manifestations of visual pathway lesions
TRANSCRIPT
![Page 1: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/1.jpg)
Anatomy and Anatomy and Manifestations of Manifestations of Visual Pathway Visual Pathway
LesionsLesionsRaed Behbehani , MD, Raed Behbehani , MD, FRCSCFRCSC
![Page 2: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/2.jpg)
Visual PathwayVisual Pathway
![Page 3: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/3.jpg)
Visual PathwayVisual Pathway
![Page 4: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/4.jpg)
Visual pathwaysVisual pathways
Prechiasmal: optic nerve-chism.Prechiasmal: optic nerve-chism. Retrochiasmal: optic tract, the optic Retrochiasmal: optic tract, the optic
radiations, and the occipital cortex.radiations, and the occipital cortex.
![Page 5: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/5.jpg)
Optic NeuropathyOptic Neuropathy
Unilateral.Unilateral. RAPD, dyschromatopsia.RAPD, dyschromatopsia. Central, cecocentral.Central, cecocentral. Arcuate (superior, inferior).Arcuate (superior, inferior). Altitudinal.Altitudinal. Generalized decrease in sensitivity.Generalized decrease in sensitivity.
![Page 6: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/6.jpg)
Optic NerveOptic Nerve
Axoplasmic transport : clearance of Axoplasmic transport : clearance of expired organelles, structural expired organelles, structural maintainance, and energy requirements.maintainance, and energy requirements.
Interruption of axoplasmic transport : Interruption of axoplasmic transport : ischemia, compression, inflammation.ischemia, compression, inflammation.
Orthograde axonal transport : Orthograde axonal transport : away away from the cell bodyfrom the cell body LGN. LGN.
Retrograde axonal transportRetrograde axonal transport : toward : toward cell body.cell body.
![Page 7: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/7.jpg)
ONH Blood SupplyONH Blood Supply
![Page 8: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/8.jpg)
RGC axonsRGC axons
http://www.city.ac.uk
![Page 9: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/9.jpg)
Intra-orbital Optic NerveIntra-orbital Optic Nerve
Myelination (oligodendrocytes).Myelination (oligodendrocytes). 20-30 mm Long.20-30 mm Long. Axons: mylein and glial cell Axons: mylein and glial cell
(metabolic support at the nodes of (metabolic support at the nodes of Ranvier).Ranvier).
![Page 10: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/10.jpg)
Intracranalicular Optic Intracranalicular Optic NerveNerve
Within the two bases of the LWS.Within the two bases of the LWS. Medial wall of canal forms lateral Medial wall of canal forms lateral
wall of sphenoid sinus (can be wall of sphenoid sinus (can be absent !).absent !).
Within canal : meninges, ophthalmic Within canal : meninges, ophthalmic artery and sympathetic plexus.artery and sympathetic plexus.
10 mm length.10 mm length. Tight space !Tight space ! Internal carotid artery.Internal carotid artery.
![Page 11: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/11.jpg)
Intracranial Optic NerveIntracranial Optic Nerve
Leaves the cranial end of the optic Leaves the cranial end of the optic canal (medially, backwards, canal (medially, backwards, upwards).upwards).
4-15 m (depending on the position of 4-15 m (depending on the position of chiasm).chiasm).
Upward 45 degree-angle.Upward 45 degree-angle. Anterior cerebral and anterior Anterior cerebral and anterior
comunicating artery lie superior.comunicating artery lie superior.
![Page 12: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/12.jpg)
ArcuateArcuate
Early Late
![Page 13: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/13.jpg)
AltitudinalAltitudinal
![Page 14: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/14.jpg)
CentralCentral
![Page 15: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/15.jpg)
ChiasmChiasm
![Page 16: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/16.jpg)
ChiasmChiasm Floor of the third ventricle.Floor of the third ventricle. 5-10 mm above the diphragma sella and the 5-10 mm above the diphragma sella and the
hypophysis cerebri.hypophysis cerebri. 12mm wide, 8mm A-P , 4 mm thick.12mm wide, 8mm A-P , 4 mm thick. Important relations: 3Important relations: 3rdrd ventricle, hypothalmus, ventricle, hypothalmus,
pituitary stalk, sella, dorsum sellam anterior pituitary stalk, sella, dorsum sellam anterior and posterior clinoid processes, cavernous and posterior clinoid processes, cavernous sinus.sinus.
Nasal fibers cross ; temporal fibers do not Nasal fibers cross ; temporal fibers do not (53:47).(53:47).
Wilband’s knee.Wilband’s knee.
