Transcript Frontal/parietal - nondominant hemisphere

Carotid Circulation
Major regions supplied
Optic nerves and retina
Cortex and deep white matter
• Frontal and parietal lobes
ventricle
• Lateral parts of the temporal and occipital lobes
Lumen
Corpus callosum - except splenium (posterior)
Most of the basal ganglia (including amygdala)
Internal capsule
ACA
Key functional areas supplied
Septal area
Primary motor cortex
• Leg and foot areas
• Area controlling urinary bladder
ventricle
Lumen
Motor planning areas in medial frontal lobe,
anterior to the precentral gyrus
Primary somatosensory cortex for leg and foot
Most of corpus callosum except splenium
MCA-superior branches
Key functional areas supplied
Primary motor cortex - face / arm areas
Pyramidal tract axons from all of the primary
motor cortex
ventricle
Primary somatosensory cortex - face
/ arm areas
Frontal eye fields
Lumen
Frontal/parietal - language-dominant hemisphere
• Broca’s and other areas for language expression
Frontal/parietal - nondominant hemisphere
• areas for 3-D visuospatial concepts of self and world
• areas for expressing emotions
MCA-inferior branches
Key functional areas supplied
Visual radiations
• Fibers representing information from contralateral
superior quadrants
ventricle
Temporal/parietal- language-dominant hemisphere
Lumen
• Wernicke’s and other areas for language comprehension
Posterior parietal - nondominant hemisphere
• areas for 3-D visuospatial perceptions of self and world
• areas for interpreting emotions
Vertebral-Basilar Circulation
Major regions supplied
Upper cervical spinal cord
Brainstem and cerebellum
ventricle
Most of thalamus and hypothalamus
Lumen
Cortex and deep white matter
• Posterior medial parietal lobes
• Medial and infrior temporal and occipital lobes
Splenium of corpus callosum
PCA
Key functional areas supplied
By long penetrating branches
• Thalamus, subthalamic nucleus, hypothalamus
• Midbrain
ventricle
By cortical branches - parietal
and occipital lobes
Lumen
• Visual radiations and primary visual cortex
• Splenium of corpus callosum
By cortical branches - medial temporal lobe
• Hippocampal formation and posterior fornix
Common Anastomoses
Collateral circulation may prevent ischemia
External-internal carotid via ophthalmic branches
Circle of Willis
ventricle
Muscular branches of cervical
arteries-vertebral
Lumen
or external carotid arteries
Short cortical branches of ACA, MCA, PCA
Branches of the major cerebellar arteries
ACA-MCA Border Zone
Key functional areas that may be present
Hip or shoulder (occasionally arm) regions of
primary motor or somatosensory cortex
ventricle
Regions involved in aspects of language
production (in the dominant Lumen
hemisphere)
Frontal Eye Fields
Motor planning areas in frontal lobe
ACA/MCA-PCA Border Zone
Key functional areas that may be present
Visual radiations
Foveal representation in the primary visual cortex
ventricle
Inferior temporal lobe cortex Lumen
for visual recognition
Regions for language comprehension and word
finding (possibly reading) in dominant hemisphere
Regions important for visuospatial perceptions in
parietal lobe of nondominant hemisphere
What is a TIA?
A Transient Ischemic Attack (TIA) is a brief
episode in which neurologic deficits suddenly
occur, but then disappear completely
• Most TIAs last a few minutes to an hour.
ventricle
• No neurologic deficits remain
once a TIA
Lumen
has ended, because little or no brain tissue is
permanently damaged.
• A TIA is an indicator that the stage is set
for an ischemic stroke.
• Treatment of patients with TIAs can significantly
reduce their risk of having a stroke.
TIAs: Carotid Territory
Transient monocular blindness
TMB (also known as amaurosis fugax) occurs
when the retina becomes temporarily ischemic.
• Patients commonly describe a gray or black fog
or a mist clouding vision in all or part of one eye.
• Attacks are typically brief (1-5 minutes), and
afterwards vision is fully restored.
• TMB often signals the presence of severe
ipsilateral carotid artery disease in older adults.
• TMB can also be caused by migraine.
TMB: What’s Mechanism?
Two Ideas:
1. Thrombus from ulcerated atherosclerotic plaque
at the origin of the internal carotid artery enters
ophthalmic artery and plugs retinal vessel.
• A small embolic particle can produce retinal ischemia
or block the central retinal artery.
• If the embolus (often a platelet-fibrin aggregate) falls
apart, blood flow is restored and and vision returns.
2. Low perfusion in the internal carotid artery,
putting distal structures like the retina at risk.
• This mechanism implies presence of severe carotid
stenosis that significantly impairs blood flow.
TIAs: Carotid Territory
Transient hemispheric attacks
Problems typically produced
• One-sided limb weakness, clumsiness or paralysis
• One-sided numbness, paresthesia, or sensory loss
• Difficulty with language production or
comprehension
• Inability to articulate words clearly, often
described as ‘I slurred my words’ (dysarthria)
• Partial or complete homonymous visual field
defects (patients seldom describe these)
Carotid Bifurcation
atherosclerotic plaque and thrombus
Plaque
Thrombus on
plaque surface
Plaque reduces the
diameter of artery
Thrombus on
plaque surface
TIAs: Vertebral-Basilar
Various combinations may be present
Problems typically produced
• Vertigo or dizziness
• Unilateral or bilateral weakness or clumsiness
• Unilateral or bilateral numbness or sensory loss
• Limb ataxia or coarse tremor, staggering gait
• Dysarthria
• Visual field defect, blindness, or diplopia
• Nystagmus (‘it jumps around when I look at it’)
Patients may ignore TIAs!
Because the episode of impaired function is brief,
patients may not tell you about it unless you ask.
Seniors with somewhat impaired memory may
simply not recall such brief events.
•
TIAs in carotid territory predict severe atherosclerosis
in the proximal internal carotid artery.
• Tests can determine actual blood flow in the carotid.
• The odds of stroke in the next 1-2 weeks are great!
• If severe narrowing is present, surgical and medical
treatments can help to reduce stroke risk.