Letter to the Editor

Iran J Public Health, Vol. 49, No.1, Jan 2020, pp.191-192

Typical MRI Imaging with Clinically Mild
Encephalitis/Encephalopathy of a Reversible Splenial Lesion(MERS) Caused by Influenza A Virus*George IMATAKA, Shigemi YOSHIHARA
Department of Pediatrics, Dokkyo Medical University, Tochigi, Japan*Corresponding Author: Email: geo@dokkyomed.ac.jp(Received 10 Apr 2019; accepted 21 Apr 2019)

Dear Editor-in-Chief
We report a case of acute encephalitis associatedwith transient MR signal intensities in the splenium of the corpus callosum (MERS; clinically mild
encephalitis/encephalopathy with a reversible
splenial lesion) caused by influenza A virus.
The case was a 6-yr-old girl was referred to Dokkyo Medical University Hospital, Shimotsuga,
Japan for persistent coma after cluster febrile seizure in winter season. Using rapid antigen test,
she was diagnosed with influenza type A infection 6 days earlier.
After we obtained informed consent from parents of the patient, she admitted our hospital andperformed both examination sand treatments.
Cerebrospinal fluid test showed increased cellcount (188/mm3), elevated protein (68 mg/dl) as
well as markedly high level of interleukine-6(14,200 pg/ml). IgG index was 0.86 at this time.
Diffusion weighted magnetic resonance image(MRI) showed increased intensity in the spleniumof the corpus callosum. Other MR findings also
including ADC-map, FLAIR, T1 and T2weighted images revealed abnormal intensities inthe splenium.
Disturbance of consciousness state never recovered, and she was treated with methylprednisolone steroid pulse therapy (30 mg/kg×3days) as
well as high dose immunoglobulin therapy (400mg/kg×5days). At the 3rd day of the dual treatment, her conscious level gradually recovered,191

and completely recovered on the 13th day fromthe onset. There were no neurological sequelae
following her discharge from the hospital after
one year from the onset.
MERS is an acute encephalopathy with decent
prognosis reported from Japan. There are often
subsequent occurrences of influenza type A infection. MRI-diffusion weighted imaging is a
powerful tool for diagnosis for this condition.
Occasionally aihigh signal is observed on T2weighted image and contrast image showed noeffect. Some previous reports also reported
MERS mainly recognized diffusion-weighted imaging (1-3). Our case demonstrated abnormal
signal intensities in the splenium of the corpus
callosum: markedly high signal intensities on diffusion-weighted imaging (DWI) (Fig. 1). Moreover, these abnormal intensities were completelydisappeared. The reasons for these abnormal
splenial lesions were considering with cytotoxic
edema or edema in the myelin sheath (4). At thebeginning, her clinical course was not mild andrevealed continue comatose. During the steroidpulse and immunoglobulin treatment, her consciousness level was gradually recovered. Her
clinical course could have been a mild type ofMERS and the case was very interesting with regard to consideration of the mechanism of theunique encephalitis in transient MR intensities inMERS.
Available at:

http://ijph.tums.ac.ir

Imataka & Yoshihara: Typical MRI Imaging with Clinically Mild Encephalitis …

Fig. 1: Brain magnetic resonance (MR) imaging on day 7 from the onset, showed abnormal signal intensities in thesplenium of the corpus callosum: markedly high signal intensities on diffusion-weighted imaging (DWI) : (A), andmarkedly low signal intensities on an apparent diffusion coefficient (ADC) map : (B), slight hyperintensity developedin the same area on fluid-attenuated inversion recovery (FLAIR) : (C: TR=9000 / TE=105) and on fast spin-echo
T2-weighted image : (D: TR=3800 / TE=99). Otherwise on spin-echo T1- weighted images showed mild decreased
intensity signal in the splenium: (E: TR=593 / TE=15). MR imaging findings on day 13, demonstrating completelyresolved of these abnormal intensities on DWI: (F), ADC map: (G), FLAIR : (H), T2-weighted image : (I) and T1weighted image : (J)Conflict of interests
The authors declare that there is no conflict ofinterests.

References
1. Takanashi J, Barkovich AJ, Shiihara T, et al(2006). Widening spectrum of a reversible
splenial lesion with transiently reduced diffusion. AJNR Am J Neuroradiol, 27, 83638.

Available at:

http://ijph.tums.ac.ir

2. Maeda M, Tsukahara H, Terada H, et al(2006). Reversible splenial lesion with restricted diffusion in a wide spectrum ofdiseases and conditions. J Neuroradiol, 33,229-36.
3. Tada H, Takanashi J, Barkovich AJ, et al(2004).
Clinically
mildencephalitis/encephalopathy with a reversible splenial lesion. Neurology, 63, 1854-58.
4. Takanashi J, Tada H, Kuroki H, Barkovich
AJ (2009). Delirious behavior in influenza
is associated with a reversible splenial lesions in children. Brain Dev, 31, 423-426.

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