Quantitative proton MR spectroscopic imaging in acute disseminated encephalomyelitis

Abstract

Serial MR imaging and quantitative proton MR spectroscopic imaging (MRSI) findings of a 4-year-old boy with acute disseminated encephalomyelitis (ADEM) are reported. Over a 2-month period characterized by an initial illness and two relapses, each with full recovery, MR imaging exhibited the appearance and disappearance of multifocal lesions throughout the CNS that correlated only partly with the neurologic impairment. During one relapse, MRSI revealed low levels of N-acetylaspartate (NAA) within the regions of prolonged T2 signal intensity. All other metabolites were normal. At follow-up, the MR imaging and MRSI abnormalities had fully resolved. MRSI might play an important role in the diagnosis of ADEM, as well as in the elucidation of underlying pathophysiologic processes in this poorly defined disorder of children. This case demonstrates that reduced levels of NAA are not always associated with neuronal loss, irreversible tissue damage, or poor neurologic outcome.

fig 1.

A–C. T2-weighted MR images at 3000/100/1 (TR/TE/excitation) at the following times after initial symptom (headache) onset. A, At 14 days, bilateral thalamic lesions (left slightly more prominent than right). B, At 21 days, thalamic lesions have increased in size and new lesion has appeared in left cerebral peduncle (lesions in left globus pallidus and forceps major not shown). C, At 32 days, further progression of thalamic lesions to involve right geniculate body, right posterior limb of internal capsule, and complete involvement of left putamen and globus pallidus tracking down to left cerebral peduncle (bilateral lesions in hemispheric white matter and left frontoparietal cortex not shown)

fig 1.

D–F. D, At 8 weeks, pattern of involvement dramatically changed, with resolution of lesions in thalami and left cerebral peduncle, and with new lesions in left caudatum, putamen, and globus pallidus, and in right globus pallidus, anterior thalamus, cerebral peduncle, and posterior limb of internal capsule. (Hyperintensity of subcortical white matter of right temporal lobe not shown.) E, At 17 weeks, nearly all lesions resolved, with only minimal hyperintensity of left caudate nucleus and frontal periventricular white matter (not shown). F, At 25 weeks, all T2 hyperintense lesions completely resolved

fig 2.

Proton MRSI at 8 (top) and 25 (bottom) weeks after initial symptom onset. Localizer T1-weighted MR images at 300/13/1 (TR/TE/excitation) and metabolic images at 2300/280/1 (TR/TE/excitation) of choline and NAA from the second of four sections shown. Selected spectrum from left caudatum shown at both time points (voxel location indicated on T1-weighted images). At 8 weeks, NAA image shows decreased levels in left caudatum, lenticular nuclei, and right internal capsule, corresponding to lesions seen in T2-weighted MR images (fig 1D). Choline signals within normal limits; note high choline signal in thalamic region is normal for these regions (Table 2). By 25 weeks, NAA recovered to normal levels in all these regions, whereas creatine and choline levels remain stable (Table 2)