Encephalitis is an inflammation of the brain tissue that causes the brain to become swollen. It is not a very common condition and, on average, affects about 10-15 individuals per 100,000 annually. The condition can be life threatening and therefore requires immediate medical attention. Encephalitis more commonly affects small children than adults. Older people are also known to be at a higher risk of the disease.

Symptoms

Encephalitis often commences with basic flu-like symptoms that may include fever, headache, body ache and nausea/vomiting.

However, over a matter of hours, days or weeks, these could develop into more serious symptoms such as:

• seizures / fits
• drowsiness
• confusion and/or disorientation
• neck stiffness
• sensitivity to light and/or sound
• speech / hearing / cognitive impairment
• double vision / uncontrollable eye movement
• behavioural changes such as irritability
• hallucinations
• loss of consciousness
• weakness or partial paralysis / loss of feeling in parts of the body, mostly arms and legs
• memory loss
• spotty rashes (which do not usually fade when a glass is pressed on them)

Complications

Encephalitis can sometimes have lasting effects, and may even be fatal despite treatment. Prompt treatment is thus imperative for a patient to have a fair chance at recovery.

Persistent problems that some patients may find themselves faced with include:

• epilepsy
• memory loss
• fatigue
• behavioural changes, such as irritability
• emotional changes, such as anxiety, depression, mood swings
• cognitive changes, such as poor concentration, attention span, problem solving
• changes motor skills, such as movement, coordination, balance

In extreme cases, some patients may even become comatose.

Causes

Encephalitis is usually attributed to one of two causal pathways:

1. Infection

Encephalitis may occur if an infection in the body, usually viral, spreads to the brain. When the condition is caused by a viral infection, it is referred to as viral encephalitis. Encephalitis that arises from bacterial, fungal or parasitic infections is rare.

The most common viruses that are associated with encephalitis are:

• herpes simplex virus (types 1 and 2)
• varicella zoster virus (chicken pox, shingles)
• measles, mumps and rubella viruses
• vector-borne viruses such as Japanese encephalitis, tick-borne encephalitis, rabies, Zika virus, equine viruses, Chikungunya, West Nile virus

• Autoimmunity

In rare instances, the body’s immune system may attack its own self (autoimmunity). When encephalitis is caused by the immune system attacking the brain in this manner, it is referred to as autoimmune encephalitis. Such an event could be triggered by:

• an infection that occurred previously (usually within a few weeks prior), in which case it may be referred to as post-infectious encephalitis
• a tumour (benign or malignant) somewhere in the body
• vaccination (extremely rarely)

Diagnosis

Diagnostic testing for encephalitis may include:

• a scan of the brain, such as an MRI scan or CT scan
• a lumbar puncture, where cerebrospinal fluid is drawn from the lower back to test for infection
• an electroencephalogram (EEG), to test for abnormal brain activity via electrical impulses
• blood, urine or other tests to check for infections or related antibodies

Prevention

Since there is no direct cause for encephalitis, reducing the risk of its incidence involves taking precautions to avoid viral (or other) infections that are associated with it. These include:

• ensuring that you and any children in your care are up-to-date on vaccines, particularly MMR and chicken pox vaccines
• avoiding travel to areas where there is a spread of viruses that can lead to encephalitis
• avoiding exposure to vectors such as mosquitoes and ticks
• following measures, such as hand hygiene, covering the mouth while coughing and sneezing, etc., to prevent the spread of infectious diseases
• taking proper care and following medical advice when ill

Treatment

The key element to treating encephalitis is to commence treatment as soon as possible.

As such, treatment may include:

• antiviral medicines to treat any underlying viral infection
• antibiotic or antifungal medicines to treat any underlying bacterial/fungal infection
• steroid injections, if the causal issue is autoimmunity (and sometimes in cases linked to chicken pox)
• immunoglobulin therapy, to control the immune system
• removal of tumours by surgery
• plasmapheresis, to remove from the blood any substances that might be attacking the brain
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In cases where symptoms are more severe, additional treatment may be required, such as:

• anti-seizure medication
• introduction of a ketogenic diet in drug-resistant epilepsy
• supportive treatment such as a breathing tube, feeding tube, catheter, etc. if the patient is not conscious

Cover illustration adapted from iStock