Lec 7 Ventricular System and Vasculature Flashcards
What are wateshed areas?
brain regions that get blood from very distal tips of two different cerebral arteries
- -> protective since multiple source of blood
- -> vulnerable since blood supply only from distal capillaries
What are the two main sources of blood to the brain?
- internal carotid arteries
- vertebral arteries
What vessels supply blood to the anterior circulation system of brain? posterior?
- anterior = internal carotid arteries
- posteriro = vertebral arteries
What is the blood supply to the brainstem?
- solely the posterior/verebral system
Where doe the vertebral arteries branch from?
the subclavian arteries
Where do the vertebral arteries anastamose? What artery do they form?
anastomose at the pontomedullary junction
form single midline basilar artery
What are the 3 types of branches in the posterior system that supply the brainstem?
- paramedian
- short circumfrential
- long circumfrential
What are the 3 major “long circumfrential” branches off of the posterior circulation?
- PICA [posterior inferior cerebellar artery]
- AICA [anterior inferior cerebellar artery]
- SCA [superior cerebellar artery]
What is PICA and what does it supply?
- a long circumfrential branch
- comes off of vertebral artery
- supplies dorsolateral medulla
What blood vessels supply the lateral and dorsal pons?
- the AICA [anterior inferior cerebellar artery] and the SCA [superior cerebellar artery], both long circumfrential branches off of the posterior circulation
What blood vessels supply the cerebellum?
- the AICA (anterior inferior), PICA (posterior inferior) , SCA (superior)
- all are long circumfrential vessels off the posterior circulation
- supply the corresponding area of the cerebellum
How/where does the basilar artery end?
bifurcates into two posterior cerebral arteries [PCA] at the junction of the pons and midbrain
What blood vessel supplies the midbrain?
the basilar artery including SCA and PCA
How/where does teh common carortid artery end?
- bifuracates into external and internal carotids
- at level of C4 vertebra
How does the IC enter the skull?
- goes through temporal (petrosal) bone then through cavernus sinus
How does the internal carotid end?
- bifurcates into anterior (ACA) and middle cerebral arteries (MCA)
What are the 4 main parts of the internal carotid?
- cervical (extracranial): from common carotid bifurcation to point of entery into carotid canal at skull base
- intrapetrosal: within petrous portion of temporal bone
- intracavernous: through cavernous sinus
- cerebral: from cavernous sinus to bifurcation into ACA/MCA
What is the carotid siphon?
the intracavernous and cerebral portions of the carotid artery together
What 5 vessels comprise the circle of wilis?
- anterior, middle, and posterior cerbral arteries [ACA MCA PCA]
- anterior and posterior communicating arteries
What is responsible for blood supply to cerebral cortex and underlying white matter?
distal branches of the cerebral arteries
Where does the MCA [middle cerebral artery] begin? path? supplies?
- begins from internal carotid lateral to the optic chiasm
- passes through lateral sulcus [sylvian fissure]
- supplies lateral cerebral cortex [areas of motor, somatosensory, auditory, taste, language, higher cognitive function]
What does the anterior communicating area connect?
the left and right anterior cerebral arteries [that come off of the IC]
What does the ACA supply?
- inferior and medial of frontal and parietal lobes as well as subcortical anterior structures
What do the posterior communicating arteries connect?
- the MCA to the PCA
What does the PCA [posterior cerebral artery] supply?
- occipital lobe and inferior/medial surfaces of temporal lobe
What do the terminal branches of the PCA anastomose wtih?
- terminal branches of ACA and MCA
Where do veins of the brain empty into?
dural sinuses
What are teh 3 main parts of the cerebral venous system?
- superficial veins
- deep veins
- venous [dural ] sinuses
What does the superficial venus cerebral system drain? where does it go?
- drains cerebral cortex and subcortical white matter into the dural sinuses
Are superficial veins or cortical arteries more superficial?
superficial veins
What are the 4 main sinuses that the superficial venous cerebral system drains into?
- superior sagital
- cavernous
- petrosal
- transverse
Where do superior cerebral veins collect from? empty into? [superficial]
- collect from medial and convex areas of cortex
- empty into superiro sagittal sinus
Where do inferior cerebral veins collect from? empty into? [superficial]
- collect from lateral area of cortex
- empty into middle cerebral vein
What is the path of middle cerebral vein? [superficial]
- runst rhough lateral sulcus [sylvian fissure] to reach cavernous sinus
What does the vein of Trolard connect?
- connects between superior and inferior cerebral veins
What does the vein of Labbe connect?
- connects between the middle cerebral vein and transverse sinus
What is the great vertebral vein of galen?
- deep vein that drains from the paired internal/deep cerebral veins
- joins with the inferior sagittal sinus to form the straight sinus
What does the basal vein of rosenthal drain?
