For Patients and Caregivers

TCD Screening and Sickle Cell Disease

Transcranial Doppler (TCD) ultrasound measures the speed of blood flowing in arteries inside the head. The narrower an artery is, the faster the blood flows through it, and the higher the risk of blockage and brain injury. TCD is a proven tool for identifying children 2-16 years old with sickle cell disease who are at risk for stroke.

TCD was used in the STOP study.1 In that study, chronic blood transfusion reduced stroke risk by 90%. The National Heart, Lung, and Blood Institute recommends that all children with sickle cell disease receive screening with TCD and that transfusions be considered for children at high risk for stroke.

TCD is:

• Proven to predict stroke risk
• Non-invasive
• Painless
• Fast (exam takes 30-45 minutes)
• Convenient (can be done same day as clinic visit)

A TCD examines intracranial vessels (middle cerebral artery and distal internal carotid artery). Greater attention is paid to these vessels because stenosis (blockage) is normally found in these vessels, especially the middle cerebral artery.

In the STOP study, TCDs were read as either normal, conditional, abnormal, or inadequate, based on time-averaged maximal mean velocities:

Reading Velocities Risk Level

Normal - Under 170 cm/sec, Low risk of stroke
Conditional - 170-199 cm/sec, Moderate risk of stroke
Abnormal - 200 cm/sec or higher, High risk of stroke
Inadequate - Unreadable or incomplete, Unknown

Stroke Research in Sickle Cell Disease

Why is TCD Important?

Stroke is an important complication of sickle cell disease. The rate of stroke in children with sickle cell disease is 300 times higher than children without sickle cell disease.2 Strokes can lead to physical and neuro-psychological impairment which can affect motor skills, school performance, and overall quality of life.

• The symptoms of stroke are:
• Paralysis on one side of the body
• Difficulty with speech or vision
• Numbness on one side of the body
• Sudden severe headache with possible loss of consciousness
• Seizures, particulary partial seizures

More information about stroke and sickle cell disease can be obtained from the Sickle Cell Information Center.

Where Can Children Get A TCD?

TCD is performed vascular ultrasound laboratories that are usually located in Radiology and Neurology Departments at many major medical centers. The availability of this service varies by state. Most major sickle cell disease clinics offer TCD or know where TCD can be obtained.

Another source of information is the Intersocietal Commission for the Accreditation of Vascular Labs (ICAVL), an agency that ensures quality standards for vascular laboratories. Labs which perform intracranial exams are identified in the ICAVL Website.

Click here for a list of TCD Exam Locations in North America

Please contact us for more information:

Fenwick T. Nichols, M.D.
Professor of Neurology
Medical College of Georgia
1429 Harper Street, HF-1154

email: fnichols@mcg.edu
phone: (706) 721-6166

What Research Is Going On Now?

In the STOP II study, the goal is to learn whether children who are receiving long-term transfusions to prevent strokes can safely stop those transfusions when their TCDs show that they have a lower risk of stroke.

This study could provide valuable information for patients and their physicians. While chronic blood transfusions are effective in preventing strokes, they also have serious side effects including iron overload. If it can be proved that transfusions do not need to be given indefinitely, this will reduce the burden on children and their families.