The characteristics of cranial magnetic resonance imaging in adult Japanese encephalitis

Objective To analyze the magnetic resonance imaging (MRI) images of patients with adult Japanese encephalitis (JE), and to investigate the diagnostic value of MRI for the disease. Methods Thirty-two adult JE patients who underwent cranial MRI at General Hospital of Ningxia Medical University between August 2016 and September 2018 were enrolled. All patients had disease onset between August and September and they aged 17 to 83 years old. The clinical data, laboratory results, MRI signal characteristics of each scanning sequence and the distribution of the brain lesions were retrospectively analyzed. Results Of the 32 adult JE patients, 29 (90.6%) cases had acute onset, 28 (87.5%) cases had unconsciousness and cognitive impairment, 26 (81.2%) cases had intracranial hypertension, 3 (9.4%) cases had meningeal irritation, 3 (9.4%) cases had Parkinson-like symptoms, 10 (31.2%) cases had epilepsy, and 15 (46.9%) cases had decreased muscle strength. Twenty patients were positive for JE virus-specific IgM antibodies. Twenty-eight patients underwent cerebrospinal fluid examination, 15 (53.6%) cases showed intracranial pressure ≥180 mmH2O (1 mmH2O=0.009 8 kPa), 7 (25%) cases developed lymphocyte reaction, and 16 (57.1%) cases showed mixed cell reaction. Twenty-three cases (71.9%) showed lesions of brain on MRI, including thalamus (17 cases, 73.9%), hippocampus (13 cases, 56.5%), cerebral peduncle (6 cases, 26.1%), cortical and subcortical (4 cases, 17.4%), basal ganglia (2 cases, 8.7%), brainstem (1 case, 4.3%) and splenium of corpus callosum (1 case, 4.3%). Positive T1 weight image (T1WI) and T2 weight image (T2WI) results were found in 21 patients, respectively, 23 patients had positive T2-fluid attenuated inversion recovery (FLAIR) images, and 20 patients had positive diffusion weighted imaging (DWI) images. Among them, T2-FLAIR and DWI images showed more lesions, wider range of lesions and clearer boundary of cortical involvement range than T1WI and T2WI images. Conclusions Bilateral thalamus and hippocampus are often involved in adult JE. T2-FLAIR and DWI sequences are more sensitive to detect lesions. Combining MRI images with epidemiological characteristics, clinical manifestations, and laboratory tests is of great assistance for early diagnosis of JE. Key words: Encephalitis, Japanese; Adult; Magnetic resonance imaging; MRI spectrum; Clinical spectrum