Fig. 1

Serial brain magnetic resonance imaging (MRI) of the patient. (A) First MRI after the onset of symptoms. The right-sided basal ganglia had a mild, low signal intensity on the T1-weighted image and high signal intensity on the fluid attenuated inversion recovery (FLAIR) image. However, matching of diffusion weighted image (DWI) and apparent diffusion coefficient (ADC) was not clearly observed. The pons and cerebellar pontine angle don’t have any abnormal signal intensity on the DWI and FLAIR image. Abnormal signal intensity was not observed in FLAIR in both medial temporal lobes. (B) Follow-up MRI after symptom aggravation. Compared with first MRI, the signal intensity in the T1-weighted image was pronounced and the size of the high signal intensity on the FLAIR image increased. Furthermore, enhancement of the lesion was observed as well as matching of the DWI and ADC. (B-1) A new lesion, which was not seen in the first MRI, was observed in the pons. Low signal intensity was observed on the T1-weighted image and high signal intensity on the FLAIR image. Matching of the DWI and ADC was observed. (B-2). (C) After plasmapheresis, the patient’s condition worsened, and follow-up brain MRI was performed. The basal ganglia enhancement was increased and the edema worsened. The matching of DWI and ADC became more prominent. (C-1) Enhancement lesion was observed in the pons. (C-2)