Anti NMDA receptor encephalitis

Anti N-methyl-D-aspartic acid (NMDA) receptor encephalitis is an autoimmune encephalitis with antibodies against the NMDA receptors. It is sometimes considered a form of autoimmune limbic encephalitis. It usually affects young patients particularly young females, in about 60% of whom ovarian teratoma is present. Patients present with psychiatric symptoms but eventually develop seizures or movement abnormalities. 

Young patients are most commonly affected with a female to male ratio of 4:1.1,3 In young female in particular up to 58% are associated with ovarian teratoma.3

Prominent psychiatric symptoms are present during a multistage illness that progresses from psychosis with or without seizures to abnormal movements, dysautonomia, catatonia and coma.1

Interesting feature in those patients who survived is an amnesia to the entire illness. This is thought to be due to disruption of synaptic plasticity which is important in memory and learning process.

Anti N-methyl-D-aspartic acid (NMDA) receptor encephalitis is an autoimmune encephalitis due to antibodies against NR1–NR2 heteromers of the NMDA receptor, in particular extracellular N-terminal domain of the NR1 subunit. These antibodies result in marked reduction of cell-surface NMDA receptors and NMDA-receptor clusters in postsynaptic dendrites 1. Underlying tumour is only detected in approximately 60% of patients, mostly teratomas. Anti-NMDA NR2 antibodies also found in approximately 15-35% patients with SLE and approximately 80% of SLE patients with severe neuropsychiatric illness. CSF shows pleomorphism. Serum titres of anti-NMDA antibodies are elevated and correlate well with the severity of the disease.

MRI brain

Abnormal MRI is seen in up to 50% of reported cases, however the findings are non specific. Abnormal FLAIR or T2 hyperintensity can be seen in the medial temporal lobe, cerebral/cerebellar cortex, basal ganglia and brainstem 1,2. Typically there is no abnormal enhancement or haemorrhage. FDG-PET may show either hyper or hypo metabolism in the affected region.3 

Management 

Medical therapy is usually a combination of immunotherapies including corticosteroids, intravenous immunoglobulins and / or plasma exchange.1 Further workup of anti-NMDA receptor encephalitis is necessary with whole body CT and pelvic US for detection of associated tumor / ovarian dermoid.1 Surgical excision of any ovarian dermoid is performed with concurrent commencement of immunotherapy.

Prognosis

Estimated 4% reported mortality for anti-NMDA receptor encephalitis mainly from respiratory or cardiac complication during intensive care stay.1 Early diagnosis and treatment have been shown to markedly improve outcome and reduce number of relapses. 

An autobiography titled "Brain on Fire: My Month of Madness" by Susannah Cahalan describes her personal experience with the disease.4

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Article Information

rID: 32981
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:
  • Anti N-methyl-D-aspartic acid (NMDA) receptor encephalitis

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