Rasmussen Encephalitis

- Rasmussen encephalitis, also known as chronic focal encephalitis, is an extremely rare chronic inflammatory neurodegenerative disease resulting in untreatable seizures and progressive neurologic deficit.

- It usually begins in childhood, between 6 and 8 years of age, in previously normal children.

- Clinically, an abrupt onset of severe and intractable epilepsy occurs, most frequently epilepsia partialis continua and, less often, generalized status epilepticus.

- Rasmussen encephalitis is a diagnosis of exclusion in patients with intractable seizures and advancing motor and cognitive deterioration.

- The disease tends to affect one hemisphere, although bilateral involvement at initial presentation has also been reported.

- The earliest abnormal MRI feature has been described as cortical swelling with hyperintensity on T2-weighted images.

- Serial scans show focal or hemispheric atrophy, and T2-weighted images may reveal areas of increased signal in the white matter and/or putamen. After seizures, a transient hyperintensity T2-weighted imaging in the temporal lobe and hippocampus may be seen related to postictal changes .

- Classification and staging criteria have been proposed based on MR imaging findings on T2-weighted and FLAIR images:

 normal volume and signal (stage 0),
 swelling and hyperintense signal (stage 1),
 normal volume and hyperintense signal (stage 2),
 atrophy and hyperintense signal (stage 3), and
 progressive atrophy and normal signal (stage 4)

- MR spectroscopy demonstrates a reduction in NAA levels that at some point may be reversible after seizure control and may be related to recovery of neuronal function. Increased choline peaks have been described, although a reduction in this metabolite was observed in one study related to a transient increase in turnover and loss of membrane components. Slightly increased myo-inositol and glutamine/glutamate peaks and markedly increased lactate levels were noted.

- Diffusion and ADC ---> shows high ADC value.

Ref : Scott.

DDs of Unilateral Brain Atrophy

1. Dyke-Davidoff-Mason Syndrome.
2. Sturge-Weber Syndrome
3. MELAS