TRANSIENT ISCHEMIC ATTACK I. Definition A. Classic definition: sudden or rapid onset of neurologic deficit caused by focal ischemia that lasts for a few minutes and resolves completely within 24 hr. B. It has been found that with more widespread use of modem imaging techniques for the brain, up to one third of patients with symptoms lasting less than 24 hr actually have a small infarct. C. Updated definition: a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction II. Incidence/prevalence A. Incidence is 160/100,000; prevalence is 135/100,000 III. Etiology A. Atherosclerotic disease 1. Aorta 2. Carotid arteries 3. Vertebral arteries 4. Intracranial atherosclerosis B. Cardiac emboli as seen in arrhythmia (atrial fibrillation), myocardial infarction (MI), congestive cardiomyopathy, and valvular disease C. Vasculitis conditions such as moyamoya disease, fibromuscular dysplasia, lupus, and others D. Hematologic causes 1. Red blood cell (RBC) disorders a. Increased sludging b. Decreased cerebral oxygenation such as in severe anemia c. Polycythemia, sickle cell anemia 2. Platelet disorders a. Thrombocytosis b. Thrombocytopenia 3. Increased viscosity/hypercoagulable conditions a. Antiphospholipid antibody syndrome (e.g., lupus anticoagulant, anticardiolipin antibody) b. Oral contraceptive and/or estrogen use c. Antithrombin III deficiency d. Protein S and C deficiency e. Tissue-type plasminogen activator (t-PA) and plasminogen deficiencies f. Patients particularly at risk for a hypercoagulable state: Older than 45 years History of thrombolytic event History of spontaneous abortion Related autoimmune conditions (e.g., lupus) Stroke of unknown cause Family history of thrombotic events 4. Myeloproliferative disorders, leukemia with white blood cell count greater than 150,000 E. Intracranial causes 1. Brain tumor 2. Focal seizure 3. Hemorrhage a. Subdural hematoma (SDH) b. Subarachnoid hemorrhage (SAH) c. Intracerebral hemorrhage (ICH), which may cause cerebrovascular dysfunction due to leakage of blood outside the normal vessels F. Subclavian steal syndrome 1. Localized stenosis or occlusion of a subclavian artery proximal to the source of the vertebral artery, so that blood is stolen from that artery 2. Blood pressure (BP) is significantly lower in the affected arm than in the opposite arm. G. Others 1. Transient hypotension 2. Osteophytes that cause compression of neck vessels 3. Cocaine abuse 4. Hypoglycemia 5. Migraines IV. Risk factors A. A transient ischemic attack (TIA) is an important predictor of stroke. 1. The 90-day risk of stroke after a TIA is as high as 17% 2. The greatest risk is within the first week 3. Approximately one third of stroke patients have a history of TIA B. Hypertension C. Cardiac disease, such as the following: 1. Mitral valve disease 2. Anterior wall MI 3. Congestive myopathy
You've reached the end of your free preview.
Want to read all 74 pages?
- Fall '17
- keisha lovence