Question 12

In a suspected case of autoimmune encephalitis:

a) List the investigations needed, and explain why they are required. (50% marks)

b) Outline a specific management plan for proven autoimmune encephalitis and its common complications. Do not include resuscitation in your answer. (50% marks)

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College answer

Not available.

Discussion

a) Investigations listed here are partly to to confirm the diagnosis of autoimmune encephalitis, and partly to exclude other competing differentials.

CT brain

To exclude structural brain lesions (stroke, haemorrhage, abscess)
To exclude the possibility of raised intracranial pressure for the LP that follows

LP and CSF analysis

Opening pressure, cell count with differential, protein, glucose (this helps exclude infections causes, and can reveal characteristic patterns)
Gram stain and bacterial culture (to exclude meningitis)
Specific infectious PCR on CSF
- HSV-1/2 PCR (if test available, consider HSV CSF IgG and IgM in addition)
- VZV PCR
- Enterovirus PCR
- Cryptococcal antigen or India ink staining
- VDRL for syphilis
- Mycobacteria PCR
Specific autoimmune biomarkers in the CSF
- Oligoclonal bands and IgG index
- Numerous antibodies (see above) which are diagnostic for autoimmune encephalitis

Peripheral blood tests

Blood cultures (to exclude systemic sepsis and septic encephalopathy)
HIV serology (consider RNA)
Treponemal testing (rapid plasma reagin, specific treponemal test)
Autoimmune vasculitis screen (to exclude cerebral vasculitis)

Imaging

MRI - because autoimmune encephalitis may have a characteristic pattern
CT imaging of the whole body, looking for:
- Occult malignancy (associated with many types of autoimmune encephalitis)
- Lymphadenopathy, granulomatous disease, etc (suspicion of TB)

Neurophysiology

Other tissues/fluids

When clinical features of extra-CNS involvement are present, this may be appropriate (e.g., biopsy of skin lesions; bronchoalveolar lavage or endobronchial biopsy)

Management options for autoimmune encephalitis, and their complications:

High dose ("pulse") methylprednisolone or dexamethasone
- Hyperglycaemia
- Insomina, agitation, psychosis
- Fluid retention
- Muscle wasting, delayed weaning from ventilation
- Impaired wound healing
- Increased propensity to infection (eg. PJP)
Rituximab
- Long term loss of humoral immunity
- Infusion reaction
- Lymphopenia
Cyclophosphamide
- Bone marrow suppression
- Renal tubular necrosis
- Pulmonary fibrosis
- Haemorrhagic cystitis
IV immunoglobulin
- Risk of anaphylaxis
- Large hyperoncotic fluid load (circulatory overload)
Plasmapheresis
- Bleeding complications of anticoagulation and vascular access
- Haemolysis and thrombocytopenia
- Hypothermia and complement activation
- Febrile reaction to replaced blood products
- Unavoidable removal of useful blood components (eg. useful drugs)
- Hypotension due to volume loss

References

Dalmau, Josep, and Myrna R. Rosenfeld. "Autoimmune encephalitis update." Neuro-oncology 16.6 (2014): 771-778.

Venkatesan, Arun, and Romergryko G. Geocadin. "Diagnosis and management of acute encephalitis: A practical approach." Neurology: Clinical Practice 4.3 (2014): 206-215.

Granerod, J., et al. "Causality in acute encephalitis: defining aetiologies." Epidemiology & Infection 138.6 (2010): 783-800.

Venkatesan, Arun. "CLINICAL APPROACH TO ACUTE ENCEPHALITIS." (2017).

Singh, Tarun D., Jennifer E. Fugate, and Alejandro A. Rabinstein. "The spectrum of acute encephalitis: causes, management, and predictors of outcome." Neurology 84.4 (2015): 359-366.

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