Session 4 - Group Work Flashcards
1) You see a patient with albinism who complains that he is unable to see well in bright sunlight.
a) Why is this?
Melanin in the pigmented epithelial layer is reduced so there is extra reflection of light, this makes images appear very bright. Melanin is what absorbs light.
1) You see a patient with albinism who complains that he is unable to see well in bright sunlight.
b) Give some additional common causes of perception of excessive glare
Cataracts Near-sightedness Far-sightedness Presbyopia Age-related degeneration of lens Astigmatism Glasses
2) A patient is under investigation for a scotoma. They have an optical coherence tomogram (OCT) which is normal.
Label the major retinal layers visible in the OCT image above. Which part of the retina was the image obtained from? Is the orientation the same as in textbook diagrams?
See lecture
- Vitreous
- Fovea
- Nerve fibre layer
- Retinal pigment epithelium
- Choroid
Near the fovea, the macula densa
Orientation is the same
3) Following a stroke affecting her left hemisphere, a patient is finding that she keeps bumping into the wall, usually on her right side.
A visual field defect is suspected.
a) Name the (probable) defect and draw a diagram of the visual pathway, highlighting where the lesion is.
Field defect is right sided temporal visual field
Homonymous hemianopia - lateral geniculate nucleus or optic nerve lesion
See Slide 7, image D
4) A patient has a pituitary adenoma compressing the optic chiasm.
a) Name the (probable) visual field defect that may result and draw a diagram of the visual pathway to illustrate how this may have arisen.
Bitemporal hemianopia
See Slide 7, image C
5) A patient suffers from homonymous hemianopia caused by a stroke.
a) How might we determine whether the lesion is in the optic tract or the visual cortex?
Macular sparing comes with a problem with our cortex, e.g. stroke, so most likely going to be vascular, most likely going to be macular sparing because there is a bit of a collateral supply, from posterior and middle arteries etc.
Visual cortex - macular sparing
Optic tract - no macular sparing e.g. end artery
5) A patient suffers from homonymous hemianopia caused by a stroke.
b) Does this hold for non-vascular lesions of the visual cortex (e.g. tumours)?
It’s not macular sparing because the collateral supply is insignificant because it is non-vascular, so it just takes all of it.
6) An 8 year old boy is admitted with fever, neck stiffness and photophobia. The boy has recently been receiving chemotherapy for leukaemia. Treatment is commenced immediately, but it is noted early on that sensation in the right half of his face is altered and that he has a right homonymous inferior quadrantanopia.
a) Give three differential diagnoses
Meningitis
Abscess
Subarachnoid haemorrhage - by minor trauma, berry aneurysms etc.
PHOTOPHOBIA = THINK MENINGISM
6) An 8 year old boy is admitted with fever, neck stiffness and photophobia. The boy has recently been receiving chemotherapy for leukaemia. Treatment is commenced immediately, but it is noted early on that sensation in the right half of his face is altered and that he has a right homonymous inferior quadrantanopia.
b) Given that the boy has focal neurology, what is the most likely site of the lesion?
Left upper parietal lobe lesion (superior radiation goes through the parietal lobe)
7) A patient with multiple sclerosis presents to their general practitioner with new onset diplopia. The GP suspects that the patient has developed a new plaque in the brainstem that has interfered with conjugate eye movements.
a) In which pathway has this plaque probably formed?
Medial longitudinal fasciculus
7) A patient with multiple sclerosis presents to their general practitioner with new onset diplopia. The GP suspects that the patient has developed a new plaque in the brainstem that has interfered with conjugate eye movements.
b) Give some examples of how this pathway controls conjugate eye movements. Diagrams will help.
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