Papilloedema Flashcards
What does optic disc swelling refer to?
Disc swelling secondary to any cause
What does papilloedema refer to?
Bilateral optic disc swelling secondary to raised intracranial pressure
What should all patients with bilateral optic disc swelling be suspected of having until proven otherwise?
Raised intracranial pressure due to a specific space occupying legion
Is raised intracranial pressure serious?
Yes = medical emergency
What is examined during ophthalmoscopy?
The optic disc = part of cranial nerve II examination
What is included in an examination of cranial nerve II?
Visual acuity, pupil exam, ophthalmoscopy, visual field assessment, colour vision
What is the different about the optic nerve?
It is actually an extension of the brain with meningeal sheaths
What is the subarachnoid space around the optic disc continuous with?
The subarachnoid space that surrounds the brain
What happens when there is raised intracranial pressure?
It is transmitted to the subarachnoid space to the optic nerve = interrupts axoplasmic flow and venous return causing the discs to swell
What components are added together to give the intracranial pressure?
Brain (80%), blood (10%) and CSF (10%)
What happens if one element of the components of the intracranial pressure rises?
There should be a compensatory decrease in the other elements to ensure the pressure remains constant
Why is it important that the intracranial pressure remains constant?
The cranium is rigid and therefore cannot cope with changes in pressure and volume
What structures may be damaged due to raised intracranial pressure?
Blood vessels are compressed leading to global ischaemia and swelling, brain herniates through foramen magnum, brainstem is compressed = death
What does the brain need its blood supply to be?
Brain requires constant blood flow over a range of pressures = very intolerant of hypo/hyper-perfusion, process of auto-regulation
What are some other causes, besides raised intracranial pressure, that may cause disc swelling?
Malignant hypertension and idiopathic intracranial hypertension
What are the functions of the CSF?
Maintains stable extracellular environment for brain, buoyancy, mechanical protection, waste removal, nutrition
Where is most CSF produced?
By the choroid plexus in the lateral ventricles
Where does CSF travel through before it reaches the subarachnoid space?
The third then the fourth ventricles
What is the choroid plexus?
Network of capillaries which filter blood to form CSF
What can cause intracranial pressure to rise?
Obstructions to CSF production, overproduction of CSF or inadequate absorption of CSF
What are some proposed mechanisms of idiopathic intracranial hypertension?
Stenosis of transverse cerebral sinuses (obstructs CSF) Increased abdominal pressure (obesity) Vitamin A (impairs CSF absorption) Micro-emboli in sagittal sinus (blocks CSF absorption)
What are some features of chronic disc swelling?
Swelling subsides = disc becomes atrophic and pale, loss of visual function and blindness may result
