Rasmussen syndrome

This is a very rare condition. Although it is not known exactly how many people are affected, it is thought to be about 1 in 750,000. It may occur at any time during childhood but usually affects children aged 6 to 8 years. It may rarely happen in children as young as 2 to 4 years of age, or in adulthood.

In this condition, the brain cells in one part of one hemisphere (half) of the brain become inflamed and swollen. Very rarely, both hemispheres may be affected. The cause of this inflammation is not entirely known. There is no evidence of a viral infection in the majority of cases, although research has shown that sometimes a virus may be present. It is possible that a virus may trigger an antibody response in the brain – which then causes the inflammation. It is the inflammation that causes the nerve cells to malfunction. This is called an ‘auto-immune’ trigger in which the body’s antibodies can damage one or more organs in the body. In Rasmussen syndrome, the brain is the organ which is damaged by the body’s antibodies.

In the past, the condition was called Rasmussen encephalitis. This was because it was thought that a virus caused an encephalitis (inflammation of the brain). We now know that is happens very rarely.


The result of the inflammation is that nerve cells malfunction, and this causes seizures. The seizures may be very infrequent at the beginning of the condition but after a few weeks or months, they become very frequent. This means they may occur many times a day. The seizures are usually focal (partial) and can cause one side of the face or limbs to jerk rhythmically. This can become continuous and may last for many hours or even days. This is called ‘epilepsia partialis continua’. The seizures are usually very difficult and sometimes impossible to control with epilepsy medicines.

After a variable period of time - from months to years - the child will usually develop a weakness of the side of the body that is affected by the seizures. This weakness is called a ‘hemiparesis’. As the seizures continue, this weakness worsens and the child may lose functions in the arm, leg or both.

Most children may also develop learning and often behaviour problems as the condition progresses. This can be as a result of the underlying progressive nature of the disorder, the number of seizures they have, side-effects of medicines, or a combination of all of these. Children can also have other difficulties depending on which part of the brain is affected. These include using language correctly, hemianopia (loss of vision in either the right or left sides of both eyes), dysarthria (difficulty speaking clearly) and swallowing difficulties.


All investigations are usually normal, except for the EEG (recording of electrical activity in the brain) and brain scans. The EEG will usually show a typical pattern called Periodic Lateralising Epileptiform Discharges (PLEDs). This is almost continuous abnormal electrical activity which involves the whole of the affected hemisphere. An initial brain scan, using magnetic resonance imaging (MRI) may be normal or show only a very slight abnormality. However, within a few months of the start of the condition, it will become abnormal. The abnormality becomes much more obvious and larger as the condition progresses. The MRI usually shows evidence of irreversible damage to nerve cells caused by inflammation. This appears on the scan as shrinkage (atrophy) of the part of the brain called the ‘grey matter’.


Seizures in Rasmussen syndrome are usually very difficult to treat. There is no particular epilepsy treatment that seems to be more effective than another. Commonly used epilepsy medicines include carbamazepine (Tegretol), levetiracetam (Keppra), topiramate (Topamax) and clobazam (Frisium).

Medicines to stop, suppress or alter the immune system may also be used. These include steroids (prednisolone), immunoglobulins, azathioprine and tacrolimus. More recently, special medicines (called monoclonal antibodies) like rituximab and natalizumab which are powerful suppressors of immune responses have been used. These medicines may help to control the seizures. They may also slow its progression in some, but not all cases. Medical management is the most important treatment if the child has no or only a very slight hemiparesis, or if both sides of the brain are affected. 

Surgery is recommended in some cases to treat the epilepsy and also to prevent further brain damage, including a worsening in learning. For some children, the disorder is confined to a part of the brain that can be safely removed, particularly the temporal lobe. In others, the whole of one side of the brain may need to be removed, called ‘hemispherectomy’. Another similar procedure is called ‘hemispherotomy’ when the abnormal hemisphere is disconnected from the other, normal hemisphere. In such cases, surgery can offer a cure for the epilepsy. A child with Rasmussen syndrome who has this surgery will be left with a permanent weakness (hemiplegia), hemianopia (loss of vision for objects coming from one side), speech loss (if the surgery is on the side of the brain responsible for language) and swallowing difficulties.

However, without surgery, the condition will nearly always continue to worsen with progressive weakness down the affected side leading to complete loss of function. The child will usually also show a worsening of their learning. The seizures will continue and not respond to any epilepsy medicines. So, although surgery is not an easy decision, it may be the best treatment available.  Rehabilitation is very important for children that have had surgery and should be started soon after surgery.

Surgery for Rasmussen syndrome is only available in very few specialist centres in the UK. These centres are called the ‘Children’s Epilepsy Surgery Service’ (CESS).

Information about epilepsy medicines for children can be found on the Medicines for Children website.

Your child is very likely to have prolonged or repeated seizures as part of Rasmussen syndrome. Your child’s hospital doctor (paediatrician or paediatric neurologist) will discuss a ‘rescue’ or emergency care plan with you to treat any prolonged or repeated seizures.

There may be research studies open that are relevant to this epilepsy syndrome. Your child’s hospital doctor will be able to discuss this with you.


After a period, usually of some years, the inflammation seems to stop of its own accord and doesn’t get any worse. Unfortunately, however, the nerve cells that have been injured continue to malfunction. As a result, the epilepsy may continue, although there is usually a better chance at this stage of bringing it under control. The inflammation may be fairly widespread within the brain. Most children with this condition also have a hemiplegia (weakness), hemianopia and also some learning difficulties. It is important that the child has assessments of their educational strengths and weaknesses. These assessments will include physiotherapy, occupational therapy, speech and language therapy and psychology. The results of these assessments will then help to provide the necessary help and support they need in school.


Charity for families of disabled children.
Freephone helpline: 0808 808 3555
Website: contact.org.uk
Email: helpline@contact.org.uk

Hemihelp at Contact
Support and information for people with hemiplegia and their families in the UK.
Website: https://www.contact.org.uk/hemihelp

What is a syndrome?

A syndrome is a group of signs and symptoms that, added together, suggest a particular medical condition. In epilepsy, examples of these signs and symptoms would be things like the age at which seizures begin the type of seizures, whether the child is male or female and whether they have physical or learning disabilities, or both. The results of an electroencephalogram (EEG) are also used to help identify epilepsy syndromes.

If you would like to know more about an epilepsy syndrome, please speak to your doctor. If you would like to know more about epilepsy in general, please contact the Epilepsy Action Helpline.


Epilepsy Action would like to thank Dr Richard Appleton, consultant paediatric neurologist and honorary professor in paediatric neurology at Alder Hey Children’s Hospital, Liverpool, and Dr Anand Iyer, consultant paediatric neurologist Alder Hey Children’s Hospital, Liverpool for preparing this information.

  • Updated January 2020
    To be reviewed January 2023

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