Neurological Disorders: Stroke (Brain Attack)
What is it?
By definition, a stroke or brain attack is an acute or rapidly occurring neurological manifestation caused by a partial or total deficiency of blood supply to a particular region of brain, or caused by a bleeding. If symptoms resolve completely within 24 hours then it is called as a TIA (transient ischemic attack).
Although the similar condition can occur with involvement of the spinal cord as well, it is much less frequent compared to the brain attack. When the term “stroke”is used, generally it only means the brain event, however strictly speaking this term encompasses similar events occurring in the spinal cord as well. It appears that the rarity of spinal cord vascular events may be the reason for associating the term stroke only with the brain event.
What are the types?
Brain attack is called as a vascular-event because the damage occurs secondary to a vascular (blood vessel) problem.
Based on which blood vessel is involved there are two types;
A third type may be considered; capillaries, vascular malformation like AVM (arteriovenous) malformation etc also can precipitate this event (usually hemorrhagic or bleeding).
Arterial type is much more common, and there are mainly two types;
Ischemic brain attack implies the blood supply to the brain is cut off due to a blockage in an artery. In the hemorrhagic type the main culprit is the bleeding in to a discrete location in the brain and resulting brain dysfunction.
The ischemic type is of two types;
The above two mechanisms cause the blockage of an artery.
Generally older people having chronic medical conditions like high blood pressure (HTN), diabetes, high cholesterol etc are susceptible to this type of stroke. In these patients a build up of cholesterol (a type of fat) along with blood cells called platelets takes place along the inner margin of an artery and this is process is called as atherosclerosis.
Atherosclerosis process generally progresses gradually and narrows the arteries more and more until when a critical build up occurs it can result in blockage of circulation causing damage to the organs supplied by that artery. If that happens with the arteries supplying the brain then it results in ischemic events. This is not the only mechanism by which thrombosis of an artery takes place. For example in younger people a trauma to an artery like carotid artery may result in thrombosis and ischemic brain events.
Sometimes these atherosclerotic plaques that build up inside the arteries may break loose and the fragments may travel down the circulation and cause a blockage at a distal site and can cause brain attack. These fragments are called as emboli (singular- embolus) and the phenomenon is called embolism. Such emboli may also originate from the heart chambers, especially in the left upper chamber (left atrium) and enter the arterial circulation, reach the brain, cause blockage and stroke symptoms.
Venous brain attacks:
These are generally the result of clot formation or thrombosis (thrombosis of the vein or venous sinus) or rupture & bleeding of these structures.
Blood supply to the brain
The brain is nourished by four major arteries; a pair of carotid and vertebral arteries (one on each side). Carotid arteries run up in the front aspect and the vertebral arteries on the back aspect of neck. The two vertebral arteries unite to form the basilar artery. All these arteries subsequently form an anastomosis called circle of willis. Various branches arising from the carotid, vertebral, basilar arteries as well as the circle of willis supply the whole brain.
How does patient present?
The manifestation depends on the area or region of the brain involved.
When they are involved then speech deficits (aphasia), limb paralysis, facial paralysis, decreased sensory perceptions are the usual symptoms.
Diencephalon (thalamus, hypothalamus etc):
Involvement of these structures may produce a loss of sensation.
Brain attacks of these regions may produce contra lateral (opposite side) limb tremors, muscle stiffness (rigidity), paucity or poverty of movements etc (the so called parkinsonian features).
Its involvement generally produces limb paralysis and decreased sensation over the limbs with certain motor & sensory manifestation of the face, eyes, oral cavity, throat etc (involvement of cranial nerves) etc.
A brain attack in this area manifests usually with in-coordination of limbs, truncal ataxia, and gait unsteadiness etc.
In general the cerebral hemispheres are supplied by anterior circulation (carotid arteries, except the back part or the occipital lobes) and the brain stem and cerebellum supplied by posterior circulation (vertebro-basilar arteries). Regions like basal ganglia, diencephalon are supplied by both anterior and posterior circulation with varying proportions. The occipital lobes (the posterior part of cerebral hemispheres) are supplied by posterior circulation.
4 or 5 Warning Signs of Stroke
A stroke is an emergency so bring the patient to the nearest health care facility immediately - for the proper diagnosis & treatments.
Ideally try to recognize as many signs (and/or symptoms) of a stroke as possible, the more you can identify the better, so that even rare presentation is not missed by you, but if it is difficult to memorize a huge list then how about able to remember and recognize at least 4 or 5 Warning Signs of Stroke? I have listed them below;
1) Unilateral or one sided weakness
2) Unilateral or one sided numbness or loss of sensation
3) Aphasia (speech difficulties)
4) Visual field defects
5) Unsteady while walking (gait unsteadiness)
So try to think at a doctor level, pick up these signs and quickly bring your beloved family member to the emergency room (ER) in a jiffy. Of course this is not an order to you from us to do it, if you are not sure what is going on with the patient or not sure what to do then do not waste time, just quickly bring the patient to ER.
The following investigations are usually necessary (ordered on case to case basis);
• CT of brain
• MRI of brain with diffusion
• Carotid ultrasound
• ECG (EKG)
• Holeter Monitor
• Blood tests including glucose, cholesterol, triglycerides, ESR, RPR etc.
During acute stroke if patient is seen within 3 to 3.5 hours of the onset of the stroke symptoms, also if patient fulfills all the criteria then clot buster (thrombolytic) treatment like tPA can be given.
For prevention of these brain events antiplatelet agents like aspirin, clopidogrel etc are used.
Heparins (regular or low molecular weight) and/or warfarin may be necessary especially if clot from the heart caused the event. Dabigatran is a recent option.
Physical, occupational, speech therapy etc are employed as necessary.
Weight loss, exercise, controlling the chronic medical condition like high blood pressure, diabetes, cholesterol, triglycerides etc are other important measures.
A Neurologist is frequently involved in the care of these patients.
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