Nerve palsies and visual fields Flashcards
what muscle is affected in a 6th nerve (abducent) palsy
lateral rectus
symptoms of a 6th nerve palsy
cannot abduct the eye
horizontal diplopia
causes of 6th nerve palsy
microvascular
^ ICP (impinges nerve of petrous tip)
tumour
congenital
signs of 6th nerve palsy
swollen optic disc from ^ICP
headaches
unable to abduct eye
What muscle is affected in a 4th nerve (trochlear) palsy
superior oblique
symptoms of a 4th nerve palsy
vertical diplopia
cannot intort or depress
eye seems to be looking up
causes of a 4th nerve palsy
congenital
microvascular
tumour
trochlear nerve is the longest CN and the only one to come out of the posterior brainstem, true or false
true
signs of a 4th nerve palsy
eye seems to be looking up because unopposed from other muscles
compensate with a head tilt
what muscles are affected in a 3rd nerve (oculomotor) palsy
superior rectus inferior rectus medial rectus inferior oblique levator palpebrae superioris sphincter pupillae muscle
causes of a 3rd nerve palsy
microvascular tumour aneurysm demyelination congenital
symptoms and signs of a 3rd nerve palsy
down and out eye position from unopposed SO muscle
ptosis from LPS
dilated pupil from sphincter pupillae muscle
absent accommodation reflex
what is a cause of a painful 3rd nerve palsy
aneurysm
main cause of a 3rd nerve palsy
aneurysm
main cause of a 4th nerve palsy
congenital
trauma
main cause of a 6th nerve palsy
^ ICP
what is inter nuclear opthalmoplegia (INO)
sign seen as a result of a problem in the medial longitudinal fasciculus (MLF) which connects the CN3 nucleus in the midbrain and CN6 nucleus in pons
- ipsilateral adduction impaired
- contralateral abduction shows horizontal nystagmus
Causes of INO
MS
stroke
vascular
causes of damage to optic nerve resulting in nasal and temporal loss of visual field
ischaemic optic neuropathy
optic neuritis
a defect in which location would result in a bitemporal hemianopia
optic chiasm
causes of bitemporal hemianopia
pituitary adenoma
craniopharyngeoma
a defect in which location would result in a homonoymous hemianopia
optic tract
causes of homonymous hemianopia
stroke
demyelination
tumour
is there macular sparing in damage to the optic tract
no
temporal optic radiations carry signals from the inferior/superior retina corresponding to superior/inferior visual fields
temporal radiations:
inferior retina
superior visual field
parietal optic radiations carry signals from the inferior/superior retina corresponding to superior/inferior visual fields
parietal radiations:
superior retina
inferior visual field
a defect in which location would result in a superior quadrantoptropia
temporal branches of the optic radiations
inferior retina –> superior visual field
a defect in which location would result in an inferior quadrantoptropia
parietal branches of the optic radiations
superior retina –> inferior visual field
a defect in which location would result in homonymous hemianopia WITH macular sparing
occipital visual cortex
