B7.057 CNS Vasculature Flashcards
origin of the posterior circulation
vertebral arteries
origin of anterior circulation
internal carotid
what does the posterior circulation perfuse
medulla pons midbrain thalamus occipital lobe and ventromedial temporal lobe
what does the anterior circulation perfuse
remaining cerebral cortex
basal ganglia
hypothalamus
why is the orientation of the circle of willis important
dual blood supply ensures less chance of interruption due to occlusion
describe the structure of the circle of willis
posterior portion arises from basilar artery and branches into superior cerebellar, posterior cerebral and posterior communicating arteries
posterior communicating loops backward and meets with the internal carotid, anterior choroidal and MCA comes off of this meeting
ACA extends the opposite direction from MCA and the two branches are eventually joined by the anterior communicating artery before they course into the frontal lobe
interruption of the posterior circulation
damages the brainstem
- body symptoms contralateral
- head symptoms ipsilateral
where are sensory and motor structures for the body located in the brainstem
medial (except ALS)
contralateral
where are sensory and motor structures for the head located in the brainstem
motor- medial
sensory- lateral (in general more lateral than body tracts)
ipsilateral
blood supply to medulla
medial = anterior spinal lateral = PICA
medial medullary structures
DCML
corticospinal
hypoglossal
~climbing fibers to cerebellum (inferior nucleus)
lateral medullary structures
ALS nucleus ambiguous dorsal nucleus X solitary nucleus descending tract of CN V vestibular nuclei
blood supply to pons
medial = penetrators from basilar lateral = AICA and circumferential basilar
medial pontine structures
DCML
corticospinal
abducens
MLF
lateral pontine structures
ALS
proper nucleus CN V
facial nerve VII
vestibular nuclei VIII
blood supply to midbrain
medial = top of basilar lateral = paramedian penetrators, proximal PCA
medial midbrain structures
oculomotor nucleus
some DCML
some corticospinal
some red nucleus
lateral midbrain structures
some DCML
some corticospinal
some red nucleus
hallmark of brainstem blood supply deficits
alternating hemiplegia
long tract and CN deficits on opposite sides of body
cortical blood supply
posterior circulation -posterior cerebral anterior circulation -middle cerebral -anterior cerebral
branches of MCA
superior (frontal)
inferior (temporal)
course of the PCA
terminal branches of the basilar artery
perforating branches supply the midbrain and posterior thalamus
cortical branches supply the undersurface of the temporal lobe and occipital and visual cortex
syndromes observed in PCA disruption
midbrain signs
cortical temporal and occipital signs
midbrain PCA lesion
due to disruption of the P1 segment or penetrating branches of the PCA
cortical PCA lesion
due to occlusion of the cortical branches of the P2 segment
P1 (midbrain) syndrome
upper alternating hemiplegia (Weber’s syndrome)
- ipsilateral oculomotor ophthalmoplegia
- contralateral hemiplegia
P1 (thalamic) syndrome
thalamogeniculate branch
contralateral hemisensory loss (all info from face and body travels through thalamus)
burning pain in affected areas
hemiparesis, hemiballismus, choreoathetosis (due to connections with cerebellum)
intention tremor
ataxia
P2 (cortex) syndrome
infarction of the medial temporal and occipital lobes
- contralateral homonymous hemianopia with macular sparing
- less extensive lesions may cause higher order visual deficits
P2 (hippocampus) syndrome
medial temporal lobe and hippocampal lesion
- acute disturbance in memory
- would need to be bilateral
MCA divisions
superior
-spreads out over lateral frontal and parietal cortices above lateral sulcus
inferior
-lateral surface of temporal lobe below lateral sulcus
MCA prior to divisions
lenticulostriate branches supply the basal ganglia and internal capsule
MCA superior division stroke
contralateral hemiparesis of face, hand, arm with sparing of leg and foot (bc these are central)
contralateral hemisensory deficit with same distribution
ipsilateral deviation of head/eyes (FEF)
with dominant hemisphere lesion motor (expressive) aphasia is due to damage of broca’s area
FEF lesion
the L FEF serves to move eyes to the R
SO if L FEF is damaged, there is a gaze preference to the L
MCA inferior division stroke
less common
dominant hemisphere leads to Wernicke’s aphasia
nondominant hemisphere may lead to a L visual neglect and an agitated and confused state
superior quadrantanopsia or homonymous hemianopsia depending on extent of infaraction (due to damage of optic radiations)
what is the internal capsule
sheets of fibers flowing to/from cortex
V shaped white matter tract
posterior limb of internal capsule
lateral to thalamus
corticospinal motor fibers
corticopontine fibers (cerebellar movement control loop)
reciprocal thalamocortical sensory connections (somatic sensation)
thalamus axons in internal capsule
travel through posterior limb
genu
point in the V shape of the internal capsule
corticobulbar fibers
corona radiata
fibers that exit the internal capsule and travel to the cortex
blood supply to the internal capsule
MCA lenticulostriate arteries
anterior limb of internal capsule
separates caudate from putamen/ globus pallidus
frontopontine fibers
anterior thalamic nuclei, including reciprocal connections between VA and motor areas
lenticulostriate arteries
penetrating branches of M1 segment of MCA
supply basal ganglia structures: head and body of caudate, globus pallidus, putamen, internal capsule
occlusion of lenticulostriate
contralateral hemiparesis and sensory deficit due to damage of corticospinal fibers and thalamosensory fibers to sensory cortex that run in the posterior limb of internal capsule
contralateral ataxia due to damage of frontopontine fibers in anterior limb
contralateral lower face hemiparesis due to damage of corticobulbar fibers in the genu
bilateral occlusion of the ACA
results in infarction of the anteromedial surface of the cerebral hemispheres
- paraplegia affecting the lower extremities and sparing hands/face
- frontal lobe syndrome (no decision making)
- urinary incontinence
unilateral occlusion of ACA
distal to anterior communicating
-contralateral sensorimotor deficits mainly involving lower extremities
occlusion of ACA proximal to anterior communicating artery
well tolerated because of cross flow
