Case report

A 46-year-old man experienced transient dizziness in early September 2008. Brain MRI retrospectively showed a slight fluid attenuation inversion recovery (FLAIR) high-intensity lesion involving the left frontal cortex (figure 1). One week later, the patient experienced a focal motor seizure in the right leg that subsequently generalised. Thereafter, he gradually developed headache and paraparesis over the course of a week. On admission, he presented with paraparesis without other neurological deficits, but the spinal MRI was normal. An electroencephalogram revealed that there were no epileptic discharges. A cerebrospinal fluid (CSF) examination revealed elevated leucocytes (56 /µL; 93% mononuclear cells, 3% polymorphonuclear leucocytes) and normal protein (36 mg/dL) and glucose (59 mg/dL) levels. The myelin basic protein (MBP) and glial fibrillary acidic protein levels in the CSF were not elevated. Cell-based assays for anti-N-methyl-D-aspartate receptor (NMDAR) antibodies, anti-voltage-gated potassium channel (VGKC) antibodies, anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) antibodies and anti-γ-aminobutyric acid-B receptor (GABA(B)R) antibodies in the CSF were negative. Blood and CSF examinations for infectious central nervous system (CNS) CNS diseases, collagen diseases, vasculitis, Behçet disease, sarcoidosis, lymphoma, paraneoplastic syndrome, vitamin B deficiency and Hashimoto encephalopathy were unremarkable.