The consequence of a brief interrupted blood supply to the brain is called a Transient Ischemic Attack. It is also called a warning stroke or a mini stroke.
The brain requires a constant supply of glucose and oxygen which is delivered by the blood. The brain accounts for 1-2 % of the body weight, receives 15% of the cardiac output and accounts for 20% of the total body oxygen consumption. It can be deprived of oxygen by -
• Hypoxia- caused by low partial pressure of oxygen, impairment of the blood’s oxygen carrying capacity or inhibition of oxygen use in the tissue
• Ischemia- Interruption in the blood flow, transient or permanent
Transient ischemic attacks are episodes of stroke symptoms that last very briefly. They last for less than 24 hours, though most of them last less than one hour.
The causes of transient ischemic attack are the causes of stroke too, but they may also herald stroke. Hence, they need to be considered as a medical emergency and addressed urgently.
The disruption to the blood supply to the brain can be because of -
• Thrombosis which is the formation of a clot in the intracranial blood supply.
• Embolus which occurs when the clot dislodges, travels in the vessels and lodges elsewhere compromising the blood supply to that area.
• Hemorrhage or bleeding in the brain.
In a transient ischemic attack, the blocked vessel opens up and blood supply is restored. When blood flow is restored quickly, the patient experiences only transient symptoms.
It is prudent to hospitalise the patient, investigate and start the requisite medication to avoid a full blown stroke.
Treatment depends on the cause, correction of the modifiable risk factors, lifestyle changes and steps to prevent a stroke.
References:1. Smith WS, English JD, Johnston SC. Cerebrovascular Diseases.In Longo DL,Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J editors. Harrison s Principles of Internal Medicine Volume 2, 18th edition The Mc Graw Hill Company 2011:3271
2. Allen C.M.C, Lueck CJ, Dennis M.Neurological Disease. In Colledge NR, Walker BR, Ralston SH editors.Davidson s Principles and Practice of Medicine.21st edition Churchill Livingstone Elsevier 2010.1131
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