SERIAL CHANGES ON DIFFUSION-WEIGHTED MRI IN CHILDREN WITH ACUTE ENCEPHALITIS OR ENCEPHALOPATHY

Objectives: It is recognized that diffusion-weighted MRI, DWI, is a sensitive method of detecting cerebral lesions in various neurological disorders. High intensity lesions seen on DWI indicate cytotoxic edema.

Methods: We present two patients with acute encephalitis or encephalopathy who showed similar serial changes on DWI.

Results: Case 1: A 9-month-old boy was diagnosed as having acute encephalopathy associated with exanthema subitum DWI revealed bilateral high intensity lesions in the subcortical white matter of the frontal lobes. Nine days later, DWI revealed high intensity lesions in the frontal cortex, caudate nucleus and globus pallidus. One month later MRI showed mild brain atrophy in the frontal lobes without any high intensity lesions on DWI. Case 2: A two-year-old boy developed right hemiconvulsion and hemiplegia associated with fever. DWI showed a diffuse high intensity lesion in the left subcortical white matter. Six days later, DWI revealed a diffuse high intensity lesion in the whole left cortex. Eighteen days later MRI showed mild brain atrophy in the left hemisphere and the high intensity lesion seen on DWI disappeared. These serial changes revealed by DWI were not recognized using other conventional methods.

Conclusion: DWI of these two patients revealed high intensity lesions in the subcortical white matter in the acute phase, and then in the cortex, or basal ganglia, or both. In the convalescent phase, high intensity lesions disappeared and brain atrophy developed. Although exact mechanism for these serial changes remains unknown, these changes might reflect some pathogenic mechanism in acute encephalopathy or encephalitis.