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Acute necrotizing encephalopathy in Korean infants and children: imaging findings and diverse clinical outcome.
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PMID:  15467414     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: The purpose of our study was to describe acute necrotizing encephalopathy in Korean infants and children, and we sought to evaluate the prognostic factors. MATERIALS AND METHODS: Acute necrotizing encephalopathy was diagnosed in 14 Korean infants and children. We retrospectively analyzed the neuroimaging findings including the follow-up changes. The clinical course of the disease was graded, and we evaluated prognostic factors including age, serum level of the aminotransferase, hemorrhage, and localized atrophy of the brain. RESULT: This encephalopathy predominantly affected the bilateral thalami (n = 14), pons (n = 12), and midbrain (n = 10) in a symmetrical pattern. Hemorrhage was observed in eight patients (57%). On the follow-up images (n = 12), the brain lesions were reduced in extent for all patients, and generalized atrophy was seen in six patients. Localized tissue loss was observed in five patients and a complete resolution occurred for one patient. All the patients survived and two recovered completely; mild (n = 6) to severe (n = 6) neurological deficits persisted in the remaining 12 patients. The significant prognostic factors identified in this study were the presence of hemorrhage (p = 0.009) and localized atrophy (p = 0.015). CONCLUSION: Acute necrotizing encephalopathy in Korean patients showed the characteristic patterns of the post-infectious encephalopathy as described in the literature. The high survival rate and the relatively favorable clinical course observed for the present study suggest a more diverse spectrum of disease severity than was previously described. The presence of hemorrhage and localized tissue loss on MR images may suggest a poor prognosis.
Ji Hye Kim; In-One Kim; Myung Kwan Lim; Man Soo Park; Choong Gon Choi; Hye Won Kim; Jee Eun Kim; Soo Jin Choi; Young Hwan Koh; Dal Mo Yang; Sung Wook Choo; Myung Jin Chung; Hye-Kyung Yoon; Hyun Woo Goo; Munhyang Lee
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Korean journal of radiology : official journal of the Korean Radiological Society     Volume:  5     ISSN:  1229-6929     ISO Abbreviation:  Korean J Radiol     Publication Date:    2004 Jul-Sep
Date Detail:
Created Date:  2004-10-06     Completed Date:  2005-02-01     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  100956096     Medline TA:  Korean J Radiol     Country:  Korea (South)    
Other Details:
Languages:  eng     Pagination:  171-7     Citation Subset:  IM    
Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Kangnam-gu, Seoul, Korea.
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MeSH Terms
Brain / pathology
Child, Preschool
Leukoencephalitis, Acute Hemorrhagic / complications,  pathology*
Magnetic Resonance Imaging*
Retrospective Studies

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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Journal Information
Journal ID (nlm-ta): Korean J Radiol
Journal ID (publisher-id): KJR
ISSN: 1229-6929
ISSN: 2005-8330
Publisher: The Korean Radiological Society
Article Information
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Copyright © 2004 The Korean Radiological Society
Received Day: 23 Month: 2 Year: 2004
Accepted Day: 08 Month: 9 Year: 2004
Print publication date: Season: Jul–Sep Year: 2004
Electronic publication date: Day: 30 Month: 9 Year: 2004
Volume: 5 Issue: 3
First Page: 171 Last Page: 177
ID: 2698159
DOI: 10.3348/kjr.2004.5.3.171
PubMed Id: 15467414

Acute Necrotizing Encephalopathy in Korean Infants and Children: Imaging Findings and Diverse Clinical Outcome
Ji Hye Kim, MD1
In-One Kim, MD2
Myung Kwan Lim, MD3
Man Soo Park, MD4
Choong Gon Choi, MD5
Hye Won Kim, MD6
Jee Eun Kim, MD6
Soo Jin Choi, MD6
Young Hwan Koh, MD6
Dal Mo Yang, MD6
Sung Wook Choo, MD1
Myung Jin Chung, MD1
Hye-Kyung Yoon, MD1
Hyun Woo Goo, MD5
Munhyang Lee, MD7
1Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea.
2Department of Radiology, Seoul National University College of Medicine, Korea.
3Department of Radiology, Incheon Medical Center, College of Medicine, Inha University, Korea.
4Department of Radiology, Asan Kang Nung Hospital, Korea.
5Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Korea.
6Department of Radiology, Gachon Medical School, Ghil Medical Center, Korea.
7Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea.
Correspondence: Address reprint requests to: Ji Hye Kim, MD, Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-gu, Seoul 135-710, Korea. Tel. (822) 3410-0511, Fax. (822) 3410-0084,

Acute necrotizing encephalopathy (ANE) represents a peculiar type of encephalopathy characterized by bilateral symmetrical lesions that are predominantly observed in the thalami and brain stem of infants and children. It has been described by Japanese pediatricians, and it is regarded as a novel disease entity based on clinico-pathological data (1, 2). Although there is some argument on specific terminology (3), the term acute necrotizing encephalopathy has been widely accepted since it was first proposed by Mizuguchi et al. (1). ANE occurs following a systemic viral infection, and death or irreversible neurological sequelae have been described as the typical result of this disease. However, the etiology and pathogenesis of the disease remain mostly unknown. ANE has been predominantly reported in Japan and Taiwan in the Far East, and although Korea is geographically close to these countries, only three Korean cases have been reported (4, 5). Thus, we have conducted the first large series study on ANE in Korea.

