Rasmussen’s encephalitis-MRI

7 Year old male child with history of chronic epilepsy of few months duration with history of hospitalization for Brain inflammation previously. MRI shows right hemispheric volume loss  with atrophy with areas of encephalomalacia-gliosis with ipsilateral ventriculomegaly with normal ICA & MCA flow voids and normal calvarium, sinuses, sphenoid wing & orbital roof possibly representing Rasmussen’s encephalitis.

Teaching points by Dr MGK Murthy,  Mr Umamaheswar, Dr sreenivas metta, Mr Hameed 

1. This is chronic inflammation of the Brain with infiltration of T Lymphocytes affecting only one cerebral hemisphere leading to atrophy and seizures. Cause not known. Viral etiology or autoimmune theory possible.
2. Presence of autoantibodies as against the NMDA type glutamate receptor subunit is recent finding. It is associated  with neurovisceral porphyria or acute intermittent porphyria or ADEM.
3. Affects children with average age 6 years. Prodromal stage of few months is followed by acute stage ( 4 to 8 months) leading to atrophy with focal motor seizures or epilepsia partialis continuae.
4. MRI shows hemispheric atrophy with normal flow voids and calvarium.
5. Differential diagnosis includes Dyke- Davidoff-masson syndrome ( calvarial asymmetry, elevation of petrous ridge, sphenoid wing  and orbital roof with hypoplasia of the anterior& middle cranial fossae, frontal sinus hyperpneumatization with displaced falx ), sturge weber syndrome  ( calcification and telangiectasia ), hemimegalencephaly( hypertrophy including the calvarium ).