Encephalitis

Definition

Encephalitis is an inflammation of the brain tissue, often caused by infections, autoimmune conditions, or other inflammatory processes. It can lead to severe neurological complications and requires prompt medical attention.

Aetiology

Encephalitis can be caused by:

Viral infections: Herpes simplex virus (HSV), Varicella-zoster virus (VZV), enteroviruses
Bacterial infections: Less common, can include Bartonella and Mycoplasma
Autoimmune conditions: Anti-NMDA receptor encephalitis
Post-infectious immune response: Acute disseminated encephalomyelitis (ADEM)

Pathophysiology

The inflammation in encephalitis is usually due to direct infection of brain tissue or an immune-mediated response to an infection or other triggers. This inflammation can cause brain swelling, increased intracranial pressure, and subsequent neuronal damage.

Risk Factors

Age (young children and elderly)
Immunocompromised state (e.g., HIV/AIDS, organ transplantation)
Geographic location and season (related to vector-borne diseases)
Exposure to infectious agents (e.g., travel history)

Signs and Symptoms

Fever
Headache
Confusion or altered mental status
Seizures
Neurological deficits (e.g., weakness, speech difficulties)

Investigations

Clinical history and physical examination
Lumbar puncture for cerebrospinal fluid (CSF) analysis
Neuroimaging (MRI preferred, CT scan)
EEG to assess for seizure activity
Blood tests to identify potential infectious agents or autoimmune markers
CSF PCR for viral DNA/RNA

Management

Primary Care Management

Immediate referral to hospital if encephalitis is suspected
Initial supportive care (e.g., hydration, fever control)

Specialist Management

Antiviral therapy for suspected viral encephalitis (e.g., aciclovir for HSV)
Management of complications (e.g., anticonvulsants for seizures, steroids for autoimmune encephalitis)
Intensive care support if needed (e.g., for severe cases with respiratory failure)
Rehabilitation for neurological deficits

Example Management for Encephalitis

A patient presenting with suspected HSV encephalitis should be started on intravenous aciclovir as soon as possible after lumbar puncture and CSF analysis. Supportive care should be provided, including antipyretics for fever and monitoring for seizures. The patient should be referred to a neurologist for further assessment and management. If autoimmune encephalitis is suspected, steroids or other immunosuppressive therapies may be initiated.

References

NICE. (2024). Encephalitis: Diagnosis and Management. Retrieved from NICE
NHS. (2023). Encephalitis. Retrieved from NHS
Davison, K., & O'Brien, M. (2020). Clinical Neurology and Neurosurgery. 8th ed. Elsevier.
Roos, K. L., & Tyler, K. L. (2018). Principles of Neurological Infections. Oxford University Press.
Solomon, T., & Michael, B. D. (2022). Encephalitis: Diagnosis and Treatment. Cambridge University Press.