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Stroke

There are two types of strokes:

  • Ischemic Stroke
  • Hemorrhagic Stroke

Ischemic stroke is the loss or lack of blood flow resulting in death of brain cells. Hemorrhagic stroke is a result of the leakage of blood outside of a blood vessel in the head, “bleeding in the brain.”

IschemicStroke_NIH

The illustration shows how an ischemic stroke can occur in the brain. If a blood clot breaks away from plaque buildup in a carotid (neck) artery, it can travel to and lodge in an artery in the brain. The clot can block blood flow to part of the brain, causing the death of brain tissue. Click on illustration to enlarge.
Image: National Institutes of Health

ISCHEMIC STROKE

About 80 percent of all strokes are ischemic strokes.  Blood clots in arteries are the most common cause.  If an artery that supplies blood to the brain becomes clogged, the brain does not receive enough blood flow, and hence, enough oxygen.  That leads to a brain infarction.

In an ischemic stroke, the blood supply to part of the brain is cut off.  There are different ways the blood supply is blocked, include the most common:

  • Embolus: This occurs when a clot that forms somewhere in the body and travels through blood vessels to an artery in the brain.
  • Thrombus: This occurs when a blood clot forms in one of the brain arteries, sticks to the blood vessel wall and gets so large that it blocks blood flow.
IschemicStroke_Devices

Recanalization is a possible treatment for ischemic stroke. Devices, such as Solitaire (top left), Penumbra (top right), and Trevo (bottom), are used to retrieve and/or aspirate the clot directly out of the artery and reopen the blocked blood vessel.

Blood clots can travel to the brain from another artery or from the heart. It is important to keep in mind other conditions can make a person vulnerable to a stroke, such as dehydration, illness and conditions that cause a hypercoaguable state, and low blood pressure.

Another possible source for stroke is a carotid or vertebral artery dissection. An injury to the blood vessel wall will result in potential blood vessel occlusion or formation of blood clots. The injury to the blood vessel can happen spontaneously or as a result of  hyper rotation, flexion or extension of the neck. Not infrequently neck pain is associated with TIA-like symptoms.

CAUSES AND RISK FACTORS OF ISCHEMIC STROKE 

Ischemic stroke can be caused by a blockage anywhere along the arteries feeding the brain. The blockages can occur for many reasons, including:

  • Build up of fatty material (plaque) along artery walls that cuts down blood flow.
  • Breaking off of plaque from the artery wall, which can flow with the blood and get stuck in a smaller artery.
  • Blood clots breaking loose from the heart or one of its valves, known as an emboli, which can travel through the arteries to the brain and lodge there causing an embolic stroke or cerebral embolism (most common in people who have recently had heart surgery or who have a problem with their heart valves or abnormal heart rate or rhythms).

Strokes may also cause swelling in the brain. The pressure from this swelling can cause damage to brain tissue creating worse neurological problems.

Risk factors for ischemic stroke include:

  • Hypertension
  • Diabetes
  • High cholesterol, elevated LDL levels
  • Smoking
  • Poor diet
  • Lack of or no regular exercise
  • Atrial fibrillation

SYMPTOMS OF ISCHEMIC STROKE

Most strokes happen suddenly and damage the brain within minutes. In rarer cases, a stroke may get worse for several hours up to a day or two as a steadily enlarging area of the brain dies. This is called “a stroke in evolution.”

The common symptoms of ischemic stroke include:

  • Loss of (or abnormal) sensations in an arm, leg or one side of the body
  • Weakness or paralysis of an arm or leg or one side of the body
  • Partial loss of vision or hearing
  • Double vision
  • Dizziness
  • Slurred speech
  • Problems with thinking of or saying the right word
  • Inability to recognize parts of the body
  • Imbalance and falling

DIAGNOSIS OF ISCHEMIC STROKE

A stroke is diagnosed by clinical exam and history and confirmed with CT and/or MRI imaging.

TREATMENT OPTIONS FOR ISCHEMIC STROKE

The treatment of ischemic stroke depends on how soon a person can get to the hospital after the onset of symptoms AND other medical conditions they may have.

If a stroke victim arrives at the hospital within 4.5 hours of the onset of symptoms, they may be eligible for a blood thinning medication to break up the clot in the arteries, called tissue plasminogen activator (tPA). However, this drug is only successful if patients receive this medication within the first 4.5 hours of onset of stroke symptoms. Fewer than 5 percent of stroke sufferers in the United States receive tPA because they do not get to the hospital fast enough to be offered treatment. Of those who are eligible, only about 30 percent of patients have improved symptoms after tPA administration; for the others, the clot is too big for tPA to breakdown.

