Rhombencephalitis-MRI

22 year old male was referred  with fever and   altered sensorium and seizures with suspicion of brain stem encephalitis. MRI shows enlarged  pons with cytotoxic oedema (with reduced ADC values ) and vasogenic oedema with unremarkable vertebra basilar flow voids  or bleed  or significant 4th ventricle compression, consistent with Rhombencephalitis. 

Teaching points by Dr MGK Murthy, Dr GA Prasad & Mr Mahesh

Also referred as Brainstem encephalitis. Infectious, Autoimmune and Paraneopalstic aetiologies are possible 

• Infectious causes (100% Abnormal MRI)   Listeria (commonest, healthy young adults , biphasic time course with Flu like symptoms, CSF pleocytosis, positive CSF and blood cultures  , best treated with Ampicillin),  Enterovirus1 (second commonest in Asia-pacific preponderance with no specific treatment available), Herpes Simplex (HSV1 (80%) , HSV2 with 50% showing supratentorial involvement as well  , respond well with acycolovir), Epstein Barr virus and Human Herpes virus etc

• Autoimmune (90% abnormal MRI) usually is Behcets disease (CSF pleocytosis)  (25% recover with steroids  and immune suppression) 

• Paraneoplastic varieties (MRI usually normal) (CSF pleocytosis with protein normal) (anti neuronal antibodies positive) (prognosis poor)