Pediatric MOG antibody-positive encephalitis with normal brain magnetic resonance imaging: a new spectrum associated with MOG antibodies?

Yan Jiang Ping Yuan Xiaojie Song Jiannan Ma Siqi Hong Xiujuan Li ^* Li Jiang ^*

• Department of Neurology, Children’s Hospital of Chongqing Medical University, Chongqing, China

Objective: To facilitate the accurate identification of clinical characteristics associated with myelin oligodendrocyte glycoprotein (MOG) antibody positive encephalitis in children presenting with normal brain magnetic resonance imaging (MRI) findings.Method: Patients hospitalized at Children’s Hospital of Chongqing Medical University from January 2016 to May 2024, who were positive for MOG antibodies and exhibited encephalitis symptoms with normal brain MRI findings, were retrospectively analyzed.Results: A total of seventeen patients (7 males and 10 females; mean age: 9.2± 2.8years) were enrolled in the study.The most prevalent clinical symptoms were fever (17/17, with a median duration of 15 days (IQR:7.5-21 days), headaches (17/17), mild alterations in mental status (17/17), seizures (6/17), vomiting (6/17), decreased binocular vision (2/17), and hemiplegia (1/17). The majority of cases (15/17) exhibited leukocytosis in peripheral blood (mean:20.63±7.09×109/L) accompanied by an elevated neutrophil ratio. C-reactive protein (CRP) and procalcitonin (PCT) levels were normal in thirteen patients (13/17). Cerebrospinal fluid (CSF) leukocyte counts were elevated in all patients (median: 82/mm3; IQR: 49-155/mm3). Six patients (6/17) had elevated CSF protein levels (mean: 1.01±0.38 g/L). CSF glucose levels were normal across all patients. Next-generation sequencing of CSF was performed in ten patients, all yielding negative results. All patients had a serum MOG antibodies titer of ≥1:32, and six children（6/17）had a CSF MOG antibody titer of ≥1:32. All patients showed clinical improvement after immunotherapy. Only one patient (1/17) experienced a relapse.Conclusion: For patients presenting with encephalitis and normal brain MRI findings, early testing for anti-MOG antibody should be considered if they exhibit the following characteristics: 1) persistent fever; 2) elevated peripheral blood white blood cell (WBC) counts, with normal or slightly elevated PCT and CRP levels; 3) mild elevation of CSF WBC counts, normal or mildly elevated protein levels, and normal CSF glucose levels; and 4) ineffectiveness of antibiotic or antiviral therapy. Encephalitis with normal brain MRI may be regarded as a potential new spectrum associated with MOG antibodies, meriting additional exploration and consideration.