3.3 MRI findings
Brain lesions were observed in all 10 patients by MRI scan. In a total of 24 episodes of the 10 patients, lesions involved the cortical region (33.3%, 8/24), deep nuclei (basal ganglia and thalamus) (25.0%, 6/24), hippocampus (20.8%, 5/24), juxta white matters (corpus callosum, cingulate gyrus) (12.5%, 3/24), brainstem (midbrain, pons, and medulla) (37.5%, 9/24), and cerebellum (4.2%, 1/24) (lesion distributions summarized in Figure 1C). All 10 patients exhibited hyperintense signals on T2-sequences (Figure 3), and 6 patients showed lesional or meningeal enhancements. In patient-6 who presented as seizures and acute confusion and infected with herpes simplex virus 1 (HSV-1) prior to NMDAR encephalitis, extensive cortical regions and hippocampi involvements were found. After treatment with intravenous acyclovir and methylprednisolone, the brain lesions were clearly adsorbed. However, extensive meningeal enhancement was observed after the contrast agent was administered (Figure 4 D-F).
Abnormal signals in the optic nerve presented in four patients with or without nerve sheath enhancement. Transverse myelitis occurred in only two patients, with one case longitudinally involving both the cervical and thoracic spinal cords (Figure 4 A-C) and one case shortly involving the superior cervical cord.