METHODS OF ACQUIRING KNOWLEDGE IN NURSING.pptx by navdeep kaur
Occipital lobe and clinical effects of its dysfunction
1.
2. Layers of cerebral cortex and its
variations.
Surface and functional anotomy of
occipital lobe.
Clinical effects of occipital lobar
dysfunction.
Differentiation between malingering and
organic visual loss.
3. › One third of the cerebral cortex is on the
exposed part of gyri remaining is buried in
sulci and gyri.
› 15 to 30 billion nerve cells.
› Thickness of the cortex from 4.5 mm in the
frontal area to 1.3 mm in the occipital area.
4.
5.
6. › The areas of where six layers can not be
identified are called as heterotypical
different from homotypical.
› Supragranular cortex high level cortical
functions.
› Archicortex and paleo cortex.
› Granular and agranular cortex.
7. › Superiolateraly occupies a small area
behind the parieto occipital sulcus.
› Medially area behind the occipetoparietal
sulcus.
› Inferiorly limited by collateral sulcus.
› medially occipital lobe is devided in to
cuneus and lingual gyrus.
8.
9.
10. Consists of Broadmann areas 17,18,19.
Primary visual cortex or striate cortex or
area 17
› Well devoloped layer 4 a thick layer of
external band of ballirager.
› Lips of calcarine with adjacent areas cuneus
and lingual gyrus.
› Perception of simple sensation
color, size, shape, motion and illumination.
11. › Stimulation or ictal activity produces simple
visal hallucinations.
12. Associative visual cortex:
› Parastiriate [area 18] and peristriate [area
19]
› receives and interprets impulses.
› Have extensive connections.
› Concerned with more complex visual
functions of perception, spatial orientation,
visual association, and visual memory.
› Stimulation produces formed or complex
visual hallucinations.
13. › In humans occipital eye field is present in the
visual association cortex concerned with
reflex eye movements.
15. Unclear .
Dual representation of macula in each
occipital pole.
Collateral blood supply from anterior
and middle cerebral artery.
Extensive cortical representation at
occipital pole and depths of anterior
calcarine fissure.
16. Cortical blindness:
› Bilateral lesions of the occipital lobe there is
loss of sight and reflex closure of eyelids to
threat and light with sparing of pupilary light
reflex.
› Most common cause bilateral pca infarcts.
› Other causes are PRES, CJD, PML and
gliomas.
17. Visual anasagnosia or Antons syndrome:
› Denial of blindness.
› Occurs with bilateral PCA infarcts.
› Sparing of tiny islands of vision
› Patient complains of fluctuation of images as
the vision is captured in spared islands of
cortex.
18. Visual illusions:
› Size, shape, movement or combination of
three.
› Occipital lesion or in combination
occipitotemporal and occipitoparietal
areas.
› Illusion of movement occurs with
occipetotemporal lesions.
› Polyopia with lesions in occipital lobe.
› Palinopsia with lesions in occipitoparietal
lesions.
19. Visual hallucination:
› Elimentary or simple visual hallucination is the
feature of striate cortex
› Includes flashes of light, luminous lightened
candles, multiple stars and geomatric forms.
› Complex or formed visual hallucination is a
feature of association cortex or its
connections
› Includes objects, animals, persons and
scenes.
20. VISUAL OBJECT AGNOSIA:
› Failure to recognize objects by vision with
preserved ability to recognize them through
touch or hearing and in the absence of
impaired primary visual perception or
dementia
21. Aperceptive visual agnosia:
› Perceived elements of object are
synthesized to whole image.
› Pick out features of the object correctly such
as lines, angles,colors or movement but fail
to appreciate the whole object.
› Examples : spectacles
› Right hemisphere particularly lingual gyrus
involved in global processing of the object
22. Left hemisphere occipital cortex
invoved in more local processing.
23. ASSOCIATED VISUAL AGNOSIA:
› Is more closely related to aphasia than
primary disorder of vision.
› Patients can copy and match the drawing
of objects but can not name them.
› They can be identified by tactile or auditary
modality.
› have associated color agnosia and
prosagnosia.
24. • Bilateral posterior hemispheric lesions involving
occipitotemporal gyrus some times lingual gyri
and adjacent white matter.
25. Charecterised by
› Simultagnosia is a disorder of visual attention
especially to peripheral field associated
inability to perform orderly visual scanning of
the environment and attention to other
sensory stimuli are intact.
› Optic ataxia is the loss of hand eye co-
ordination with difficulty in touching or
reaching the objects under visual guidance.
26. • Optic apraxia is inability project gaze voluntarily
in the peripheral field despite intact
occulomotor movements.
27.
28. › Inability to recognise familiar faces or
pictures.
› Associated with inability to memorise new
faces.
› Inability to name the species of birds,
animals or car model.
› Bilateral ventromesial occipital lesions.
29.
30.
31. The classic syndrome of pure alexia
without agraphia is caused by a left
posterior cerebral artery occlusion in a
right-handed individual
All visual information enters only the right
hemisphere
The right visual cortex perceives the
written material but cannot transmit it to
the left hemisphere because of the
callosal lesion
32. The inferior parietal lobule in the dominant
hemisphere (primarily area 39, the angular
gyms) is the association cortex that combines
the visual and auditory information necessary
for reading and writing
A second distinct type of alexia, classically
called alexia with agraphia, results from
damage to the inferior parietal lobule itself
(angular gyrus and environs).
This lesion renders the patient unable to read or
write
33. › Differentiated between perceptual color
disturbance or anomia
› Congenital retinal color blindness is the most
common type tested by using ishihara
charts.
› Acquired color blindness due to cerebral
lesion is called central achromatopsia.
› Associated visual field defects and
prosopagnosia.
34. › Most often the lesions are bilateral and tend
to affect the upper quadrants with lesions in
bilateral ventro mesial temporal lobes and
lower part of the striate cortex.
35. Color anomia can be a part of pure
word blindness or anomic aphasia.
36. Signing
Shmidt Rimpler test
A functionally blind person ignorant of
laws of reflection may have much
improved vision reading an acuity chart
held at his chest in a mirror 10 ft away
than reading the chart 20 ft away.
Optokinetic nystagmus.
Photic drive on eeg and VER.
37. 1. Effects of unilateral disease:
› Contraletral homonymous hemianopia,
which may be central or peripheral.
› Visual hallucinations.
2. Left occipital disease:
› Rt. Homonymous hemianopia
› Alexia with out agraphia, color anomia.
38. › Visual object agnosia.
3. Rt. Occipital disease:
› Lt. Homonymous hemianopia.
› Visual illusinations and hallucinations
› loss of topographic memory and visual
orientation.