Term
| What is the functional importance of Cerebral blood flow? |
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Definition
In resting state, brain receives 15% cardiac output and consumes 20% available oxygen. Without oxygen for a few minutes, cells DIE.
1) Providing oxygen and removing carbon dioxide and brain metabolites
2) Supplying glucose (!!) |
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Term
| What is the effect of local CO2 concentration of CBF? |
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Definition
LOCAL changes
1) Increases in CO2 lead to vasodilation and increased CBF
2) Decreases in CO2 lead to vasoconstriction and decreased CBF |
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Term
| What are the common Cerebrovascular Pathologies? |
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Definition
1) Ischemic stroke (clot or embolic blockage of vessel)
2) Hemorrhagic stroke (breaking of a vessel with extravasation of blood into CNS)
3) Aneurysm (90% benign)
4) Arteriosclerosis (lipid deposits and calcification is medium and large vessels) often causing Senility |
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Term
| Which factors need to be balanced by the BBB capillaries to maintain proper relations between the blood and brain? |
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Definition
1) Rapid oxygen and nutrient supply to neurons
2) Osmotic and ionic balance in brain
3) Pathogen protection |
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Term
| What unique structural features imbue the BBB with its functionality? |
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Definition
1) Brain capillaries lack fenestrations and form continuos sheets with tight junctions (under basement membrane).
**Only fenestrated capillaries are those that supply Circumventricular organs**
2) The end-feet of astrocytes wrap around capillaries, covering 90% of surface (not strictly a part of BBB, but involved in its maintenance) |
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Term
What are the Circumventricular Organs?
What is their blood supply? |
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Definition
1) Neurohypophysis (Posterior pituitary): release vasopressin, oxytocin and other hormones
2) Area postrema (vomiting center): chemoreceptors which trigger vomiting via vagal efferents in response to emetics.
3) Organum vasculosum: Release LHRH and somatostatin
-Located along midline of brain as interruptions of BBB, detecting hormone levels in the blood and releasing substances directly into the blood stream.
- Supplied by fenestrated capillaries without tight junctions |
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Term
| What abnormalities are associated with the BBB? |
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Definition
1) Tumors, ischemia, meningitis, hemorrhage all cause endothelial cells to become permeable to serum proteins, ions and fluids
- Causes VASOGENIC EDEMA (increased fluid in white matter and increased ICP
** CONTROL BP fast!** |
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Term
| What regions are supplied by the Middle Cerebral Artery? |
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Definition
Direct continuation of internal carotid, passing through Sylvian fissure and supplying 1) lateral 2/3 of cortex and 2) subcortex.
1) Lateral 2/3 of cortex (frontal, parietal, and temporal lobes and insular cortex)
2a) Lateral Striate (lenticulostriate) Artery supplies putamen anad caudate nucleus and adjacent regions of anterior limb genu and posterior limb of internal capsule
2b) Anterior Choroidal: choroid plexus of temporal horn of lateral ventricles, amygdala, hippocampus, tail of caudate nucleus, ventral regions of the genu, posterior and inferior limb of internal capsule, optic tract, and portions of globus palladus |
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Term
| What regions are supplied by the Anterior Cerebral artery? |
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Definition
Supplies medial 1) 2/3 cortex and 2) subcortex
1) Medial 2/3 of cortex supplied by orbitofrontal, frontopolar, callosomarginal and pericallosal arteries
2a) Medial striate (Recurrent a. of Heubner): anterior caudate and putamen, and anterior internal capsule
2b) Midline perforating arteries: optic chiasm and adjacent optic tract, and supraoptic area of hypothalamus. |
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Term
| What regions are supplied by the Posterior Cerebral Artery? |
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Definition
Part of Vertebral-basilar system (off of basilar artery) supplying 1) Cortical and 2) Subcortical structures
1) Branches supply ventral temporal lobe, all of occipital lobe and medial regions of posterior parietal lobe.
2a) Posterior choroidal: choroid plexuses of third and lateral ventricles and body and crura of fornix
2b) Posteromedial and -lateral branches: anterior, medial and posterior thalamus, tectum, tegmentum, cerebral peduncles and posterior limb of internal capsule
** (posterior communicating artery supplies mammilary bodies, posterior hypothalamus and subthalamus) |
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Term
| What regions are supplied by the posterior communicating artery (PCA)? |
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Definition
| PCA runs between middle and posterior cerebral arteries and supplies the mammilary bodies, posterior hypothalamus and subthalamus (Mesencephalic structures). |
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Term
| What are Arterial Border Zones (Watersheds) and what is their clinical importance? |
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Definition
Anastomotic networks (leptomeningeal anastomoses) between distal arteries of major arterial systems.
- If one system if occluded, the other can fill in (border zones are most susceptible to ischemic damage) |
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Term
| What is the Circle of SWillis and what is its clinical importance? |
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Definition
Anastomotic ring encircling optic chiasm and hypothalamus formed by anterior and posterior communicating arteries and the proximal portions of the anterior, middle and posterior cerebral arteries
**Equalize blood flow** |
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Term
| What is supplied by the Vertebral-Basilar System? |
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Definition
1) Medulla, Pons, Caudal Mesencephalon (3 cerebellar arteries, anterior spinal, collaterals of vertebral, posterior spinal and pontine arteries
2) Cerebellum (PICA, AICA and Superior Cerebellar) |
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Term
| What are the arterial supplies of the Cerebellum? |
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Definition
Portion of the Vertebral-Basilar System
PICA (Vertebral a.)
