Anatomy 6 - Raised ICP Flashcards
What is raised intracranial pressure?
Increase in pressure within the cranial cavity (chronic or acute)e
What causes raised ICP?
An increased pressure in fluid surrounding the brain or an increase in pressure within the brain itself e.g. brain tumour, head injury, hydrocephalus, meningitis, stroke
What is hydrocephalus?
Increased fluid around the brain
Why is ICP such a serious problem?
It can cause damage to the brain and the spinal cord
How does the intracranial volume normally fluctuate?
It is normally constant
What is the main idea of the Monro-Kellie Hypothesis?
3 things exist within the fixed minions of the skull: blood, CSF and the brain - an increase in any one component must lead to a decrease in one (or both) of the other components, otherwise intracranial pressure will increase
In what way can raised ICP damage the brain and spinal cord?
Causes damage to tissues, shifts in tissues, herniation and constriction of blood vessels
What kind of visual/ eye problems can increased ICP cause?
Transient blurred vision Double vision Loss of vision Transient flickering Decreased colour perception Pupillary changes Papilloedema (swelling of optic disc due to increased ICP)
What is the name of the membranes that line the skull and vertebral canal and enclose the brain and spinal cord?
meninges
What are the 3 layers of meninges?
Dura
Arachnoid
Pia
Name of the space between the arachnoid and pia?
Sub-arachnoid space
What is the toughest layer of the meninges?
Dura mater
What provides the sensory supply to dura mater?
CN V
What does the dura mater enclose?
The dural venous sinuses
What is the name for the projections of arachnoid membrane into the dural sinuses?
What is the purpose of this?
Arachnoid granulations
To allow CSF entrance from the subarachnoid space into the venous system
What is contained within the subarachnoid space?
Circulating CSF and blood vessels
Describe the appearance of the pia?
Adherent to the brain with vessels and nerves entering or leaving
What is the purpose of the subarachnoid space?
Completely surrounds both brain and spinal cord and contains circulating CSF = cushions and protects
Where is CSF produced?
In the choroid plexus of the ventricles
Where is CSF reabsorbed?
Into the dural venous sinuses via arachnoid granulations
At what levels can CSF be drawn during a lumbar puncture?
L3/4 or L4/5 IV disc level
At what level does the subarachnoid space end/ close?
S2
Name of the sinus within the cranium that can be seen surrounding the brain when it is cut longitudinally in half?
Superior sagittal sinus
What ventricle is located within the right cerebral hemisphere?
Right lateral ventricle
What ventricle is located in the midline within the diencephalon?
The 3rd ventricle
What part of the spinal cord is continuous with the 4th ventricle?
The central canal
Where is the 4th ventricle located?
Between the cerebellum and pons
What connects the third and 4th ventricles in the midline?
The cerebral aqueduct
Where is the choroid plexus located?
Within the lateral and third ventricle
How does raised ICP affect the optic nerve?
Raised ICP will be transmitted along the subarachnoid space in the optic nerve sheath compressing the optic nerve and can lead to bulging or swollen optic discs
How does raised ICP affect the other structures of the retina (apart from the optic nerve)?
Will also compress the central artery and vein
What type of damage is the oculomotor nerve susceptible to?
Compression
Tentorial herniation
What effect can damage to the oculomotor nerve have on the eye? (3)
Paralysis of somatic motor innervation
Paralysis of parasympathetic innervation of the sphincter of the pupil
Ptosis
What is the name of the triangular opening in the tentorium cerebelli through which the brainstem extends?
Tentorial notch
Name of the 4 folds of dural mater that divides up the cranial cavity?
Falx cerebri
Tentorium cerebelli
Falx cerebelli
Diaphragm sellae
What nerve can be damaged if raised ICP causes medial temporal love to herniate through tentorial notch?
Oculomotor nerve
What type of damage is the trochlear nerve susceptible to?
Stretching, compression
What symptom can damage to the trochlear nerve cause?
Why?
Paralysis of superior oblique muscle = inferior oblique is unopposed -> eye cannot move inferomedially = diplopia when looking down
What type of damage is the abducent nerve susceptible to?
Damage by stretching
What eye movements cannot occur if the abducent nerve is damage?
Eye cannot move laterally in horizontal plane (due to paralysis of lateral rectus muscle)
What is the name of the sign in infants/ children where the eyes appear driven downward, the sclera may be seen between the upper eyelid and iris and part of the pupil may be covered by the lower eyelid?
What is this a sign of?
Sunset sign
Hydrocephalus
What dural fold is located right down the centre between the 2 hemispheres?
Falx cerebri
What dural fold separates the cerebellum from the rest of the brain?
Tentorium cerebelli
What dural fold separates the 2 hemispheres of the cerebellum?
Falx cerebelli
How many grades of papilloedema are there?
5
What does grade I papilloedema look like?
C-shaped halo around the disc
What does grade II papilloedema look like?
Circumferential halo with blurred edges
What does grade III papilloedema look like?
Vessels on edge of disc disappear
What does grade IV papilloedema look like?
loss of major vessels on disc
What does grade V papilloedema look like?
Extremely blurry edges of disc with total or partial obscuring of vessels on disc
