Circle of Willis
Made by Ant. cerebral artery, Middle cerebral artery (internal carotid artery), Post. comm. artery, and Post. cerebral artery, which joins together to form basilar artery
-PCA just anterior to CN3
Middle Cerebral Artery
- blood supply to most of the cerebral hemisphere
- lateral frontal, parietal, temporal lobes
- most of BG
- most of deep white matter (usually including internal capsule)
Anterior Cerebral Artery
- medial frontal and parietal lobes
- wraps around corpus callosum
Posterior Cerebral Artery
- medial temporal and occipital lobes
- most or all of thalamus
Variable arterial supply
deep branches of the ACA, MCA or PCA
-posterior limb of the internal capsule and lateral thalamus
Border zone
AKA watershed zone
- meeting between MCA and other (ACA or PCA) supply territory
- anastomosis
Cerebral arterial imaging
Ultrasound - carotid duplex (fast, safe, variable resolution) Magnetic resonance angiogram -slow, safe, good resolution -magnet contraindications Computed tomographic angiogram (CTA -fast, better resolution -iodinated contrast and radiation Catheter angiogram -best resolution -iodinated contrast, radiation, catheter risks
Cerebral venous sinuses
between dural layers
Syndrome: Retinal artery
internal carotid –> ophthalmic –> retinal
- common
- complete (or entire retina) or branch (infarct)
- monocular visual loss
- altitudinal (shade coming down)
- transient (amaurosis fugax)
- **vision flipped
- -> superior infarct = lower vision field affected
Syndrome: Left MCA
-common
lateral frontal (face & arm) affected
-motor cortex (hemiparesis, dysarthria, dysphagia, apraxia)
-frontal eye field (gaze preference/paresis)
> eyes rest IPSI, paresis is CONTRA
-broca’s area (Broca’s aphasia)
-prefrontal cortex (decreased motivation, attention, exec fx)
lateral parietal (face & arm)
- somatosensory cortex (hemisomatosensory loss, apraxia)
- optic radiation (quadrantanopsia - inf. vision, CONTRA loss)
Lateral temporal
- Wernicke’s area (Wernicke’s aphasia)
- Optic Radiation
Deep white matter
-Long tracts (hemiparesis, hemisomatosensory loss)
Syndrome: Right MCA
lateral frontal same as left MCA, except not aphasia (language is mostly on left side)
Lateral parietal
-add association cortex (hemineglect, anosognosia) to left MCA
Lateral temporal = optic radiation, no Wernicke’s
Syndrome: ACA
UNCOMMON
Medial frontal
-motor cortex (leg weakness, apraxia)
-prefrontal/cingulate cotex (decreased motivation, attention and exec fx)
Medial parietal
-somatosensory cortex (leg somatosensory loss)
Syndrome: PCA
common
Medial occipital
-visual cortex (hemianopsia with macular sparing)
>macula is more central and superficial, so there is enough collateral flow from MCA to keep macula alive
Medial temporal - usually nothing obvious
Thalamus - somatosensory loss
Syndrome: Lacunes
small subcortical cerebral arteries
common
internal capsule = subcortical weakness
thalamus = subcortical somatosensory loss
lacunes are left as arteries deteriorate and are often asymptomatic