Thursday, April 27, 2017

Transient Ischemic Attacks

Transient Ischemic Attack is defined as a condition in which the symptoms of stroke are lasting less than 24 hours. The symptoms usually reach their peak in seconds and lasts for minutes or hours (but by definition less than 24 hours).

TIA has a tendency to recur and to predispose to a complete stroke. There is a complete functional recovery after a TIA and the focal neurological deficits during the episode depend on the artery involved.

Etiology: Transient ischemic attacks are caused by the passage of emboli in about 90% of cases and less commonly it is due to a fall in cerebral perfusion (e.g due to a cardiac dysrhythmia, postural hypotension or reduced blood flow through atheromatous vertebral arteries).

The principal source of emboli is atheromatous plaque within the carotid or vertebral arteries or from mural thrombus formed on diseased heart muscle.

Clinical features
  • TIA’s cause sudden loss of function in one region of the brain depending on the artery involved.
  • Consciousness is usually preserved.
  • On examination of the patient there may be flaccid weakness, sensory loss, hyperreflexia and extensor plantar response on the affected side.
  • Sources of emboli may be evident such as valvular heart disease, endocarditis, recent MI or atrial fibrillation.
  • Associated diseases may be diagnosed like atheroma, hypertension, braydycardia or diabetes.
  • Sometimes patients present with transient monoocular blindness termed as Amaurosis fugas.
  • Some patients may experience episode of amnesia with confusion lasting for several hours caused by ischemia of posterior circulation.
Investigations:  The patient should have the initial basic laboratory workup that includes:
  • CBC
  • FBS
  • Serum cholesterol
  • ECG
  • X-ray chest
  • Echocardiography if cardiac source is likely
  • Blood culture if endocarditis is suspected
  • Carotid doppler.

Medical treatment is aimed at preventing further attack and stroke. The treatment options includes:
  • Anticoagulants such as heparin followed by warfarin should be given in case of embolism from heart provided there is no contraindication to anticaogulation.
  • If anticoagulants are contraindicated platelet aggregation inhibitor such as aspirin is used in a dose of 300 mg/day.
  • If there is embolization from extracranial or intracranial cerebral circulation give either aspirin 300 mg/day or Ticlopidine 250 mg twice daily if patient is intolerant to aspirin. If giving ticlopidine monitor for neutropenia.
  • Treatment of the predisposing factor is essential.
Surgical treatment
  • Carotid endarterectomy reduces the risk of stroke and is indicated when the carotid artery is severely stenosed (70-99% in luminal diameter on angiography)
  • Now symptomatic patients with 50-60% stenosis are also considered for endarterectomy.
  • Surgery is not indicated when stenosis is mild and it can be managed by medical treatment.
  • Patients who are not good candidates for surgery because of medical co morbidities they can be considered for angioplasty and stenting.

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