Retrochiasmal Flashcards
Optic Radiations: Parietal Lobe receives fibers from (upper/lower) retina, which controls the (upper/lower) VF.
Parietal: upper retina, lower VF
Optic Radiations: Temporal receives fibers from (upper/lower) retina, which controls the (upper/lower) VF.
Temporal: Lower retina, upper VF
Blood Supply: Optic Tract
Middle Cerebral Artery
(Specifically: Anterior Choroidal & Posterior Communicating)
Blood Supply: LGN
Branches of MCA and PCA
Blood Supply: Optic Radiations
MCA and PCA
Blood Supply: Calcarine Sulcus
Mostly PCA
MCA — anterior portion, corresponds with Macula
The more (anterior/posterior), the more congruous
Anterior
Retrochiasmal defects are always
homonymous
T/F: Congruity can only be assessed in an incomplete hemianopia
TRUE
Most common cause of RC-VF defects in children
Trauma and tumors
Most common cause of RC-VF defects in adults
Infarcts
Most common location of RC-VF defects in adults
Occipital lobe
Most common location of RC-VF defects in children
Optic radiations
TRUE/FALSE: there are more uncrossed than crossed fibers in the optic tract
FALSE: there are more crossed (53:47)
—> lesion in optic tract produces APD
T/F: VA is preserved in Optic Tract lesion
TRUE
Describe the pallor in optic tract lesion
Contralateral: bow tie
Ipsilateral: temporal atrophy
Abnormalities seen in Optic Tract lesion: (4)
- VA preserved
- Contralateral low-grade APD
- OU pallor
- Contralateral incongruous homonymous hemianopia
What role does LGN play in visual processing?
Organizes fibers and sends to visual cortex
Ipsilateral layers of LGN
2, 3, 5
Contralateral layers of LGN
1, 4, 6
Describe defect and the lesion that would cause this defect
Quadruple sectoranopia
Occlusion of anterior choroidal artery (branch of MCA) —> infarcts in horns / hilum is spared
Describe defect and the lesion that would cause this defect
Horizontal sectoranopia
Occlusion of posteriolateral choroidal artery (branch of PCA) —> infarction of hilum / spare horns
Most common parietal lesion
Stroke
Most common temporal lesion
Tumor
“Pie in the sky”
Aka Upper Quadrantanopsia
(Contralateral) Temporal lobe defect
Superior radiations originate from the _____ retina, corresponding with the ____ VF, travels through the _____ lobe and ends up in the ____ occipital lobe.
Superior retina (Inferior field) —> Parietal lobe —> Superior occipital
Inferior radiations originate from the _____ retina, corresponding with the ____ VF, travels through the _____ lobe and ends up in the ____ occipital lobe.
Inferior retina (superior VF) —> temporal lobe (aka Meyer’s Loop) —> inferior occipital lobe
Lesion in anterior Meyer’s Loop — what defect?
Lateral to vertical midline in superior field
Lesion in posterior Meyer’s Loop — what defect?
Superior field: superior to horizontal midline
Signs/Symptoms for Temporal Lobe/Meyer’s Loop defect (3)
- Visual agnosia
- Seizures
- Personality changes
Signs/Symptoms for Parietal Lobe defect (3)
- Hemiparesis
- Aphasia/Acalculia
- Spatial distortion
Parietal Lobe defect is denser (inf/sup)
Inf
Temporal lobe defect is denser (inf/sup)
Sup
Why might there be ON atrophy or GCC/NFL loss with optic radiation lesion?
Transynaptic retrograde degeneration
Why might there be gaze preference with optic radiation lesion?
Looking away from hemianopia
Cogan’s Spasticity of Conjugate Gaze
Abnormal Bells Phenomenon (up and away from lesion)
Bells Phenomenon
Eyes up and out on force closure
Visual Cortex aka…
Striate Cortex
Brodmann’s 17
V1
Explain why macular sparing occurs
Dual blood supply from MCA/PCA
Riddoch Phenomenon
Blindsight (HM, LP)
Most common cause of occipital lobe hemianopia
PCA stroke
TRUE/FALSE: PCA stroke —> macular sparing
Not necessarily, can be +/- sparing
Most common cause of stroke
Embolus or thrombosis
Ocular Managament for RC-VF defect (4)
- Low Vision
- Driving Recs
- Visual scanning/mobility training
- Prism
