Viral Encephalitis

Viral Encephalitis

Overview

Overview Encephalitis, inflammation of the brain parenchyma, can be caused by either an infection or autoimmune process. Clinical features of encephalitis include fever, altered mental status, neurological deficit and seizures. Definitive diagnosis rests on a lumbar puncture with CSF examination. Encephalitis can be difficult to distinguish from meningitis. Young, old and especially those who are immunocompromised are susceptible to developing encephalitis.

Remember In menigitis cerebral function remains normal where as, in encephalitis causes altered mental status/confusion.

Signs and symptoms

  • Meninges involvement
    • Neck stiffness
    • Photophobia
  • Altered level of consciousness
  • Hallucination
  • Personality changes
  • Seizures
  • Focal neurological disturbance
    • aphasia
    • ataxia
    • upper motor neuron weakness
    • lower motor neuron weakness
    • cranial nerve palsy

Think Meningeal involvement (photophobia and nuchal rigidity) are usually absent with a pure encephalitis. Meningoencephalitis both involve the brain parenchyma and meninges

Aetiology

Herpesviruses

  • Herpes Simplex Virus
  • Ebstein Barr Virus
  • Varicella Zoster Virus

Arthropod-bourne viruses

  • Japanese encephalitis
  • West Nile Virus

Enteroviruses

Remember HSV-1 encephalitis is the most common cause of viral encephalitis

West Nile virus infection triad encephalitis, flaccid paralysis with a polio-like presentation. A differential for Gullian Barre Syndrome

Pathophysiology

Differential Diagnosis

  • Infective meningitis
  • Chemical meningitis
  • Primary intracranial or metastatic tumors
  • Medication side effects effecting brain
    • PML from rituximab
  • Autoimmune disease
    • Cerebral lupus
    • Anti-NMDA receptor
    • Anti-LGI1 encephalitis
  • Paraneoplastic diseases
    • Limbic encephalitis 
    • Anti-Hu encephalomyelitis
    • Ma2-associated encephalitis 
    • Anti-CRMP5 encephalomyelitis 
    • Stiff man syndrome - Anti GAD

Investigations

  • FBC
  • EUC
  • LFT
  • CMP
  • VBG
  • Blood cultures
  • Urinalysis
  • Electroencephalogram
  • CT brain
  • MRI brain
  • Lumbar puncture with CSF examination
    • cell count
    • protein
    • glucose
    • culture

INSERT TABLE DIFFERENTIATING CSF RESULT BETWEEN INFECTIONS 

Remember Temporal lobe involvement is strongly suggestive of herpes simplex virus (HSV) encephalitis

 

Treatment

Empirical therapy with acyclovir

Complications and Prognosis

Complications

  • Increased intracranial pressure
  • Seizures

Prognosis

  • 80% of patients will have severe neurologic sequelae

References

UptoDate

Related posts