Diagnostic Criteria for Autoimmune Encephalitis

Encephalitis is a severe inflammatory disorder of the brain with many possible causes and a complex differential diagnosis.

Diagnostic criteria for possible autoimmune encephalitis
Diagnosis can be made when all three of the following criteria have been met:

  1. Subacute onset (rapid progression of less than 3 months) of working memory deficits (short-term memory loss), altered mental status, or psychiatric symptoms
  2. At least one of the following:
    • New focal CNS findings
    • Seizures not explained by a previously known seizure disorder
    • CSF pleocytosis (white blood cell count of more than five cells per mm3)
    • MRI features suggestive of encephalitis†
  3. Reasonable exclusion of alternative causes

Diagnostic criteria for definite autoimmune limbic encephalitis
Diagnosis can be made when all four* of the following criteria have been met:

  1. Subacute onset (rapid progression of less than 3 months) of working memory deficits, seizures, or psychiatric symptoms suggesting involvement of the limbic system
  2. Bilateral brain abnormalities on T2-weighted fluid-attenuated inversion recovery MRI highly restricted to the medial temporal lobes
  3. At least one of the following:
    • CSF pleocytosis (white blood cell count of more than five cells per mm3)
    • EEG with epileptic or slow-wave activity involving the temporal lobes
  4. Reasonable exclusion of alternative causes

Diagnostic criteria for definite acute disseminated encephalomyelitis
Diagnosis can be made when all five of the following criteria have been met:

  1. A first multifocal, clinical CNS event of presumed inflammatory demyelinating cause
  2. Encephalopathy that cannot be explained by fever
  3. Abnormal brain MRI:
    • Diffuse, poorly demarcated, large (>1–2 cm) lesions predominantly involving the cerebral white matter
    • T1-hypointense lesions in the white matter in rare cases
    • Deep grey matter abnormalities (eg, thalamus or basal ganglia) can be present
  4. No new clinical or MRI findings after 3 months of symptom onset
  5. Reasonable exclusion of alternative causes

Diagnostic criteria for anti-NMDA receptor encephalitis
A- Probable anti-NMDA receptor encephalitis
Diagnosis can be made when all three of the following criteria have been met:

  1. Rapid onset (less than 3 months) of at least four of the six following major groups of symptoms:
    • Abnormal (psychiatric) behaviour or cognitive dysfunction
    • Speech dysfunction (pressured speech, verbal reduction, mutism)
    • Seizures
    • Movement disorder, dyskinesias, or rigidity/abnormal postures
    • Decreased level of consciousness
    • Autonomic dysfunction or central hypoventilation
  2. At least one of the following laboratory study results:
    • Abnormal EEG (focal or diffuse slow or disorganised activity, epileptic activity, or extreme delta brush)
    • CSF with pleocytosis or oligoclonal bands
  3. Reasonable exclusion of other disorders (appendix)

Diagnosis can also be made in the presence of three of the above groups of symptoms accompanied by a systemic teratoma

B- Definite anti-NMDA receptor encephalitis
Diagnosis can be made in the presence of one or more of the six major groups of symptoms and IgG anti-GluN1 antibodies, after reasonable exclusion of other disorders

Diagnostic criteria for Bickerstaff’s brainstem encephalitis
A- Probable Bickerstaff’s brainstem encephalitis
Diagnosis can be made when both of the following criteria have been met:

  1. Subacute onset (rapid progression of less than 4 weeks) of all the following symptoms:
    • Decreased level of consciousness
    • Bilateral external ophthalmoplegia
    • Ataxia
  2. Reasonable exclusion of alternative causes

B- Definite Bickerstaff’s brainstem encephalitis
Diagnosis can be made in the presence of positive IgG anti-GQ1b antibodies even if bilateral external ophthalmoplegia is not complete or ataxia cannot be assessed, or if recovery has occurred within 12 weeks after onset

Diagnostic criteria for Hashimoto’s encephalopathy
Diagnosis can be made when all six of the following criteria have been met:

  1. Encephalopathy with seizures, myoclonus, hallucinations, or stroke-like episodes
  2. Subclinical or mild overt thyroid disease (usually hypothyroidism)
  3. Brain MRI normal or with non-specific abnormalities
  4. Presence of serum thyroid (thyroid peroxidase, thyroglobulin) antibodies
  5. Absence of well characterised neuronal antibodies in serum and CSF
  6. Reasonable exclusion of alternative causes

Criteria for autoantibody-negative but probable autoimmune encephalitis
Diagnosis can be made when all four of the following criteria have been met:

  1. Rapid progression (less than 3 months) of working memory deficits (short-term memory loss), altered mental status, or psychiatric symptoms
  2. Exclusion of well defined syndromes of autoimmune encephalitis (eg, typical limbic encephalitis, Bickerstaff’s brainstem encephalitis, acute disseminated encephalomyelitis)
  3. Absence of well characterised autoantibodies in serum and CSF, and at least two of the following criteria:
    • MRI abnormalities suggestive of autoimmune encephalitis
    • CSF pleocytosis, CSF-specific oligoclonal bands or elevated CSF IgG index, or both*
    • Brain biopsy showing inflammatory infiltrates and excluding other disorders (eg, tumour)
  4. Reasonable exclusion of alternative causes

 

 

References:

  1. Graus F, Titulaer MJ, Balu R, Benseler S, Bien CG, Cellucci T, Cortese I, Dale RC, Gelfand JM, Geschwind M, Glaser CA, Honnorat J, Höftberger R, Iizuka T, Irani SR, Lancaster E, Leypoldt F, Prüss H, Rae-Grant A, Reindl M, Rosenfeld MR, Rostásy K, Saiz A, Venkatesan A, Vincent A, Wandinger KP, Waters P, Dalmau J. A clinical approach to diagnosis of autoimmune encephalitis. Lancet Neurol. 2016 Apr;15(4):391-404. [Medline]
  2. Younger DS. Autoimmune Encephalitides. Neurol Clin. 2019 May;37(2):359-381. [Medline]

 

Created Apr 22, 2019.

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