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Vascular lesions of the parietal
cortex and their clinical
implications for vision
Vascular lesions of the parietal
cortex...
Overview
• “Lesion”
any localized abnormal structural change in a bodily
component
• Interruption of tissue perfusion
• Tu...
Types of stroke
• Ischaemic – 87%
Obstruction of a blood vessel
Thrombus – blood clot
Embolus – fragment of clot stuck in ...
Frontal lobe stroke
most common
ACT FAST
• Facial weakness
• Arm and leg weakness
• Speech problems
• Time to call 999
Uni...
Risk factors of stroke
• Transient Ischaemic Attack (TIA)
“Mini Stroke” (<24 hours), 25% patients die within a year
• Most...
Risk factors of stroke
just a 10 mmHg increase in the middle aged individual can increase the risk factor of
stroke by 40%...
Gross anatomy of the brain
• Left and right hemispheres
Divided by central sulcus, connected by corpus callosum
• Folds, g...
Arterial vasculature
• Brain has two main supplies
R+L internal carotid arteries
R+L vertebral arteries
• Both form the ci...
• The circle of Willis reduces the
probability of stroke
Anastomosis of 3 arteries
Blood can still flow along an alternate...
Parietal lobe vasculature
• Anterior cerebral arteries
Not associated with areas of vision
Can be disregarded for this stu...
Border zone infarction
• Areas where main arteries meet
at their distal ends
Blood at low pressure
Tissue here susceptible...
General symptoms of
parietal damage
• Parietal lobe function
Integration of sensory information & spatial sensation
Dorsal...
General symptoms of
parietal damage
• Parietal lobe function
Integration of sensory information & spatial sensation
Dorsal...
Contralateral neglect
syndrome
Purves et. al., 2008
• Failure to respond to a stimulus
on the side contralateral to a lesi...
Contralateral neglect
syndrome
Purves et. al., 2008
the saccadic eye movements of a “normal” individual. In free viewing o...
Bilateral posterior parietal
infarcts
Purves et. al., 2008
• The left and right brains are affected
Right brain compensate...
Simultagnosia
• The patient perceives whole objects
But can only see a single object at once
Regardless of object size or ...
Simultagnosia
(Rafal, 2001)
The patient was presented with a comb, which he could identify
correctly.
When a spoon was pla...
Simultagnosia
Robertson and Grabowecky, unpublished observations (Rafal, 2001)
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S...
RehabilitationTreatment
• Remedial approach
Re-train the damaged CNS with general daily activities
• Functional approach
U...
References
• BUPA (2007) The British United Provident Association Limited, England, accessed 1 March 2009,
<http://www.bup...
Stroke & Balint's syndrome
Stroke & Balint's syndrome
Stroke & Balint's syndrome
Stroke & Balint's syndrome
Stroke & Balint's syndrome
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Stroke & Balint's syndrome

