Flashcards in Clinical Neuro-opthalmology Deck (22):
Do all the fibers in CN II go to the lateral geniculate nucleus?
Nope, some branch off to affect circadian rhythms, pupil constriction, etc. instead of heading to the visual cortex.
What part of the visual field is represented in the posterior tip of the occipital cortex? Significance?
The macula/fovea. Lesions to the occipital cortex that spare the most posterior aspect of the occipital lobe may spare the very center of the visual field (where the fovea is).
What will an infarct affecting the inferior branch of the retinal artery of the left eye cause?
Left superior altitudinal defect. (left eye will lose upper field)
What will a tumor compressing the optic nerve cause?
Complete lack of vision in the affected eye.
What will a lesion to the optic chiasm cause?
What is the most common cause of lesions to the optic chiasm?
If a patient can't see the entire left visual field, where is the lesion? What's this called?
In the right optic tract / optic radiations. Left homonymous hemianopia (complete)
If someone has a right temporal lobectomy for epilepsy, what might result? Why?
Loss of right Meyer's loop -> left homonymous upper quadrantanopsia (both eyes, "pie in the sky")
A left PCA embolism knocks out most of the left occipital cortex, but the posterior-most aspect is intact. What vision loss will the patient have?
Right homonymous hemianopia with macular sparing.
A bullet enters posteriorly into the right occiptal lobe. What vision deficit might you expect?
Left homonymous hemianopia (without macular sparing)
A post-op CABG patient gets bilateral PCA infarcts that knock out both occipital cortices. Vision deficit? What would happen if you shine a light in the patient's eyes?
Cortical blindness - complete vision loss. Pupils will still constrict in light, as that reflex does not use the occipital cortex.
Review: What is the "dorsal path" of visual information for?
Determining "where" an object is
What is the dorsal pathway from ganglion cell in the retina to cortex?
M cells -> Magnocellular layes of LGN (layers 1 & 2) -> V1 -> V5 -> Parietal lobe
Review: What is the ventral path of visual information for?
Identifying "what" an object is
What is the ventral pathway from ganglion cell in the retina to the cortex?
P cells -> Parvocellular layers (3-6) of LGN -> V1 -> V4 complex -> Inferior Temporal Lobe
What's alexia without agraphia? Where does it localize? Why does this localization make sense?
Unable to read, but able to write. (usually accompanied by right homonymous hemianopia). Lesion to left occipital lobe AND the left splenium of the corpus callosum. Visual information from the intact right visual cortex can't get to language centers in the left side of the brain.
List 3 syndromes that lesions to the ventral pathway can cause.
Alexia without agraphia.
Visual agnosias (can't ID objects) and Prosopagnosia (can't recognize faces)
Cerebral hemi-achromatopsia (loss of color)
List 3 syndrome that lesions to the dorsal pathway can cause.
Balint's syndrome / simulatagnosia (can't see big picture)
Akinetopsia (can't detect motion)
What's the most important facial recognition area? Where is it?
The Fusiform Face Area (FFA) -located... if you look on the underside of the brain, in the middle of the second most medial gyrus of the temporal lobe...
Where does hemi-achromatopsia localize? What is it often associated with?
V4c on the fusiform and lingual gyri in the inferior occipital lobe. Often associated with upper quandrantanopsia of same side.
What's Balint's syndrome? Where does it localize?
Aka. simultanagnosia -can't see the big picture, but can describe individual elements in a scene. Bilateral parieto-occipital lesion.