Raised Intracranial Pressure Flashcards
What are the causes of raised intracranial pressure?
Head injury
Space occupying lesion, abscess or haemorrhage
Hydrocephalus
Meningitis
What is the sunset sign
Whites of eyes showing above iris- pressure on nerve
What are the three layers surrounding the brain?
Dura Mater
Arachnoid mater
Pia Mater
What are the layers of dura mater?
1) endosteal
2) meningeal
What is found in between the layers of dura mater?
Venous blood
Where do the two layers of dura mater separate?
1) longitudinal fissure between the two hemispheres
2) tentorial notch
What is the tentorial notch?
Brainstem passes through it, any raised ICP pushes the brainstem through it and raises the chances of hypothalamus compromised
What runs along the tentorial notch?
Cranial nerves
Describe arachnoid mater?
Spidery thin layer with CSF deep to it
Pool of CSF can be larger areas or smaller areas
Describe pia mater
Soft mother
Single layer that surrounds the brain tissue; not visible to naked eye
What are the ‘veins’ of the dura?
Sinuses; have no walls but are surrounded by two layers of dura
What carries CSF from arachnoid to dural venous sinuses?
Arachnoid Villi
How does CSF pass though the ventricular system?
Passes through channels from lateral to third then fourth ventricles
What surrounds the brain and spinal cord?
Subarachnoid space
Where do veins of the brain pass into?
Dural venous sinuses
What visual problems are reported as a result of raised ICP
Transient blurred vision
Double vision
Loss of vision
Papilloedema
Describe the monro-kellie hypothesis
Cranium is an incompressible space, any increase in one component (CSF, brain, blood) must be compensated by a change in another
Why is the optic nerve considered an extension of the brain?
CNS tract covered by meninges
What is the subarachnoid space?
Space between pia and arachnoid
Why does raised ICP cause direct globe manifestations?
The subaracnoid space extends to the back of the globe
What leads to bulging/swollen optic discs?
raised ICP will compress the central artery and vein of the retina as well as the optic nerve
What are the visual symptoms of papilloedema?
Transient visual obscurations (grading out of vision) Transient flickering Blurring of vision Constriction of the visual field Decreased colour perception
Describe the grading of papilloedema
Grade 1: blurry C shaped halo
Grade 2: halo becomes circular, more blurry, larger
Grade 3: you cant see some of the surrounding vessels
Grade 4: central vessels start to disappear
Grade 5: vessels disappear completely
Why is the oculomotor nerve susceptible to damage?
Compression
Tentorial herniation (ICP)
What does the oculomotor nerve contain?
Motor nerve that contains parasympathetics
Which cranial nerves contain parasympathetics?
CN 3, 7, 8, 10
What is the first thing to be damaged in a nerve due to Raised ICP?
Parasympathetics (outside of nerve)
What happens if the oculomotor nerve is damaged?
-paralysis of somatic motor innervation
(extra ocular eye muscles)
-paralysis of parasympathetic innervation
(constrictor pupillae)
What may someone with raised ice SHOW?
NO/slow pupillary light reflex
Dilated pupil
Ptosis
Position of eye; down and out
Why is the trochlear nerve susceptible to damage?
Long intracranial course
- stretching
- compression
- only nerve that comes from posterior brainstem
Describe the function of the eye when the trochlear nerve has been damaged?
Inferior oblique is unopposed
Eye cannot move inferomedially
Diplopla
How is the abducens nerve susceptible to damage?
By stretch
What happens to the function of the eye when the abducens nerve is damaged?
Paralysis of lateral rectus
Medial deviation of the eye