The purpose of this multi-institutional study was to describe the radiological findings and the clinical course of ANE in Korean infants and children, and we sought to evaluate the clinico-radiological prognostic factors related to this disease.


Fourteen infants and children with ANE that was diagnosed in six Korean institutions over the past 10 years were the study subjects. The diagnoses were based on the criteria proposed by Mizuguchi et al. (6) (Table 1). The ages of the 14 patients ranged from 5 months to 12 years with a median age of 26 months, and there were 8 boys and 6 girls. The clinical findings during their hospital admission are summarized in Table 2. Presenting symptoms included fever and seizure followed by impairment of consciousness; this was often precipitated by seizures in all patients except for one (patient 3) who stayed alert throughout the clinical course. All of the patients had experienced preceding symptoms, and they all had signs of upper respiratory tract infection (n=11) or acute viral gastroenteritis (n=3). The time interval between the most recent viral infection and the onset of encephalopathy varied from 3 to 15 days with a mean period of 8 days. None of the patients had been recently immunized.

The serum levels of the aspartate aminotransferase and alanine aminotransferase were found to be elevated to variable extents in 13 patients. The serum ammonium levels were not elevated in any of the 10 patients tested. Cerebrospinal fluid (CSF) analysis was done for 12 patients and none of them exhibited pleocytosis. A mild increase in the protein level of the CSF was noted in 5 patients. Serum anti-viral antibody and polimerase chain reaction (PCR) analysis for viral DNA were performed for 6 patients; all of them were negative except for one in whom inflenza A virus was cultured from the CSF and nasal secretions (patient 12). Stains and cultures for bacteria in the CSF were all negative.

All the patients underwent an MR examination between one and seven days from the encephalopathy onset, and a total of 28 MRIs and 3 CT scans were obtained. Because the cases were collected from multiple institutes, MR imaging were performed on various equipment, including 1.5-T, 1.0-T and 0.5-T superconducting systems (Siemens AG, Erlangen, Germany/ General Electric Medical Systems, Milwaukee, U.S.A.), and the images included spin echo T1-, T2-weighted images and fluid attenuated inversion recovery sequences having combinations of axial, sagittal and coronal image planes. Post-contrast enhancement images were obtained for eight patients. The slice thickness used was usually 5 mm.

The neuroimaging findings were analyzed in terms of the distribution and pattern of the lesions, the presence of hemorrhage and temporal evolution. We classified the patients into favorable and severe sequelae groups according to the clinical outcome, where the favorable group included those patients who recovered completely or had only mild sequelae. Mild sequelae were defined as a restored gait and speech abilities in spite of the residual neurological deficits (6). The remaining subjects were included in the severe sequelae group. Several prognostic factors were evaluated with respect to the patient outcome: 1) age < 2 years, 2) elevated serum levels of aspartate aminotransferase or alanine aminotransferase of > 100 IU/liter, 3) presence of hemorrhage, and 4) localized tissue loss on follow-up MR images. Statistical analysis was performed using Fisher's exact test in a 2×2 table. A p-value of < 0.05 was regarded as statistically significant.

Neuroimaging findings

The neuroimaging findings are summarized in Table 3. The major involved sites were the thalami (n=14), pons (n=12), midbrain (n=10), and internal capsule (n=7) in a bilateral symmetrical pattern (Figs. 1, 2). The brainstem involvement was predominantly tegmental (Figs. 1B, 3B) in eight patients, and both the ventral and dorsal brainstems were involved for four patients. The temporal lobe (n=4), external capsule (n=4), cerebral deep white matter (n=3), cerebellum (n=2), putamen (n=2), frontal lobe (n=1), and caudate nuclei (n=1) were also involved in some patients. The observed lesions were initially edematous with T1 and T2 prolongation. There were hyperintense thalamic lesions noted on the T1-weighted images in eight patients on the initial images (n=5) or on the follow-up images (n=3, Fig. 1D); this suggested that there was a subacute stage of hemorrhage, which was also seen in the pons in one patient. These hemorrhagic lesions showed variable T2 signal intensity. Contrast enhancement was performed for eight patients and enhancement occurred in four of them, usually on the follow-up images (n=3).

Follow up images were obtained for 12 patients from day 7 to day 180 after the first MR scan. The lesion swelling had subsided and the extent of the abnormal signal intensity decreased in all the patients (Figs. 1, 2). For patient 5, along with the clinical recovery, the brain lesions having abnormal signal intensity disappeared on the follow-up MR images obtained 18 days after the first images were taken, and the last MR imaging taken 6 months after the initial scan revealed a generalized CSF space widening (Fig. 2). Shrunken thalami (n=3) or localized cystic encephalomalacia (n=2, Figs. 1C, D) were noted on the relatively long-term follow-up images. Generalized CSF space widening was noted for 6 patients (Figs. 1C, D, 2E), and it was considered to be atrophy.

