Raised intracranial pressure Flashcards
Name five potential causes of raised ICP.
space occupying lesion increased CSF volume stroke meningitis head injury/trauma
Why can’t the cranial cavity cope with increased pressure?
cavity is an enclosed space, not flexible or elastic.
What is the Monroe-Kellie hypothesis?
the cranial cavity is incompressible- an increase in the volume of one of its constituents (i.e. brain tissue, blood, CSF) must be compensated for by a decrease in one of the others
What visual symptoms may be seen in raised ICP?
blurred vision double vision loss of vision papilloedema pupillary changes
What are the three layers of the meninges?
From exterior to interior: dura mater arachnoid mater (subarachnoid space) pia mater
Where is CSF produced?
Choroid plexus of the ventricles
Describe the ventricular system of the brain.
The right and left lateral ventricles within the right and left cerebral hemispheres; the 3rd ventricle in the midline within the diencephalon; the 4th ventricle between the cerebellum and pons
What connects the 3rd and 4th ventricles?
the cerebral aqueduct
Where is CSF reabsorbed?
Via arachnoid granulations protruding into the dural venous sinuses
Why is raised ICP transmitted along the optic nerve sheath?
optic nerve is a CNS tract covered by meninges, and has a sub-arachnoid space, hence raised ICP is transmitted along the optic nerve sheath
Which structures will be compressed within the optic nerve sheath in raised ICP?
the optic nerve, the central artery and vein of the retina
What effect can raised ICP have on the optic disk?
bulging or swollen (papilloedema)
What consequences can compression of the oculomotor nerve have?
paralysis of somatic muscle innervation- ptosis, eye turned inferolaterally
paralysis of parasympathetic innervation of the pupil- loss of pupillary light reflex, dilated pupil
What consequence does compression of the oculomotor nerve have?
paralysis of superior oblique muscle- eye cannot move inferomedially
What consequence does stretching of the abducent nerve have?
Paralysis of lateral rectus- medial deviation of the eye
