Abstracts

Rationale: Rasmussen’s Encephalitis (RE) is a rare cause of autoimmune encephalitis. The median age of onset is 6 (Lancet Neurol, 2014, Vol. 13, p. 195-205). It is a refractory focal epilepsy with cerebral hemi-atrophy and often three phases: prodromal, acute, and residual. Pathophysiology is likely T-cell mediated inflammation. Treatment is immunotherapy. Less than 10% of cases are diagnosed in adulthood (Rev Neurol, 2022, Vol. 178, p. 675-691). These may present differently, e.g. slower progression than typical disease. We report additional cases of the uncommon adult-diagnosed RE.


Methods: The Electronic Medical Record was queried for patients seen in our adult neurology division at Mayo Clinic Arizona, searching “Autoimmune encephalitis” OR “Limbic encephalitis” OR “Limbic disorder” OR “Rasmussen syndrome”. After chart review, those meeting RE diagnostic criteria and diagnosed at age ≥12 were included.


Results: Four patients met the inclusion criteria. The age of diagnosis ranged from 16 to 36. The age of seizure onset ranged from 5 to 27. Three patients initially manifested with generalized convulsion; one presented with focal motor seizure. All had eventual daily to weekly focal seizures and hemi-atrophy on brain imaging. There was a delay of 17, 11, 9, and 12 years from seizure onset to RE diagnosis. All were refractory to anti-seizure medication (ASM). Three patients received immunotherapy; IVIG or rituximab, while 1 lacked insurance approval. One also received vagal nerve stimulation. A patient with symptom onset at 16, diagnosis at 19 and treatment with intravenous immunoglobulin (IVIG) had improvement with seizure freedom for years. Another with seizure onset at 27 and diagnosis at 36 was treated with intravenous methylprednisolone with significant but not sustained improvement; treatment with IVIG and rituximab achieved sustained response. A patient with symptom onset at age 5, despite no immunotherapy until 16, improved after IVIG. A patient with the latest symptom onset (27) was the only one with no cognitive deficit.


Conclusions: In all cases trialed, immunotherapy improved seizure frequency, with multiple ASMs ineffective, independent of whether IVIG was started during the acute or residual phase. Significant delay was seen from seizure onset to diagnosis, despite interval findings of hemi-atrophy. The variability in age of onset, age at radiographic findings, and diagnosis may preclude early intervention. Immunotherapy appears to be better than ASMs alone, and delay in diagnosis should not deter its use. Further study is needed to better characterize this rare phenotype.


Funding: None.