- the basal cortical areas
Where is teh superior sagittal sinus located?
- at the midline at the superior edge of the falx cerebri
Where is the inferior sagittal sinus located?
- at the midline at theinferior edge of the falx cerebri
What is the blood supply to the spinal cord?
- radicular [segmental] artiers
- 1 anterior spinal artery
- 2 posterior spinal arteries
What is the artery of adamkiewicz?
- anterior radicular artery
- larger than the rest
- enters on left between T9 and T12 then reinfoces anterior spinal artery
- reinforces blood supply to anterior 2/3 of lumbar and sacral spinal cord including lumbo-sacral enlargement
What happenes of artery of adamkiewicz is occluded?
- blood supply to lumbar cord is compromised
What part of the spinal cord is most vlunerable due to occlusion of a radicular artery?
- thoracic area of spinal cord
- because fewer radicular arteirs
What is the 4th ventricle?
the portion of ventricular system present in medulla and pons
What are the 3 important channels in the 4th ventricle that provide conduits between ventricular system and subarachnoid space?
- foramen of magendie
- 2 foramina of luschka
Where does the foramen of magendie go?
- posterior directed channel from 4th ventricle that opens into cisterna magna
Where doe the foramina of luschka go?
- lateral extensions of 4th ventricle that open into the pontine cistern
What is the obex of the ventricular system?
- the caudalmost point of the 4th ventricle
- where it merges with the central canal of the spinal cord
What is the cerebral aqueduct of sylvius?
- narrow midline cannal that tunnels through the midbrain
- continuous with the 4th ventricle
What is the 3rd ventricle?
- the area of ventricular system in the diencephalon
- continuous with cerebral aqueduct of sylvius
What are the largest recesses of the 3rd ventricle?
- optic recesses
- infudibular recess
- pineal recess
- habenular recess
What is the inerventricular foramen of Monro?
- y-shaped conduit from single 3rd ventricle to the two lateral ventricles of the 2 cerebral hemispheres
Where the the laterral ventricles?
the part of the ventricular system in the 2 cerebral hemispheres
What is the septum pellucidum?
- sheet of ependyma that separates the two lateral ventricles from each other
Where is CSF produced?
epithelial cells in choroid plexus in the lateral and 4th ventricle secrete CSF by selective transport [requires ATP]
small amount produced by ependymal cells
What are the functions of the CSF?
- prevent contact between neural structures and surrounding bones
- support brain
- transport nutrients/chem messengers/waste
- act as signal transducer of hormones
Where is the ependymal lining of the ventricular system freely permeable?
everywhere except at choroid plexus
What drives CSF resorption?
- passive process
- driven by pressure gradient between intracranial space [ICP] and venous system [CVP]
What is the flow of CSF from choroid plexus into venous system?
- choroid plexus
- -> through lateral ventricles
- -> foramina of monro
- -> central 3rd ventricle
- -> cerebral aqueduct [of sylvius]
- -> 4th ventricle
- -> either 2 foramen of luschka or single foramen of magendie
- -> subarachnoid space
- -> into venous system through arachnoid villi along the dural venous sinuses
Passive or active transport to secrete CSF into ventricles?
both passive and active
How do you evaluate CSF?
- via lumbar puncture at L4-L5
What are routine things you measure from lumbar puncture?
- opening pressure
- protein
- glucose
- cell count
- culture
- sensitivity
What are complications of lumbar puncture?
- infection
- low pressure headache
- herniation
What is difference between CSF and blood plasma?
CSF has HIGHER: Cl, Mg, Na
What is average volume of CSF in adult?
120 mL
What 2 factors influence movement of CSF through the ventricular system + subarachnoid space?
- pressure gradient between choroid plexuses and arachnoid villi [CSF tends to move this direction]
- mechanical means of movement in the subarachnoid space
What is normal color of CSF? opening pressure? protein? glucose? mononuclear cells?
- clear/colorless
- opening pressure: 50-180 mmH20
- protein: 15-45 mg/dl
- glucose: 50-80 mg/dl
- 0-5 mononuclear cells
What is normal ratio WBC to RBC in CSF?
1 WBC : 700 RBC
What is normal ratio protein to RBC in CSF?
1 dl protein : 1000 RBC
What is normal ratio of glucose in CSF to blood?
glucose in CSF is 2/3 of glucose in blood
What three areas of the brain are exceptions to blood brain barrier?
portions of:
- hypothalamus
- pineal gland
- choroid plexus
What 3 structures make up the BBB?
- endothelial cells lining capillary wall with tight junctions between them
- astrocyte foot processes
- capillary basement membrane
What is commonicating vs non-communicating vs obstructive mean in hydrocephalus?
