What are the symptoms? Most children present with seizures (see entry Epilepsy) involving one side of the body (focal epilepsy). The epilepsy is usually difficult to control. As time goes on, children also become weak on the same side of the body as the seizures. This weakness usually becomes permanent (hemiplegia) and they lose some of their visual fields (they can still see, just not in every direction). Children also begin to have problems with their learning (cognitive decline). Eventually they are likely to have learning disability. They may have particular problems with speech if the side of the brain controlling language is involved (language dominant hemisphere). For some children these symptoms and their severity progress very quickly over months, for others the disease goes slowly over years. What are the causes? Whilst we do not know what triggers RE, we do know that RE is an autoimmune disorder. This means that T lymphocytes, a type of white blood cell, are involved in the inflammation and damage of the brain tissue. How is it diagnosed? Diagnosis is based on the clinical picture of epilepsy, emerging weakness, MRI brain scans showing the loss and damage to brain tissue, and electroencephalographs (EEG) showing abnormal electrical activity in the brain. There is no specific blood test, and brain biopsies are not needed to make the diagnosis. How is it treated? Anti-epileptic drugs can help to control seizures (see entry Epilepsy), but they do not stop the condition. There are also treatments targeting the autoimmune basis of RE. These include oral steroids, azathioprine, tacrolimus and intravenous immunoglobulins, although new medical treatments are being considered, so this list is not complete. However, it is important to remember that, whilst these treatments may slow down RE, they do not cure it. Surgery is the only treatment known to stop RE. The affected side of the brain is disconnected from the healthy brain (the operation is usually called a functional hemispherectomy). Unfortunately, while surgery is very good at stopping seizures, it does result in a permanent weakness on one side of the body (hemiplegia) and visual field loss (if the child doesn’t already have these as a result of RE). Deciding on surgery should be done by the family, young person, doctors and a specialist epilepsy surgery service. Inheritance patterns and prenatal diagnosis Inheritance patternsNone. Prenatal diagnosisNone. Is there support? Information and support in the UK for Rasmussen’s encephalitis is provided by the Encephalitis Society (see entry Encephalitis).