3. Blood supply, hemorrhage & herniation Flashcards
What are the parts of the internal carotid A? & what are their characteristics
- Cervical: bifurcation to carotid canal
- Petrous: carotid canal in petrous part of temporal B
- Cavernous: in cavernous sinus, surrounded by sym plexus (CN 3, 4, V1, 6)
- Cerebral part
What are the parts of the Vertebral A & what are the respective characteristics?
- Cervical part: transverse foramina of C1-C6
- Atlantic part: lay on C1 - pass dura/arachnoid & pass thru foramen magnum
- Intracranial part: cranium, unite at caudal border of pons to form basilar A
what is vertebral insufficency & what causes it?
reduced blood flow from vertebral A to brain (2 possible ways)
- extreme hyperextension of head: compress vertebral A btn C1 & occipital bone
- extreme rotation of head (Bow Hunters syndrome): torsion and narrowing of vessel as you turn
when will the subclavian A “steal” blood from the vertebral A
occlusion of subclavian A proximal to vertebal A
= Subclavian Steel Syndrome
instead of blood flowing up after the 2 vertebral As converging, it goes back down to feed into the subclavian A
What are the relationships of CNs & the Circle of Willis?
- CN II - near ICA & Anterior Communication A
- CN III - inbtn Posterior Cerebral A, Superior Cerebellar A & close to Posterior Communicating A
- CN V: sup cerebellar A
- CN VI - near labyrinthine & AICA (Ant Inf. Cerebellar A)
- CN VII: AICA
What are the characterisitics of the Circle of Willis?
= ring of 9 As that supply the cerebral hemisphere ( 6 large As anastomose via 3 small As)
= 2 Ant. Cerebral As, 2 Post. Cerebral A & 2 Internal Carotid As
=via 1 Ant. Communicating A & 2 Post. Communicating As
What does the Anterior Cerebral A (ACA) supply?
most of the medial & superior surface of the frontal & parietal lobes
What does the Middle Cerebral A (MCA) supply?
lateral surface of the frontal & parietal lobes
and superior part of the temporal lobe
Wht does the Posterior Cerebral A (PCA) supply
occipital lobe and inferior temporal
How are cerebral As susceptible to damage?
at border zones: btn As = area where terminal branches reside
damage when –> sudden systemic hypotension or hypoperfusion
anterior border zone - motor/sensory/language/behavior probs
posterior border zone - visual/language probs
*RMR brain has poor anastomoses*
What are the names of the segments of the ACA?
- Precommunicating: ICA to AcomA (anterior communicating A)
- Infracallosal: AcomA to the jxn of rostrum & genu of corpus callosum (below corpus callosum)
- Precallosal: arch around genu
- Supracallosal: superior to corpus callosum
- Postcallosal: caudal to corpus callosum
What are the segments of the MCA?
-
Sphenoidal/horizontal: ICA to bifurcation at insula
- –> Lenticulostriate A comes off of M1
- Insular: in front of insula (circular sulcus of insula)
- Opercular: operculum area (external surface of lateral fissure)
- Cortical: on cortex - thru lateral sulcus
What are the segments of the PCA?
- Basilar bifurcation to PcomA (posterior communicating A)
- PcomA to around midbrain
- Quadrigeminal: w/i quadrigeminal cistern (*location of superior & inferior colliculi*)
- Cortical
What space is btn the cranium and periosteal dura
Epidural (extradural space) = potential!
What space is at the dura-arachnoid interface?
Subdural = potential
What is the “real space” btn the meninges? What does it contain
Subarachnoid space: btn arachnoid & pia
contains CSF, Circle of Willis & Vs
What type of hemorrhage has MCA as the source?
Intracerebral (subpial) hemmorrhage
- 2-3% of all head injuries
clinical: HTN or degenerative arterial disease
What are the causes of Herniation syndromes?
Hemorrhage
Mass/tumor
Trauma
Abscess
Infection
Metabolic conditions
=overall increased ICP
What are the divisions of herniation syndromes?
- Supratentorial compartment: divided into right/left by falx cerebri
- Infratentorial compartment: below tentorium cerebelli
- Tentorial Notch: continuation of supra & infratentorial compartment
(supra / infratentorial compartment seperated by tentorium cerebelli)
What are the characteristics of Subfalcine Herniation
(AKA cingulate/falcine/falx herniation)
= Supratentorial compartment - f_alx cerebri shifted bc of mass & then displace brain tissue underneath_
- May compress ACA (frontal/parietal lobes) => lower limb probs, both motor & sensory
- May turn into transtentorial herniation
What are the characteristics of transtentorial herniation?
