Anatomy: The Eye and Raised ICP Flashcards
Describe the clinical presentation of CN IV damage
Inferior oblique is unopposed - eye cannot move inferomedially, resulting in diplopia when looking down
Damage to CN III results in paralysis of ________________ and _______________
Somatic motor innervation to 4 extra-ocular muscles and eyelid, and paralysis of parasympathetic innervation of sphincter of pupil
Damage to CN IV results in paralysis of ________________
Superior oblique muscles
Define papilloedema
Bulging or swollen optic discs as a result of raised ICP
How can raised ICP compress the optic nerve and vasculature of the retina?
Optic nerves are CNS tracts so are covered by meninges and are found in the subarachnoid space
Raised ICP will be transmitted along the subarachnoid space in the optic nerve sheath
Describe the clinical presentation of CN IV damage
Means eye cannot move laterally in horizontal plane, resulting in medial deviation of the eye
Damage to CN VI results in paralysis of ________________
Lateral rectus muscle
How can raised ICP damage the oculomotor nerve?
Raised ICP can compress/stretch oculomotor nerve if medial temporal lobe herniates through tentorial notch
What is the Monro-Kellie hypothesis?
The intracranial volume is constant - blood, brain, CSF are in equilibrium
Describe the impact of raised ICP on the dural septae
Brain can herniate through openings (tentorial notch, foramen magnum)
Describe the clinical presentation of CN III damage
Lose/slowness of pupillary light reflex, dilated pupil, ptosis, eye turned inferolaterally (‘down and out’)
Which nerve has been damaged?
CN IV
Which nerve has been damaged?
CN VI
Which nerve has been damaged?
CN III
Why is raised intracranial pressure such a problem?
Increased ICP causes damage to tissues, shifts in tissues, herniation and constriction of blood vessels as the cranial cavity is an enclosed space and intracranial volume is constant
