Encephalitis means inflammation of the brain. This can be the result of infective or non-infective causes. Non-infective causes are autoimmune, meaning antibodies are created that target brain tissue.
The most common cause is infection with a virus. Bacterial and fungal encephalitis is also possible although much more rare in the UK. The most common viral cause is herpes simplex virus (HSV). In children the most common cause is herpes simple type 1 (HSV-1) from cold sores. In neonates it is herpes simplex type 2 (HSV-2) from genital warts, contracted during birth.
Other viral causes include varicella zoster virus (VZV) associated with chickenpox, cytomegalovirus associated with immunodeficiency, Epstein-Barr virus associated with infectious mononucleosis, enterovirus, adenovirus and influenza virus. It is important to ask about vaccinations, as the polio, mumps, rubella and measles viruses can cause encephalitis as well.
- Altered consciousness
- Altered cognition
- Unusual behaviour
- Acute onset of focal neurological symptoms
- Acute onset of focal seizures
Children with features of encephalitis need some key investigations to establish the diagnosis:
- Lumbar puncture, sending cerebrospinal fluid for viral PCR testing
- CT scan if a lumbar puncture is contraindicated
- MRI scan after the lumbar puncture to visualise the brain in detail
- EEG recording can be helpful in mild or ambiguous symptoms but is not always routinely required
- Swabs of other areas can help establish the causative organism, such as throat and vesicle swabs
- HIV testing is recommended in all patients with encephalitis
Contraindications to a lumbar puncture include a GCS below 9, haemodynamically unstable, active seizures or post-ictal.
Intravenous antiviral medications are used to treat the suspected or confirmed underlying cause:
- Aciclovir treats herpes simplex virus (HSV) and varicella zoster virus (VZV)
- Ganciclovir treat cytomegalovirus (CMV)
Repeat lumbar puncture is usually performed to ensure successful treatment prior to stopping antivirals
Aciclovir is usually started empirically in suspected encephalitis until results are available. Other viral causes have no effective treatment and management is supportive.
Followup, support and rehabilitation is required after encephalitis, with help managing the complications.
Complications of Encephalitis
- Lasting fatigue and prolonged recovery
- Change in personality or mood
- Changes to memory and cognition
- Learning disability
- Chronic pain
- Movement disorders
- Sensory disturbance
- Hormonal imbalance
Last updated January 2020