Week 1 - E - Anatomy of EYE and raised ICP - & ventricles Flashcards
When testing the extra-ocular movements of the eye how do you do this?
So you move the index finger in an H shape Move medially for medial rectus Then move up for inferior oblique and down for superior oblique Move laterally for lateral rectus Then move up for superior rectus and down for inferior rectus
What nerves supply the extra-ocular muscles of the eye?
Medial rectus Inferior rectus Superior rectus Inferior oblique All supplied by the oculomotor nerve Superior oblique - trochlear nerve Lateral rectus - abducent nerve
What fills the anterior and posterior chambers of the eye?
The aqueous humour
What is the drainage of the aqueous humour of the eye?
Drains from posterior to anterior chamber and then through the trabecular network into the canal of schlemm which exists at the corneal iridocorneal junction
What are 4 examples of distrubances that may cause a raised intracranial pressure?
Head injury Intracranial lesion eg trauma or haemorrhage Hydrocephalus Meningitis
What are 3 signs of raised intracranial pressure?
A combination of headache, papilloedema and vomiting
When the photoreceptors are hit by light and convert the enrgy waves to neurones, they tavel to the ganglion cells of the retina via the bipolar cells What do the ganglion cell axons join to form? Where does it travel?
Forms the optic nerve which travel through the optic canal to converge at the optic chiasm
What is hyrdrocephalus?
It is the accumulation of CSF in the brain
What is the condition hydrocephalus better known as? Why can babies skulls grow large in hydrocephalus?
Better known as water on the brain Can grow as the cranial sutures have not closed yet therefore fluid can leak
On the left it shows hydrocephalus What colour is the CSF on MRI? If there is a hole in the skull where can CSF leak?
CSF is white on MRI CSF can leak into ears or nose
What are the three protective membrane layers surrounding the brain and spinal cord?
These are the meninges
What are the three meninges from outer to inner?
Dura mater Arachnoid mater Pia mater
The dura mater consists of two layers What are these? and which layer lines the inside of the cranium?
CO onsists of the endosteal layer and the meningeal later The endosteal layer lines the inside of the cranial cavity
What exists between the endosteal and meningeal layer of the dura mater?
https://s3.amazonaws.com/classconnection/403/flashcards/11907403/jpg/picture1-15A518725434F0211F1.jpg
Where does the dural venous sinus drain? What space is located beneath the dura mater?
Drains into the internal jugular vein The subdural space separates the dura and arachnoid mater
What is the space in the arachnoid mater where the CSF flows?
This is the subarachnoid space - can have a pathological haemorrhage here sometimes
What is the most common cause of a subarachnoid haemorrhage?
The majority of subarachnoid haemorrhages are caused by a brain aneurysm bursting. A brain aneurysm is a bulge in a blood vessel, caused by a weakness in the blood vessel wall. Subarachnoid haemorrhage is a type of stroke
The dura matter lines the cranial cavity What is the large, crescent-shaped fold of meningeal layer of dura mater that descends vertically in the longitudinal fissure separating what structure sin the brain?
This is the falx cereberi Separates the two hemispheres of the brain
What does the tentorium cerebelli separate in the brain?
The tentorium cereblli is a tent like part of dura matter separating the cerebellum from the inferior portion of the occipital lobe of the brain
What is the small triangular oepning in the tentorium cerebelli through which the brainstem extends known as?
This is known as the tentorial notch
What i the purpose of the Falx cerebri? The tentorium cerebelli? The tenotrial notch?
Falx cerebri runs in the lontitudional fissure and separates the right and left hemisphere of the cerebrum Tentroium cerebelli separates the cerebellum from the inferior partion of the occipital lobes Tentorial notch allows space for the branistem to pass through
What does the pituitary gland lie in? (what is the depression in the spehnoid bone known as? What is the roof of the pituitary gland with a central hole for the passage of the infundibulum?
