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Stroke risk in children with sickle cell, and the TCD scan that finds it | CION Cancer Clinics
Children with sickle cell disease, especially HbSS, can have a stroke while seeming well. A yearly TCD ultrasound, advised from 2 to 16 years, measures blood speed in the brain's arteries and finds children at high risk early. A reading of 200 cm/s or more usually leads to regular transfusions. If your child shows stroke signs, call 108 now. This page explains the scan, the results and the next steps. At CION Cancer Clinics, our haematologist cares for anaemia, bleeding, clotting and inherited blood disorders, with ArogyaSri, CGHS and cashless insurance accepted.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- Why are children with sickle cell at risk of stroke?
- What happens during a TCD scan?
- What do the TCD result bands mean?
- What treatment is offered after an abnormal scan?
- What do parents often believe about stroke and sickle cell?
- What about silent strokes, and what can the scan not show?
- Common questions about stroke and TCD screening
!
If a child with sickle cell shows stroke signs, act now
A drooping face, a weak arm or leg, slurred or lost speech, a sudden severe headache, a fit, sudden trouble seeing or walking, or unusual drowsiness: call 108 or go to the nearest emergency department straight away. Tell the staff the child has sickle cell disease. Do not wait to see whether it passes, and do not give home remedies first. Even signs that settle within minutes need the same urgent check.
The short answer
Why are children with sickle cell at risk of stroke?
Children with sickle cell disease, especially the HbSS type, can have a stroke even when they seem well. A yearly ultrasound of the brain's blood vessels, called a TCD scan, finds the children at highest risk early, so treatment can start before a stroke happens.
What is going on inside the blood vessels
Sickled red cells stick to the lining of the large arteries that feed the brain. Over time the lining thickens and the arteries narrow. Blood has to rush faster through the narrow part, much as water speeds up when you squeeze a hose. A TCD scan measures that speed.
Why screening matters so much
Before screening became routine, about one child in ten with the most severe type had a stroke by early adulthood. Many of those strokes came without any warning. Finding the fast blood flow first, and treating it, has made strokes in screened children far less common.
Which children are usually screened
Guidance covers children with HbSS and HbS beta-zero thalassaemia. Your haematologist will say whether other types, such as HbSC, need the scan. Sickle cell trait does not raise stroke risk in this way.
This page cannot tell you your own child's risk. Only their scan results, read over time, can do that.Not sure whether this applies to you?
Ask an oncologistOn the day
What happens during a TCD scan?
Come when the child is well
The scan is best done on a calm, healthy day. Fever, a crisis, a recent transfusion or a very low haemoglobin can all change the reading, so tell the team if any of these apply and the date may move.
Lying down, awake
Your child lies on a couch with their head resting. They need to stay awake but still, because sleep changes blood flow. Bring a favourite toy or a phone video to keep them calm.
The probe on the temple
Gel is placed on the side of the head, just in front of the ear. A small probe is moved gently to find the arteries. There are no needles and no radiation, and it does not hurt.
Reading the speeds
The scan takes around half an hour. The person scanning records the fastest average speed in each main artery, on both sides, and the report goes to the haematologist.
On the report
What do the TCD result bands mean?
Result
What usually happens next
Normal: speed below 170 cm/s
Repeat the scan once a year through childhood
Conditional: 170 to 199 cm/s
Repeat sooner, within a few months, and review treatment
Abnormal: 200 cm/s or higher
Repeat quickly to confirm, then discuss regular transfusions
Inadequate or low speed
The scan could not read clearly; an MRI may be needed
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If the reading is high
What treatment is offered after an abnormal scan?
These are the options your haematologist will discuss. The choice depends on the repeat scans, an MRI, and what your family can keep up over years.
Regular transfusions
Blood every few weeks keeps the share of sickle cells low. This is the treatment with the strongest evidence for preventing a first stroke in a child with an abnormal scan.
What it asks of you
- Planned hospital visits
- Iron checks and sometimes iron-removing medicine
Hydroxyurea
A daily medicine that makes red cells less likely to sickle. In some children it can take over after at least a year of transfusions, if MRI pictures show no serious narrowing. The dose is set only by the team.
An MRI and MRA of the brain
These pictures look for narrowed arteries and small silent strokes. They help decide how long transfusions continue and whether a switch is safe.
A transplant discussion
For some children with a matched brother or sister, a bone marrow transplant may be raised. It is done only at specialised transplant centres, and it does not suit every child.