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Stroke & Balint's syndrome

  1. 1. Vascular lesions of the parietal cortex and their clinical implications for vision Vascular lesions of the parietal cortex and their clinical implications for vision
  2. 2. Overview • “Lesion” any localized abnormal structural change in a bodily component • Interruption of tissue perfusion • Tumour Trauma Blood clots Stroke
  3. 3. Types of stroke • Ischaemic – 87% Obstruction of a blood vessel Thrombus – blood clot Embolus – fragment of clot stuck in another vessel • Haemorrhagic – 13% Haematoma – collection of blood outside vessels Compression of tissue Reduced blood flow Rosamond, W. et al., 2008
  4. 4. Frontal lobe stroke most common ACT FAST • Facial weakness • Arm and leg weakness • Speech problems • Time to call 999 Unilateral damage Contralateral effect
  5. 5. Risk factors of stroke • Transient Ischaemic Attack (TIA) “Mini Stroke” (<24 hours), 25% patients die within a year • Most likely candidates for stroke Diabetic women above the age of 55 Smokers twice as likely High cholesterol, alcohol intake and little exercise • Biggest risk factor? High blood pressure!
  6. 6. Risk factors of stroke just a 10 mmHg increase in the middle aged individual can increase the risk factor of stroke by 40%! The danger in this is that such a small increase has no physiological signs associated with it and often goes unnoticed.
  7. 7. Gross anatomy of the brain • Left and right hemispheres Divided by central sulcus, connected by corpus callosum • Folds, grooves and clefts Gyri, sulci and fissures • Four lobes of the brain... Frontal Temporal Occipital Parietal
  8. 8. Arterial vasculature • Brain has two main supplies R+L internal carotid arteries R+L vertebral arteries • Both form the circle of Willis on the ventral brain surface Plays a huge role in reducing the risk of stroke in individuals Netter, 2002 Vertebral Internal Carotid
  9. 9. • The circle of Willis reduces the probability of stroke Anastomosis of 3 arteries Blood can still flow along an alternate route in case of a blockage Not a likely preventative measure in the case of embolus formation of lacunar stroke Arterial vasculature Netter, 2002 Anterior Cerebral Middle Cerebral Posterior Cerebral
  10. 10. Parietal lobe vasculature • Anterior cerebral arteries Not associated with areas of vision Can be disregarded for this study • Middle cerebral arteries Continuation of internal carotids • Lacunar stroke Occlusion of one of the brain’s main penetrating arteries Netter, 2002
  11. 11. Border zone infarction • Areas where main arteries meet at their distal ends Blood at low pressure Tissue here susceptible to infarction when blood pressure is reduced (Image B) • Lacunar stroke Depicted in image C Caplan et. al., 1999
  12. 12. General symptoms of parietal damage • Parietal lobe function Integration of sensory information & spatial sensation Dorsal pathway of vision • ‘Silent’ region of the brain No obvious visible symptoms as with frontal stroke • Contralateral neglect • Bilateral infarcts
  13. 13. General symptoms of parietal damage • Parietal lobe function Integration of sensory information & spatial sensation Dorsal pathway of vision • ‘Silent’ region of the brain No obvious visible symptoms as with frontal stroke • Contralateral neglect • Bilateral infarcts
  14. 14. Contralateral neglect syndrome Purves et. al., 2008 • Failure to respond to a stimulus on the side contralateral to a lesion • Apraxia – motor deficits Reaching for objects, writing & drawing • Only affects the right parietal cortex Mediates attention to right and left So lesions on the left side are compensated for by right Right side affected and there is no compensation!
  15. 15. Contralateral neglect syndrome Purves et. al., 2008 the saccadic eye movements of a “normal” individual. In free viewing of this “interesting scene”, the entire field is scanned If we introduce a right hemisphere lesion, the right visual field is observed, while the patient ignores the opposite side of the world
  16. 16. Bilateral posterior parietal infarcts Purves et. al., 2008 • The left and right brains are affected Right brain compensates for left field BUT Left brain cannot sense right field Severe right field neglect • Bálint’s syndrome Lesions at the parieto-occipital border Psychic paralysis of visual fixation Optic ataxia Simultagnosia
  17. 17. Simultagnosia • The patient perceives whole objects But can only see a single object at once Regardless of object size or spatial orientation • NOT like tunnel vision Where the visual field constricts single
  18. 18. Simultagnosia (Rafal, 2001) The patient was presented with a comb, which he could identify correctly. When a spoon was placed in front of the comb, the patient still only reported the comb to be visible When the spoon was moved. The patient could see the spoon only, and not the comb When both the spoon and comb were moved, the patient only reported to see “what looks like a blackboard with some writing on it” When the examiner turned round, he saw a blackboard behind him
  19. 19. Simultagnosia Robertson and Grabowecky, unpublished observations (Rafal, 2001) S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S A L I P Y B G H C F X T I U C W R W S J H N S U V Q Z U C U E L X Q J Z B R Q P F S M N G Y S F S B G VTHE ALPHABETTWICE! In a more recent study, the question that needed clarifying was what exactly an “object” was to the patient. An image was constructed of several small letter Ss that were arranged to make an overall H shape This image was presented to a subject, who reported to only seeing the local S On repeated testing over several months, he only reported seeing the global H shape twice! When the H shape was constructed from many different letters The subject reported to seeing “the alphabet”
  20. 20. RehabilitationTreatment • Remedial approach Re-train the damaged CNS with general daily activities • Functional approach Use a person’s strengths and abilities to compensate • Multicontext approach Targeted strategies within varied environments
  21. 21. References • BUPA (2007) The British United Provident Association Limited, England, accessed 1 March 2009, <http://www.bupa.co.uk/about/asp/history/index.asp> • Caplan, L.R., Hurst, J.W., Chimowitz, M.J. (1999) Clinical Neurocardiology, Informa Health Care, 14 • Al-Khawaja, I., (2001) Neurovisual rehabilitation in Balint's syndrome, J Neurol Neurosurg Psychiatry, 70, 416 • Moore, K.L., Dalley, A.F. (2006) Clinically Oriented Anatomy, 5th Edition, Lippincott Williams & Wilkins, 921- 932 • Mensah, G.A. (2008). Epidemiology of stroke and high blood pressure in Africa. Heart, 94, 697-705. • Netter, F.H. (2002) Interactive Atlas of Human Anatomy, CD-ROM, 3rd Edition, Saunders • Purves, D., Augustine, G.J., Fitzpatrick, D. et al. (2008), Neuroscience, 4th Edition, Sinauer Associates Inc, 668-671 • Rafal, R. (2001), Handbook of Neuropsychology, 2nd Edition, Elsevier Science, Vol. 4, 121-139 • Rosamond, W., Flegal, K., Furie, K., Go, A., Greenlund, K., Haase, N., Hailpern, S.M., Ho, M., Howard, V., Kissela, B., et al. (2008). Heart disease and stroke statistics--2008 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation 117, e25-146.

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