Pituitary gland lies in the sella turcica which is a depression in the sphenoid bone The roof of the pituitary fossa is the diaphragma sella
What are the four ventricles of the brain? (where does each lie)
Ventricles are fluid-filled cavities within the brain. o One lateral ventricle within each cerebral hemisphere o A third within the diencephalons o A fourth that lies between the pons and cerebellum and extends into the superior portion of the medulla oblongata.
What are the parts of the lateral ventricles?
Frontal anterior horns Joined to occipital posterior horns by the body Temporal inferior horns also
What connects the lateral ventricles to the thrid ventricle?
Connected to the third ventricle by the interventricular foramen (of Monroe)
What connects the third and fourth ventricle?
Connected by the cerebral aqueduct (Duct of Sylvius)
Describe the CSF circulation from choroid plexus to the superior sagiital sinus (dural venous sinuses) before drianage into the internal jugular vein? There are choroid plexus in each ventricle
CSF - travels from lateral ventricles through the interventricular foramen into the third ventricle The travels via the cerebral aqueduct into the fourth ventricle where there is one median and two lateral apertures - The median apertures drains into the subarachnoid space of the central canal of spinal cord The lateral apertures drain into the subarachnoid space of the brain Subarachnoid CSF then enters arachnoid villi (granulations) to enter the superior saggital sinus
What are the arachnoid villi? (or arachnoid granulations)
They are small prtrusions of the arachnoi dmater into the dura mater through which CSF drains into the dural venous sinuses
Name the numbers 1-7
1 - lateral ventricles 2 - interventricular foramen 3 - third ventricle 4 - cerebral aqueduct 5 - fourth ventricle 6 - medial aperture 7 - lateral apertures
Name numbers 8 onwards
8 - central spinal cord 9 - subarachnoid space 10 - arachnoid villi 11 - superior saggital sinus 12 - occipital sinus 13 - straight sinus 14 - confluence of sinuses
The confluence of sinuses then drains into the transverse sinus What does the transverse sinus drain?
- Superior sagital sinus, straight and occipital sinuses drain into the confluence of sinuses
- Confluence of sinuses drains into transverse sinuses which drains into the sigmoid sinuses
- Sigmoid sinuses drain into the internal jugular veins
Most patients with Raised intracranial pressure will report with eye problems What are some of these problems?
Blurred vision Loss of vision Double vision Papilloedema (swelling of optic disc due to raised ICP)
Pupillary changes can also arise if there is a rasied ICP This can compress the oculomotor nerve The parasympathetic part of the oculomotor nerve is usually on the outside of the nerve If this is compressed what may be a sign?
COmpression of parasympathetics of oculomotor nerve The paraympathetics supply the sphincter pupillae iris muscles therefore if this supply is lossed then there will be unopposed sympathetic dilator pupillae actionc causing a fixed dilated pupil
Optic ‘nerves’ are actually CNS tracts Covered by sheath of meninges What can happen if raised ICP compresses the optic nerve?
This can lead to bulging or swollen discs known as papilloedema
What visual symptoms can occur in papilloedema?
Can have BLURRING of vision Transient flickering Decreased colour perception
This is a normal fundus of the eye, How can you tell which side of the eye it is?
The macula lies in the middle of the four quadrants with the optic disc in the slightly upper nasal quadrant usually This should be your righteye
The 3 Cs of optic disc on opthalmoscopy are colour, contour and cup What is lost in papilloedema?
The contour of the disc is lost as the disc margins become blurry
Grade I papilledema is characterized by a C-shaped halo with a temporal gap
With Grade II papilledema, the halo becomes circumferential
Which grade of papilloedema is it where there is a loss of major vessels as they leave the disc with very slight optic disc margins visible?
Grade III
papilledema is characterized by loss of major vessels ON THE DISC. What grade is this?
This is grade IV
What is the final grading of papilloedema? What is visible here?
Grade V papilledema has the criteria of grade IV plus partial or total obscuration of all vessels of the disc.
