Ventricular and Vascular System Stephens Test #2 Flashcards
Which ventricles are frequently enlarged in hydrocephalus?
Lateral
What foramen would a choroid plexus ependymoma obstruct?
Interventricular foramen of Monroe, which connects the lateral ventricles to the third
What would a midbrain tumor such as an astrocytoma disrupt?
CSF flow from third ventricle through the cerebral aquaduct into the fourth ventricle resulting in hypertrophied lateral ventricles
What is Syringomyelia?
The central canal enlarges and develops its own cavity called syrinx. It causes patients to have bilateral anesthesia of shoulders and upper limbs
Where are choroid plexuses located and what is the significance?
Located on floors of lateral and roof of third and fourth ventricles. They produce CSF
Describe the composition of CSF.
similar to blood ultrafiltrate with higher concentrations of sodium, chloride, and magnesium. Lower concentrations of potassium and calcium and glucose and protein
Presence of greater than ___ RBC’s or lymphocytes is abnormal?
six
What is normal CSF pressure and amounts?
100-200 mm of water and 20-25 ml in ventricles and 140 ml in the system
How does transient hydrocephalus occur with SAH?
The arachnoid villi can become temporarily blocked with a sub arachnoid hemorrhage and cause increase in pressurer
Describe flow of CSF
From ventricular system to subarachnoid space to the venous system via venous lacunae
How does hydrocephaly differ in infants/young children vs adults?
Infants and young children have fontanelles or unfused sutures while adults have fused sutures. The fused sutures do not allow for the head to expand therefore pressure builds intracranially. With infants and young children their heads expand due to the lack of fusion of the sutures.
What is external hydrocephalus?
Excessive accumulation of CSF in subarachnoid space with enlargement of that space by compression of CNS. can be supratentorial, infratentorial or both
What is supratentorial external hydrocephalus?
most commonly associated with senile atrophy of the cortex as seen with alzheimers
What is infratentorial external hydrocephalus?
seen in combo with communicating hydrocephalus
What is internal/noncommunicating hydrocephalus?
CSF doesn’t drain into subarachnoid space due to obstruction of intraventricular foramen, cerebral aqueduct, and medial and lateral foramina. Results in dilation of ventricles proximal to obstruction with.
What is communicating hydrocephalus?
Combo of infratentorial external and internal hydrocephalus. Due to adhesions and fibrosis in the subarachnoid spaces, cerebral edema or uncal herniation the space btw tentorial notch and midbrain can be obstructed. CSF can freely move through ventricular system, but cannot circulate over cerebrum to be reabsorbed at arachnoid villi next to and in the superior sagittal sinus
What supplies most of the blood to the brain?
ICA and then vertebral
How long does it take for a person to become unconscious if blood flow is interupted?
5-20 seconds
What happens if blood flow is interrupted for 4-8 minutes?
irreversible brain damage
Regional or focal ischemia is seen in ____ when theres an occlusion of a large nutrient artery
athero-cerebral infarction (stroke)
What is focal ischemia?
neuronal injury or necrosis to central core territory of arterial supply and varying degrees of dysfunction to potential viable tissue in surrounding marginal territory (ischemic penumbra)
What areas of the brain are damaged in an ischemic injury? (Dr. Stephens highlighted and underlined “remember” this fact)
Distal branches of cerebral arteries and particular neuronal populations such as pyramidial cells of hippocampus, especially CA1 or Sommer’s sector are damaged.
Which type of stroke is more common hemorrhagic or ischemic?
Ischemic 85%
Which two arteries pierce the dura mater and course in the subarachnoid space?
ICA and vertebral
Where is the BBB absent?
Pineal body area postrema and median eminence of hypothalamus
What are the branches of the ICA?
Opthalmic PCoA AChA
Describe the PCoA.
Located btw ICA and posterior cerebral arteries. Its ganglionic or penetrating branches suppply internal capsule and the basal ganglia
What does the cisternal segment of the anterior choroidal artery supply?
internal capsule, lateral geniculate nucleus, lateral cerebral peduncle, globus pallidus, caudate nucleus, uncus
What does the intraventricular segment of the anterior choroidal artery supply?
Anterior portion of the choroid plexus
What causes a complete anterior choroidal stroke?
Due to cardioembolic sources and carotid stenosis.
What causes small strokes of the AChA?
T2 DM Htn and hyperlipidemia
What does an infarction to the AChA territory result in?
AChA syndrome with triad of hemiplegia hemianesthesia and contralateral hemianopia.
The ACA is a terminal branch of the ____. What circulation does it provide?
ICA. This artery has the highest incidence of cerebral aneurysms and provides important collateral circulation btw anterior and posterior circulations
Approximately 25% of cerebral aneurysms occur in this artery. This artery connects the two anterior cerebral arteries and it can be absent. What is it?
Anterior communicating artery ACoA
This artery supplies the anterior 2/3 of the medial side and supero-lateral portion of the hemisphere. Occlusions of this artery can result in contralateral paresis or paraesthesia of leg and foot. What is it?
Cortical branches of the ACA
In the ACA, what happens when A2 is occluded?
Occlusion of this segment or distal to it can cause deficits with the affected cortical area ACA syndrome
What happens in the ACA with an occlusion to the A1 segment?
doesn’t produce symptoms bc of the collateral circulation
Where does MCA come from, what % of aneurysms occur there, what are its branches and what do they supply? Which artery from the lateral striate artery branch is prone to rupture?
- ICA
- 25%
- Penetrating branches called the medial and lateral striate or the thalamostriate arteries also Cortical branches
- supply parts of the internal capsule corpus striatum and thalamus
- Artery of cerebral hemorrhange
Describe the cortical branches from the MCA,
- Central artery and Frontal branches come from the cortical branches
- Central artery is in the central sulcus and supplies primary amotor and somesthetic cortices
- Frontal branches supply premotor and prefrontal cortices and brocas area
What would result if thrombosis of the central artery occured?
Contralateral spastic paralysis &/or paraesthesia of face and upper half of the body
What results from thrombosis of the frontal branches of the Cortical artery from the MCA?
The frontal branches supply brocas area as well as premotor and prefrontal cortices. Therefore a thrombosis would result in expressive or Broca’s aphasia where patients cannot initiate speech motor patterns.
What are the four segments to the MCA?
- M1: sphenoidal or horizontal segment originating at the bifurcation of the ICA
- M2: Insular segment terminates at circular sulcus of insula and makes a right angle turn
- M3: Opercular segment
- M4: Cortical segment originates at the surface of sylvian fissure and terminates at cortical territory
What happens if there is obstruction of the angular artery?
- Wernicke’s aphasia, patients are talkative but it doesn’t make sense, they lack content and meaning in their spokekn and written comprehension of language
- Angular artery supplies supramarginal and angular regions
What is central cord syndrome?
Disruption of blood flow to anterior spinal artery so ischemia to the central region. Thrombosis to the anterior spinal artery causes this syndrome.
- Characterized by central necrosis and cavitation of the spinal cord and development of syrinx
Which artery could be compromised secondary to thoracolumbar fracture or surgical repair of abdominal aorta?
Great anterior artery of Adamkiewicz
Thrombosis of the PICA results in?
Lateral Medullary (wallenbergs) Syndrome
What are the four segments of the PCA?
- P1: Pre communicating segment
- P2: post communicating segment
- P3: Quadrigeminal segment
- P4: Cortical segments
