Blood Supply, Hemorrhage, And Herniation Flashcards
What is the circle of willis?
Ring of 9 arteries supplying blood to the cerebral hemispheres
What is the circle of willis composed of?
6 large arteries anastomoses via 3 small communicating as.
Communicating (ant.) -1 Anterior cerebral a. -2 Internal carotid -2 Communicating (posterior) -2 Posterior cerebral a. -2
what comes off of basilar a?
S.P.A.
Superior cerebellar a.
Pontine as.
Anterior cerebellar a.
What makes the basilar a.?
United vertebral arteries
What comes off the vertebral as?
Posterior inferior cerebellar a. (PICA)
1 anterior spinal a.
2 posterior spinal a.
What comes off the ICA?
Are they part of circle of willis?
Anterior cerebral a. - yes
Middle cerebral a. - no
Ophthalmic a. - no
Anterior choroidal as. - no
What supplies the superior, middle and inferior cerebellar peduncles?
Superior — Superior cerebellar a.
Middle — anterior inferior cerebellar a. (And some superior cerebellar a.)
Inferior — posterior inferior cerebellar a. (From Vert. A.)
What vasculature is CN 2 close to?
ICA
Ant. Comm. a.
Ant. Cerebral a.
What happens if there is an aneurysm in ICA, Ant. Comm. a. Or ACA?
Compression of CN2 - visual deficits
What vasculature is CN 3 close to?
What happens to compress CN 3? Result?
B/w Posterior cerebral a. & Superior cerebellar a.
(Post communicating also close)
Aneurysm can compress- Oculomotor pasly (down and out)
What vasculature is CN 6 close to?
What can cause compression of CN 6? Result?
B/w labyrinthine and AICA
Aneurysms - Abducens nerve palsy
What vasculature is CN 5 close to?
What can cause irritation of CN5? result?
Superior cerebellar a.
Aberrant loops can cause trigeminal neuralgia or Tic Douloureux
What vasculature is CN 7 close to?
What can cause irritation of CN 7? Result?
Close to AICA
Aberrant loops - CN 7 palsy with all effects from origin
What are the four parts of the internal carotid a.?
Cervical part
Petrous part
Cavernous part
Cerebral part
What does the cervical part of the ICA do?
Anterior circulation
When does the cervical part bifurcate?
What does it travel thru?
Carotid canal
Anterior to Transverse processes of upper 3 vertebrae
Where is the petrous part of the ICA?
Where does it course?
Carotid canal in petrous part of temporal bone
Upward and medially above foramen lacerum
Where is the cavernous part of the ICA located?
What surrounds it?
In cavernous sinus
Sympathetic plexus surround it - CN 3, 4, 5, 6 (6 is the closest)
What does the vertebral a. Do?
Posterior circulation
What are the 3 parts of the vertebral a. ?
Cervical part
Atlantic part
Intracranial part
Where is the cervical parts of Vertebral As. Found?
In the transverse foramina of the 1st six cervical vertebrae
Where do you find the Atlantic part of the vertebral a. ?
What does it go thru?
Laying on C1 making an Acute angle
Thru perforated dura and arachnoid thru foramen magnum
Where is the intracranial part of the vertebral a. Found?
In cranium
What does the intracranial parts of the vertebral As. Do?
Unites at caudal border of pons to form basilar a.
When does vertebral basilar insufficiency occur?
Occurs when there is reduced blood flow from Vertebral A. To brain
What can cause Vertebral Basilar insufficiency?
- Hyperextension of head
(compressing vertebral A. B/w C1 and occipital bone at that angle) - Extreme head rotation “Bow-hunter’s syndrome”
(Causes torsion of Vert. A. And narrows it)
What is subclavian steal syndrome?
Subclavian a. Steals blood from vertebral as.
Blood will go up and down to other subclavian a.
When does Subclavian steal syndrome occur?
If there is an occlusion of the subclavian a. PROXIMAL to where the vertebral arteries come off
What does the ACA supply?
