Stroke - Ischemic and Hemorrhagic Stroke

Overview

A stroke occurs when blood flow is significantly decreased to a portion of the brain, causing brain damage. A stroke can also occur when an artery bleeds inside the brain, resulting in brain injury. Also known as cerebrovascular accidents, strokes are serious, life-threatening events that often permanently impair bodily functions.

Types and Causes of Stroke

Ischemic stroke

An ischemic stroke occurs when blood flow is blocked in an artery that supplies blood to a section of the brain. This blockage deprives the brain of oxygen and injures brain tissue. The most common cause of ischemic strokes is a blood clot that clogs a brain artery.

Types of ischemic strokes:

  1. Thrombotic stroke. A thrombus is a blood clot that develops inside an artery and blocks the blood flow. Certain individuals with arterial plaque (atherosclerosis) experience plaque rupture, which triggers thrombus formation that blocks an artery and causes a stroke.
  2. Embolic stroke. Embolic stroke is caused by a blood clot or other material, such as plaque that builds up, breaks off from another part of the body, and travels to the brain. Atrial fibrillation (AF), a fast irregular heart rhythm, is a common cause of stroke. During AF blood pools in the upper chambers of the heart (atria), and this increases the risk for clot formation and stroke. 

Hemorrhagic stroke

A hemorrhagic stroke occurs when an artery inside the brain ruptures and bleeds. The bleeding creates a pool of blood that presses on the brain and damages brain cells.

Types of hemorrhagic strokes:

  1. Intracerebral hemorrhage: bleeding from a blood vessel inside the brain.
  2. Subarachnoid hemorrhage: bleeding on the brain’s surface.

Hemorrhagic strokes are commonly caused by the following conditions:

  • High blood pressure
  • A budging defect (aneurysm) in the wall of an artery, which suddenly breaks open and bleeds
  • Abnormal tangle of blood vessels (arteriovenous malformation).

Transient ischemic attack (TIA)

A transient ischemic attack occurs when the blood flow to an area of the brain is decreased for a short period of time. In a TIA, the brain is not permanently damaged.

Risk Factors for Stroke

  • Unhealthy diet (low in vegetables, fruits and whole grains; high in fat, salt, and processed sugars)
  • Elevated cholesterol 
  • Smoking
  • Hypertension
  • Diabetes
  • Heart disease
  • Abnormal heart rhythms, especially atrial fibrillation
  • Advanced age
  • Brain aneurysm
  • African American, Native American, or Alaskan Native ethnicity
  • Sedentary lifestyle
  • Stress
  • Depression.

Symptoms

Symptoms of a stroke vary depending on the area of the brain that is injured. The associated loss of bodily functions may be temporary or permanent.

Common stroke symptoms:

  • Sudden weakness or inability to move the arms or legs or face (paralysis), typically affecting one side of the body
  • Numbness
  • Difficulty speaking
  • Confusion
  • Visual difficulties
  • Dizziness
  • Loss of balance
  • Abrupt onset of a severe headache
  • Loss of consciousness.

Diagnosis

When stroke symptoms occur, patients should call 911 for immediate transportation to the hospital, because rapid treatment is essential to prevent permanent brain damage.

The diagnosis of stroke is based on the symptoms and physical examination. Further testing is required to determine the area of the brain affected.

  • Computed tomography is an x-ray that provides detailed images of brain tissues.
  • Magnetic resonance imaging uses radio waves and a magnet to generate images of the brain.
  • Carotid ultrasound uses sound waves to provide a visual image of the carotid arteries.
  • Carotid angiogram is performed with an injection of dye that creates a more detailed image of the carotid arteries.
  • Echocardiogram uses sound waves to evaluate heart structures and detect a clot in the heart.

Treatment of Ischemic Stroke

Medication

  • Tissue plasminogen activator (tPA) is used to dissolve the clot causing the stroke. To be effective, it must be administered within four hours of the start of symptoms.
  • Antiplatelet medication inhibits platelets, the blood cells involved in clot formation.
  • Blood thinning medications (anticoagulants) prevent clot formation.

Procedures

  • Clot-dissolving medication can be delivered to the brain through a catheter.
  • The clot can be physically broken up and removed with a tiny instrument inserted into the affected artery.
  • Angioplasty and stent involves inserting a small balloon into the carotid artery and dilating a narrowed area. A rigid device is left in place to keep the artery open. 
  • Carotid endarterectomy is surgery that removes plaque from a blocked carotid artery.

Treatment of Hemorrhagic Stroke

Surgery

  • Aneurysm clipping blocks the flow of blood into an aneurysm and prevents re-bleeding.
  • Coiling (endovascular embolization) is the placement of small coils inside of an aneurysm to block blood flow into an aneurysm.
  • Arteriovenous malformations can sometimes be removed.
  • Intracranial bypass is a technique to re-route blood flow and restore circulation to areas of poor blood flow.
  • Stereotactic radiosurgery uses beams of radiation to treat blood vessel abnormalities in the brain.

Rehabilitation and Prevention

A variety of special therapists help patients recover as much strength and function as possible. However many patients experience some degree of permanent disability after a stroke.

Most strokes are preventable through adherence to a healthy lifestyle. A healthy low-fat diet emphasizing fruit, vegetables, and whole grains reduces the risk of stroke. Patients should also maintain a normal weight, quit smoking, and exercise regularly.

Sources

  • What Is a Stroke? National Heart, Lung, and Blood Institute website. http://www.nhlbi.nih.gov/health/health-topics/topics/stroke/. Accessed July 31, 2015.
  • Stroke. Mayo Clinic website. http://www.mayoclinic.org/diseases-conditions/stroke/home/ovc-20117264. Accessed July 31, 2015.
  • The Role of Nutrition in the Prevention & Treatment of Stroke. Cleveland Clinic website. http://my.clevelandclinic.org/health/diseases_conditions/stroke/hic_The_Role_of_Nutrition_in_the_Prevention_and_Treatment_of_Stroke. Accessed July 31, 2015.
  • Stroke (Brain Attack). Johns Hopkins Medicine Health Library website. http://www.hopkinsmedicine.org/healthlibrary/conditions/adult/nervous_system_disorders/stroke_brain_attack_85,P00249/. Accessed August 2, 2015.