title: Clinically mild encephalitis with a reversible splenial lesion (MERS) after mumps vaccination.
abstract: We retrospectively collected three patients with clinically mild encephalitis with a reversible splenial lesion (MERS) after mumps vaccination, and reviewed five patients, including two patients previously reported. The five patients (all males, aged 1 to 9) presented with fever, vomiting, or headache as the initial symptoms (day 0), suggesting meningitis, at 13 to 21 days after mumps vaccination. Consciousness disturbance, delirious behavior, seizures, or dysarthria was observed on days 1 to 3, which had completely resolved before day 11. Hyponatremia was observed in all patients. A cerebrospinal fluid study showed pleocytosis, and confirmed the vaccine strain genome. MRI revealed reduced diffusion in the splenium of the corpus callosum on days 2 to 4, which had completely disappeared on the follow-up studies performed on days 7-15. EEG showed high voltage slow wave in three patients, which later normalized. These findings led to a diagnosis of MERS after mumps vaccination. MERS after mumps vaccination may be more common than previously considered. MERS is suspected when a male patient after mumps vaccination presents with neurological symptoms with hyponatremia, following symptoms of aseptic meningitis, and MRI would be performed to examine the splenium of the corpus callosum.
authors.affiliation: Department of Pediatrics, Tokyo Women's Medical University, Yachiyo Medical Center, Yachiyo, Japan. Electronic address: jtaka44@hotmail.co.jp.
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Takanashi
authors.affiliation: Department of Neurology, Gunma Children's Medical Center, Shibukawa, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Shiihara
authors.affiliation: Department of Pediatrics, Soka Municipal Hospital, Soka, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hasegawa
authors.affiliation: Division of Pediatrics, Sendai City Hospital, Sendai, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Takayanagi
authors.affiliation: Department of Pediatrics & Child Health, Kurume University School of Medicine, Kurume, Japan.
authors.forename: Munetsugu
authors.initials: M
authors.lastname: Hara
authors.affiliation: Department of Pediatrics, Aichi Medical University, Nagakute, Japan.
authors.forename: Akihisa
authors.initials: A
authors.lastname: Okumura
authors.affiliation: Department of Developmental Medical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Mizuguchi
mesh_terms: D002648:Child; D002675:Child, Preschool; D003337:Corpus Callosum / Q000473:pathology*; D004569:Electroencephalography; D004660:Encephalitis / Q000209:etiology* / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000097:blood / Q000209:etiology; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D009108:Mumps Vaccine / Q000009:adverse effects*; D014764:Viral Proteins / Q000276:immunology*
chemical_list: D009108:Mumps Vaccine; D014764:Viral Proteins
keywords: Clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS); Diffusion; Hyponatremia; MRI; Mumps vaccination; Splenium