Anatomy- Raised intracranial pressure

Question 1

what can cause raised intracranial pressure

Answer 1

head injury, lesion/tumour/abscess/haemorrhage,

hydrocephalus (blockage in CSF circulation)

Question 2

what eye sign can you get in hydrocephalus

Answer 2

sunset sign (sclera showing above iris)

Question 3

what are the meninges

Answer 3

layers surrounding the brain

Question 4

what are the layers of the menignes

Answer 4

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)

Question 5

where is CSF

Answer 5

in space between arachnoid and pia (dura venous sinuses) = subarachnoid space

Question 6

what goes through the tentorial notch

Answer 6

(is a gap in dura mater)

brain stem and cranial nerves- at risk if ICP increases - esp hypothalamus which controls respiration

Question 7

describe the two layer of dura mater

Answer 7

periostial lines the insides of the bone

meningeal, comes away from the periosteal layer to creat the dural venous sinuses

Question 8

what is in the dura venous sinuses

Answer 8

CSF- they drain the brain of venous blood and CSF

Question 9

what is the role of the CSF in the subarachnoid space

Answer 9

act as cushion for brain

Question 10

what makes up the ventricle system

Answer 10

two lateral ventricles
thrid ventricle between thalami
cerebral aqueduct
fourth ventricle between pons/medulla and cerebellum

Question 11

what are the ventricles of the brain for

Answer 11

spaces filled with CSF

Question 12

describe the path of CSF

Answer 12

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

Question 13

which ventricles make CSF

Answer 13

all four

Question 14

where other than brain is there subarachnoid space

Answer 14

spinal chord

Question 15

what should CSF look like

Answer 15

gin clear, more viscous than water

Question 16

what brain vessels are at risk of causing a sub dural haemorrhage in head injury

Answer 16

superior cerebral vein

Question 17

what vision problems can result from raised intracranial pressure

Answer 17

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

Question 18

why are the optic nerves thought to be extensions of the brain

Answer 18

as they are covered by meninges

Question 19

where is the subarachnoid space

Answer 19

between the arachnoid and pia meninges

Question 20

where in orbit does the subarachnoid space extend to

Answer 20

the back of the eyeball- why eye is affected by raised ICP

Question 21

how does raised ICP affect the eye

Answer 21

compresses the optic nerve
compresses central artery and vein of the retina
can cause bulging/swollen optic discs (papilloedema)

Question 22

what can damage the oculmotor nerve

Answer 22

compression, tentorial herniation (raised ICP- brain bulges throufh tentorial notch)

Question 23

what happens if there is paralysis of the somatic motor innervation of CN III

Answer 23

paralysis of extraocular muscles (eye will look down and out, ptosis)

Question 24

what happens if there is paralysis of the parasympathetic innervation of CN III

Answer 24

paralysis of constrictor pupillae- fixed dilated pupil, slow pupillary light reflex

Question 25

what innervation constricts the eye

Answer 25

parasympathetic innervation carried by CN III to constrictor pupillae

Question 26

what can damage the cranial nerve

Answer 26

streching and compression- is a very thin nerve with a long intracranial course

Question 27

what muscle will be affected if the trochlear nerve is paralysed - what will be the result

Answer 27

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

Question 28

what can damage the abducent nerve

Answer 28

stretching- has a long intracranial nourse

Question 29

what muscle will be affected by paralysis of the abducent nerve - what is the result

Answer 29

lateral rectus muscle

eye cannot move laterally in horizontal plane- medial deviation of the eye

Question 30

what causes fixed pupil dilation

Answer 30

unopposed action of the dilator pupillae (sympathetic supply)

fixed pupil dilation is a very bad sign