Cerebrospinal fluid, aqueous humour and intercranial pressure Flashcards
Describe CSF
Clear colourless fluid slightly more viscous than water
Where is CSF synthesised?
Choroid plexus in brain ventricles
Describe the circulation of the CSF
Produced in lateral and 3rd ventricles and circulates to the 4th ventricle and central canal then into the subarachnoid space before being absorbed into the venous circulation
What is the purpose of CSF?
Provide protection to the brain
Supply it with nutrients and remove waste
Homeostatic control- sense pH therefore alter ventilation
What is contained in the CSF?
Little protein (15-45mg/dl)
Little immunoglobulin
1-5 cells/ml
What is the choroid plexus found?
3rd and 4th and lateral ventricles.
What is CSF derived from?
Blood that passes close to the choroid plexus
What ions are transported from the blood to create CSF?
Na
Cl
HCO3 (Bicarb)
H2O
Where can CSF be accessed to measure?
Lumbar puncture
Cervical (somewhere)
How many ventricles are there in the brain?
4
What are the 4 ventricles in the brain?
Two lateral ventricles
3rd ventricle
4th ventricle
What links the lateral ventricles with the 3rd ventricle?
Interventricular foramina
What links the 3rd ventricle to the 4th ventricle?
Cerebral Aqueduct
What does the interventricular foramina do?
Link the lateral ventricles to the 3rd ventricle
What does the Cerebral Aqueduct do?
Link the 3rd ventricle to the 4th ventricle
What do the foramen Magendie and Luschka do?
Link the 4th ventricle to subarachnoid space
What links the 4th foramen to the subarachnoid space?
Foramen Magendie and Luschka
What extends inferiorly our of the 4th ventricle?
Central canal
What does the central canal do?
Carry CSF to the spinal cord
Where does CSF return to the venous circulation?
Arachnoid granulations/dura arachnoid vili
What separates the blood from the CSF?
Blood CSF barrier
What kind of pathologies can affect the ventricles or CSF?
Tumours
Hemorrhage
Hydrocephalus
Idiopathic intracranial hypertension
What can brain hemorrhages lead to?
Blood accumulation in the ventricles
What is the lay term for hydrocephalus?
Water on the brain
What is hydrocephalus?
Accumulation of CSF leading to enlargement of ventricles
What is papilloedema?
Swelling of the optic disk due to increased intracranial pressure
What are some symptoms of papilloedema?
Enlarged blind spot
Blurred vision
Loss of vision
What is aqueous humour?
Fluid that fills the anterior chamber of the eye
What does aqueous humour do?
Supplies oxygen, metabolites and bicarb to the cornea and iris etc
What is the importance of the bicarb in aqueous humour?
To buffer the H+ produced by anaerobic met in the cornea
What is ascorbate?
A strong antioxidant
Why is ascorbate found in the aqueous humour?
To help protect the eye from anaerobic met
What ions are found in aqueous humour?
Na
Cl
What is an overproduction of aqueous humour called?
Glaucoma
What is glaucoma?
Overproduction of aqueous humour
What medication types can be used to prevent glaucoma?
Carbonic Anhydrase Inhibitors
Why do CA Inhibitors help prevent glaucoma?
Block CA which in turn prevents Na uptake
Give some examples of CA Inhibitors used in glaucoma
Dorzolamide
Acetazolomide
How is dorzolamide administered?
Eye drops
How is acetazolomide administered?
Oral- kidney problems
What can cause raised intracranial pressure?
Tumours, abscess, hemorrhage
Hydrocephalus
Meningitis
What are the three layers of the meninges?
Dura mater- Durable mother
Arachnoid mater- Spider like
Pia mater- Soft mother
What flows in the subarachnoid space?
CSF
What is the dura mater a continuation of?
Periosteum of cranial cavity
Are the meninges restricted to the contours of the skull or can they dive down into the sulci?
Dive down into the sulci
What does the dura mater form in the sulci of the brain?
Falx cerebri
Cerebellar tentorium
What is the falx cerebri?
Invagination of dura mater in the longitudinal fissure
What does falx mean?
SIckle
What are the cerebellar tentorium?
Invagination of dura mater between the cerebellum and occipital lobes of cerebrum
What runs along the edge of the cerebellar tentorium?
Several nerves associated with the eye
What passes through the hole in the cerebellar tentorium?
Brainstem
What can be found between layers of the dura mater?
Dural venous sinuses
What are dural venous sinuses?
SInuses of venous blood without vein walls
What happens in the Arachnoid granulations/dura arachnoid vili?
CSF returned to venous blood
Where are Arachnoid granulations/dura arachnoid vili found?
Dura venous sinuses
Why can raised intracranial pressure lead to visual disturbances?
Because meninges and subarachnoid space extend along the optic nerve to the eye
What extends along the optic nerve to the eye?
Meninges and subarachnoid space
Why can raised intracranial pressure lead to visual disturbances?
Because meninges and subarachnoid space extend along the optic nerve to the eye
What extends along the optic nerve to the eye?
Meninges and subarachnoid space
What visual disturbances can raised intracranial pressure cause?
Transient blurred vision Double vision- Diplopia Loss of vision Papilloedema- Swelling of optic disk Pupillary changes
What is diplopia?
Doube vision
What is the correct term for a swelling of the optic disk due to raised intracranial pressure?
Papilloedema
How many eyes can raised ICP affect
One or both
What is the correct term for a swelling of the optic disk due to raised intracranial pressure?
Papilloedema
How many eyes can raised ICP affect
One or both
What are some of the symptoms of trochlear nerve damage?
Eye cannot move inferomedially
Diplopia when looking down
What are some symptoms of oculomotor nerve damage?
No/slow pupillary light reflex
Dilated pupil
Ptosis
Position of eye: looking ‘down and out’
What are some of the symptoms of trochlear nerve damage?
Eye cannot move inferomedially
Diplopia when looking down
What is the symptom of abducens nerve damage?
Medial deviation of the eye