![Page 17: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/17.jpg)
ChiasmChiasm
![Page 18: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/18.jpg)
Chiasmal syndromeChiasmal syndrome
Unilateral or Bilateral.Unilateral or Bilateral. Junctional scotoma.Junctional scotoma. Bitemporal defect.Bitemporal defect. Homonymous defects.Homonymous defects. Diplopia (III, IV, VI cranial nerves or Diplopia (III, IV, VI cranial nerves or
hemi-field slide phenomenon).hemi-field slide phenomenon).
![Page 19: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/19.jpg)
Causes of Chiasmal Causes of Chiasmal syndromesyndrome
Pituitary adenoma Pituitary adenoma Suprasellar meningiomas Suprasellar meningiomas Supraclinoid internal carotid artery Supraclinoid internal carotid artery
aneurysms aneurysms Craniopharyngiomas Craniopharyngiomas Optic nerve gliomasOptic nerve gliomas Uncommon : Optic nerve or chiasmal Uncommon : Optic nerve or chiasmal
neuritis ,Pachymeningitis , neuritis ,Pachymeningitis , Trauma,Inflammatory (e.g., sarcoidosis) Trauma,Inflammatory (e.g., sarcoidosis)
![Page 20: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/20.jpg)
Bitemporal defectBitemporal defect
![Page 21: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/21.jpg)
Junctional Scotoma Junctional Scotoma (Anterior chiasmal (Anterior chiasmal
syndrome)syndrome)
![Page 22: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/22.jpg)
Traquair scotomaTraquair scotoma
A monocular hemianopic visual field A monocular hemianopic visual field loss is referred to as junctional loss is referred to as junctional scotoma of Traquair.scotoma of Traquair.
![Page 23: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/23.jpg)
Posterior Chiasmal Posterior Chiasmal SyndromeSyndrome
90% of chiasmal fibers have macular 90% of chiasmal fibers have macular origin (superior and posterior origin (superior and posterior portions of chiasm).portions of chiasm).
![Page 24: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/24.jpg)
ChiasmChiasm
![Page 25: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/25.jpg)
Band atrophyBand atrophyFrom (Practical viewing of the optic disk)
![Page 26: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/26.jpg)
Retrochiasmal Visual Retrochiasmal Visual Pathway LesionsPathway Lesions
Bilateral.Bilateral. Homonymous.Homonymous. Complete or incomplete.Complete or incomplete. Congrous or incongrous.Congrous or incongrous.
![Page 27: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/27.jpg)
Optic Tract LesionsOptic Tract Lesions
Contralateral RAPD Contralateral RAPD ((may be an may be an ipsilateral afferent pupillary defect if a ipsilateral afferent pupillary defect if a concomitant optic neuropathy existsconcomitant optic neuropathy exists) )
A specific form of optic atrophy (band A specific form of optic atrophy (band atrophy) due to the involvement of atrophy) due to the involvement of nasal fibers (temporal field) in the nasal fibers (temporal field) in the contralateral eye contralateral eye
An incongruous homonymous An incongruous homonymous hemianopsia. hemianopsia.
![Page 28: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/28.jpg)
Optic TractOptic Tract
Travel around the cerebral Travel around the cerebral peduncles at dorsal midbrain.peduncles at dorsal midbrain.
Divides into lateral rootDivides into lateral root LGN , and LGN , and a smaller medial roota smaller medial root pretectal pretectal area (pupillary light reflex)area (pupillary light reflex)
![Page 29: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/29.jpg)
Optic TractOptic Tract
![Page 30: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/30.jpg)
Optic tract lesionsOptic tract lesions
Band Atrophy due to compressionof the left tract.Hoyt Wf,
Kommerell G. Der fundus oculi bei homonyermeinaopia.
Klin Monatsblat Augenheilkd 1973; 162: 456-464)
![Page 31: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/31.jpg)
Lateral Geniculate Bodies Lateral Geniculate Bodies LesionsLesions
Part of the thalamus.Part of the thalamus. Hilum, medial and lateral horn.Hilum, medial and lateral horn. Six laminae (layers 1-6), crossed Six laminae (layers 1-6), crossed
fibersfibers1,4,6 , uncrossed fibers 1,4,6 , uncrossed fibers 2,3,5.2,3,5.
medial
lateral
![Page 32: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/32.jpg)
LGBLGB
Upper quadrantUpper quadrant medial aspect of medial aspect of LGN, Lower quadrantLGN, Lower quadrant lateral lateral aspect of LGN.aspect of LGN.
Macular fibersMacular fibers central wedge of central wedge of LGN.LGN.
