The ventricular system

Question 1

How do the ventricles form

Answer 1

• Lumen expands at cranial end to form ventricles

Question 2

What are the parts of the lateral ventricles that are associated with each lobe

Answer 2

• Anterior horn - frontal lobe
• Body - parietal lobe
• Posterior horn - occipital lobe
• Inferior horn - temporal lobe

Question 3

What is T1 in CT scans

Answer 3

• Fluid is black, brain tissue appears white - good for looking at structure

Question 4

What is T2 in CT scans

Answer 4

• Fluid is white, brain tissue appears black - good for looking at fluid

Question 5

What are the borders of the lateral ventricles

Answer 5

• Septum pellucidum separates lateral ventricles

- Corpus callosum sits in roof

Question 6

Location of the caudate nucleus

Answer 6

• Sits in lateral wall

Question 7

Location of the hippocampus

Answer 7

• Hippocampus sits in floor of inferior horn

Question 8

How do the lateral ventricles communicate with the third ventricle

Answer 8

• Through ventricle through the internventricular foramen AKA foramen of monro

Question 9

Location of third ventricle

Answer 9

• Slit like cleft between thalami

- Fornix forms roof

Question 10

What type of matter are corpus callosum, septum pellucidum and fornix

Answer 10

• White matter

Question 11

What type of matter are caudate nucleus, lentiform nucleus, thalamus and hippocampus

Answer 11

• Gray matter

Question 12

How does the third ventricle communicate with the 4th ventricle

Answer 12

• Through the cerebral aqueduct AKA aqueduct of sylvius

Question 13

Location and shape of fourth ventricle

Answer 13

Surrounded by hindbrain

• Cerebellum posterior
• Pons and medulla anterior
• Cerebellar peduncles lateral
• Characteristic peduncles lateral
• Continuous with the central canal of the spinal cord and subarachnoid space

Question 14

What are the three foramen exits into subarachnoid space

Answer 14

• Two foramen of luschka(lateral)

- One foramen of magendie(middle)

Question 15

Where do the foramina of luschka and magendie exit into

Answer 15

• Cisterna magna

Question 16

Role of superior colliculi

Answer 16

• Vision

Question 17

Role of inferior colliculi

Answer 17

• Hearing

Question 18

Role of choroid plexus

Answer 18

• CSF production

- Filters blood from branches of internal carotid and basilar arteries

Question 19

Describe the structure of the choroid plexus -

Answer 19

• Very simple

- Capillary network surrounded by cuboidal epithelium

Question 20

How is blood filtered by the choroid plexus

Answer 20

• Blood filtered through fenestrated(has holes) capillaries
• Components transported through cuboidal epithelium into ventricles
• There are tight junctions between epithelial cells which prevent macromolecules from entering CSF
• Permeable to water and CO2
• Forms blood-CSF barrier

Question 21

Describe the cuboidal epithelium in the ventricles

Answer 21

• Specialised ependyma
• Villi present to increase surface area
• Active transport of CSF components
• Bidirectional(uptake of metabolites into circulatory system)
• 60% CSF produced in ventricles
• 40% CSF from other sites within brain

Question 22

Protein content in CSF in comparison to plasma and why

Answer 22

CSF protein - 0.18 g/l
plasma protein - 75 g/l

• Protein levels low in CSF as the CSF has to be sterile and macromolecules are stopped by tight junctions

Question 23

What is the cisterna magna

Answer 23

• Is one of the three principal openings in the subarachnoid space between the arachnoid and pia mater layers of the meninges of the brain

Question 24

What is the subarachnoid space

Answer 24

• Lies between pia and arachnoid

- Subarachnoid space follows contours of brain

Question 25

Purpose of cSF

Answer 25

Functionally important - CSF in contact with brain parenchyma - transfer of micronutrients into brain - removal of metabolites

Question 26

What are arachnoid granulations

Answer 26

- Herniations of arachnoid membrane(villi) through dura mater into venous sinuses - Mainly within the superior sagittal and transverse sinuses

Question 27

Pressure difference between csf and sinuses

Answer 27

- CSF pressure must exceed that in venous sinuses - 150mm water in subarachnoid space - 80mm water in venous sinuses - If venous pressure exceeds CSF pressure, tips of villi close off(prevents reflux of blood into subarachnoid space) - Arachnoid villi act as one-way valves

Question 28

How much CSF is produced per day

Answer 28

- 500ml CSF produced per day(0.35ml/min)

Question 29

What is the total volume of CSF in the system

Answer 29

90-140ml

Question 30

What happens to excess CSF

Answer 30

- Absorbed by arachnoid granulations

Question 31

What are the main functions of CSF

Answer 31

- Hydraulic buffer to cushion brain against trauma - Vehicle for removal of metabolites from CNS - Stable ionic environment for neuronal function(communicates with brain interstitial fluid via pia) - Transport for neurotransmitters and chemicals

Question 32

What does yellow(xanthochromia) CSF indicate?

Answer 32

- Due to conversion of haemoglobin to billirubin - eg subarachnoid haemorrhage - lysis of red blood cells, haemoglobin release

Question 33

What does cloudy CSF indicate?

Answer 33

- Due to presence of lots of antibodies and white blood cells - eg multiple sclerosis - Protein content(gamma globulin) increase - eg bacterial meningitis - Leukocytes are increased, indicative of infection

Question 34

How is CSF sampled

Answer 34

- Taken by lumbar puncture at lumbar cistern(no spinal cord) - L3/4 for adults - L4/5 for children - Vertebrae is slower growing than

Question 35

What is hydrocephalus

Answer 35

- Dilation of brain ventricles - Due to blocked CSF circulation, impaired absorption or over secretion - increased intracranial pressure - Pressure on surrounding tissues affects neurological function - Can be congenital or acquired

Question 36

What are the symptoms of hydrocephalus

Answer 36

- Headaches - Vomiting - Visual disturbances - Pailledema(swelling of optic disc) - Seizures - Altered cognition - Balance and coordination problems

Question 37

What is non-communicating hydrocephalus?

Answer 37

- Blockage within the ventricular system - Due to tumour, cyst, stenosis(eg narrowing of cerebral aqueduct) - CSF does not circulate over surface of brain

Question 38

Normal treatment for non-communicating hydrocephalus

Answer 38

Surgery - insert shunt to reduce intracranial pressure | - Blockage often in the cerebral aqueduct

Question 39

What is dandy-walker syndrome

Answer 39

- Congenital malformation of the cerebellum - Obstruction within foramina of fourth ventricle - Symmetrical dilation of lateral, third and fourth ventricles

Question 40

Treatment for dandy-walker syndrome

Answer 40

- Insert a shunt to reduce intracranial pressure | - In infancy, child's head may become enlarged, tend to have a large skull

Question 41

What is communicating hydrocephalus

Answer 41

- Obstruction in the arachnoid villi - Movement of CSF into venous is impeded - eg impaired absorption following subarachnoid haemorrhage trauma or bacterial meningitis