The age of onset ranges from infancy to adulthood, but onset is most commonly during childhood. Prior to the acute phase of disease, there may be a prodromal phase of mild hemiparesis or well-controlled focal epilepsy for up to several years. The acute phase is characterized by rapidly progressive seizures, hemiparesis, hemianopia, aphasia (if the dominant hemisphere is involved), and cognitive decline over the first year. The final stage consists of permanent neurological deficits and relapsing epilepsy. Adolescent- or young adulthood-onset occurs in about 10% of patients.
Adolescent-onset disease has a slower rate of progression and less severe fixed neurological deficits compared to the childhood-onset disease. These patients may present with unilateral movement disorders such as hemiathetosis and hemidystonia. Although early seizures are common in Rasmussen syndrome, cases with delayed seizure onset or even absence of seizures have been reported.
G04.81 – Other encephalitis and encephalomyelitis
230191005 – Rasmussen syndrome
Differential Diagnosis & Pitfalls
- Sturge-Weber syndrome – look for characteristic facial port-wine stain
- Dyke-Davidoff-Mason syndrome
- Unihemispheric cerebral vasculitis
- Mitochondrial encephalopathy, lactic acidosis, and stroke (MELAS syndrome)
- Parry-Romberg syndrome (progressive facial hemiatrophy)
- Landau-Kleffner syndrome – may present similarly but does not typically have associated hemiparesis or imaging findings of unilateral cerebral atrophy
- Anti-NMDA receptor encephalitis – may present similarly but does not typically have associated hemiparesis or imaging findings of unilateral cerebral atrophy
- Viral encephalitis – may present similarly but does not typically have associated hemiparesis or imaging findings of unilateral cerebral atrophy
- Cerebral vasculitis