6.1.14 Assesses signs and symptoms of neurological significance. Flashcards
What are signs of ONH dysfunction?
- reduced VA in both near and distnace
severe impaired CV - RAPD
- VF defect
- impaired CS
what should a good neuro history have?
- normal h+s
- cheif complaint - degree, sveerity and duration
v3. visual loss - bino/mono / dist /near - dip / mono / binocular
- medical hist (meds, diseases, surgery)
what are the diffrences between macula / onh dysfunction?
ON = rapd macula = no cv = severe
onh = reduced brightness macula = augmented cv = mild for macula
what is optic neuritis?
inflmmation / demyelination of the ON - MS, TB , viral
why do you get rapid vision loss in optic neuritis?
Rapid vision loss : demylination / damage to the erve fibre layers = slowed transmission = loss of vision.
inflamm response : acute inflammatory response to the optic nerve –> signal distruptions
why do people with ms get optic neuritis?
Autoimmune attack –> immune attacks the CNS
why do you get ocular / retrobulbar pain with optic neuritis?
the optic nerve does not have any pain receptors but the shealth / tissues around it does
when inflammed these become more sensitive = pain when moving eyes
when the tissues in the orbit are inflammed = pain behind the eye
PAIN with eye movmeents
why does heat/ exercise increase visual loss in optic neuritis?
heat will temporarly breakdown the nerve signal transmission = conduction block = in a inflammed nerve the symptoms are more pronounce
why do you get RAPD in optic neuritis?
RAPD = asymmetry in the pupillary light reflex between the two eyes
optic neuritis = inflammation / demylination of the optic nerve = impaired tramission of visual signals to the brain
what will happen during RAPD?
when light is shone into the healthy eye, both will constrict as the afferent (incoming) pathway intact and normal efferent (outgoing) pathway.
when light is shone into the effected eye the response in both pupils is weaker+ slower as this optic nerve dose not transmit effectievly
D + C in optic neuritis?
SLOW for direct + consensual when shone into the effected eye
Swinging light test for optic neuritis?
when swinging to the effected eye , both eyes will appear dilated slightly –> reduction in the afferent signal from the affected eye
why do you get central scotoma with optic neurtis?
distruption of the signals from the central retinal region
why do you get severely imparied colour vision with ON?
The optic nerve has fibres which are sensitive to colour contrast .
cones are responsible for colour vision = high threshold response. == very sensitive to distruptions in signal tranmission –> inflmmation - impaired
why do you get blurry margins?
margins blurred as they are inlfmmated / swollen
why do you get swollen veins?
inflmmation around the disc = congestion = swelling of the viens = impedes the ormal venous outflow
what to do with ON?
emergency / urgent / steroids
What is Anterior ischaemic optic neuropathy? ANION
occlusion of the PCA - common in elderly people
ANION : assiocated with giant cell arteritis . Arteritic
NANION : atherosclerosis non- artertic
Why do you get HA with ANION?
Temporal arteries –> they become tender and inflamed. there are inflammed = manifest into a headache
ischemia –> inflmmation leads to narrow arteries -> reducd blood flow to the sclap and temples –> tissues become ischemic and = pain
what are systemic signs og GCA?
- jaw pain when chewing
- scalp/ temple tender
Why do you get sudden / profound / permanent vision loss with Anterior ichemic optic neuropathy?
compromised blood flow to the optic nerve head - ischemia –> posterior ciliary arteries
Optic nerve head is sensitve to reduciton in blood flow because it is highly metabolic. _ ischmia = immedican vision loss
ischemia - infarction - damage to pathways from onh to hte brain
why permeant damage?
when axons are damaged due to the ischemia they have limted ability to regenerate
why do you get an altitudianl defect -lower? with ANION + nANION
Specific pattern of the posterior ciliary arteries -> they divide into smaller branches –> the lower side is more vunerable then the upper / gravity
these defects are sudden –> acute
why does the fundus become pale in ANION / NANION?
more temporal ; more vascular on this side .. pale = ischemia
what is NAAION?
this is asscoiated with artiosclerosis
how does artioscleriosis cause anion?
blood flow impairment -> does not meet the nerves metabolic needs.
risks are poor systemic health like HBP, diabetes , hyperlipidema and smoking.
mechanism of artioscleriosis?
build up of plaques !
makes the ONH vunerable..
sudden pailess, vision loss VF defect lower altitudanl
why is colour vision effected?
the optic nerve head has loads of diffrent fibres in. the colur vision fibre bundles appear to be vunerable to damage.
What is papilloedma?
Swollen optic disc due to raised intracranial pressure - EMERGENCY
why do you get headaches with papilloedma?
increased pressure stimulates the pain receptors in the membranes covering the brain and the spinal cord
Worse in the morning as a build of CSFluid at night when the body is horizontal + worse when bending over as this increases the pressure more
Why you feel nausea with pap?
Increased Intracranial pressure = stimulate the VAGUS nerve = in charge of the digestive system –> sickness
Pressure in the medulla - vomiting reflex
Normal / sudden blankning of vision in pap?
swollen –> but it can still funcition
Transient visual disturbances -> intermitten compression of the axons in the optic nerve head -> distrupts the slow of signals
why do we get elevation to the ONH with ICP?
increased ICP = distrupted axoplasmic flow = swelling
Why are the margins blurred?
fluid + swelling
Why is the cup filled up?
the depressed cup fills up with fluid
why does the retina and the choroid fold with pap?
due to the head swelling it causes mechanical compression + folding
why do we get hyperamie at the disc with pap?
increased dilation of the vessels
Why do we lose SVP with pap?
The ICP impede the the normal venous
Why do we get heams at the disc?
increased pressure = stress on the small capillaries = ruptre
Why do we get hard exudates with pap
increased icp = increased venous pressure = distruptes the blood-retinal barrier = leakage of lips+ proteins
Why do we get cotton wool spots with pap?
ischemic areas due to the elevated ICP
why do you get diplopia with pap?
It can initiate a 6th nerve palsy - affecting the abducens nerve which conteols the lateral rectus (moving the eye outwards)
ICP = strechs / compresses the abduceens nerve –> vunerable as it has a long path
because the eye cannot move outwards the affected eye may turn inwards (medically) casuign horizontal diplopia–> eyepatch prism
why do you get halos with pap?
cornea + viterious humour changes //
retinal distortions –> the layers chnage alignment and this chnages the normal refractive index = light rays spread / diffract = halos around light sources
what is stage one papilloedma?
- blurry OD margins
- Hyperaemia
- Los of SVP
C shaped oedmea surround the disc
grade 2 pap?
all of grade 1 + halo arround the OD
Grade 3 pap
oedma coveres the BV as they leave the disc
Grade 4
Covers the bv on the disc too
What is chiasmial syndrome?
this is is mainly due to pit tumours
what are visual feilds like with chiasmal syndromes?
they all respect the midline - pit = bitemporal hemianopia
what does the parasympathetic innervation look like with pupillary reflexes?
- photoreceptor to the optic nerve
- optic nerve to the pretectal nucleus
- pretectal nucleus to the edinger-westphal nuclus
- edinger-westphal nuclsu to the pupil
