Encephalitis is an inflammation of the brain. The inflammation is caused either by an infection invading the brain (Infectious Encephalitis) or through the immune system attacking the brain in error (Post-infectious or Autoimmune Encephalitis).
Who can get Encephalitis?
Anyone at any age can get Encephalitis. There are up to 6,000 cases of Encephalitis in the UK and potentially hundreds of thousands worldwide each year.
What causes Infectious Encephalitis?
Viruses are the most commonly identified cause of Infectious Encephalitis. Within the British Isles herpes simplex virus (HSV or the cold sore virus) is the virus most frequently identified. Worldwide other viruses are responsible, many of which are transmitted by mosquito. In some patients, the identity of the infecting virus is not conclusively determined despite extensive laboratory testing. More rarely bacteria, fungus and parasites can cause Encephalitis.
What causes Post-infectious Encephalitis / Autoimmune Encephalitis?
Autoimmune Encephalitis may be triggered by infection in which case the term “Post-infectious Encephalitis” is used. ADEM (Acute Disseminated Encephalomyelitis) is a Post-infectious Encephalitis. The illness usually follows in the wake of a mild viral infection (such as those that cause rashes in childhood) or immunisations. Typically there is a delay of days to two to three weeks between the triggering infection and development of the Encephalitis.
Not all forms of Autoimmune Encephalitis are triggered by infection. Other forms of Autoimmune Encephalitis are associated with finding specific antibodies in blood. This group of causes of Encephalitis is called Antibody-Associated or Antibody-Mediated Encephalitis such as Voltage-gated Potassium Channel Complex Antibody-associated Limbic Encephalitis and N-Methyl-D-Aspartate-Receptor- associated Encephalitis.
What are the main symptoms?
Infectious Encephalitis frequently begins with a ‘flu-like illness or headache. Typically more serious symptoms follow hours to days, or sometimes weeks later. The most serious finding is an alteration in the 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), aversion to bright lights, inability to speak or control movement, sensory changes, neck stiffness, or uncharacteristic behaviour.
Autoimmune Encephalitis often has a long onset. Symptoms will vary depending on the cause but may include: confusion, altered personality or behaviour, psychosis, movement disorders, seizures, hallucinations, memory loss, or sleep disturbances.
How is Encephalitis diagnosed?
Diagnosis of Encephalitis is made when evidence of inflammation or swelling of the brain is identified. The range of possible symptoms and their rate of development vary widely, and are not just found in Encephalitis. Therefore making the diagnosis can be difficult.
What tests are undertaken?
Lumbar Puncture (LP) - to detect inflammation, as well as the possible presence of infection, in the spinal fluid.
Brain scans such as Computerised Tomography (CT) or Magnetic Resonance Imaging (MRI) - to exclude brain tumours, aneurysms (a bulge in a blood vessel) and strokes and show the extent of any inflammation.
Blood tests - to exclude metabolic encephalopathy (neurological disorders caused by systemic illnesses such as diabetes, renal failure, heart failure).
It is not unusual for the results of tests to be “normal”, however they are also important in excluding some other diseases.
What is the treatment for Encephalitis?
Treatment of patients with Encephalitis has two aims. The first aim is to ensure that the patient receives specific treatment for the cause of their Encephalitis. Where the Encephalitis is thought to be caused either by a virus or bacteria, patients are treated with anti-viral and/or antibiotic drugs. Patients are frequently given several different drugs at once. It is important that these drugs are started promptly, and hence they will often be started before a definite cause is found. Acyclovir is the most frequently used anti-viral drug. It is effective against the Herpes Simplex and Varicella Zoster viruses. Unfortunately for many viral infections there are no specific treatments at present.
The second aim is to treat the complications arising from the Encephalitis and to support the patient whilst they are not able to perform their usual bodily functions. Often treatment with anti-convulsants to control seizures, or sedatives to reduce agitation is required. Sometimes patients require Intensive Care treatment including ventilation (mechanical help with breathing).
Because Autoimmune Encephalitis is due to the immune system acting inappropriately, treatments aim to modify immune system function. These include drugs such as steroids (drugs to relieve inflammation), intravenous immunoglobulin (IVIG) (a blood product given into a vein in a drip) or plasma exchange (when some of a person’s blood is taken out from a vein, washed and then put back into the vein in a drip).
Do people get better?
Nerve cells may be damaged or destroyed by the viral infection, the immune reaction and by pressure resulting from the inflammation. This damage is termed “Acquired Brain Injury (ABI). Some loss of brain function is therefore a probable outcome of Encephalitis. In some cases, however, this loss occurs on a relatively small scale resulting in very minor impairment, such as some loss in speed of thinking. In other cases damage can be extensive leading to significant impairments.
Coming to terms with these problems can be potentially distressing and challenging for everyone concerned. The child or adult you knew, or who was you, may have changed and the child or person they have become, or you have become, may present with a number of problems. It is important to consider that it may take time for the individual and the whole family to adjust, in both practical and emotional terms, to their new situation
What are the after-effects of Encephalitis?
There will be a wide variation in how Encephalitis affects the person in the long term. Tiredness, recurring headaches, difficulties with memory, concentration and balance, mood swings, aggression and clumsiness are often reported. Epilepsy, as well as being a feature of the acute illness, may develop weeks or months after the illness has subsided. Physical problems may include weakness down one side of the body, loss of sensations and of control of bodily functions and movement. Speech and language problems may also be common features. Speed of thought and reaction may be reduced.
Significant changes may occur in personality and in the ability to function day-to-day even if there is a complete physical recovery.