Acute necrotizing encephalopathy: diffusion MR imaging and localized proton MR spectroscopic findings in two infants

Abstract

In this report, we describe the findings of diffusion MR imaging and proton MR spectroscopy in two infants with acute necrotizing encephalopathy in which there was characteristic symmetrical involvement of the thalami. Diffusion MR images of the lesions showed that the observed apparent diffusion coefficient (ADC) decrease was more prominent in the first patient, who had more severe brain damage and a poorer clinical outcome, than in the second. Proton MR spectroscopy detected an increase in the glutamate/glutamine complex and mobile lipids in the first case but only a small increase of lactate in the second. Diffusion MR imaging and proton MR spectroscopy may provide useful information not only for diagnosis but also for estimating the severity and clinical outcome of acute necrotizing encephalopathy.

Fig. 1

A 10-month-old boy with sequelae of severe motor deficit. A. Axial fast spin-echo T2-weighted MR image (TR/TE=3500/120) shows symmetric high signal intensity in the bilateral thalami. B. Axial T2*-weighted gradient-echo MR image (TR/TE=800/30, flip angle = 20°) at the same level as A shows conspicuous low signal intensity within the thalamic lesions, possibly due to the presence there of acute petechial hemorrhage. C. Apparent diffusion coefficient (ADC) map of diffusion imaging reveals low ADC in the thalamic lesions (arrows), which may represent the presence of cytotoxic edema. In the central portion of the lesions, however, ADC is high, suggesting tissue necrosis. D. Short echo-time proton MR spectrogram (STEAM 3000/30) of a thalamic lesion shows increased glutamate/glutamine complex peak intensities at 2.0-2.5 ppm and lipid/lactate complex peak intensities at 0.8-1.5 ppm, as compared with an age-matched control subject (E). Broadening of the line-width may be caused by the occurrence of petechial hemorrhage within the lesion. E. Short echo-time proton MR spectrogram (STEAM 3000/30) of normal thalamus in a 9-month-old age-matched control subject. Note.-Ins=myoinositol, Cho=choline compound, tCr=creatine complex, Glx=glutamate/glutamine complex, NAA=N-acetyl aspartate

Fig. 2

A 6-month-old girl without significant neurologic sequelae. A. ADC map of diffusion imaging shows that the thalamic lesions have a concentric appearance. They have high-signal centers with low-signal rims (arrows), and the ADC values of their remaining portion are high. B. Initial proton MR spectrogram (STEAM 3000/30) of a lesion shows a small lactate peak (arrow). The N-acetyl aspartate peak is within the normal range. C. Follow-up proton MR spectrogram (STEAM 3000/30) obtained one week later shows no lactate peak (arrow). The N-acetyl aspartate peak shows no interval change and is still within the normal range. Note.-NAA=N-acetyl aspartate