Anatomy- Raised intracranial pressure Flashcards
what can cause raised intracranial pressure
head injury, lesion/tumour/abscess/haemorrhage,
hydrocephalus (blockage in CSF circulation)
what eye sign can you get in hydrocephalus
sunset sign (sclera showing above iris)
what are the meninges
layers surrounding the brain
what are the layers of the menignes
dura mater (outermost, fibrou- tough mother)- has a periostial layer and meningeal layer
arachnoid mater (spiderly, thin layer with CSF deep to it)
pia mater- (soft mother, single cell layer that covers brain, goes into sulci)
where is CSF
in space between arachnoid and pia (dura venous sinuses) = subarachnoid space
what goes through the tentorial notch
(is a gap in dura mater)
brain stem and cranial nerves- at risk if ICP increases - esp hypothalamus which controls respiration
describe the two layer of dura mater
periostial lines the insides of the bone
meningeal, comes away from the periosteal layer to creat the dural venous sinuses
what is in the dura venous sinuses
CSF- they drain the brain of venous blood and CSF
what is the role of the CSF in the subarachnoid space
act as cushion for brain
what makes up the ventricle system
two lateral ventricles
thrid ventricle between thalami
cerebral aqueduct
fourth ventricle between pons/medulla and cerebellum
what are the ventricles of the brain for
spaces filled with CSF
describe the path of CSF
choroid plexus lateral ventricles interventricular foramen third ventricle cerebral aqueduct fourth ventricle either: fourth ventricle to two lateral aperatures to subarachnoid space or fourth ventricle to median aperture to subarachnoid space or fourth ventricle to central canal of spinal chord
from subarachnoid space to arachoind villi (granulations) to superior sagital sinus
re-absorbed into venous system
which ventricles make CSF
all four
where other than brain is there subarachnoid space
spinal chord
what should CSF look like
gin clear, more viscous than water
what brain vessels are at risk of causing a sub dural haemorrhage in head injury
superior cerebral vein
what vision problems can result from raised intracranial pressure
transient blurred vision diplopia (douple vision) loss of vision papilloedema (swelling of optic disc due to increased ICP) pupillary changes transient flickering constriction of the visual field decreased colour perception
why are the optic nerves thought to be extensions of the brain
as they are covered by meninges
where is the subarachnoid space
between the arachnoid and pia meninges
where in orbit does the subarachnoid space extend to
the back of the eyeball- why eye is affected by raised ICP
how does raised ICP affect the eye
compresses the optic nerve
compresses central artery and vein of the retina
can cause bulging/swollen optic discs (papilloedema)
what can damage the oculmotor nerve
compression, tentorial herniation (raised ICP- brain bulges throufh tentorial notch)
what happens if there is paralysis of the somatic motor innervation of CN III
paralysis of extraocular muscles (eye will look down and out, ptosis)
what happens if there is paralysis of the parasympathetic innervation of CN III
paralysis of constrictor pupillae- fixed dilated pupil, slow pupillary light reflex
what innervation constricts the eye
parasympathetic innervation carried by CN III to constrictor pupillae
what can damage the cranial nerve
streching and compression- is a very thin nerve with a long intracranial course
what muscle will be affected if the trochlear nerve is paralysed - what will be the result
superior oblique
inferior oblique will not be opposed= eye cannot move inferomedially (when looking right affect eye will look right an up), diplopia when looking down
what can damage the abducent nerve
stretching- has a long intracranial nourse
what muscle will be affected by paralysis of the abducent nerve - what is the result
lateral rectus muscle
eye cannot move laterally in horizontal plane- medial deviation of the eye
what causes fixed pupil dilation
unopposed action of the dilator pupillae (sympathetic supply)
fixed pupil dilation is a very bad sign
