The clinical and neuroradiological features of acute disseminated encephalomyelitis (ADEM) were determined by a retrospective review of medical records and MRI findings in 31 children (mean age 5.9 yrs; range 2-16 yrs) examined at the Royal Children’s Hospital, Melbourne, Australia, between 1993 and 1998. Prodromal illnesses, mainly upper respiratory or nonspecific infections, occurred in 22 (71%). Two had received hepatitis B vaccine 3 to 6 weeks prior to symptom onset. Neurologic symptoms, developing over a mean of 4 days, included ataxia (65%), cranial nerve pareses (45%), headache (45%), vomiting (35%), neck stiffness (26%), impaired consciousness (68%), seizures (13%), optic neuritis (13%), hemiparesis (23%), and language disturbance (29%). CSF protein was elevated in 50% (0.4-0.6g/L), and csf white cell counts were abnormal, mainly lymphocytes (52xl0⁶/L or less), in 62%. Oligoclonal bands in csf were present in only one. EEGs showed slow background activity in 5 of 7 tested. Serologic testing showed elevated immunoglobulin M titers to M. pneumoniae in 4, and to Epstein-Barr virus in 2. PCR was negative in csf of 23 tested. MRI showed bilateral, asymmetrical involvement of white matter of frontal and parietal lobes in all but 3 patients; the lesions resembled tumor masses in 2 with the diagnosis of demyelination confirmed by biopsy. Corpus callosum and periventricular lesions characteristic of MS were present in 29%. Deep gray matter was involved in 61% and the spinal cord in 16%. High-dose IV methylprednisolone was usually effective in treatment. Recovery was complete in 81%, and sequelae were mild in the remainder. [1]

COMMENT. Serial MRI may be necessary to distinguish ADEM from MS in some cases. In the absence of a clinical relapse, new lesions should not appear in ADEM. The diagnosis of ADEM is usually apparent at presentation. Characteristic features are the prodromal viral illness, early onset of ataxia, large lesions on MRI with involvement of deep gray matter including thalamus, and absence of oligoclonal bands.

ADEM in a patient with autoimmune hemolytic anemia. A 16-year old girl with a 3 year history of hemolytic anemia had received immunosuppressive prednisolone treatment at Chang Gung Children’s Hospital, Taoyuan, Taiwan. She developed a systemic infection with Cryptococcus neoformans which triggered the encephalomyelitis. Her symptoms included ataxia, drowsiness, and coma. MRI showed multiple bilateral, asymmetrical lesions involving subcortical white matter, basal ganglia, and frontoparietal lobes. She responded to IV immunoglobulin IVIG, the ataxia and weakness resolving after 2 weeks. Follow-up MRI in 1 month was almost normal, and neurologic symptoms had completely resolved. No relapse had occurred at 1 year follow-up [2]. The authors suggest a link between the chronic steroid treatment in an immunosuppressed patient and the development of ADEM.