Most medial and superior surface of frontal and temporal lobes
How many segments does the ACA have?
5
What is A1 called?
Where is it from?
Precommunicating
ICA to ant. Communicating
What is A2 called?
Where is it from?
Infracallosal segment
Ant. Comm. a. To where rostrum and genus of corpus callosum meet
What is A3 called?
Where is it from?
Precallosal
Attaches around Genu of corpus callosum - ends when vessels turn caudal
What is A4 called?
Where is it from?
Supracallosal
Superior to corpus callosum
What is A5 called?
Where is it from?
Postcallosal
Caudal to corpus callosum
Where is the peri colossal a.?
Up against the corpus callosum
Where is the callosomarginal a.?
Around cingulate gyri
What does the MCA supply?
Lateral surface of frontal and parietal lobes
Superior part of temporal lobe
How many segments of the MCA are there?
4
What is M1 called?
Where is it from?
Sphenoidal (horiz.) segment
ICA to bifurcation at insula
What comes off of M1? What do they supply?
Lenticulostriate arteries
Supply internal capsule
What is M2 called?
Where is it from?
Insular segment
Bifurcation at insula to circular sulcus of insula (makes a right turn)
What is M3 called?
Where is it from?
Opercular segment
Circular sulcus of insula to external surface of lateral fissure
What is M4 called?
Where is it?
Cortical segment
Out on cerebral cortex
What does PCA supply?
Occipital lobe and inferior temporal lobe
Where is P1 from and to?
Basilar bifurcation to PCA
Where is P2 from and to?
PCA to around midbrain
What is P3 called?
Where is P3 from and to?
Quadrigeminal segment
Segment w/in quadrigeminal cistern
Where is P4 from and to?
Cortical segment
Out on cerebral cortex
What are the border zones?
Areas between cerebral arteries that are susceptible to damage under conditions of sudden systemic hypotension or hypoperfusion
What happens if there is damage in the border zone between:
ACA and MCA?
Motor/sensory deficits
Language issues
Behavioral problems
What happens if there is damage in the border zone between:
MCA and PCA?
Vision and language deficits
What is the blood supply to the medulla?
Vetebral a.
2 posterior spinal a.
1 anterior spinal a.
Posterior inferior cerebellar a.
(Plus paramedian branches of caudal portions of basilar a.)
What do the posterior spinal As. Supply?
Spinal cord
Dorsal aspect of medulla
What does PICA supply?
Lateral aspect of medulla
What does AICA supply?
Medulla
***Cochlear nuclei for CN 8
What does the Anterior Spinal a. Supply?
Medial aspect of the medulla
What is the blood supply to the pons?
All basilar branches
Paramedian branches Lon circumferential Short circumferential Branches of AICA Branches of Superior Cerebellar a.
What is the blood supply to the midbrain?
P1’s anteriomedial branches of basilar bifurcation
P3 - anterolateral branches of P3 and posteiror medial choroidal as. (At level of superior colliculus)
P3 and superior cerebellar as. - at level of inferior colliculus
quadrigeminal branches of P3 and Posterior medial choroidal As. At level of superior colliculus
Thalamogeniculate as.
What are some major arteries to the forebrain?
Thalamogeniculate branches of PCA
Anterior choroidal a.
Lenticulostriate as.
In the medulla:
What is supplied by Anterior spinal a.?
Hypoglossal nucleus
Medial lemniscus (sensory tract)
Pyramid (motor tract)
In the medulla, what is supplied by the posterior inferior cerebellar a.?
Nucleus ambiguus ALS Rubrospinal tract Spinal trigeminal nucleus Spinal trigeminal tract Solitary nucleus and tract Accessory cuneate nucleus Inferior vestibular nucleus Medial vestibular nucleus Dorsal motor nucleus of vagus
In the pons what is supplied by
Paramedian branches of basilar a.?
Abducens nucleus Medial longitudinal fasciculus Abducens n. Medial lemniscus Corticospinal fibers
In the pons, what is supplied by the
Long circumferential branches of the basilar a.
