The eye and raised ICP

Question 1

what is the meninges

Answer 1

a protective covering for the brain and spinal cord within the bone

Question 2

what 4 layers makes up the meninges (outside in)

Answer 2

dura mater, arachnoid mater, subarachnoid space and pia mater

Question 3

what does the meninges exit the cranial floor via

Answer 3

foramen magnum

Question 4

describe the dura mater

Answer 4

hard matter with sensory supply from CNV, encloses dural venous sinus (contains deoxygenated blood from brain)

Question 5

describe the arachnoid mater

Answer 5

spidery mater with arachnoid granulations

Question 6

describe the subarachnoid space

Answer 6

in-between the arachnoid and the pia mater - contains CSF and blood vessels

Question 7

describe the pia mater

Answer 7

adheres to and follows contours of the brain

Question 8

at what spinal level does the subarachnoid space close

Answer 8

S2

Question 9

what is the function of CSF

Answer 9

completely surrounds the brain and spinal cord for cushioning and protection - provides nutrients and removes waste

Question 10

at what level would you do a lumbar puncture for a CSF sample

Answer 10

L3/4 or L4/5

Question 11

what secretes CSF

Answer 11

the choroid plexus in the lateral and 3rd (midline) ventricles of the brain

Question 12

after the CSF has been secretes by the lateral and 3rd ventricles, by which structure does it then travel to the 4th. ventricle

Answer 12

cerebral aqueduct

Question 13

after the CSF has travelled to the 4th ventricle what happens to it

Answer 13

most of it enters the subarachnoid space and some enters the central canal to provide cushioning

Question 14

where is the CSF reabsorbed to and via what mechanism

Answer 14

reabsorbed to the dural sinuses where it mixes with deoxygenated blood and enters via the arachnoid granulations

Question 15

what is raised intracranial pressure and what causes it

Answer 15

raised pressure within the cranial cavity caused by: tumour, trauma, hydrocephalus, meningitis

Question 16

why can’t the cranial cavity cope well with changing pressure

Answer 16

inter-cranial volume is constant: brain, blood, CSF etc and it is an enclosed space so increased pressure can cause damage, herniation and constriction of vessels and brain

Question 17

what are some symptoms of raised ICP

Answer 17

transient blurred vision, double vision, loss of vision, papilledema, pupil changes, headache

Question 18

how does raised ICP affect the optic nerve and retinal vessels

Answer 18

CNII is surrounded by meninges and increased pressure of CSF compresses the optic nerve and central artery/ vein of retina

Question 19

how does raised ICP affect the oculomotor nerve

Answer 19

compression and tentorial herniation of other tissue

Question 20

what is tentorial herniation

Answer 20

folds in the brain which can herniate through

Question 21

what other cranial nerves can be damaged by raised ICP and what symptoms would they display

Answer 21

trochlear (SO dysfunction), abducens (LR dysfunction), oculomotor (down and out eye)