Dental Neuroanatomy
Visual System cases
April 8, 2010
Suzanne S. Stensaas
Visual System Cases to reinforce the Anatomy in a clinical context
FACULTY VERSION - KEY
Case 1
A patient’s visual fields were plotted on a tangent screen and appear below. The hatched area represents the visual field deficit.
Right homonymous hemianopia with macular sparing
(Circle the correct answer)
T-F The lesion is prechiasmal.
T-F The lesion could involve the thalamus.
T-F The lesion could involve a clot in the left posterior cerebral artery.
T-F The lesion could be related to right temporal lobe tumor.
T-F The lesion involves only cortex below the left calcarine fissure.
Case 2
A thirty-seven-year-old was in a car accident in which he sustained a left parietal compressed skull fracture and was unconscious. Many bone spicules were removed from his cortex. Moderate aphasia was present after recovery. He complains of poor vision. On testing he had 20/20 vision in both eyes.
Right homonymous inferior quadrantanopia sparing part of upper right quadrant and macular sparing
1. Where in the visual pathway is the lesion? Left parietal portion of the optic radiation
2. How do you explain that he still had 20/20 vision?
Visual acuity is based on the integrity of the macula and the macula is not affected. Macular sparing may be due to bilateral representation of the macula in the cortex or collateral blood supply, or both.
3. Why is he aphasic?
Left parietal lobe-temporal area involbved
Case 3
A thirty-year-old white female complained of headaches. Her neurologic exam was normal. Headaches persisted as well as amenorrhea. Careful tangent screen visual fields were plotted and shown below.
1. What do you call this lesion? Bitemporal partial superior quadrantanopia
2. To get this field defect, what axons are compromised? Chiasm
3. You call the radiology department and order a lateral skull film. What are you going to be looking at carefully? Enlargement or erosion of the sella turcica
4. What is the most probable site of the patient’s underlying pathology? Tumor, anterior lobe of the pituitary.
5. Will the pupillary light reflex be present?
YES
Case 4
A 23-year-old woman with marked loss of vision in the right eye only. Pain was noted in the right eye during eye movements. A similar episode occurred three years previously and again a year ago. Vision improved to 20/30. All the visual fields are from the right eye over the three-year period. OD = oculus dextra; OS oculus sinestra
Three stages in the right eye,
3 years ago 12 months ago this visit
1. What is the anatomical location? Right optic nerve.
2. If retinal ganglion cells can not regenerate, how do you explain that the vision improved?
The disease could be due to inflammation that subsided or demyelination with remyelination, or both.
3. This history is typical for what disease? Multiple Sclerosis
Case 5
A 25-year-old man accidentally drove his car over a cliff in Little Cottonwood Canyon. In the ambulance en route to UUMC, he had a generalized seizure. Upon regaining consciousness, he complained of severe headache and difficulty with his vision.
After admission to the Neurocritical Care Unit (NCC), he was found to have normal pupils and normal extraocular movements. Twenty minutes later, he cried out in pain from his headache, was found to have a right-sided ptosis and an enlarged right pupil. He rapidly became paralyzed on the left. Subsequently he became comatose with decerebrate posturing, his respiration and heart rate slowed, and he died.
1. Where and what is the uncus?
The most medial portion of the anterior parahippocampal gyrus of the temporal lobe
2. Pressure on the temporal lobe can push the uncus over the edge of the ______
Tentorium (compressing the CN III, cerebral peduncle, reticular activating system, PCA, aqueduct)
3. For this to occur, the pressure or mass must be (choose one) supratentorial or
infratentorial? Explain.
Supratentorial, to cause downward herniation of the uncus
4. What is the explanation for
a. the pupillary dilation?
Compression of CN III. The pupilloconstrictor fibers are superficial and thinly
myelinated. They are the first to be compressed, before the larger axons that innervate theextraocular muscles.
b. For the ptosis?
Compression of CN III. While not autonomic, the fibers in CN III for lid elevation seem to be more vulnerable than those to the other extraocular muscles.
[Complete oculomotor paresis would also exhibit ophthalmoplegia with the eye turned down and out in neutral gaze.]
c. for the hemiplegia?
Cerebral peduncle. The lesion is above the decussation so hemiplegia is on contralateral side.
d. for the coma?
Involvement of reticular activating system.
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visual cases Dental Fac 2010.doc