Download PDF Rasmussen's encephalitis

by Alina Ellerington, Encephalitis Society and reviewed by Dr. Sophia Varadkar, Consultant Pediatric Neurologist, Great Ormond St Hospital for Children NHS Foundation Trust & UCL Institute of Child Health

What is Rasmussen's encephalitis (RE)?

Rasmussen's encephalitis (RE), also called Rasmussen' syndrome, is a rare, progressive, chronic encephalitis (inflammation of the brain). It occurs mainly in children (most cases are seen in six to seven-years-old children). However, around 10% of all cases are adolescents and adults. RE occurs usually in healthy individuals. It is estimated that no more than two new cases per year are identified in large epilepsy centres.

Symptoms of Rasmussen's encephalitis (RE)

RE is characterised mainly by intractable seizures, progressive hemiparesis, and cognitive loss (learning difficulties).

  • Seizures

Seizures may have different forms and characteristics: simple partial seizures, complex partial seizures, generalised tonic-clonic seizures or status epilepticus. But the most notable seizure manifestation of RE is epilepsia partialis continua (EPC) which is continuous twitching of the face, arm or leg on one side of the body. About 50% of patients with RE have EPC.

  • Hemiparesis

Hemiparesis is a weakness on one side of the body. The wiring of the nervous system determines that a lesion on one side of the brain causes problems on the opposite side of the body. Thus, involvement of one hemisphere causes weakness on the other side of the body.

  • Cognitive impairment and other characteristics

Other symptoms depend on which hemisphere is affected. Over time, patients may develop cognitive impairment, aphasia (difficulties with using language correctly), hemianopia (loss of vision in either the right or left sides of both eyes), sensory deficits, dysarthria (difficulty speaking), dysphagia (swallowing difficulties) and psychiatric problems. Language and cognition disturbances are almost always seen in patients with left-side involvement.

The cause of Rasmussen's encephalitis (RE)

The exact cause of RE is not known. However, there is increasing evidence of an underlying immune disorder. The certainty is that only one hemisphere is affected in most cases (cases when both hemispheres are affected are very rarely) and the disease starts focally (one specific area) and spreads across the hemisphere.

Evolution and prognosis of Rasmussen's encephalitis (RE)

Most children are healthy before the onset of Rasmussen’s encephalitis. The progression of the symptoms to significant neurological impairment usually occurs within months to a few years. Some patients have a fast evolution with the rapid development of hemiparesis, while others have a slow evolution with hemiparesis developing more than one year after seizure onset. There are patients who develop only a mild hemiparesis or language disturbance.

In the long-term, the disease is usually expected to ‘burn itself out’ but not before the patient is left with significant hemiparesis, visual field loss, learning difficulties and, usually, on-going epilepsy. Unfortunately, either quickly or slowly, children begin to show difficulties with learning. At first, their academic performance may stabilise and, then, they fall behind their peers. Supporting their education is extremely important. The syndrome can spontaneously stabilize at any time. Very rarely, in rapidly progressive cases, RE is a cause of death.

Diagnosis of Rasmussen's encephalitis

Diagnosis is made based on clinical features (symptoms) and results of radiological investigations. The most useful investigations are:

  • Electroencephalography (EEG) which may reveal brainwave patterns characteristic of certain types of epilepsy
  • Serial Magnetic Resonance Imaging (MRI) which show progressive atrophy (shrinkage) and scarring of the affected side of the brain

Brain biopsies are not usually needed to make the diagnosis and can often be inconclusive.

Treatment of Rasmussen's encephalitis

The treatment has two aims:

  • an anticonvulsive treatment with as few side-effects as possible
  • a treatment that stops the brain cells destruction and improves the long-term outcome regarding neurological and neuropsychological functions

Early diagnosis and therefore subsequent intervention may contribute to improved responses.

Anticonvulsant treatment (AED)

EPC is usually unresponsive to anti-convulsive treatment. However, the frequency of focal and secondary generalised tonic-clonic seizures in RE may be reduced by anticonvulsive medication. This is the aim of drug treatment rather than trying to achieve seizure freedom.

Immunomodulatory therapy 

These treatments target the autoimmune system and include steroids, tacrolimus, azathioprine and intravenous immunoglobulin (IVIg). More recently, treatments with other drugs (monoclonal antibody therapies) such as natalizumab and rituximab are being trialled. These treatments slow down the illness, but they do not stop the disease. Steroids and IVIg may also reduce seizures.

Hemispherectomy (HE)

Surgery—HE remains the only cure for the seizures caused by RE. HE (disconnection of the affected side of the brain from the healthy brain) in one of its modern variants offers a very high chance of seizure freedom.  However, HE can have significant consequences:

  • irreversible loss of functions located in that affected hemisphere
  • hemiplegia (if there isn’t one already from the disease). The patients are expected to walk again but they are not expected to have fine finger function.
  • hemianopia (loss of vision for objects coming from one side)
  •  speech loss if the surgery is on the side of the brain generating language (language dominant side)
  • swallowing difficulties

Despite these concerns, HE is less debilitating in children than in adults. Rehabilitation is very important and should begin early in the postoperative period. The decision to go ahead with surgery and choosing the best time is difficult and individual to each child. Careful decisions should be made by the parents and young person in conjunction with a specialist epilepsy surgery service. 

Medical therapy prior to HE may be considered in two scenarios:

  • in patients with minimal or no motor deficits
  • in patients with RE involving the dominant hemisphere or bilateral hemisphere

Further information on RE

  • RE Children’s Project was founded in 2010 to increase awareness regarding Rasmussen's encephalitis (RE) for the primary purpose of supporting scientific research directed towards a cure. The organisation also supports research dedicated the recovery process following hemispherectomy.

  • The Hemispherectomy Foundation provides emotional, financial, and educational support to individuals and their families who have undergone, or will undergo, hemispherectomy or a similar brain surgery.


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Date created: May 2003/ Last updated: December 2017/ Review date: December 2020

Disclaimer: We try to ensure that the information is easy to understand, accurate and up-to-date as possible. If you would like more information on the source material the author used to write this document please contact the Encephalitis Society. None of the authors of the above document has declared any conflict of interest which may arise from being named as an author of this document