The Encephalitis Society @ European Neuro Convention

What is Encephalitis?

Encephalitis is an inflammation of the brain. Inflammation is caused either by an infection invading the brain (infectious encephalitis); or through the immune system attacking the brain (post-infectious/autoimmune encephalitis).

Encephalitis is different from meningitis. Meningitis means inflammation of the protective layers that cover the brain. Sometimes patients have both meningitis and encephalitis and this is called meningoencephalitis.  If the spinal cord is also inflamed this is called meningoencephalomyelitis.

Encephalitis can affect anyone of any age.  There are around 6000 cases a year in the UK and the estimated cost to the NHS is circa £40 million.  Both these figures are considered an underestimate and the cost to the health services does not include costly in-patient rehabilitation, long-term care, and loss of productivity among many working-age survivors


The types of symptoms seen in encephalitis reflect the specific areas of the brain affected by inflammation. The range of symptoms and their rate of development vary widely and can make the diagnosis of encephalitis difficult.  In infectious types of encephalitis it frequently begins with a ‘flu-like' illness and/or severe headache. More serious symptoms follow hours to days later.  The most serious of which is an alteration in level of consciousness. This can range from mild confusion or drowsiness, to loss of consciousness and coma.  Other symptoms include a high temperature, seizures (fits or convulsions), aversion to bright lights, inability to speak or control movement, sensory changes, neck stiffness, or uncharacteristic behaviour.   Although infections are a major cause of encephalitis, the body's reaction to infection can also lead to encephalitis.  This occurs when an infection outside the brain triggers an abnormal immune response, which results in damage to the brain. This condition is called post-infectious encephalitis.  Post-infectious encephalitis has a variety of other names which include acute disseminated encephalomyelitis (ADEM), parainfectious encephalitis and post-vaccinal encephalitis.  In these cases there is often a delay of days to several weeks between the triggering infection and development of encephalitis.  Not all forms of autoimmune encephalitis are triggered by infection.  In the last decade it has been recognised that there are other forms of autoimmune encephalitis that are associated with finding specific antibodies in blood. These causes of encephalitis are called antibody-associated or antibody-mediated encephalitis.   Autoimmune causes of encephalitis can present particular difficulties as the onset may be longer than seen in infectious types and symptoms (confusion, altered personality or behaviour, psychosis, movement disorders, hallucinations, memory loss, and sleep disturbance) may be mistaken for a developing psychiatric illness or mental health problem.  

What are the consequences of Encephalitis?

The consequences of encephalitis can be many and varied.  People may make a good recovery or they may be left with severe, life-changing sequelae.  Unfortunately mortality (death) rates remain high and even with treatment, up to three in 10 people will die.  Figure one below illustrates some of the consequences that survivors might experience.

Figure One.  Reproduced with kind permission © The Encephalitis Society

Recovery and Rehabilitation

The acute phase of the illness (the time of active brain inflammation) can last anything from a few days to several weeks.  In some cases the person may be in a coma for a much longer period.  This acute stage may be followed by a phase of fairly rapid improvement which slows down but recovery can continue over the years to come. 

Outcomes vary between those who are able to return to their former work and lifestyle (with perhaps only a slight change in their abilities) to those left profoundly disabled, physically, cognitively or both. 

Nerve cells may be damaged or destroyed by both the infection and inflammation. The resulting damage is termed an acquired brain injury (ABI).  The loss of brain function from ABI can range from very minor impairment, such as some loss in speed of thinking, to more significant impairments. The degree and type of damage will vary according to the cause, the severity of the inflammation, the parts of the brain affected, and any delay in treatment.  It is this combination which will determine the pattern of difficulties that remain after the illness. Significant changes may occur in personality and in the ability to function day to day even if there is a complete physical recovery.  Coming to terms with these problems can be very distressing and challenging for everyone concerned.  The person you knew, or who was you, may have changed and the person they have become, or you have become, may present with a number of problems.

It is important not to underestimate the time that the person and the whole family will need to adjust, in both practical and emotional terms, to their new situation.  Those involved have, in some cases, suffered a complicated form of bereavement.  It is not unrealistic, therefore, to think of allowing several months and sometimes years to come to terms with what has happened. 

What help is available for people and families affected by Encephalitis?

 The Encephalitis Society has a range of services available for people affected by encephalitis, their families, and those professionals supporting them.  This ranges from a helpline, NHS accredited information, training packages, local support, a neuropsychology service and a range of annual events and activities.  Please visit or contact us +44 (0) 1653 699599 or


Dr Ava Easton

The Encephalitis Society