[Positron emission tomography in acute disseminated encephalomyelitis: a case report]

Sequential positron emission tomography (PET) and single photon emission tomography (SPECT) were performed in an 11-year-old girl who was clinically diagnosed as acute disseminated encephalomyelitis (ADEM). She had fever, stupor, loss of sight and left hemiparesis on admission to our hospital. X-ray CT (XCT) demonstrated a hypodense lesion in the right fronto-parietal white matter. In the 1st PET study, CBF and CMRO2 were reduced in both hemispheric white and gray matter, particularly in the right fronto-parietal lesion. The XCT abnormality was improved in the subsequent scan when the patient had improved except visual disturbance. When visual disturbance was worsened again, and a new hypodense lesion was appeared in the left frontal white matter on XCT, the 2nd PET study was performed. CBF and CMRO2 were recovered except the left frontal white and gray matter. SPECT study was also performed and the image was almost similar to CBF image of PET scan. The changes and distributions of CBF and CMRO2 were related to her symptoms and clinical course. Reduced CBF and CMRO2 of whole brain is thought to be characteristic of ADEM. From the experiences of this case, PET measurements is useful for the understanding of neuronal functional abnormalities of ADEM, and is more useful for the detection of recovery or relapsing process than XCT.