A cerebrovascular accident, or stroke, can be a crippling and occasionally deadly event. Strokes are classified as either hemorrhagic or ischemic, depending on the cause; the effects depend on the area that is supplied by the compromised blood vessel. Ischemic stroke occurs when the lumen of a blood vessel is occluded, usually by a clot; in hemorrhagic stroke, the blood vessel actually ruptures, causing bleeding in the brain. One difference between the two is that hemorrhagic-type strokes may have a sudden onset of nausea, vomiting, loss of consciousness and usually elevated blood pressure. The signs are not uniform, however, and often their presentation can be identical to that of ischemic stroke in the same area of distribution. The effects of stroke can be categorized by blood vessel supply.
Anterior Cerebral Artery
The anterior cerebral arteries (right and left) supply the medial parts (on the "inside" of the brain) of the frontal lobes on both sides. Occlusion in the anterior cerebral artery usually leads to deficits in frontal lobe function. Altered mental status along with impaired judgment is common. Primitive reflexes that vanished in infancy reappear, such as the suck and grasp reflexes. Paralysis and altered sensations in the lower limb on the side opposite the stroke are very common, as is bladder and bowel incontinence. Arm weakness is not as severe as leg weakness in the distribution of anterior cerebral stroke.
Middle Cerebral Artery
The middle cerebral artery supplies the lateral parts of the frontal and parietal lobes (area of supply can be seen as the "outside" of the brain). Sensory and motor disturbances are very prominent in middle cerebral stroke. These occur in limbs on the side opposite the stroke, and arm and face deficits are considerably more severe than lower limb deficits. Blindness in half of the visual field in an eye occurs on the same side as the artery where the stroke occurs. Patients also tend to move their head toward the side of the lesion and can develop agnosia, a lack of ability to recognize previously known objects or persons. Aphasia, which is basically a disorder of language, can also develop. This can result in inability to understand and process communication, or in problems communicating despite adequate understanding.
The Vertebrobasilar System
The vertebrobasilar system is a combination of the vertebral arteries and basilar arteries. Areas supplied include the brainstem, cerebellum, and the pons. Stroke in the vertebrobasilar system results in the widest variety of symptoms, reflecting the different centers in the brain supplied by this arterial system. Loss of consciousness with vomiting is common, reflecting brainstem involvement in the stroke. The posterior cerebral artery is involved in this system, and results of compromise of this artery include loss of vision and thought-processing deficits. "Crossed" deficits can also occur--motor deficits on one side of the body and sensory deficits on the other. Curiously, "neglect," such as visual neglect, is also possible: the patient is not aware of the deficit. Other symptoms include vertigo, dysarthria (problem with the muscles involved in speech), spasticity, deficits in gaze and ocular movement and ataxia (clumsiness).
References
- "Rosen's Emergency Medicine, 7th Edition;" J. Marx, M.D., et al.; 2009
- "Cecil Medicine, 23rd Edition;" L. Goldman, M.D., and D.A. Ausiello; 2007
- "The Lancet Neurology;" Medical Complications After Stroke; S. Kumar et al.; January 2010