AICA and Superior Cerebral (Basilar a.)
1) Posterior inferior cerebellar (PICA): arises from vertebral a. and supplies posterior and inferior regions of cerebellar hemispheres, vermis and inferior cerebellar peduncle, and choroid plexus of 4th ventricle
2) AICA: Arises from basilar artery and supplies lateral and inferior cerebellar hemispheres, flocculus and middle cerebellar peduncle.
3) Superior Cerebellar: Arises from Basilar artery and supplies superior surfaces of cerebellar hemispheres, deep cerebellar nuclei and superior cerebellar peduncle. |
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Term
| What is the arterial supply of the Brainstem (Pons, Medulla and Caudal mesencephalon)? |
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Definition
7 Arteries! (3Cs, Ant and Post spinals, Vert. collaterals and Pontines)
1) 3 cerebellar arterial collaterals to medulla and pons (lateral and posterior regions at successively higher levels)
2) Anterior Spinal: anterior and midline regions up through open medulla (corticospinal tracts, medial lemniscus and hypoglossal nucleus)
3) Vertebral collaterals
4) Posterior spinal (lateral vestibular nuclei and portions of nucleus soltiarius)
5) Pontines: circumferential arteries from basilar artery supplying anterior and lateral regions of the pons, including corticospinal tracts, medial lemniscus, abducens nucleus and facial nerve. |
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Term
| How does Lateral Medullary Syndrome (Wallenberg's) arise and present? |
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Definition
Occlusion of PICA (posterolateral medulla) causing
1) Dysarthria and dysphagia (nucleus ambiguous)
2) Pain and temperature loss to ipsilateral face due to spinal trigeminal and tract
3) Pain and temperature loss to contralateral body due to spinothalamic tract involvement
4) Ipsilateral Horner's (ptosis, myosis and anhydrosis) from loss of descending sympathetic fibers
5) Ipsilateral ataxia due to damage to inferior cerebellar peduncle
5) Vertigo, due to vestibular nucleus damage. |
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Term
| How does Medial Medullary Syndrome arise and present? |
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Definition
Occlusion of anterior spinal artery off of the vertebral arterties (at level of medulla)
Contralateral hemiparesis (pyramidal tract) and tactile deficits (medial lemniscus), and ipsilateral tongue deflection (hypoglossal nucleus).
1) Contralateral hemiparesis due to pyramidal (corticospinal) tract damage
2) Impaired tactile discrimination contralaterally due to medial lemniscus
3) Ipsilateral tongue paralysis with deviation toward side of lesion due to CNXII |
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Term
| How does Paramedian Pontine Syndrome arise and present? |
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Definition
Damage to Paramedian branches of basilar artery (pons)
1) Ipsilateral sixth nerve palsy from VI
2) Ipsilateral facial weakness due to VII
3) Contralateral hemiparesis from corticospinal tract
4) Tactile discrimination from medial lemniscus
5) Horner's syndrome from descending sympathetic fibers (maybe) |
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Term
| A patient is having difficulty producing speech and is experiencing right hemiparesis. What arterial infarction could be causing this? |
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Definition
The left MCA supplies lateral 2/3 of cortex and sub-cortex (caudate and putamen, and superior internal capsule), which includes Broca's area, which is found in inferior frontal gyrus.
As far as the hemiparesis, the internal capsule is an important part of the corticospinal tract, which processes information from primary motor cortex before it crosses at the pyramidal decussation of the caudal medulla (it would be destined for right body in this case). |
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Term
You notice a patient is having difficulty regulating body temperature and appetite and suspect an issue with his hypothalamus.
Infarction of what arteries could cause this? |
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Definition
| PCA (between Posterior cerebral and middle cerebral arteries) supply the mammary bodies of hypothalamus, the hypothalamus and the subthalamus |
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Term
A patient presents with non-communicating hydrocephalus and you suspect it is arising from overproduction of CSF in the roof of the 4th ventricle.
What artery supplies the structure that is producing this CSF? What else does this artery supply? |
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Definition
The choroid plexus of the 4th ventricle is supplied by PICA (arising from vertebral arteries).
PICA also supplies the inferior cerebellar peduncle, the nucleus ambiguus, the solitary nucleus, the spinothalamic tract, the spinal nucleus of V, the descending sympathetics from the hypothalamus to the cervical chain ganglia and vestibular nuclei (remember Wallenberg) |
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Term
A patient is experiencing difficulties with balance and you suspect there is an issue with cortical inputs to the cerebellum.
What artery supplies the cerebellar input from the cortex? What else does this artery supply? |
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Definition
This is the middle cerrebellar peduncle, and it is supplied by AICA (off of basilar artery)
AICA also supplies lateral and inferior cerebellar hemispheres. |
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Term
A patient presents with weakness of his left lower body.
His right eye is pointed in and downwards and he is complaining of facial weakness of the right side of his face. Additionally, he is having difficulty feeling tactile stimulation on his left side.
What is going on? |
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Definition
CN VI and VII on his right side are involved (ipsilateral lateral rectus muscle and facial muscle weakness)
The hemiparesis suggests corticospinal involvement and the tactile deficit suggests medial lemniscus involvement.
It sounds like Paramedian Pontine Syndrome and you should do an angiogram to look for infarction in paramedian branches of the basilar artery. |
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