Neuroscience Clerkship at UH/VA
 

Large Vessel Stroke in the Anterior Circulation

A stroke may result from occlusion of a vessel in the anterior or posterior circulation of the brain with varying clinical manifestations. This learning objective first defines the arterial vessels that comprise the anterior circulation of the brain. It then reviews the clinical manifestations of stroke resulting from occlusion of each of these vessels. It is important to contrast these clinical manifestations with those involving strokes of the posterior circulation, as the etiology and treatment may differ. For this information, please refer to the next learning objective, large vessel strokes of the posterior circulation.

 

A large vessel stroke of the anterior circulation occurs when either a carotid artery or a large arterial branch of a carotid artery including the middle or anterior cerebral arteries are blocked. The resulting clinical manifestations, depend on the vascular territory supplied by the blocked artery, as well as the degree of collateral vessels helping to perfuse the given area of brain. The carotid arteries stem from the aortic arch. In the neck, they bifurcate into the internal and external carotids. In the brain, at the “Circle of Willis” the internal carotid artery branches into the middle cerebral artery and the anterior cerebral artery. The anterior cerebrals may communicate via the anterior communicating artery. In a small percentage of people, the posterior cerebral artery also stems from the anterior circulation. Remember, that the anterior circulation usually connects to the posterior circulation via the posterior communicating artery. Only about 20% of the population has a complete “Circle of Willis.” Please refer to the diagrams below to review the cerebral blood supply and the cortical areas supplied.


Medial View of the Brain

Lateral View of the Brain


MRA of the Aortic Arch with Contrast Bolus. (1) Aortic arch; (2) Brachiocephalic artery; (3) Right Subclavian artery; (4) Left Subclavian artery; (5) Left Common Carotid artery; (6) Right Common Carotid artery; (7) Left Vertebral artery; (8) Left Common Carotid artery; (9) Left Carotid Bifurcation; (10) Right Vertebral artery; (11) Right Carotid Bifurcation; (12) Right Internal Carotid artery; (13) Left Internal Carotid Artery; (14) Left External Carotid artery; (15) Right External Carotid artery; (16) Basilar artery; (17) Right Internal Carotid artery (intracranial); (18) Left Internal Carotid artery (intracranial); (19) Top of the Basilar artery; (20) Vertebral arteries; (21) Vertebral arteries

MRA of the Neck - Extracranial Large Vessels.  ECA - External Carotid Artery; ICA - Internal Carotid Artery; CCA - Common Carotid Artery; Vert - Vertebral Artery

Magnetic Resonance Angiography (MRA) Intracranial Study. ACA - anterior cerebral artery; MCA - middle cerebral artery; PCA - posterior cerebral artery; SCA - superior cerebellar artery; AICA - anterior inferior cerebellar artery; PICA - posterior inferior cerebellar artery
The next part of this learning objective will review the major clinical manifestations of different types of large vessel anterior circulation including the anterior cerebral, middle cerebral and internal carotid arteries.

 

 

Anterior Cerebral Artery

Stroke

Incidence:


Relatively rare. ACA strokes make up only 0.6-3.0% of acute ischemic strokes if vasospasm, or aneursymal causes are excluded.

Etiologies:

Most often embolic from heart, aorta or the internal carotid artery. Rarely, due to intrinsic atherosclerotic disease of the ACA. 

 

 

 

Note that the lower extremity resides on the homunculus over the medial brain, in the distribution of the ACA.

Major Signs/Symptoms:
 

Contralateral leg weakness / sensory impairment

Akinetic mutism (abulia) – a state of severely limited responsiveness to the environment in the absence of gross alteration of sensorimotor mechanisms.

Disturbance of judgment and/or emotion

Transcortical motor aphasia (with dominant lesions)

Non-dominant limb apraxia (with dominant lesions)

Urinary dysfunction


 

 

Middle Cerebral Artery

Stroke

The MCA is the largest of the intracranial cerebral vessels arising from then internal carotid artery.  The MCA first supplies deep penetrators to the basal ganglia and internal capsule. In the Sylvian Fissure, the MCA typically bifurcates in a Superior and Inferior Division. The Superior Division supplies the lateral Frontal and Parietal lobes, while the Inferior Division supplies the Temporal and Posterior Parietal Lobes. 
Incidence:


Very common, especially strokes in the Superior Division.

Etiologies:

Most often embolic from heart, aorta or the internal carotid artery. Rarely, due to intrinsic atherosclerotic disease of the MCA.

 

 

 

Note that the upper extremity, face and bulbar muscles resides on the homunculus over the lateral brain, in the distribution of the MCA.


 

 

Superior Division

MCA

Major Signs/Symptoms:
 

Contralateral hemiplegia, usually face and arm > leg

Contralateral sensory loss (esp. cortical sensory - two point discrimination, graphesthesia, stererognosia, etc.)

Contralateral homonymous hemianopia (predominantly lower quadrant)

Gaze preference to the ipsilateral side of stroke

Aphasia, expressive (dominant hemisphere)

Neglect syndrome (non-dominant hemisphere)


 

 

Inferior Division

MCA

Major Signs/Symptoms:
 

Contralateral homonymous superior quadrantanopsia

Aphasia, receptive (dominant hemisphere)

Constructional apraxia (non-dominant hemisphere)

Behavioral disturbance (non-dominant hemisphere)


 

 

Proximal Stem of

the MCA

Major Signs/Symptoms:
 

Contralateral hemiplegia, usually face = arm = leg (the leg is involved as the internal capsule is affected as well)

Contralateral sensory loss (esp. cortical sensory - two point discrimination, graphesthesia, stererognosia,etc.)

Contralateral homonymous hemianopia

Gaze preference to the ipsilateral side of stroke

Aphasia, global (dominant hemisphere)

Neglect syndrome (non-dominant hemisphere)

High risk of increased intracranial pressure, herniation and death


 

 

 

 

 

Internal Carotid

Artery Stroke

The clinical manifestations of ICA stroke overlap with those of the ACA and MCA. The deficits seen can vary from minor, if good collateral flow exists, to a massive infarction causing rapid cerebral edema, herniation and death.

 

The only way to differentiate clinically if a stroke is secondary to ICA stroke versus MCA stroke would be a history of amaurosis fugax (transient visual loss in one eye). This occurs due to disruption of blood flow in the ophthalmic artery, a branch of the ICA.


View of the Optic Fundus. Note the cholesterol embolus in one the retinal arteries. In patients with amaurosis fugax (transient monocular blindness), the symptoms may result from hemodynamic hypoperfusion or from emboli, as the case here.


Etiologies:
 

ICA stroke is most commonly due to atherosclerotic disease of the vessel near its origin at the bifurcation of the common carotid artery.

Rarely, a large embolus from the heart or aortic arch can occlude the ICA

In young patients without stroke risk factors, also consider carotid dissection, especially in the setting of trauma, neck pain, or especially if a Horner’s syndrome is present. The latter occurs from disruption of sympathetic fibers that travel in the carotid sheath.

Major Signs/Symptoms:
 

See above lists for ACA and MCA stroke

Rarely, symptoms referable to the Posterior Cerebral Artery (PCA), can occur with carotid disease as 20% of the population has a “fetal origin PCA” where the PCA originates directly from the carotid via a large posterior communicating artery and not from the top of the basilar artery.