Patient outcome

All the patients survived and two of them (14%) completely recovered. Mild neurological deficit remained in six patients (43%) and moderate to severe neurological deficits or mental alterations persisted in six patients (43%). For the prognostic factors that we tested, we found that hemorrhage (p = 0.009) and localized tissue loss (p = 0.015) were associated with a poor prognosis.


ANE has been recently established as a disease entity and it predominantly affects infants and young children in Japan and Taiwan. Despite the fact that these countries and Korea are in close geographical proximity, the first case in Korea was reported as recently as 2003 (4). However, we were able to identify another 12 patients in six institutions over the last 10 years, and this suggests that most ANE patients have remained unreported in Korea. Nevertheless, it is not known whether the cause of this racial or geographic predilection is related to genetic or environmental factors. Having considered the recent cases from outside the Far East (7, 8-14), it appears that the geographic distribution of this malady could be wider than was previously thought.

The outcome of ANE is generally grave, although the prognosis has improved recently. We reviewed the outcomes of the 92 reported cases in the literature (6-26) that occurred in countries other than Korea, and we found that 65% of the patients died or were left with severe neurological sequelae. In contrast to the literature cases, all of the patients in our study survived and 57% completely recovered or were left with only mild deficits (Table 5). There are several other reported cases with good outcomes in the literatures (10, 14, 18, 26, 27). Those patients with good outcomes, including several cases in the present study, could be categorized as having a "mild" form of ANE, as has been described by Yoshigawa et al. (26). The pathologic process of ANE is presumed to be reversible in the less severely affected patients who proceed on to a complete clinical recovery and disease resolution, as was demonstrated by the MRI findings.

It is interesting that all our patients with severe neurological sequelae had hemorrhagic lesions on the MR images (Fig. 1), and the presence of localized atrophy or cystic encephalomacia seemed to be related to the severe sequelae. In addition, it is known that older patients, non-Japanese children and those patients with low values of serum aminotranferase, and also those patients without brainstem lesions tended to recover well (6). However, the patients' age and serum aminotranferase levels were not found to be significantly correlated with the clinical outcome in the present study. This was possibly due to the relatively small number of cases, which undoubtedly is a limitation of this study.

The distributions of lesions detected on CT or MRI scans in the present study were typical of ANE as described in the literature; the locations included thalami, upper brainstem tegmentum, cerebral white matter, internal capsule, putamen and the cerebellar medulla. Hemorrhage usually occurred in the thalami, and it was occasionally accompanied by brainstem hemorrhage. The cerebral white matter may be involved, although hemorrhage was seldom seen. The involved brain was often initially edematous, and it subsequently became atrophic. The temporal evolution of brain lesions on the MR images ranged from cystic encephalomalacia (n=2, Fig. 1) to complete resolution (n=1, Fig. 2), and this could indicate a more diverse spectrum of this disease's severity.

In clinical practice, ANE should be differentiated from viral encephalitis and the other types of parainfectious encephalopathies. Viral encephalitis may have a specific site of symmetrical brain involvement including the thalami, hypothalami, basal ganglia, or brainstem, and probably this is the result of a specific route of infection or from a molecular interaction between a viral protein and a receptor on the host cells (28). Of these, Japanese encephalitis virus involves the bilateral thalami; this disease is an endemic encephalitis spread by mosquitoes and it occurs only during a specific season. Unlike ANE, the thalamic lesions in Japanese encephalitis are not necessarily symmetrical, and brainstem involvement is relatively uncommon. Moreover, other brain areas such as the hippocampus, basal ganglia, substantia nigra, cerebellum, cerebral cortex and white matter are the frequently involved areas (29, 30).

Radiological findings are very helpful for differentiating the other types of postinfectious encephalopathies such as Reye syndrome or acute disseminated encephalomyelopathy (ADEM). However, the ANE having a favorable outcome may not be easily differentiated from ADEM with bilateral thalamic involvement (31, 32), although the involvement of other sites and the response to steroid therapy for patients with ADEM may be helpful. It's also interesting that the high apparent diffusion coefficient (ADC) of ADEM and the decreases in the ADC value in ANE on the diffusion-weighted images have been reported to suggest the different nature of the edema (20). The other radiological differential diagnoses that must be considered before arriving at a final diagnosis of ANE are; the acute form of infantile bilateral striatal necrosis, thrombosis of the internal and great cerebral vein, central pontine/extrapontine myelinolysis, Wernike encephalopathy, urea encephalopathy and Leigh encephalopathy. The other brain disorders that should be clinically excluded are listed in Table 1.

In summary, ANE in Korean patients was found to be a post-infectious brain disorder predominantly involving the bilateral thalami and the brainstem, the disease will occasionally be accompanied by hemorrhage. The high survival rate with a relatively favorable clinical course and the various neuroimaging evolution patterns observed in the present study also suggest that there is a mild form of ANE and a more diverse spectrum of disease severity. The presence of hemorrhage and localized tissue loss on MR images may suggest a poor prognosis.

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Keywords: Brain, encephalopathy, Infants and children, disease, Brain, MR.

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