Ans. a. First 48 hoursTransient ischemic attack (TIA) is sudden, transitory loss of neurologic function that comes on without headache and resolves spontaneously within 24 hours (but usually lasts less than 1 hour), leaving no neurologic sequelae.The specific symptoms depend on the area of the brain affected, which is in turn related to the vessels involved. The most common origin is high-grade stenosis (>=70%) of the internal carotid, or ulcerated plaque at the carotid bifurcation.Stroke may be indistinguishable from a TIA at the time of presentation: Duration of symptoms is the determining difference.Symptoms are transient with a TIA because reperfusion occurs, either because of collateral circulation or because of the breaking up of an embolus.The blockage in blood flow does not last long enough to cause permanent infarction.Once a patient has a TIA, there is a high risk of stroke in 10-15% in the first 3 months, with most events occurring in the first 2 days. The risk of a stroke in a patient with a history of TIA is about 10% per year. TIAs carry a 30% 5-year risk of stroke. Therefore, cardiac risk factors should be closely investigated and, if possible, eliminated in a patient who has had a TIA.Cases may present only with transient loss of vision in one eye, known as amaurosis fugax. This happens during a transient ischemic attack because the first branch of the internal carotid artery is the ophthalmic artery.Note:TIAs are never due to hemorrhage; hemorrhages do not resolve in 24 hours.The importance of TIAs is that they are predictors of stroke, and timely elective carotid endarterectomy may prevent or minimize that possibility.Workup starts with.noninvasive Duplex studies.Carotid endarterectomy is indicated if the lesions are found in the location that explains the neurologic symptoms.Angioplasty and stent can be performed in high risk surgical patients