Background: ADEM (acute disseminating encephalomyelitis) is an autoimmune disease in which immunologic reaction to myelin is activated by an unknown factor. The incidence is not known and in the developed countries it is now seen most frequently after non-specific upper respiratory tract infections with the etiological agent remaining unknown. Young adults and children are most commonly affected. Systemic symptoms like fever, malaise, headache, nausea & vomiting often precede the neurological symptoms of ADEM but the hallmark is the development of initial clinical features including coma, hemiparesis, seizure, cranial nerve palsy and fever. ADEM is one of the causes of sudden coma in adolescents which has similar pattern of abnormalities on conventional MRI images with multiple sclerosis, but probably in primary approach with patients it is misdiagnosed. This paper presents a case of ADEM referring to Hamadan Sina Hospital in 2005.

Case Report: The patient was a 22-year old female, complaining of sudden and acute coma and then status epilepticus.The patient’s past medical and drug history was negative. Positive finding in physical examination was low grade fever and in neurological exam, involvement of bilateral cortico spinal tract was remarkable. After intubation and control of status epilepticus and routine tests brain CT scan lumbar puncture was done which was normal. Patchy areas of increased signal intensity on conventional T₂-weighted images in cortical and subcortical hemispheres was apparent on MRI. Corpus callosum was not involved. After diagnosis of ADEM high dose of cortico therapy within 10 days showed to improve the outcome So that, the patient was discharged for physiotherapy.

Discussion: White matter disorder is responsible for determining the occurrence of neurological coma in patient because metabolic, infectious, toxic, trauma, vascular lesion (absence of focal neurological deficit) sol, developmental and congenital factors could be ruled out. The criteria emphasizing ADEM disorder (against MS) are: 1-Fever, loss of consciousness & epilepsy 2- Absence of oligoclonal band in CSF 3- Intacted corpus callosum 4- Absence of new lesion after first attack in MRI and 5- shorter duration of symptoms & more severe initial symptoms.

Conclusion: According to the report, in every young adult patient with acute onset neurological coma without previous, metabolic, infectious, toxic, and traumatic etiology, and negative developing space occupying lesion, demyelinating disease should be suspected.