Commonly believed
What do parents often believe about stroke and sickle cell?
"Strokes only happen to old people."
In sickle cell disease, stroke is most common in young children. It can happen to a child who plays, eats and studies normally, which is exactly why the scan is done when nothing seems wrong.
"His last scan was normal, so we do not need another."
Blood flow changes as a child grows. A normal result this year says nothing firm about next year, so the scan is repeated regularly through childhood.
"The weakness went away in ten minutes, so it was nothing."
Short-lived weakness or speech trouble can be a warning stroke. It needs the same same-day emergency check as signs that last, and it often changes the treatment plan.
"Our child is on regular blood, so we can stop once the scan looks better."
A better scan usually means the transfusions are working. Stopping them without a plan can bring the risk back. Any change is made only by the haematologist, after further tests.
Beyond the scan
What about silent strokes, and what can the scan not show?
A TCD scan measures speed in large arteries. It does not show small areas of damage deep in the brain, often called silent strokes. These cause no sudden weakness, but they can affect memory, attention and schoolwork over time.
Signs that are easy to miss
Falling marks at school, trouble following instructions, or a teacher saying your child seems slower than before. These can have many causes. Mention them at the next haematology review, because an MRI may be suggested.
When the machine speeds differ
Different TCD methods give slightly different readings, and one scan can be thrown off by fever or a low haemoglobin. That is why a single high reading is repeated before a big decision, and results are read alongside the child's health at the time.
Getting the scan in Telangana and Andhra Pradesh
TCD is not available in every district. Ask your haematologist where it is done, keep every report in one folder, and note the date the next scan is due. CION's haematology team can review the reports and help you plan with centres that offer the scan.
Questions we are asked
Common questions about stroke and TCD screening
At what age should TCD screening start?
American guidance advises a TCD scan once a year from age 2 to age 16 for children with HbSS or HbS beta-zero thalassaemia. Your haematologist may adjust this based on your child's type and past results. If your child is older and has never had one, ask about it at the next review.
Is TCD the same as an MRI or a CT scan?
No. TCD is an ultrasound, done with gel and a probe on the side of the head. It measures how fast blood moves. An MRI takes detailed pictures of the brain itself, and a CT uses X-rays. Each answers a different question, so a child may need more than one.
Does my child need sedation for the scan?
Usually not, and sedation is avoided because sleep changes blood flow and can make the reading look lower than it really is. Your child simply lies still and awake. Practising lying quietly at home for a few minutes, with a story or a video, often helps younger children on the day.
My child's result was conditional. How worried should we be?
A conditional result means the speed is higher than normal but below the abnormal band. It is a reason for closer watching, not panic. The scan is repeated sooner, and your haematologist may talk about hydroxyurea. Keep every appointment, because some conditional results move up over time.
Can hydroxyurea alone prevent a stroke?
In some children, after a period of regular transfusions, hydroxyurea has been shown to keep the scan speeds down. It is not a replacement for transfusion in every child, especially where the MRI shows narrowed arteries. Never start, stop or change it on your own; the team decides and sets the dose.
What should we do if our child has already had a stroke?
After a stroke, the risk of another one is high, so a long-term plan to prevent a second stroke is started, most often regular transfusions. Rehabilitation, school support and regular MRI reviews follow. Ask the team about physiotherapy and speech therapy close to home.
Does sickle cell trait carry the same stroke risk?
No. People with sickle cell trait carry one sickle gene and usually do not have the blood vessel changes that lead to childhood stroke. TCD screening is not advised for trait alone. If you are unsure which your child has, a confirmatory blood test settles the question.
Can the scan be done under a government scheme?
The national sickle cell mission and state schemes such as Aarogyasri and PM-JAY cover a growing range of sickle cell care, but coverage for TCD differs between hospitals and changes over time. Carry your sickle cell card and ask the hospital to check the current rules before the visit.
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Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- NHLBI — Evidence-Based Management of Sickle Cell Disease: Expert Panel Report
- NHS — Sickle cell disease
- American Society of Hematology — Sickle Cell Disease Guidelines
- NHS — Stroke: symptoms
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Transfusion in Sickle Cell: When and WhyWhat regular transfusions involve after a high scanHydroxyurea in Sickle Cell DiseaseThe daily medicine that may follow transfusionsWhen a Sickle Cell Crisis Needs HospitalOther warning signs that cannot waitSchool, Work and Sickle CellSupport if schoolwork is affectedSickle Cell DiseaseThe full guide for families
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