Late-onset Rasmussen Encephalitis: A literature appraisal

Rasmussen Encephalitis (RE) is classically described as a childhood encephalopathy due to a unilateral inflammation of the cerebral cortex with a presumed immune-mediated pathophysiological basis. Unusual variant forms, including adolescent and adult-onset RE have been described but there is still a doubt whether these atypical cases correspond to classical RE patients. To review evidence, a systematic PubMed search was conducted to retrieve papers addressing late onset RE to assess (i) the positivity rate of classical childhood-onset diagnostic criteria for RE in late-onset RE, (ii) the specific clinical and radiological features that could help earlier diagnosis and therapeutic interventions, (iii) the arguments for an autoimmune pathophysiology including (iiia) the association with autoimmune markers or diseases and (iiib) the effects of immunomodulatory or immunosuppressive treatments. A total of 50 papers were considered. We identified 102 late-onset RE patients with a sex ratio of 8 women for 2 men. 67% fulfilled the consensus diagnostic criteria for RE. As compared to classical RE, the late-onset RE patients exhibited: i) more frequent focal complex partial seizures, ii) less frequent epilepsia partialis continua throughout evolution, iii) a slower evolution with a delayed occurrence of cortical deficit, iv) less cognitive deterioration and v) a better outcome. A specific association with autoimmune markers or diseases was not found. Immunomodulatory therapies, even performed in a late stage, improved late-onset RE patients in 61% of cases. This review proves that late-onset RE is a reality with specific clinical and radiological features. The good response to immunomodulatory treatments brings further arguments for an immune-regulated process.