The Eye and Raised ICP Flashcards
what are meninges?
protective coverings of the brain and spinal cord
what are the three layers of the meninges?
dura mater
arachnoid mater
pia mater
what provides the sensory nerve supply to the dua mater?
CN V
what is enclosed in the dura mater?
the dural venous sinuses
what are the two layers the dura mater splits into around venous sinuses?
periosteal layer (outer) meningeal layer (inner)
what does the pia mater adhere to?
the brain and any vessels entering/leaving
what is found between the arachnoid mater and the pia mater?
the subarachnoid space
what is found in the subarachnoid space?
CSF
blood vessels
how can the subarachnoid space be accessed clinically and why would this be done?
lumbar puncture
to get a CSF sample
where is a lumbar puncture done?
L3/4 or L4/5 levels
when does the subarachnoid space end?
vertebral level S2
what are the four ventricles of the brain?
lateral x 2 (left and right)
third ventricle
fourth ventricle
what secretes CSF?
the choroid plexus in the lateral and third ventricles
what connects the third and fourth ventricles?
the cerebral aqueduct
how is CSF reabsorbed and where?
via arachnoid granulations
into the dural venous sinuses
what is raised ICP?
increased pressure in the cranial cavity
what causes raised ICP?
increased pressure either in the CSF or within the brain itself
why is raised ICP a serious emergency?
can damage the brain and spinal cord by compressing them
what is a common symptom experienced by patients with raised ICP?
visual problems
what is CN II?
the optic nerve
what covers CN II?
meninges
what does the optic nerve being surrounded by meninges mean?
increased ICP will be transmitted around the optic nerve = results in papilloedema
what is papilloedema?
swollen optic discs
what are dural septae?
folds of dural matter that create septae in the cranial cavity
what are the four dural septae?
falx cerebri
tentorium cerebelli
falx cerebelli
diaphragma sellae
what is the largest dural septa?
falx cerebri
what does falx cerebri divide?
the two cerebral hemispheres
what does the tentorium cerebelli divide?
the cranial cavity into supratentorial and infratentorial areas
what does the falx cerebelli divide?
the cerebellum into the right and left halves
what does the diaphragma sellae cover?
the roof of the pituitary fossa
what is CN III?
the oculo motor nerve
how can raised ICP compress CN III?
if the medial temporal lobe herniates through the tentorial notch
what is the tentorial notch?
the free edge of the tentorium cerebelli where the brainstem exits
how does CN III compression present?
absent pupillary light reflex
dilated pupil
ptosis
eye turned inferolaterally (out and down)
what is CN IV?
the trochlear nerve
what does damage to CN IV cause?
paralysis of the superior oblique muscle
