Encephalitis

Question 1

Definition/Etiology

Answer 1

=> Inflammation of the brain due to:
* Direct infection (e.g. HSV-1, other viruses)
* Post-infectious immune-mediated mechanisms
* Autoimune -(e.g. anti-NMDAR, ADEM, paraneoplastic)

ADEM- acute disseminated encephalomyelitis

Question 2

Common Causes

Answer 2

->Viral
* HSV-1: most common; causes focal encephalitis, usually affecting temporal/frontal lobes
* Other viruses:
- Japanese encephalitis virus
- West Nile virus
- Tick-borne viruses

-> Bacterial
* TB, Listeria, Rickettsia, Mycoplasma

->	Others
*	Fungal, syphilis, parasitic

*	West Nile  M/C/C of endemic encephalitis– Africa, Middle East, West Asia, Europe)

Question 3

Clinical Presentation

Answer 3

• Altered mental status, fever
• Personality/behavioural changes
• Focal neurological signs
• Speech disorders
• Seizures
• Movement disorders (esp. in autoimmune encephalitis)

Question 4

Diagnostic Clues
For
Encephalitis
NMDAR Encephalitis
HSV Encephalitis

Answer 4

• Encephalitis = encephalopathy + focal neurological findings
• NMDAR encephalitis: psychiatric symptoms, seizures, orofacial dyskinesia
• HSV: temporal lobe involvement, haemorrhagic CSF

Temporal lobe functions- Memory, emolional processing, Language so, dysfunction causes- memory problems, psychiatric symptoms, language difficulties and seixures.

Question 5

Investigations

Answer 5

CSF
EEG
Imaging

Question 5

CSF findings

Answer 5

• CSF pleocytosis, elevated protein
• CSF PCR: detects viral DNA (e.g. HSV, enteroviruses)
• Specific CSF antibodies (e.g. for West Nile virus)
• Autoimmune panel:
  
  • CNS autoantibodies: Anti-NMDAR, others
• Oligoclonal bands, flow cytometry as adjuncts
  
  • Serum: ANA, dsDNA etc.

Question 6

EEG

Answer 6

• May show epileptiform discharges or slow wave activity in temporal lobes
• Extreme delta brush pattern is specific for anti-NMDAR encephalitis
• Useful to:
  • Exclude non-convulsive status epilepticus(frequently complicates encephalitis)
  • Detect seizures mimicking encephalitis or secondary to it

Question 7

• MRI brain

Answer 7

T2/FLAIR changes;
Temporal lobe involvement (HSV)
Basal ganglia (autoimmune/West Nile)

Question 8

Tt Specific for HSV

Answer 8

=>Antiviral
* Empiric acyclovir (10 mg/kg IV TDS, renally adjusted) pending HSV PCR
* Continue minimum 14 days if HSV confirmed
* Some suggest repeat CSF PCR before stopping
* Treat HSV-2, EBV, CMV as per specific recommendations
* Aggressive Tt of Seizures
*No evidence to support empirical Tt with steroids for cerebral oedema

Question 9

CMV (Cytomegalovirus)
Treatment

Answer 9

->Ganciclovir or Valganciclovir
-> In immunocompromised (e.g. transplant, HIV):
- Can cause cranial ganglionitis & polyradiculitis
- May cause subacute encephalitis

Question 9

Prognosis & Follow-Up

Answer 9

• Residual deficits (esp. cognitive, seizures) are common
• Sequelae more likely in delayed treatment

Question 10

Autoimmune encephalitis
Tt

Answer 10

• Immunotherapy:

=>First line
* steroids
* IVIG
* plasmapheresis (for NMDAR, ADEM, etc.)

=>Second line(No strong evidence)
Rituximab
Cyclophosphamide

Question 11

JC Virus

Answer 11

• Reactivates in immunosuppressed (e.g. HIV, transplant, chemotherapy)

Question 12

Progressive Multifocal Leukoencephalopathy (PML)

Answer 12

Classically in AIDS patients(CD4 count<50-100/microlitre)
Can occur in haem malignancies, HCT,solid organ transplant, SLE
Destruction of oligodendrocytes → demyelination

Oligodendrocytes normally form myelin sheath

Question 12

PML
* Clinical Features
* Onset
* Areas of brain involved

Answer 12

-> Gradual onset; affects subcortical white matter, periventricular regions, cerebellum, brainstem

->May present with:
* Focal deficits
* Cognitive decline
* Ataxia
* Visual disturbances

-> Asymmetric involvement

-> No enhancement or mass effect on imaging

Question 12

Diagnosis

Answer 12

-> MRI: White matter lesions, typically without contrast enhancement

-> CSF PCR: JC virus

-> Brain biopsy if diagnosis uncertain

Question 12

Tt of PML

Answer 12

Mainly supportive
Tt of underlying conditions