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  • Slide 1
  • Posterior Cortical Atrophy Jose Rivest, Ph.D., C.Psych. Baycrest : Neuropsychology and Cognitive Health Program York University : Psychology, Glendon College Centre for Vision Research October 6, 2014 The visual variant of Alzheimers Disease
  • Slide 2
  • Outline Review The Visual System: Anatomy & Cognitive Deficits Posterior Cortical Atrophy: Syndrome Parallel with the anatomy of the visual system Case presentation: Data over 4 years Objectives Learn what is Posterior Cortical Atrophy (PCA) Establish parallels with the visual system Compare PCA and AD
  • Slide 3
  • Dorsal and Ventral Streams Motion Form & Color Ungerleider, L.G., Mishkin, M. (1982). Two cortical visual systems. Cambridge (MA): MIT Press p. 549-586. Goodale, M.A., Milner, A.D. (1992). Separate visual pathways for perception and action. Trends in Neurosciences. 15:20-25. Dorsal stream: Where/How system Ventral stream: What system ACTION Modular organization Visual System RECOGNITION
  • Slide 4
  • Ventral Stream Shape Pattern Texture Color Vision for perception (recognition) Allocentric coding Sustained representations Critically linked to awareness Schenk, T., & Mcintosh, R. D. (2010). Discussion Paper: Do we have independent visual streams for perception and action? Cognitive Neuroscience, 1(1), 52-78. Spatial aspects (where) Dorsal Stream The visual brain in action (Miller & Goodale, 1995, 2006) Vision for action Egocentric coding Transient representations Independent of awareness
  • Slide 5
  • Visual neglect Visuo-motor impairment (optic ataxia) Extinction Simultagnosia Apraxia Akineotopsia (motion blindness) Spatial dysperception (e.g. depth, length, size) Hand-eye incoordination Finger agnosia Right-left confusion Dysgraphia/agraphia: writing Dyscalculia/acalculia: math Damaged Dorsal Stream
  • Slide 6
  • Blint syndrome Ocular apraxia: Inability to voluntarily look around in space Optic ataxia: Inability to reach for an object under visual guidance Simultagnosia Gerstmann syndrome Agraphia Acalculia Finger agnosia Left-right disorientation
  • Slide 7
  • Object agnosia Prosopagnosia Alexia Achromatopsia Damaged Ventral Stream
  • Slide 8
  • Declined: Neurodegenerative syndrome Termed in 1988 by Benson et al. Posterior Cortical Atrophy Visuo-spatial Visuo-perceptual Literacy Praxic Skills Language Memory Insight Benson, D.F., Davis, R.J. Snyder, B.D. (1988). Posterior Cortical Atrophy. Arch. Neurol., 45, 789-793. Preserved: Visual variant of AD; Biparietal AD; Benson syndrome Non Verbal IQ < Verbal IQ
  • Slide 9
  • Clinical presentation Posterior Cortical Atrophy Depressive symptoms: tearfulness sadness insomnia loss of weight Non-specific visual complaints: Poor vision: optometry, ophthalmology: nothing is wrong
  • Slide 10
  • Visuo-spatial & visuo-perceptual impairments Neuropsychological features Posterior Cortical Atrophy Alexia Blints syndrome: Simultagnosia Oculomotor apraxia Optic ataxia Gerstmanns syndrome: Acalculia Agraphia Finger agnosia Left-right disorientation
  • Slide 11
  • Prosopagnosia Neuropsychological features Posterior Cortical Atrophy Achromatopsia Visual field defects Hemineglect Constructional dyspraxia Apraxia - dressing - ideomotor: imitate hand gestures and voluntarily pantomime tool use Working memory
  • Slide 12
  • Posterior Cortical Atrophy Age of onset: 50-65 years Snowden, J.S., Stopford, C.L., Julien, C.L. et al. (2007). Cognitive phenotypes in Alzheimer's disease and genetic risk. Cortex, 43(7), 835-845. Epidemiology Unknown: underestimation AD n=523 5% PCA (Snowden et al., 2007) No gender difference
  • Slide 13
  • Alzheimers Disease Age of onset: > 65 years 60-80% of all dementia cases Prevalence < 65 4% of population 65-74 6% 85 + 46% **** > 65 13% **** Women > Men The global prevalence of dementia has been estimated to be as high as 24 million, and is predicted to double every 20 years until at least 2040.