![Page 33: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/33.jpg)
LGBLGB 1- Optic nerve 2- Optic chiasma 3- Optic tract 4- Lateral geniculate body 5- Optic radiation 6- Visual cortex 7-Superior colliculus of the midbrain 8- Putamen 9- Long association bundle - inferior occipitofrontal fasciculus 10- Pulvinar of the thalamus 11-Calcarine fissure 12- Posteroinferior horn of the lateral ventricle
![Page 34: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/34.jpg)
Lateral Geniculate Lateral Geniculate NucleusNucleus
Posterior thalamus.Posterior thalamus. Mushroom-shaped structure (6 Mushroom-shaped structure (6
layers).layers). Hilum, medial and lateral horn.Hilum, medial and lateral horn. Six laminae (layers 1-6), crossed Six laminae (layers 1-6), crossed
fibersfibers1,4,6 , uncrossed fibers 1,4,6 , uncrossed fibers 2,3,5.2,3,5.
![Page 35: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/35.jpg)
Lateral Geniculate Lateral Geniculate NucleusNucleus
![Page 36: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/36.jpg)
Lateral Geniculate Lateral Geniculate NucleusNucleus
Upper quadrantUpper quadrant medial aspect of medial aspect of LGN, Lower quadrantLGN, Lower quadrant lateral lateral aspect of LGN.aspect of LGN.
Macular fibersMacular fibers central wedge of central wedge of LGN.LGN.
Layers 1,2: magnocellular. (motion)Layers 1,2: magnocellular. (motion) Layers 3-6: Parvocellular. (color)Layers 3-6: Parvocellular. (color)
![Page 37: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/37.jpg)
LGB lesionsLGB lesions
An incongruous wedge defect An incongruous wedge defect tending to point toward fixation tending to point toward fixation ((spears to fixationspears to fixation) )
Usually complete or nearly Usually complete or nearly complete field homonymous defect.complete field homonymous defect.
![Page 38: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/38.jpg)
LGB lesionsLGB lesions
![Page 39: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/39.jpg)
Optic radiationsOptic radiations
Nerve fibers bundles with cell bodies Nerve fibers bundles with cell bodies in the LGN.in the LGN.
Loop of Meyers (around temporal Loop of Meyers (around temporal and inferior horn of LV).and inferior horn of LV).
Inferior fascicle.Inferior fascicle. Superior fascicle.Superior fascicle.
![Page 40: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/40.jpg)
Optic radiationsOptic radiations
Inferior fascicleInferior fascicle anterior pole of anterior pole of temporal lobetemporal lobe lower calcarine lower calcarine cortex.cortex.
Superior fascicleSuperior fascicle parietal lobe parietal lobe upper calacrine cortex.upper calacrine cortex.
![Page 41: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/41.jpg)
Parietal lesionsParietal lesions
““Pie on the floor” homonynous Pie on the floor” homonynous defect.defect.
Associated neurologic signs and Associated neurologic signs and symptoms (e.g., hemiplegia, symptoms (e.g., hemiplegia, hemisensory loss, visual, or hemisensory loss, visual, or neglect) may be present .neglect) may be present .
![Page 42: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/42.jpg)
Anterior temporal lobeAnterior temporal lobe
““Pie on the sky” homonymous.Pie on the sky” homonymous. Often incongrous.Often incongrous. Seizures, hemiparesis, Seizures, hemiparesis,
hemianesthesia.hemianesthesia. Contralateral neglect (Non-Contralateral neglect (Non-
dominant).dominant). Aphasia (Dominant).Aphasia (Dominant).
![Page 43: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/43.jpg)
Optic radiation lesionsOptic radiation lesions
![Page 44: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/44.jpg)
Occipital lobe lesionsOccipital lobe lesions
![Page 45: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/45.jpg)
Primary Visual Cortex Primary Visual Cortex
Optic radiations terminate in layer 4 Optic radiations terminate in layer 4 (lamina granularis) .(lamina granularis) .
Layer 4 is divided into 3 layers (Line Layer 4 is divided into 3 layers (Line of Gennari).of Gennari).
P-cells P-cells 4C bets. 4C bets. M-cells M-cells 4C alpha. 4C alpha. Macular fibers – terminate posterioly.Macular fibers – terminate posterioly. Lateral fibes – termriate anteriorly.Lateral fibes – termriate anteriorly.
![Page 46: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/46.jpg)
Primary Visual Cortex Primary Visual Cortex ( V1)( V1)
Upper bank and lower bank Upper bank and lower bank (Calcarine fissure).(Calcarine fissure).
Inferior visual filed (upper bank) , Inferior visual filed (upper bank) , Superior visual field (lower bank).Superior visual field (lower bank).
