Flashcards in Cardiovascular disease & its effect on vision Deck (92):
1
what is a transient ischaemic attack known as
a temporary disruption go blood supply (that results on no long term damage)
2
what can a transient ischaemic attack be the result from
an embolism (such as a circulating fragment of an atheromatous plaque) temporarily blocking a vessel, the function of the area supplied by the vessels in impaired
3
what happens when the embolism moves on in a transient ischaemic attack
function returns
4
name an example of a specific TSA associated with the eyes
amaurosis fugax (fleeting darkness/blindness)
5
what is amaurosis fugax
a painless unilateral loss of vision resulting from a transient retinal ischaemia caused by an embolism in the retinal vasculature
6
what is the loss in vision described as by a patient, of amaurosis fugax
vision goes dark, like a curtain descending or ascending on the eye for a short period of time, which then vision goes back to normal
7
what do the inner 5 layers of the retina receive oxygenated blood from
central retinal artery
8
what is the central retinal artery a branch off
ophthalmic artery
9
what does the ophthalmic artery arise from
carotid artery (a branch off the aorta)
10
what happens in the ophthalmic artery as a result of amaurosis fugax
a dislodge is stuck in the ophthalmic artery, patient goes blind as the retina becomes ischaemic & stops functioning, then the blood clot breaks up and resolves itself whereby patient can see again
11
what may form a transient occlusion of a retinal vessel
an atheromatous plaque in the carotid artery which may disintegrate
12
what may emboli of an atheromatous plaque in the carotid artery which may form a transient occlusion of a retinal vessel be made of
various materials such as:
cholesterol crystals
platelet aggregates
lipid
13
instead of an emboli (which is most common), what else can be the cause of transient ischaemic event
vasopastic events such as:
unusual narrowing of vessels (artery contracts itself)
or
haematological causes such as:
abnormalities in blood constituents e.g. sickle cell anaemia
14
why is the CNS particularly susceptible to infarction
it needs a continuous supply of oxygen & CNS tissue does not regenerate
15
what are cerebrovascular accidents CVAs most commonly know as, and what causes it
stroke
blood supply to vessels which supply the brain become blocked so it becomes non functional (infarct)
16
what are the two sources which supply the brain with oxygenated (arterial) blood
- 2 internal carotid arteries
- 2 vertebral arteries
17
which part of the brain do the 2 internal carotid arteries supply
anterior
18
which areas do the 2 vertebral arteries supply
poster brain & spinal chord
19
what do the 2 vertebral arteries merge to form
basilar artery
20
what are the internal carotid & basilar arterial supplies united by
anterior & posterior communicating arteries at the circle of willis (found at the base of the brain)
21
why does the brain have two blood supplies
if one blood supply is impaired, the other can supply the brain
22
which three arteries arise fro the circle of willis
anterior cerebral artery
middle cerebral artery
posterior cerebral artery
23
what area of the brain does the anterior cerebral artery supply
front
24
what area of the brain does the middle cerebral artery supply
middle
25
what part of the brain does the posterior cerebral artery supply
back
26
what are the two types of stroke
- hemorrhagic
- occlusive (ischaemic)
27
what is a hemorrhagic stroke caused by
a ruptured aneurysm or an AVM
(blood comes/leaks out & that area of the brain does not receive oxygen from the vessel & that part of the brain stays dead forever)
28
what % does a hemorrhagic stroke account for from all strokes
20%
29
what is an occlusive (ischaemic) stroke caused by
a thrombosis (blood clot) on an atheromatous plaque
30
how many % of strokes does an occlusive ischaemic stroke account for
80%
31
which type of stroke will be helped by medication
occlusive (ischaemic)
32
how does medication treat an occlusive (ischaemic) stroke
by unblocking the vessel
33
why is medication not suitable for hemorrhagic strokes
medication can make it worse (if for stopping clotting)
34
what is a result of both hemorrhagic and occlusive (ischaemic) strokes
brain tissue at one part of the brain to die
35
how does a CVA effect vision
by effecting one of the 30 visual areas of the brain (different parts of brain deal with different aspects of vision)
36
what does the early part of the visual pathway consist of
projections from the retina, along the optic pathway, via the LGN to v1 (area 17 or striate cortex)
can have a stroke at any of these areas
37
which part of the brain is the striate cortex located
occipital lobe/back of the brain
38
what supplies the occipital lobe/back of brain
posterior cerebral artery
39
what can a blockage of the PCA e.g. from a thrombosis result in
death of cells in v1 and patient will become blind in that hemifield (bilateral hemianopia) BUT with macular sparing
40
what is the reason for macular sparing of a patient who has had a blockage of their PCA which resulted in the death of v1 cells
the posterior part of the occipital cortex, which subserves macular vision, also receives blood supply from the MCA (so lose most vision in that field due to blocked PCA, except macula)
41
what type of attribute do v1 cells do for an image
basic attributes
42
what does stroke to a particular area of extra striate cortex cause
a particular attribute of vision loss i.e. specific agnosias
43
what does a lesion to area v4 result in
achromatopsia (form vision normal etc)
(not due to loss of visual pigment, things actually look black & white)
44
what can a lesion to area v5 result in
disturbed motion detection - akinotopsia (won't see cars moving or pouring of tea will look like frozen glacier)
45
what can a lesion/damage to the temporal lobe by a stroke result in
inability to distinguish faces, even familiar ones - prosopagnosia
46
what can also impair visual function, apart from a hemorrhagic or occlusive stroke
an aneurysm
47
where do 80-90% of aneurysms occur
in the circle of willis
48
where do aneurysms most often form and why