A mechanical thrombectomy that aims to mechanically retrieve and/or aspirate the clot directly out of the artery via an angiogram procedure may be an option. This procedure is often used in conjunction with IV tPA administration and/or if IV tPA has been unsuccessful in reopening the blocked blood vessel. It involves the use of stent retriever devices and/or aspiration systems to pull the clot out of the blood vessel, reopen the blocked vessel and reestablish normal blood flow to the brain.

Dr. Lopes and his team are currently participating in stroke trials that monitor the use and outcomes of such devices. A mechanical thrombectomy can be offered up to 8 hours post stroke onset. In certain cases, it can be offered beyond 8 hours of onset.

It is important to understand: TIME IS BRAIN. The sooner blood flow resumes, the less chance brain cells will continue to die.

Ultimately, the best treatment against stroke is prevention.

HemorrhagicStroke_NIH

The illustration shows how a hemorrhagic stroke can occur in the brain. An aneurysm in a cerebral artery breaks open, which causes bleeding in the brain. The pressure of the blood causes the death of brain tissue. Click on illustration to enlarge.
Image: National Institutes of Health

HEMORRHAGIC STROKE

A brain bleed is the type of stroke known as hemorrhagic stroke. It occurs when a blood vessel breaks or ruptures causing bleeding into the brain and killing brain cells. This type of stroke accounts for about 20 percent of all strokes. Hemorrhagic stroke often occurs due to long-term high blood pressure. Bleed from this type of stroke can occur:

  • Inside the brain, known as intraparenchymal hematoma
  • Between the brain and its covering membranes, or meninges, known as subarachnoid hemorrhage
  • Between the layers of the membranes covering the brain, known as subdural hematoma
  • Between the skull and the covering membranes of the brain, known as epidural hematoma

There are two types of hemorrhagic strokes:

  • Intracerebral or Intracranial Hemorrhage (ICH) occurs when there is bleeding into the brain itself. High blood pressure is most often the cause of small blood vessels bulging and eventually bursting, spilling blood into the brain. This bleeding damages brain cells and the damaged area of the brain cannot function properly.
  • Subarachnoid Hemorrhage (SAH) occurs when there is bleeding into the area that surrounds the brain. This space contains the “cerebrospinal fluid (CSF)” and is called the subarachnoid space.  There are many causes for a SAH. A ruptured cerebral aneurysm (see Cerebral Aneurysms) is one of the most dangerous and life threatening ones. Blood from a ruptured aneurysm may bleed into the space between two membranes on the surface of the brain. This bleeding can increase the pressure in and on the brain, injuring brain cells and possibly affecting brain function. Other causes of SAH can include the rupture of an arteriovenous malformation (AVM), trauma, or rupture of a fistula.

CAUSES AND RISK FACTORS OF HEMORRHAGIC STROKE

These include:

  • Head injury is most common cause of brain bleeding for people under age 50.
  • Abnormalities in blood vessels are typically only found if symptoms develop.  These include AVMs and are typically present from birth.
  • Aneurysms, the weakening in a blood vessel wall that bulges over time, can burst and bleed into the brain leading to a stroke.
  • High blood pressure that is uncontrolled over a long period of time can weaken blood vessel walls.
  • Amyloid angiopathy is an abnormality in the blood vessel walls that occurs more often as people age and may cause many small, unnoticed bleeds before causing a large one.

SYMPTOMS OF HEMORRHAGIC STROKE

Signs of bleeding inside the skull tend to come on rapidly and include:

  • Sudden headache
  • Steadily increasing neurologic losses, such as weakness on one side of the body, inability to move one or more extremity, numbness, loss of speech or vision, confusion
  • Nausea and vomiting
  • Seizures
  • Loss of consciousness

DIAGNOSIS OF HEMORRHAGIC STROKE

Description of the symptoms will typically lead a doctor to suspect a brain bleed and order a series of tests, which can include:

  • Computed (CT) tomography scan of the brain
  • Spinal tap, also known as a lumbar puncture
  • Magnetic Resonance Imaging (MRI)
  • CT Angiogram (CTA)
  • Cerebral angiogram or Digital Subtraction Angiography (DSA)

TREATMENT OPTIONS FOR HEMORRHAGIC STROKE

Treatment for bleeding inside the head varies on type of bleed, location and size—and may include:

  • Neuroendovascular intervention, such as an angiogram and embolization, to treat leaky vessels, inculding aneurysms or vascular malformations
  • Microsurgical techniques, such as a craniotomy and clipping, to treat abnormal or leaky vessels, inculding aneurysms and vascular malformations