Facial n. Mesencephalic nucleus and tract Spinal trigeminal tract and nucleus Facial motor nucleus ALS
In the midbrain, what is supplied by P1 segment of PCA?
CN 3 nucleus and nerve
Medial longitudinal fasciculus
Red nucleus
Substantia nigra
What are the spinal cord arteries?
(1) Anterior spinal a.
(2) Posterior spinal a.
Ant. spinal medullary Post. Spinal medullary Post. Radicular a. (To post. Root) Ant. Radicular a. (To ant. Root) Arterial vasocorona Segmental a.
What comes off the anterior spinal a. And what does it supply?
Sulcal artery
Dorsal/ventral horns
What is supplies the corticospinal tract?
Anterior spinal a.
Posterior spinal as.
What space is the circle of willis in?
Subarachnoid space
Epidural hematoma:
Bleeds into? Common site? Source? Clinical? Ct shape?
- potential space b/w skull and dura mater
- fx of squamous temporal bone or pterion
- middle meningeal a.
- lucid period of hours to 1-2 days
- lens
Subdural hematoma:
Bleeds into? When? Common site? Source? Clinical? Ct shape?
- Subdural space
- when head strikes fixed object or after lumbar punctures
- venous- usually cortical veins opening into superior sagittal sinus (bridging veins)
- slower accumulation of blood due to pressure and often self limiting
- crescent
Subarachnoid hemorrhage:
Bleeds into? Occurs when? Source? Clinical? Ct shape?
- subarachnoid space
- rupture of aneurysm or severe head injury
- arterial bleeding from cerebral As.(circle of willis)
- massive bleeding into CSF compartment;
- ”worst headache of my life”*; detoriorating level of consciousness; seen in older people or those postmenopausal
-spiderweb
Intracerebral (subpial) hemorrage:
Bleeds into?
Source?
Clinical?
- bleeding w/in brain substance (stroke)
- middle cerebral a.
-complication in 2-3% of all head injuries; common w/ hypertension or degenerative arterial disease; increase risk w/ smoking or genetic FHx
Commonly seen at autopsy
What are the causes of herniations?
Hemorrhage Mass/tumor Trauma Abscess Infection Metabolic conditions
Where is the supratentorial compartment?
Above tentorium
Falx cerebri divides it left and right
Where is the infratentorial compartment?
Below tentorium cerebelli
What is the tentorial notch?
Continuation of Supra and infratentorial compartment
What is a subfalcine herniation?
Herniation in supratentorial compartment that displaces brain tissue under falx cerebri
What does a subfalcine herniation compress?
Compress ACA
Affects the frontal and parietal lobes and lower limbs (via homunculus)
What can a subfalcine herniation evolve into?
Transtentorial herniation
What is a transtentorial herniation?
Brain is displace downward toward tentorial notch
Aka a central herniation
What can a transtentorial herniation compromise?
Causes?
Upper brainstem
CN 3
Some lower structure (basilar artery and posterior cerebral a.)
Decorticating rigidity
Decerebrate rigidity
Where is the uncus located?
Most anterior part of parahippocampal gyrus next to temporal lobe
What is an uncal herniation?
Uncus and parts of parahippocampal gyrus extrude over edge of tentorium cerebelli and thru tentorial notch
What will an uncal herniation impinge on and cause?
Impinges on midbrain
Damage cerebral peduncle and motor tracts going thru that
CN 3 palsy -ipsilaterally
motor deficits - contralaterally
What is the Kernoham phenomena?
Uncal herniation that shifts the midbrain left to right
-compressed cerebral peduncle on the opposite side
CN 3 palsy ipsilaterally
Motor deficits IPSIlaterally
What is a tonsillar herniation?
Cerebellar tonsils go thru foramen magnum
What can a tonsillar herniation compress?
What can this cause?
Medulla and upper cervical spinal cord
Since the cardiac and respiratory centers are in the medulla, it can cause no heart beat =death
Where else will you see a tonsillar herniation?
Chiari Type II