Macular projections represented by Macular projections represented by 50%-60% of the area of the calcarine 50%-60% of the area of the calcarine cortex.cortex.
Occipital tip is for foveal vision.Occipital tip is for foveal vision.
![Page 47: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/47.jpg)
Occipital cortex lesionsOccipital cortex lesions
Isolated Isolated ((ii ..ee.., without other , without other neurologic deficitneurologic deficit))زز
Congruous.Congruous. Paracentral or peripheral. Paracentral or peripheral. Complete or incomplete Complete or incomplete Macular involvement or macular Macular involvement or macular
sparing of the central 5 degrees may sparing of the central 5 degrees may occur (occipital pole involvement). occur (occipital pole involvement).
![Page 48: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/48.jpg)
Occipital cortex lesionsOccipital cortex lesions
![Page 49: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/49.jpg)
Visual cortexVisual cortex
--Anterior striate Anterior striate cortex (8%-10%) is cortex (8%-10%) is monocularly monocularly innervated innervated (temporal crecsent (temporal crecsent of contralateral of contralateral eye).eye).
![Page 50: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/50.jpg)
Visual association areasVisual association areas
![Page 51: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/51.jpg)
Visual Association AreasVisual Association Areas
V2: input from V1.V2: input from V1. V3: sends info to basal ganglia and V3: sends info to basal ganglia and
midbrain.midbrain. V3a: perceive motion and direction.V3a: perceive motion and direction. V4 : (lingual and fusiform gyrus) color.V4 : (lingual and fusiform gyrus) color. V5 : (medial temporal visual region) speed V5 : (medial temporal visual region) speed
and direction, origin of pursuit movemen.and direction, origin of pursuit movemen. V6 : (parietal) represent “extra personal V6 : (parietal) represent “extra personal
space”. space”.
![Page 52: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/52.jpg)
““What” PathwayWhat” Pathway
Ventral stream (occipitotemporal) : Ventral stream (occipitotemporal) : object recognition , color, shape, and object recognition , color, shape, and pattern.pattern.
Continuation of the parvocellular Continuation of the parvocellular pathway.pathway.
V1V1 V2 V2V4V4 inferotemporal inferotemporal cortexcortex angular gyrus angular gyrus limbic limbic structures.structures.
Alexeia, anomia, agnosia, amenesia.Alexeia, anomia, agnosia, amenesia.
![Page 53: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/53.jpg)
““Where” PathwayWhere” Pathway
Dorsal stream (occipitoparietal): Spatial Dorsal stream (occipitoparietal): Spatial orientation ,visual guidance of orientation ,visual guidance of movement.movement.
V1V1 V3 V3 V5 V5Parietal and Parietal and superotemporal cortex.superotemporal cortex.
Continuation of magnocellular pathway.Continuation of magnocellular pathway. Simultagnosia, optic ataxia, acquired Simultagnosia, optic ataxia, acquired
oculomotor apraxia, and hemispatial oculomotor apraxia, and hemispatial neglect.neglect.
![Page 54: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/54.jpg)
Cortical blindnessCortical blindness
Due to bilateral occipital lobe Due to bilateral occipital lobe lesions.lesions.
Often misdiagnosed as functional Often misdiagnosed as functional vision loss.vision loss.
Stroke, severe blood loss, Eclampsia, Stroke, severe blood loss, Eclampsia, hypertension, angiography, CO hypertension, angiography, CO poisoning, cyclosporine.poisoning, cyclosporine.
![Page 55: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/55.jpg)
DyschromatopsiaDyschromatopsia
Bilateral occipital lobe lesions in the Bilateral occipital lobe lesions in the lingual or fusiform gyri of the medial lingual or fusiform gyri of the medial occipital lobe (medial occipito-occipital lobe (medial occipito-temporal lobe).temporal lobe).
Rarely no field defect.Rarely no field defect. Unilateral involvement may cause Unilateral involvement may cause
hemidyschromatopsia.hemidyschromatopsia.
![Page 56: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/56.jpg)
Alexia without AgraphiaAlexia without Agraphia
Loss of ability to read but can write.Loss of ability to read but can write. Left occipital lobe and splenium of Left occipital lobe and splenium of
corpus callosum. corpus callosum.
![Page 57: Manifestations of visual pathway lesions](https://reader035.vdocument.in/reader035/viewer/2022081508/556b177fd8b42adb338b472f/html5/thumbnails/57.jpg)
PalinopsiaPalinopsia
Persistant or recurrence of visual Persistant or recurrence of visual stimulus after it has been removed.stimulus after it has been removed.