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Occipital lobe
This document discusses lesions in the occipital lobe and their effects. It covers topics such as field defects from lesions of the primary visual cortex, including homonymous hemianopia. It also discusses cortical blindness, Anton's syndrome, and other syndromes. Lesions of the ventral stream can cause visual agnosias like object agnosia and prosopagnosia. Disorders of the dorsal stream include Balint's syndrome and simultanagnosia. Various visual hallucinations and other positive visual phenomena are also covered. The document provides detailed information on the anatomical localization and clinical features of different visual disorders.
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Occipital lobe
- 1. Occipital Lobe Anatomy andFunction with clinical correlation By Dr Srimant Pattnaik, DM PDT Neuromedicine , BIN
- 10. Lesions in theoccipital lobe • Lesion of the primary visual area • Lesion of the dorsal stream • Lesion of ventral stream
- 11. Lesions of primaryvisual cortex 1. Field defects 2. Cortical blindness 3. Anton ‘ s syndrome
- 12.
- 13. • Binocular fielddefect usually localizes to or beyond optic chiasm • Retrochiasmal lesions are usually homonymous hemianopia • Bilatreal optic nerve or retinal disease can produce bilateral field defect • Retinal disease has ophthalmoscoic finding • Optic nerve problem has acuity problem
- 15. left lower bankof calcarine sulcus Left upper bank of calcarine sucus
- 16. case • A patientrecovering from a right hemipareisis, presented to hospital with right sided visual disturbance
- 18. Half moon ortemporal crescent syndrome
- 19. Cortical blindness • Conceptualizedas bilateral homonymous hemianopia. Clinically blind. • Due to blockage of bilateral PCA or distal Basilar artery • Bilateral Area 17 involvement • Central vision may be present (macular sparing): reason for optokinetic nystagmus • Pupilary reflex present • Menace reflex ± • VEP : no cortical potential • EEG : loss of alpha rythm
- 20. • Visual imaginationand visual imagery preserved • Less complete bilateral lesion leave the patient with varying degrees of visual perception • There may be visual hallucination of either complex or elementary type • Recovery occurs in a regular fashion from cortical blindness through visual agnosia and partially impaired perceptual function to recovery • After recovery , there may be p[roblems of visual fatigue,fusion or fixation (3F’s)
- 21. Anton syndrome • VisualAnosognosia : self unawareness of visual deficit. Denies blindness • Iinvolvement of primary visual area along with visual association area • Behaves as if he can see • Confabulates. Has excuses for blindness
- 22. Inverse Anton Syndrome •Also known as Blindism or Blindsight • As such patient can not see but eye movements are noticed in response to stimulus such as flashes of light • Due to nonconscious visual processing • Pathways – Retino tectal – Retino tecto pulvino extrastriate – Geniculoextrastriate • Simulates hysterical blindness
- 23. Riddoch syndrome • Corticalblindness but area V5 is spared • Otherwise blind Patient can percieve moving objects • Hypothesis is of a direct connection between LGB or Pulvinus to V5
- 24. Lesions of ventralstream 1. Visual object agnosia 2. Colour vision abnormality 3. Prosopagnosia 4. Pure Alexia
- 25. VISUAL OBJECT RECOGNITION VISUALSTIMULI PRIMARY SKETCH VIEWER CENTERED REPRESENATION OBJECT CENTERED REPRESENTATION SEMANTIC CONCEPTUAL FIELD VISUAL ANALYSIS PHONOLOGICAL LEXICON
- 26. SEMANTIC-CONCEPTUAL SYSTEM PRIMARY SKETCH-2D VIEWERCENTERED SKETCH-2.5D OBJECT CENTERED SKETCH-3D MARR’S MODEL OF VISUAL OBJECT RECOGNITION
- 27. Visual Object Agnosia •Apperceptive Visual agnosia – Perceptual categorization defect • Associative visual agnosia
- 28. Apperceptive visual agnosia VISUALSTIMULI PRIMARY SKETCH VIEWER CENTERED REPRESENATION OBJECT CENTERED REPRESENTATION SEMANTIC CONCEPTUAL FIELD VISUAL ANALYSIS PHONOLOGICAL LEXICON
- 30. Apperceptive visual agnosia •Localization : • bilateral lesion of calcarine cortex • Occipitotemopral regions • Pathology: mostly ischemic • Most commonly seen during recovery from cortical blindness
- 31. Clinical feature • Pickout details of the object in fragments i.e lines adges, intensity but fail to identify the whole picture • They can not name objects presented to them or draw them or match them • Mostly act as blind but avoid obstacles while walking
- 32. Besdside tests • Matchtest • Figure copying test
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- 35. Perceptual categorization defect VISUALSTIMULI PRIMARY SKETCH VIEWER CENTERED REPRESENATION OBJECT CENTERED REPRESENTATION SEMANTIC CONCEPTUAL FIELD VISUAL ANALYSIS PHONOLOGICAL LEXICON
- 36.
