Stroke and Sickle Cell Disease

People with sickle cell disease (SCD) have a higher risk of developing brain complications. Children with SCD often experience acute stroke, which is a medical emergency. Stroke and other brain complications happen when sickle cells block large arteries leading to the brain.

Children and adults with SCD may experience a “silent stroke,” which does not show any signs and can only be detected on MRI. Children should be screened often for stroke risk. Chronic (regular) transfusions can reduce the rate of strokes.

What brain complications do people with sickle cell disease experience?

Acute stroke and chronic low blood flow to the brain are severe complications of SCD. About 11 percent of people with SCD have a stroke before 20 years old. This increases to 24 percent by age 45.1

The risk is highest for children between 2 and 5 years old and adults between 40 and 49 years old. Children with SCD are 300 times more likely to have a stroke than children without SCD or heart disease. Children who have had a stroke also have a higher risk of having a second stroke.1,2

There are 2 types of stroke that people with SCD experience:3

  • Ischemic stroke – this type of stroke happens when blood flow to the brain is blocked
  • Hemorrhagic stroke – this type of stroke happens when blood vessels burst and bleed into the brain. Hemorrhagic stroke is most common among adults between 20 and 29 years old.

Ischemic stroke is usually the first diagnosis in people with SCD showing signs or symptoms of a brain complication. However, other possible diagnoses include:3,4

  • Hemorrhagic stroke
  • Transient ischemic attack (mini-stroke lasting less than 24 hours)
  • Cerebral venous sinus thrombosis (blood clot in a vein in the brain)
  • Infection, including meningitis
  • Seizure
  • Migraine

What causes brain complications?

SCD causes ischemic stroke when sickle cells block large arteries leading to the brain. It can often happen as a complication of acute chest syndrome. Sickle cells are more rigid and sticky, and tend to clump along walls of large arteries. This damages vessel walls, narrows blood vessels, and prevents oxygen delivery to the brain.5,6

We do not completely understand how SCD causes hemorrhagic stroke. It could be because people with SCD have weaker blood vessels. It may also be linked to aneurysms (enlarged arteries).5,7

People with more severe forms of SCD, such as sickle cell anemia and sickle beta zero thalassemia, have a higher risk of ischemic stroke. Genetic factors, such as alpha thalassemia, may reduce the risk of ischemic stroke. Other risk factors include oral birth control, smoking, and sleep disordered breathing.1,5,8

What are the symptoms of a stroke?

A clinical stroke is a stroke that shows signs or symptoms.This includes: 9

  • Altered level of consciousness
  • Numbness or weakness, particularly on 1 side of the body
  • Confusion
  • Trouble speaking or understanding speech
  • Difficulty seeing
  • Difficulty walking, dizziness, or loss of balance
  • Severe headache

However, children and adults with SCD also experience “silent stroke.” This is a brain injury that does not cause any outward signs of stroke. Silent strokes can only be detected by MRI. People with sickle cell anemia or sickle beta zero thalassemia should be screened at least once for risk of a silent stroke.5,10

About 17 percent of children with SCD under age 14 have silent strokes. They often occur in frontal areas of the brain and can affect intellectual ability, academic ability, attention, language, and long-term memory.6,10

How are brain complications prevented and treated?

The strongest risk factor of stroke in children with SCD is a previous stroke. Other risk factors of a stroke include:5,6

  • History of seizures
  • Previous transient ischemic attack (mini-stroke)
  • New or increased frequency of acute chest syndrome
  • Nervous system infections
  • Trauma
  • Increased blood pressure
  • History of snoring or sleep apnea

If your child with SCD has any of these conditions, talk to your doctor about their risk of stroke. Your doctor may assess stroke risk using a test called transcranial Doppler (TCD) velocity. This is an ultrasound procedure that measures the velocity of blood flow through blood vessels in the brain. Children with SCD have higher velocities because of narrower arteries.5,11,12

TCD screening can identify children who have a higher risk of stroke. Children with high-risk SCD types should be screened regularly with TCD. Chronic (regular) blood transfusions or hydroxyurea treatment can then decrease stroke risk.5,12,13

People with SCD showing signs or symptoms of a stroke should be treated immediately in a hospital. The exact treatment depends on the type of stroke. Treatment will usually involve:3,4,12

  • Evaluation, including a CT, MRI, or other imaging
  • Consultation with a neurologist and hematologist
  • Rapid exchange transfusion
  • Chronic transfusion to decrease risk of secondary stroke
  • Monitoring of oxygen levels, blood pressure, and seizures

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Written by: Matthew Zajac | Last reviewed: January 2021