August 2014

Transient Ischemic Attacks

Transient Ischemic Attacks --TIA’s

A transient ischemic attack (TIA) is caused by a temporary reduction of oxygenated and glucose rich blood in the brain. Generally most episodes last only few seconds to a few minutes. Basically it has the same identical origins as ischemic stroke.

TIAs are most frequently caused by atherosclerotic cerebrovascular disease. This occurs when cholesterol plaque is deposited inside the major or minor arteries which feed the brain. This plaque forms after the inner lining of an artery has been injured. The plaque causes narrowing of the blood vessels and reduced blood flow, increased the pressure of the blood within the vessel and slows blood flow down. When circulation is slowed, blood platelets tend to clump at the area of injury or blockage. This, along with the deposition of cholesterol causing the atherosclerosis buildup creates a mass which protrudes into the artery hence further slowing down blood flow and eventually either the vessel closes to no longer allow blood flow at all or a blood clot or thrombosis is created. A plaque fragment can break off and be carried by through blood stream to lodge at a distant site in the brain. These are the two main causes of a TIA.

 

Signs and Symptoms

  • Sudden onset of weakness, tingling, or numbness typically involving one side of the body.
  • Vision loss
  • Speech difficulty, vertigo, double vision, imbalance, or lack of coordination of the limbs.
  •  

    What Risk Factors Increase the Chance of a TIA Occurring?

    The major risk factors contributing to TIAs are:

  • High blood pressure
  • Certain types of heart and valvular diseases
  • Smoking
  • Diabetes mellitus
  • Advancing age
  •  

    Making The Diagnosis

  • The most significant symptom of TIA is the speed at which it comes and goes: rapid onset, brief
      
    duration, and then a return to normal is the usual sequence.
  • Recurrence of the same or similar symptoms is also significant.
  • Weakness in only one arm or leg.
  •  

    Final diagnosis as with stroke is based on the pattern of symptoms the type of symptoms, past medical history, family history, present signs and symptoms and findings upon a complete physician examination

    Physical examination should include evaluation of both eyes and blood pressure and listening for a noise (or a bruit) which can only be heart with a stethoscope when listening over the artery which feeds the area of impairment.

    Diagnostic Testing can be helpful in finalizing the diagnosis and determining the extent of the process, especially ruling out the causes of hemorrhagic stroke. The testing done, may include CAT Scan or MRI of the Head or Cerebral Arteriography to provide images of the arteries for evaluation.

     

    How Serious Is Transient Ischemic Attack?

    The signs and symptoms of TIA are very similar to those of ischemic stroke, with one important difference, that is they disappear completely within 24 hours. An individual may have one or more TIAs in the same day or they can be separated by days, week's, months or even years. Generally they will lasts no more than a few minutes.

    Any TIA should be considered to be a warning sign that a stroke may follow in the near future, even within a few minutes. Approximately one-third of all persons who have TIAs will later have a stroke. A third will have more TIAs and another third will have no further cerebrovascular symptoms.

    While arterial atherosclerotic plaque deposits are very common, they are not necessarily the only cause for TIA. The separate arterial networks in the brain have a built-in safety factor through extensive, small interconnections between them. When blood flow is gradually impeded in one network, these interconnections tend to enlarge so another arterial network can take over the blood supply to that region, a phenomenon called collateral circulation. As a result, a completely blocked artery may be harmless if collateral circulation is sufficient.

    An additional safety factor is that the arteries to the brain are usually large enough to provide an adequate blood supply even when they are narrowed up to 75 percent by a plaque deposit. A TIA, therefore, is a warning that your safety factors are being overwhelmed.

     

    Treatment

    The purpose of treatment of TIA is primarily to prevent the occurrence of a stroke. This is done by improving arterial blood flow to the brain and so that a subsequent stroke can be avoided.

    Medication:

  • High blood pressure must be treated and brought into normal levels.
  • If high blood pressure does not exist then prevention is directed primarily at reducing the risk of any blood clots
       forming.
  •  

    Presently the most common medication used for this purpose is aspirin. (In addition to its pain-relieving ability, aspirin also inhibits the way platelets clump together; the presence of too many platelets at a narrowed site may further compromise the flow of blood to the brain.)

    The physician may prescribe it first on a trial basis. Anticoagulants (such as heparin or sodium warfarin) may be recommended in some situations. Anticoagulants or blood thinners also reduce the tendency for blood clots to form.

     

    Surgery:

    Surgery is generally a last resort and the primary surgery performed when dealing with TIAs is carotid endarterectomy. Here the arterial plaque is removed to lower the risk of further TIAs.

    The ideal candidate for this operation is an individual who has one or more TIAs without complications and diagnostic testing demonstrates that these TIAs were most likely caused by atherosclerotic plaque deposits in the arteries of the neck providing blood flow to the brain. It is best if the individual has no other symptoms suggestive of a stroke.

    A less than ideal person, is anyone else, especially someone with high blood pressure of symptoms of an ongoing stroke.

    To Learn About Ischemic Strokes.

    To Learn About Hemorrhagic Strokes.