- 37. Perceptual categorization defect: contd •Localization: right parietal lobe • Patient can appreciate objects , match them and and recognize them later as long as they are presented in same conventional orientation
- 38. tests VOSP Incomplete letter test Silhouettes BORB Gollinfigures Unusual view test Foreshortened match
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- 44. Associative visual agnosia VISUALSTIMULI PRIMARY SKETCH VIEWER CENTERED REPRESENATION OBJECT CENTERED REPRESENTATION SEMANTIC CONCEPTUAL FIELD VISUAL ANALYSIS PHONOLOGICAL LEXICON
- 45. SEMANTIC-CONCEPTUAL SYSTEM PRIMARY SKETCH-2D VIEWERCENTERED SKETCH-2.5D OBJECT CENTERED SKETCH-3D MARR’S MODEL OF VISUAL OBJECT RECOGNITION
- 46. • Perception isstripped of meaning • Patient can copy , match figures still can not say what it is • Can identify if object is presented by any other modality • Localized to bilateral posterior hemisphere involving fusiform ot occipitotemporal gyri, sometimes lingual gyrus and adjacent white matter
- 47. Tests • Questionnaire • Sortingof stimuli • Matching visually dissimilar objects according to similar function • Real and unreal objects • Pyramids and palm trees test
- 51. Optic aphasia VISUAL STIMULI PRIMARYSKETCH VIEWER CENTERED REPRESENATION OBJECT CENTERED REPRESENTATION SEMANTIC CONCEPTUAL FIELD VISUAL ANALYSIS PHONOLOGICAL LEXICON
- 52. • Optic aphasiaor optic anomia, an intermediate between agnosia and aphasia • Localization: left occipitotemporal area • Can not name object presented visually but can recognise when given cue • Preserved recpognition of the objects differentiates frm associative agnosia • Recognition with auditory or tactile cue differentiates it from anomic aphasia
- 53.
- 55. test • Face identificationfrom photographs • Benton facial recognition test
- 56. Prosopagnosia • Difficulty inrecognising familiar faces • Recognise faces from a singular feature like glasses , beards etc or non visual cues like voice or social context • Apperceptive vs associative • Localization – B/L damage to fusiform & lingual gyri – U/L Rt OP lesion – B/L or U/L anterior temporal lesion
- 57. Causes of Prosopagnosia •Congenital – Hereditary : autosomal dominant inheritance – Autistic spectrum disorder • Acquired – Stroke – Herpes encephalitis – Alzheimer – Carbon monoxide poisoining
- 60. COLOUR STIMULI COLOUR DISCRIMINATION COLOUR CATEGORISATION SEMANTIC CONCEPTUAL FIELD COLORNAMING ACHROMATOPSIA COLOUR AGNOSIA COLOUR AMNESIA
- 64. Cerebral Achromatopsia • Localization: bilateral or nondominant inferior occipito temporal lesions that damage lingual and fusiform gyri sparing of calcarine cortex
- 65. COLOUR AGNOSIA • Colouris stripped off its meaning • Can see and discriminate though • Can not point or paint • Inferomedial aspect of dominant occipital anfd temporal lobe
- 66. Colour Amnesia • Defectin colour object association • Can see, discriminate and point • Can not paint • Dominant hemisphere lesions
- 67. Colour Anomia • Basicallythe optic aphasia for colours • Defective naming only
- 68.
