high levels of accuracy, all of the optic ataxic patients were unable to perform the task. We interpret this finding as further evidence that the key difficulty experienced by optic ataxic patients across a range of behavioural tasks may be an inability to simultaneously and directly compare two spatial representations so as to compute the difference between them.
Topics: Adult; Aged; Ataxia; Humans; Male; Psychomotor Performance; Touch Perception; Visual Pathways; Young Adult
PubMed: 28456391
DOI: 10.1016/j.cortex.2017.03.023