Brain Magnetic Resonance Imaging in Influenza A (H1N1) 2009-Associated Encephalopathy

Response to “Brain Magnetic Resonance Imaging in Influenza A (H1N1) 2009-Associated Encephalopathy”

We would like to discuss the article “Brain MRI in Pandemic Influenza A (H1N1) 2009-Associated Encephalopathy[1]” by Ishida et al who performed a questionnaire survey and concluded that “…MRI is useful for determining fatal cases of pandemic influenza A (H1N1) 2009 infection when performed in the acute phase. However, MRI is not useful in predicting the development of sequelae.”[1] ^{(p. 20)} In fact, the reliability of the questionnaire in this study is questionable. According to another previous report by the same investigating team on brain magnetic resonance imaging (MRI) in the cases with pandemic influenza A (H1N1) 2009–associated encephalopathy according to national survey in Japan, only 25% of the cases had “abnormalities on MRI[2].” Of interest, more cases with abnormal MRI were reported in this study despite the present report was performed on the similar number of overall cases in the same setting. Hence, the reliability of the present questionnaire study should be raised. In addition, in another report, it is noted that the pandemic influenza A (H1N1) 2009 infection “can cause mild encephalopathy with a reversible lesion in the splenium of the corpus callosum” and this can be seen in any phase of the pediatric infection.[3] Hence, MRI follow-up can help predict resolution of brain lesion. This means if a continuous follow-up MRI is not done, the resolution of brain lesion might not be detectable.[4]

• References

• 1 Ishida Y, Kawashima H, Morichi S , et al. Brain magnetic resonance imaging in acute phase of pandemic influenza A (H1N1) 2009-associated encephalopathy in children. Neuropediatrics 2015; 46 (1) 20-25
• 2 Kawashima H, Morichi S, Okumara A, Nakagawa S, Morishima T ; collaborating study group on influenza-associated encephalopathy in Japan. National survey of pandemic influenza A (H1N1) 2009-associated encephalopathy in Japanese children. J Med Virol 2012; 84 (8) 1151-1156
• 3 Iwata A, Matsubara K, Nigami H, Kamimura K, Fukaya T. Reversible splenial lesion associated with novel influenza A (H1N1) viral infection. Pediatr Neurol 2010; 42 (6) 447-450
• 4 Zeng H, Quinet S, Huang W , et al. Clinical and MRI features of neurological complications after influenza A (H1N1) infection in critically ill children. Pediatr Radiol 2013; 43 (9) 1182-1189