12A. Encephalitis

Definition

Encephalitis refers to inflammation of the brain, which causes CNS damage and damage to the blood-brain barrier.

Etiology

  • Viral
    • HSV – topic 19B
    • HZV – topic 19B
    • Tick-borne encephalitis (TBE)
    • Poliomyelitis
    • Rabies
  • Immune-mediated
    • Postvaccination and parainfectious encephalomyelitis
    • Autoimmune-limbic encephalitis
    • Paraneoplastic encephalitis – topic 24A
  • Bacterial (rare)

Classification

We can also classify types of encephalitis according to the part of the brain which is affected:

  • Polioencephalitis – grey matter affected
    • HSV encephalitis
    • Tick-borne encephalitis
    • Poliomyelitis
    • Rabies
  • Leukoencephalitis – white matter affected
    • Postvaccination and parainfectious encephalomyelitis
    • Progressive multifocal leukoencephalopathy (PML)
  • Panencephalitis – grey and white matter affected
    • Subacute sclerotizing panencephalitis
    • Rubeola panencephalitis

Clinical features

The clinical features of all types of encephalitis are similar. The patient may have:

  • Flu-like symptoms
  • Meningeal signs
  • Focal neurological deficits
  • Epileptic seizures
  • Altered mental status
  • Behavioural changes

Altered mental status, seizures, and focal neurological deficits is very suspicious for encephalitis.

Diagnosis and evaluation

Lumbar puncture is the most important evaluation. The CSF will have oligoclonal bands, lymphocytes, and high protein levels.

MRi is also important. On the MRi we can see focal or multifocal lesions and oedema.

In case of seizures, EEG is important.

Treatment

The treatment depends on the cause. HSV should be treated with acyclovir, and immune-mediated types should be treated with steroids.


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