Encephalitis is a severe inflammatory disorder of the brain with many possible causes and a complex differential diagnosis. Advances in autoimmune encephalitis research in the past 10 years have led to the identification of new syndromes and biomarkers that have transformed the diagnostic approach to these disorders. However, existing criteria for autoimmune encephalitis are too reliant on antibody testing and response to immunotherapy, which might delay the diagnosis. We reviewed the literature and gathered the experience of a team of experts with the aims of developing a practical, syndrome-based diagnostic approach to autoimmune encephalitis and providing guidelines to navigate through the differential diagnosis. Because autoantibody test results and response to therapy are not available at disease onset, we based the initial diagnostic approach on neurological assessment and conventional tests that are accessible to most clinicians. Through logical differential diagnosis, levels of evidence for autoimmune encephalitis (possible, probable, or definite) are achieved, which can lead to prompt immunotherapy.

These definitions are proposed for clinical and research purposes. Their utility will depend on the outcomes of their application in prospective research.

Forty-eight children with disseminated demyelination of the CNS, 28 with acute disseminated encephalomyelitis (ADEM), seven with multiphasic disseminated encephalomyelitis (MDEM) and 13 with multiple sclerosis were studied for a mean follow-up period of 5.64 years. The presentation findings of the ADEM/MDEM group were compared with those of the multiple sclerosis group. The following findings were more commonly seen in ADEM/MDEM presentation compared with the multiple sclerosis presentations: predemyelinating infectious disease (74 versus 38%, P: < 0.05); polysymptomatic presentation (91 versus 38%, P: < 0.002); pyramidal signs (71 versus 23%, P: < 0.01); encephalopathy (69 versus 15%, P: < 0.002); and bilateral optic neuritis (23 versus 8%, not significant). Seizures occurred only in the ADEM/MDEM group (17 versus 0%, not significant). Unilateral optic neuritis occurred only in the multiple sclerosis patients (23 versus 0%, P: < 0.01). There were no differences in the frequencies of transverse myelitis, brainstem involvement, cerebellar signs and sensory disturbance between the two groups. ADEM/MDEM patients were more likely to have blood leucocytosis (64 versus 22%, P: < 0.05), CSF lymphocytosis (64 versus 42%, not significant) and CSF protein elevation (60 versus 33%, not significant). Patients presenting with multiple sclerosis were more likely to have intrathecal synthesis of oligoclonal bands on presentation (64 versus 29%, not significant). MRI showed that subcortical white matter lesions were almost universal in both groups, though periventricular lesions were more common in multiple sclerosis (92 versus 44%, P: < 0.01). By contrast, in ADEM/MDEM there was absolute and relative periventricular sparing in 56 and 78% of patients, respectively. Follow-up MRI revealed complete or partial lesion resolution in 90% and no new lesions in the ADEM/MDEM group. All of the multiple sclerosis patients had new lesions on repeat MRI (five during relapse and six during asymptomatic convalescent phases). The outcome in the ADEM patients was mixed; 57% of patients made a complete recovery. The mean follow-up for the 35 ADEM/MDEM patients was 5.78 years (range 1.0-15.4 years). Eight of the 13 multiple sclerosis patients relapsed within the first year; 11 had a relapsing-remitting course, one a primary progressive course and one a secondary progressive course. These differences in the presentation of ADEM/MDEM compared with multiple sclerosis may help in the prognosis given to families regarding the possibility of later development of multiple sclerosis.

ObjectiveWe characterised the clinical course, treatment and outcomes in 59 patients with relapsing myelin oligodendrocyte glycoprotein (MOG) antibody-associated demyelination.MethodsWe evaluated clinical phenotypes, annualised relapse rates (ARR) prior and on immunotherapy and Expanded Disability Status Scale (EDSS), in 218 demyelinating episodes from 33 paediatric and 26 adult patients.ResultsThe most common initial presentation in the cohort was optic neuritis (ON) in 54% (bilateral (BON) 32%, unilateral (UON) 22%), followed by acute disseminated encephalomyelitis (ADEM) (20%), which occurred exclusively in children. ON was the dominant phenotype (UON 35%, BON 19%) of all clinical episodes. 109/226 (48%) MRIs had no brain lesions. Patients were steroid responsive, but 70% of episodes treated with oral prednisone relapsed, particularly at doses <10 mg daily or within 2 months of cessation. Immunotherapy, including maintenance prednisone (P=0.0004), intravenous immunoglobulin, rituximab and mycophenolate, all reduced median ARRs on-treatment. Treatment failure rates were lower in patients on maintenance steroids (5%) compared with non-steroidal maintenance immunotherapy (38%) (P=0.016). 58% of patients experienced residual disability (average follow-up 61 months, visual loss in 24%). Patients with ON were less likely to have sustained disability defined by a final EDSS of ≥2 (OR 0.15, P=0.032), while those who had any myelitis were more likely to have sustained residual deficits (OR 3.56, P=0.077).ConclusionRelapsing MOG antibody-associated demyelination is strongly associated with ON across all age groups and ADEM in children. Patients are highly responsive to steroids, but vulnerable to relapse on steroid reduction and cessation.