  • Slide 14
  • Pathologic heterogeneity Posterior Cortical Atrophy Dr. David Tang-Wai University Health Network Memory clinic Tang-Wai, D.F. & Graff-Radford, N.R. (2011). Looking into posterior cortical atrophy. Providing insight into Alzheimer disease. Neurology, 76, 1778-1779. Causes: Alzheimers disease: senile plaques & neurofibrillary tangles Dementia with Lewy bodies Corticobasal degeneration Prion disease (Creutzfeldt-Jacob disease & Fatal-familial insomnia transmissible spongiform encephalopathies)
  • Slide 15
  • Tang-Wai, D.F. & Graff-Radford, N.R. (2011). Looking into posterior cortical atrophy. Providing insight into Alzheimer disease. Neurology, 76, 1778-1779. Posterior Cortical Atrophy Parietal, Occipital, & Occipito-temporal cortices Atrophy or metabolic changes in the posterior regions: 3D MRI reconstruction and selected coronal sections of the brain of a PCA patient Prominent widening of the parietal and lateral occipital sulci
  • Slide 16
  • PCA: Extensive & symmetrical hypoperfusion in the occipital, parietal & posterior temporal cortices AD: Hypoperfusion in posterior associative cortex, prefrontal cortex & bilateral hippocampus Kas, A., de Souza, L. C., Samri, D., Bartolomeo, P., Lacomblez, L., et al. (2011). Neural correlates of cognitive impairment in posterior cortical atrophy. Brain, 134, 1465-1478. doi: 10.1093/brain/awr055. SPECT: 39 PCA, 24 AD & 24 controls
  • Slide 17
  • PCA: more hypoperfusion in the parieto-occipital cortex (blue) More higher perfusion in the frontal, anterior cingulate, inferior & medial temporal regions (red) than AD Kas et al. (2011)
  • Slide 18
  • Different forms? Posterior Cortical Atrophy Participants: N=20 PCA; n=20 matched controls TASKS (basic visual functions) : Form detection Form coherence Form discrimination Color discrimination Motion coherence Point localization Basic visual processing (striate cortex; caudal) form Ventral form Dorsal form Lehmann, M., Barnes, J. Ridgway, G.R., Wattam-Bell, J., Warrington, E.K., Fox, N.C. & Crutch, S. J. (2011). Basic visual function and cortical thickness patterns in posterior cortical atrophy. Cerebral Cortex, 21, 2122-2132. Related to: Recognition (ventral form)? Action/Space (dorsal form)?
  • Slide 19
  • Cortical thickness PCA < Controls Cortical thickness PCA > Controls Lehmann, et al. (2011)
  • Slide 20
  • Findings 1. Each PCA participant impaired on at least one basic visual processing task 2. Heterogeneity within the basic visual processing capacities 3. Type of basic visual processing dysfunction: Impact upon the nature of their higher-order visual dysfunctions: form detection, form coherence, & color performance object and space perception form detection object but not space perception point localization space but not object perception No impact upon nonvisual parietal functions (e.g. calculation & spelling) No correlation with recognition memory, MMSE, or disease duration Lehmann, et al. (2011)
  • Slide 21
  • ANATOMY Space subgroup greater posterior parietal cortical thinning? Object subgroup greater inferior temporal cortical thinning? Space (dorsal) PCA vs. ControlsObject (ventral) PCA vs. Controls Cortical thickness PCA < Controls Cortical thickness PCA > Controls Lehmann, et al. (2011)
  • Slide 22
  • Object (ventral) vs. Space (dorsal) Cortical thickness Space < Object Cortical thickness Space > Object Space subgroup thinning in the occipital & inferior parietal lobes Object subgroup thinning in the fusiform gyrus & inferior temporal lobe BUT NO significant difference multiple common areas of tissue loss across the subgroups Findings Lehmann, et al. (2011)
  • Slide 23
  • Different forms? Posterior Cortical Atrophy Lehmann, M., Barnes, J. Ridgway, G.R., Wattam-Bell, J., Warrington, E.K., Fox, N.C. & Crutch, S. J. (2011). Basic visual function and cortical thickness patterns in posterior cortical atrophy. Cerebral Cortex, 21, 2122-2132. Basic visual processing (striate cortex; caudal) form? one dysfunction Ventral form Dorsal form Continuous range of object-space difference
  • Slide 24
  • Myelodysplasia (bone marrow malfunction insufficient number of normal blood cells) Arrhythmia Prostate cancer Pneumonia Hypercholesterolemia Case presentation: GB 79 year old man Born in New Zealand Immigrated in Canada in 1962; Specialized MD (retired) Lives with his wife & has 2 healthy children Red/green color deficiency Hobbies: reading, music, theatre, golf Medical history:
  • Slide 25
  • GB Neuropsychology cognitive profile followed yearly since 2010 Complaints (2010) Reading** (even after cataract surgery) Word finding difficulties Neurology Dr. Tang Way: MRI (2010-2011): enlargement of cortical sulci and lateral ventricles (cerebral atrophy)
  • Slide 26
  • 2011 GB
  • Slide 27
  • 2012 GB
  • Slide 28
  • 2012 GB
  • Slide 29
  • KaplanBaycrest Neurocognitive Assessment (KBNA)
  • Slide 30
  • Mean KBNA index scores of Group Dementia and Control expressed as (M = 50, SD = 10). Leach L Arch Clin Neuropsychol 2010;25:359-370 The Author 2010. Published by Oxford University Press. All rights reserved. For permission

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