Rasmussen’s encephalitis is a rare chronic childhood encephalitis with unexplained hemispheric lateralization; earlier descriptions suggest an increased severity with younger age.

A retrospective single-centre case series from South India with 39 patients between 2005 to 2017, defined by the European Consensus Criteria for diagnosis, were studied. Clinical, EEG, radiological and pathological data were classified and described with treatment outcomes. Radiologically severe (pan-hemispheric) cases were compared with less severe (sub-hemispheric) phenotypes to identify  predictors of severity. Efficacy of immunosuppression therapy and disconnection surgery toward seizure control was studied.

Demographic and clinical features were consistent with previous descriptions; apart from focal seizures (35.8%), frequent presentations with generalized seizures (17.9%) and status epilepticus (28.2%) occurred. Radiologically, cortical disease patterns were typically persistent (69.2%) rather than confluently enlarging (5.1%). Pan-hemispheric cases were significantly younger (p<0.001), with history of adverse peri-natal events (p<0.001) and delayed milestones (p=0.016) encountered exclusively in this group. An onset with status epileptics was more likely in them (O.R. 7.5, 95% CI 1.3 – 43.3, p=0.025).  Electroencephalographic evidence of cortical damage with progression to low amplitude background rhythms occurred only among pan-hemispheric cases (O.R. 4.8, 95% C.I. 1.1 – 20.1, p=0.028). On multivariate analysis, the odds for pan-hemispheric disease decreased with older onset (O.R. 0.49, 95% C.I. 0.27 – 0.89, p=0.020). Surgery for seizure control (n=15) was associated with Engel Class 1 outcomes in all, compared to 37.5% in those without surgery (n=24, p<0.001). Medical immunosuppressive therapy did not demonstrate significant efficacy toward seizure remission (O.R. 0.36, 95% CI 0.09 – 1.37).

A childhood predominant, age-dependent process, linked to brain development, which persistently affects discrete cortical sites is observed. Molecules with homologous immune and neural developmental roles, such as the neuro-developmental MHC-1 receptors, may explain such distribution patterns and merit further study.