Introduction

Anti-NMDA receptor encephalitis is a paraneoplastic syndrome. Ovarian teratomas are detected in up to half of all female adult patients

Epidemiology

  • Incidence: 0.10 cases per 100,000 person-years
  • Peak incidence: 20-30 years
  • Sex ratio: 1:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Clinical features

Psychiatric features including agitation, hallucinations, insomnia, delusions and disordered thinking

Seizures

Dyskinesias

Autonomic instability

Investigations

MRI head can be normal but abnormalities can be visualised on FLAIR sequences in the deep subcortical limbic structures.

CSF may demonstrate pleiocytosis but can be normal initially.

Antibodies
  • Anti-MuSK is an autoantibody specific to muscle kinase in myasthenia gravis with no evidence of a thymoma and without antibodies to acetylcholine receptors.
  • Anti-GM1 is an autoantibody specific to acute inflammatory demyelinating polyneuropathy (AIDP) variant of Guillain-Barre syndrome.

Management

Treatment of anti-NMDA encephalitis is based of immunosuppression with intravenous steroids, immunoglobulins, rituximab, cyclophosphamide or plasma exchange, alone or in combination. Resection of teratoma is also therapeutic.