Box 2.

Most common causes and mimics of encephalitis in immunocompetent adults in the UK

Causes:
Viral: Herpes simplex virus types 1 and 2, varicella zoster virus, enteroviruses, adenovirus, parechovirus, measles virus, HIV
Autoimmune (main tumour associations in brackets): Antibodies against neuronal surface antigens: NMDAR antibody encephalitis (ovarian teratoma), LGI-1 antibody encephalitis (thymoma), antibodies against intracellular antigens: anti-Hu (small cell lung tumour), anti-Ma (testicular tumours), anti-GAD, acute disseminated encephalomyelitis, Bickerstaff's encephalitis
Mimics:
Infective: Systemic sepsis with encephalopathy, bacterial meningitis, TB, opportunistic infections in immunocompromised patients (eg crytococcus, toxoplasma, cytomegalovirus)
Inflammatory: Vasculitis, systemic lupus erythematosus with CNS involvement, Beh├žet's disease, neurosarcoidosis
Metabolic: Hypoglycaemia, hyponatraemia, hepatic encephalopathy, toxins (drugs, alcohol)
Neoplastic: Primary brain tumour (particularly low grade glioma mimicking CNS inflammation), metastases
Others: Status epilepticus from other causes, haemorrhagic or ischaemic stroke, psychiatric disease
  • CNS = central nervous system; GAD = glutamic acid decarboxylase; LGI-1 = leucin-rich glioma inactivated 1; NMDAR = N-methyl D-aspartate receptor; TB = tuberculosis