- if CSF path is open strat to finish [CSF can travel freely from choroid plexus to arachnoid granulations] –> there is no obstruction = communicating hydrocephalus
- if CSF can’t travel freely from start to finish –> there is obstruction = non-communicating hydrocephalus
What are symptoms of hydrocephalus?
- headaches, nausea, vomitting
- papilledema, diplopia [double vision], lethaargy, coma
What is hydrocephalus?
- abnormal accumulation of CSF in ventricles, increases size of ventricles and puts pressure on brain
What happens in communicating hydrocephalus?
- more CSF production than absorption
- increased intracranial pressure [ICP]
- ventricular system dilates uniformly
- can lead to papilledema, herniation
What can cause communicating hydrocephalus?
- congenital absence of arachnoid villi
- blood [villi partially blocked by RBC after subarachnoid hemorrhage]
- high level of protein in CSF (>500 mg/dL)
- papilloma [tumor] of choroid plexus
What is treatment for communicating hydrocephalus? complications?
- shunt placement [ventriculo-peritoneal]
- complications = infection, seizures, high incidence of shunt failure,
What are signs of communicating hydrocephalus?
- disproportional increase in head circumfrence compared to rest of face/body in children whose cranial sutures have not fused
- in older children/adutls: high ICP –> nausea/vomitting, headahce, gait disturbance
When are choroid plexus tumors common? symptoms?
- rare, more common between birth and 10 yrs
- most often occur in 4th ventricle
- signs: increase ICP –> hydrocephalus, deficits of eye movement, headache, N?V
What is hydrocephalus ex vacuo?
- generalized atrophy of brain –> ventricles relatively larger due to loss of white matter
- no increased ICP
- no treatment
- in alzheimers, HIV, pick disease
What is normal pressure hydrocephalus (NPH)?
- rare reversible cause of dementia
- urinary incontinence, gait disturbance, rapid dementia
- no increase in subarachnoid space volume
- expansion of ventricles distorts fibers of corona radiata
- usually in elderly
What is classic triad of normal pressure hydrocephalus
- wet, wobbly, wacky
wet: urinary incontience
wobbly: gait disturbance
wacky: rapidly progressive dementia
What do you see on CT/MRI with normal pressure hydrocephalus?
looks like communicating hydrocephalus
What do you see in opening pressure on LP with normal pressure hydrocephalus?
- normal opening pressure
What treatment for normal pressure hydrocephalus?
- remove some CSF by VP shunting procedure
What is most likely symptom of NPH to improve with shunting? least likely?
most likely = incontinence
least likely = dementia
What is non-communicating hydrocephalus?
- CSF flow obstructed at some point along CSF circulation within the ventricular system
- ex. stenosis of aqueduct of sylvius
- can be gradual symptom onset [if from mass] or rapid [if from acute obstruction]
What are some possible causes of non-communicating hydrocephalus
- aqueductal stenosis
- tumors
- cysts
- infection
- hemorrhage/hematoma
- congenital malformation
What is an ependymoma?
- tumor of ependyma that lines ventricles
Where are most epenymomas found? In who?
- most commonly in 4th ventricle, posterior fossa
- in children younger than 5 years
- can lead to hydrocephalus
- poor prognosis
What are signs of ependymom in supratentorial region?
- hydrocephalus, seizure
What are signs of ependymoma in infratentorial region?
- N/V
- headache
- hydrocephalus
What are histologic characteristics of ependymomas?
- true rosettes [clustered tumors composed of polygonal or columnar cells facing a lumen]
- perivascular rosettes [clusters of tumor cells in a small blood vessel
- rod-shaped blepharoplasts [basal ciliary bodies] found near nucleus
What causes congenital hydrocephalus?
- genetic
- intrauterine infection
- secondary to immaturity/birth trauma
What causes aqueductal stenosis?
- tumor in midbrain that compresses brain and occludes cerebral aqueduct
- cellular debris following intraventricular hemorrhage, by infections, by ependymal proliferation due to viral infection of CNS [mumps]
What is a major sequela of aqueductal blocaked?
- enlargement of 3rd and both lateral ventricles [triventricular hydrocephalus]
What is effect of colloid cyst obstructing one of the interventricular foramen?
- enlargement of lateral venticle on that side
What is treatmetn for acute hydrocephalus?
- whether communicating or not –> urgent placement of external ventricular drain [EVD] that drains CSF
What is psuedotumor cerebri?
- idiopathic intracranial hypertension
- seen in obese women of child-bearing age and people with chornic renal failure
What are some causes of pseudotumor cerebri?
- vitamin A toxicity
- endocrinopathies
- tetracycline [TCN]
What happens in pseudotumor cerebri?
- increase in ICP (>25 cm H2O)
- little evidence of pressure increase on CT or MRI
- have headache and visual defects up to blindness
What is treatment for psuedotumor cerebri?
- weight loss
- meidcation
- if needed lumboperitoneal shunting