where vessels branch, as they are the weakest here
49
what happens to the BV from an aneurysm
BV bulges out and presses on things
50
what can an aneurysm of the internal carotid artery compress
the lateral aspect of the chiasm
51
what does the lateral aspect of the chiasm house
uncrossed temporal fibres from the ipsilateral eye
52
what will a lesion to the uncrossed temporal fibres from the ipsilateral eye (from internal carotid aneurysm) result in
disruption of the temporal retina of the ipsilateral eye, causing nasal field loss (ipsilateral nasal hemianopia)
53
as well as an aneurysm compressing the visual pathway, what can it also affect which can affect vision
compressing a cranial nerve
54
what other type of aneurysm of the carotid is there, as oppose to one causing damage to the chiasm
damage to the wall of the cavernous sinus (where the carotid also lies near)
55
how many % do intracavernous carotid aneurysms account for of all intracranial aneurysms
2-3% rare
56
what are the unique set of symptoms of an intracavernous carotid aneurysm based on
arrangement of cranial nerves and symptoms are largely ocular
57
what does the carotid artery lie within
the walls of the cavernous sinus
58
what system is the cavernous sinus a part of
venous drainage system of the brain
59
which wall of the cavernous sinus does the internal carotid lie within
medial wall of cavernous sinus
60
of which arteries is the blood pressure highest
in the major arteries nearest the heart
61
why is venous pressure much lower than arterial
they are far from the pump of the heart and due to elasticity nature of veins
62
when can an aneurysm within the artery wall compress the sinus
as the pressure in the internal carotid artery exceeds that of the cavernous sinus
63
what will a compression of the cavernous effect
the cranial nerves that lire within the walls of the sinus, which will impact several ocular structures
64
what can damage to the oculomotor CN 3 cause
damage to fibres which go to:
- ciliary muscle - effects/impairs accommodation
- iris sphincter - impairs pupil constriction
- levator palpebrae - impaires eyelid to open/raise causing ptosis
- 4 EOMS - MR, SR, IR, IO - impaires eye movements
65
what can damage to the trochlear CN 4 cause
loss of innervation of superior oblique EOM
66
what can damage to the ophthalmic division of the trigeminal CN 5 cause
loss of sensation of anterior eye e.g. cornea
67
what can damage to the abducens CN 6 cause
loss of innervation of lateral rectus EOM
68
list the CNs which disrupt eye movements
- oculomotor 3rd
- trochlear 4th
- abducens 6th
69
why are pupil anomalies complex
as both parasympathetic fibres in the 3rd CN and sympathetic fibres from the SCG are associated with the cavernous sinus, so both may be affected, therefore the pupil may be sluggish and smaller than usual/not normal
70
what is a fistula
any connection between two structures which shouldn't be connected
71
what can there be a fistula of, as a direct result of ruptured aneurysms
cavernous venous sinus & carotid artery
72
what type of people are connections/fistula of the cavernous sinus and carotid artery in
middle ages females or caused by head trauma (75%)
73
what does the cavernous sinus do
takes deoxygenated blood from the eye
74
due to higher pressure in the arterial system, what will fistula od the cavernous sinus and carotid artery result in
the sudden onset of many of the symptoms associated with a carotid artery aneurysm such as ophthalmegia (paralysis of intra and extra ocular muscles)
75
as the cavernous sinus receives venous blood from the eye, what can happen in a case of an accident such as whiplash & which mainly occurs in women
ocular vessels become engorged i.e. blood goes in the opposite direction in the vein
76
what things can severe engorgement result in
- chemosis
or
- exophthalmus/pulsatile proptosis
77
what is chemosis (as a result of severe engorgement)
bulba conjunctiva full of blood, cornea is fine
78
what is exophthalmus/pulsatile proptosis, (as a result of severe engorgement)
as the heart pumps, the eye pushes out
79
what can an aneurysm of the posterior communicating artery in the circle of willis present
- a sudden onset of full 3 CN palsy - ptosis, abnormal eye position, dilated and fixed pupil
&
- a severe unilateral frontal headache
80
what is cranial arteritis
inflammation of the medium to large arteries coming off the aorta, (most notably those associated with the carotid system)
81
what actions should be taken is cranial arteritis is detected
ocular emergency, immediate referral
82
what part of the BV/artery gets inflamed in cranial arteritis
lots of inflammatory cells within the tunica interna of artery leading to its fragmentation & among these are giant multinucleate cells & one of those inflammatory cells is a huge macrophage
83
what leads to the occlusion of the vessels as a result of cranial arteritis
lots of inflammatory cells within the tunica interna of artery leading to its fragmentation & among these are giant multinucleate cells & one of those inflammatory cells is a huge macrophage, & the proliferation of cells within the tunica interna
84
what are the major symptoms of a cranial arteritis
headache & tenderness of the scalp
85
why is headaches & tenderness of the scalp symptoms of cranial arteritis
due to involvement of the superficial temporal arteries and pain of the jaw when eating
86
how can cranial arteritis also result in severe visual defects
as the ophthalmic artery (which arises from the internal carotid) is also affected & as this artery supplies to most of the eye, its disruption can result in a large number of ocular symptoms
87
which branch of the ophthalmic artery is particularly effected in cranial arteritis
posterior ciliary arteries (which form a circle around the ONH)
88
what do the posterior ciliary arteries supply
the circle of Zinn-Haller
89
what do the circle of Zinn-Haller supply
nutrients to the ONH
90
what does the disruption of the ciliary arteries cause
anterior ischaemic optic neuropathy (neuropathy of the anterior part of the optic nerve) can cause blindness in that eye
91
which other artery which supplies the retina can also be effected by cranial arteritis
central retinal artery
92