Introduction

Encephalitis is a common and potentially devastating illness in childhood. The aetiology includes infectious and non-infectious subgroups. Antibody-mediated encephalitis has emerged as an important and treatable subgroup of encephalitis. These autoantibodies bind to antigens on neuronal cell surface. They include the N-Methyl-D-Aspartate receptor (NMDAR), voltage gated potassium channel complex (VGKC)-complex and dopamine-2 receptor (D2R). This study particularly investigated the frequency of autoimmune encephalitis in children.

Methods

A retrospective study on 164 immunocompetent patients diagnosed with encephalitis at the Children’s Hospital at Westmead from January 1998 to October 2010. The clinical features and MRI brain (n=149) data were reviewed. Autoantibodies were tested on stored acute samples of 78% of patients [acute disseminated encephalitis (ADEM) patients excluded].

Results

The most common identified aetiology in descending order of frequency was ADEM (21.3%), enterovirus (12.2%), mycoplasma pneumonia (6.7%), NMDAR encephalitis (6.1%), herpes simplex virus (5.5%) and VGKC-complex encephalitis (4.3%). The aetiology was unknown in 28% of patients. The outcome at median follow up of 6.5 years was abnormal in 56.1% of patients. The MRI brain was abnormal in 81.2% of patients. The most common MRI phenotypes were ADEM, multifocal grey matter, basal ganglia and limbic encephalitis.

Discussion

Immune-mediated encephalitis (ADEM, NMDAR, VGKC-complex and D2R) is the most common (34.1%) potentially treatable aetiology of childhood encephalitis in Australian children. The long-term outcome of childhood encephalitis remains a concern. The limbic, basal ganglia and multifocal grey matter encephalitis MRI phenotypes were more frequently seen in antibody-mediated encephalitis and mycoplasma encephalitis.