the eye and raised ICP Flashcards
what are the features of the meninges?
a protective cover of brain and spinal cord
sensory supply from CN V
it encloses the dural venous sinuses
what are the features of the arachnoid mater?
has arachnoid granulations
what is the function of the pia mater of the meninges?
adheres to brain
what are the features of the sub arachnoid space?
Between arachnoid mater and pia mater
Contains circulating cerebrospinal fluid (CSF)
- produced inside the brain
- completely surrounds both brain & spinal cord
Can be accessed via lumbar puncture at L3/4 or L4/5 IV disc levels to obtain a sample of CSF
ends inferiorly at vertebral level S2
Communicates in specific locations with another series of CSFfilled spaces located within the brain (& spinal cord): the
ventricles
how does CSF circulate?
- secreted by the choroid plexus (located in the lateral and third ventricle)
- then secreted from the right and left lateral and the third ventricle
- then via the cerebral aqueduct to the 4th ventricle then mainly into the sub arachnoid space
- it is then reabsorbed via the arachnoid granulations and then into the dural venous sinuses
what is Raised ICP?
Increase in pressure within the cranial cavity
Chronic or acute
Caused by an increased pressure in fluid surrounding the brain or an increase in pressure within the brain itself
Serious medical problem
Can cause damage to the brain and the spinal cord
does raised ICP cause visual problems?
yes (60-75% of patients report this)
is ICP meant to change at any point?
no
what is the monro-kellie hypothesis?
The sum of volumes of brain, cerebrospinal fluid (CSF) and intracerebral blood is constant. An increase in one should cause a reciprocal decrease in either one or both of the remaining two.
what covers optic nerves?
meninges
what does the fact that optic nerves are covered by meninges mean?
raised ICP will be transmitted along the subarachnoid space in the optic nerve sheath
can cause papilloedema
what are the visual symptoms of raised ICP?
transient visual obscurations (graying-out of vision),
transient flickering
blurring of vision
constriction of the visual field
decreased colour perception
what is the significance of folds in the dura mater?
it creates septa in the cranial cavity
divides cranial cavity using the falx cerebri and tentorium cerebelli
the brain can herniate through openings
which notch can the brain herniate through
the tentorial notch (where the brain stem passes through
what happens when there is herniation through the tentorial notch?
raised ICP can compress/stretch oculomotor nerve if the medial temporal lobe herniates through the tentorial notch