(AKA central herniation)
=brain displaced down toward tentorial notch bc increased pressure in supratentorial compartment
-hurts upper brainstem, CN III & maybe lower structures (& maybe basilar A and PCA)
(CN III compromised = parasym fibers not working –> dilated eyes bc cant constirct)
Decorticate/Decerebrate rigidity
What can the Uncal Herniation Impinge?
Impinge midbrain
-uncus & parts of parahippocampal gyrus extend over edge of tentorium cerebelli & thru tentorial notch
Which herniation compressed the medulla and the upper cervical sp. cord?
Tonsillar Herniation
- cerebellar tonsils thru foramen magnum
- medulla contains cardio & resp centers –> damage = dont breath & no heart rate
What comes off of ICA
ACA, MCA & PComA
what comes off MCA
lenticulostriate A & ant. choroidal A
MCA is NOT apart of circle of willis!!!
What comes off of basilar A
AICA,
Labyrinthine A,
Superior Cerebellar A
& PCA
what comes off the vertebal A
- anterior spinal A (supply sp. cord & medulla)
- PICA (give off posterior spinal A & supply sp cord & medulla)
where is CN II located & how can it be injured
close to ICA, ACA & AcomA
-aneurysm of any of these = compression –> visual defects
where is CN III located & how can it be injured
btn PCA & superior cerebellar A
close to PComA
-aneurysm in any of these –> compress –> oculomotor palsy
Where is CN V located & how can it be injured
close to superior cerebellar A
-if aberrant loops –> irritate N –> trigeminal neuralgia
Where is CN VI located and how can it be injured
btn labyrinthine A & AICA
-aneurysm of either of these –> compression–> abducens N palsy
where is CN VII located & how can you injure it
close to AICA
-aberrant loops –> compress –> all facial N defects
what A’s supply the medulla
Ant. spinal A (medial)
Post. spinal A (dorsal)
PICA (lateral)
AICA (cochlear nuclei)
vertebral A & paramedian branches basilar A (upper medulla, medial)
what is supplies the medial medulla
ant. spinal a
= hypoglossal nucleus, medial lemniscus, pyramid
What supplies to lateral medulla
PICA
what As supply the Pons
branches of basilar A
-paramedian branch = medial
long circumferential branch = lateral
what supplies the medial pons?
paramedian branch of the basilar A
what supplies the lateral pons?
long circumferential branches of the basilar A
what As supply the midbrain?
many of the As from PCA
P1 (paramedian branch) = medial
P3 (quadrigeminal branch) = lateral
what supplies the medial midbrain
P1 segment of PCA
What As supply the forebrain? (3 big ones mentioned in class)
- thalamogeniculate branches of PCA ==> lateral/medial geniculate nucleus
- lenticulostriate As & anterior choroidal A ==> internal capsule
what is the blood supply to the spinal cord
- (2) posterior spinal As- dorsal (posterior) columns & corticospinal tract
- Anterior spinal A –> sulcal A - doral/ventral horns & corticospinal tract
In epidural hematomas:
- you are bleeding into ______
- the common site of injury is ______ & the source of bleed is _______
- you feel ___________
- the CT shows _______
- bleeding into epidural space (potential space) btn skull & dura
- common site = pterion &/or squamous part of temporal B & source = middle meningeal A
- you feel poorly/unconscious for a little bit –> then feel better –> then rapid decline
- CT shows lens shape
treat: surgically
Which hematoma is a result of venous bleeds?
Subdural Hematomas
Source: venous blood; cortical Vs like BRIDGING Vs that open up into superior sagittal sinus
- bleed btn dura & arachnoid
- due to head strike, fall, car accident
- causes a slow accumulation of blood b/c of pressure; self limiting (may occur after lumbar puncture)
- CT = crescent
What are the clinical signs & source of bleeding for subarachnoid hemorrhages
clinical signs “worst headache ever” ; deteriorating levels of consciousness (CT = spider like)
source = ARTERIAL blood - circle of willis (commonly with rupture of aneurysm)
what are the two possible ways uncal herniations can be a problem
- damage cerebral pedencle & CN III on same side –> CN III prob same side and motor deficit opp side
- Kernoham phenomenon: herniation shifts midbrain & affects CN III on side of herniation but also cerebral peduncle on OPP side of herniatio –> CN III & motor deficit on SAME SIDE!
What is a Subpail hemorrhage
aka intracerebral/ intraparanchymal/ hemorragic stroke
= bleeding w/i brain tissue (stroke)
Source: MCA
risk factors: HTN, degnerative arterial disease, genetics, smoking