- 69. simultanagnosia • Inability tocomprehend a complex visual scene despite being able to comprehend individual items • Divided into • Ventral • Dorsal
- 70. SIMULTANAGNOSIA DORSAL VENTRAL LOCALIZATION B/LOCCIPITOPARIETAL LEFT OCCIPITOTEMPORAL PATHOPHYSIOLOGY RESTRICTED VISUAL ATTENTION SLOW VISUAL PROCESSING CLINICALLY BLIND NOT SO LEVEL OF PERCEPTION LIMITED TO ONE OBJECT SEVERAL OBJECTS PERCIEVED, ONE RECOGNIZED SCATTERED DOT COUNTING NOT ABLE TO DO ABLE TO DO WORD READING CAN NOT READ WORDS READS BUT LETTER BY LETTER
- 71. Tests of ventralSimultanagnosia Mixed figure testing Cookie theft picture
- 72. Disorders of Dorsalstream 1. Balint Syndrome 2. Visual disorientation 3. Akinetopsia 4. Astereopsis 5. Visual extinction
- 73. Balint syndrome • Occursdue to lesion in b/l parieto occipital lesion in the convexity of the hemisphere • Components – Dorsal simultanagnosia – Oculomotor apraxia – Optic ataxia
- 74. Dorsal Simultanagnosia • Dueto restriction of visual attention • Perception is limited to point of fixation without the awareness of presence of other parts • Miss forest for trees. • Functionally blind as they find it difficult to move about
- 77. Oculomotor apraxia • Nota true apraxia as the higher level motor control is intact • Also known as psychic paralysis of gaze • Defective vision for action • Deficit is a difficulty in shifting visual attention to appropriate target
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- 79.
- 80. • Inability toreach a target under visual guidance • Defective action for vision • No difficulty in touching body parts • Tested by asking the patient to touch examiner’s ear followed by touching own ear
- 81. Visual disorientation • Errorin judging the location and distance of an object, and in judging the relative distance between the two objects • Bump into things while walking • Difficulty in finding door handle • Problem arises when things are placed at different level
- 82. • Difficulty inreaching things becomes difficult, mimics optic ataxia • However, visual disorientation improves with repeated attempts, differentiating from optic ataxia
- 83. Astereopsis • Loss ofdepth perception • Depth is computed from binocular visual information • Retinal disparity is processed by the dorsal stream • Area 18 is primarily concerned with stereopsis • Abnormality is seen due to bilateral damage, more to the right side
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- 85.
- 86. • Aquired defectof motion perception • Sees moving people here and there • Difficulty in pouring water from a cup to bottlr as the water appears as ice
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- 88. Visual hallucination • Positivevisual phenomena in absence of external stimuli • Simple formed hallucination • Light dots, bars, lines , stars, fog, coloured senasation • Mostly after occpital stroke: good recovery • Psychiatric conditions • Multicoloured wth spherical or circular pattern seen in Occipital epileptic seizure • Degenerative : AD,DLB • Infective: CJD-Heidenhain variant • Unformed hemifield hallucination post exercise : occiptal lobe tumor
- 89. Peduncular Hallucinosis • Charcot– Willebrand syndrome • Vivid,colourful,formed hallucination of p[eople and animal • Usually hypnogogic • Pseudohallucinosis as patient knows they are unreal • Also seen in midbrain lesion as a release hallucination
- 90. Charles Bonnet Syndrome •Seen in patients with visual loss due to ophthalmological condition • Well defined, organized and vivid scenes of animals, flowers and people • Also a pseudohallucination • Can be abolished by repeated closing and opening of eyes • Deafferentiation of visual assdociation areas leading to a form of phantom vision
- 91. Miscellaneous Positive visual phenomena •Metamorphopsia( distortions of shape) • scintillating scotomas • Teichopsia( irregular shapes) • macropsia and micropsia • palinopsia (perseveration of visual images) • Visual allesthesia (spread of a visual image from a normal to a hemianopic field) • polyopia (duplication of objects) • All these phenomena are disturbances of higher visual perception rather than agnosias
Editor's Notes
- #3 Pyramidal in shape, 17 to 18% of weight
- #6 A- amount of myelinated fibers, b – appearance of 6 cortical layers c; lesion based d; developmental e functional area f mri tactography
- #7 Striate cortex : part of area 17 along lips of calcarine cortex,parastriate is 18. peristriate is 19
- #20 Korsakoff amnestic defect, akinetic mute stagemay be acco pained,Adams
- #23 Usual pathway is retino geniculo striate pathway
- #28 Lissauer made this clasification around 1890, which still is used. By 30 he died
- #32 How to exclude anomia in this patient
- #34 Match test
- #54 Skin conductance response
- #81 Touching body parts does not require visual guidance