The analysis of cerebrospinal fluid (CSF) showed a cell count of 9 Mpt/l (lymphocytes and monocytes), protein of 0.575 g/l, glucose 3.74 mmol/l and lactate 2.2 mmol/l, and no oligoclonal bands. The SARS-CoV-2 RT-PCR in CSF was performed and tested negative. Biological tests were not in favor of a recent infection with Borrelia, Treponema pallidum, Campylobacter jejuni, mycoplasma, EBV, HSV1 or 2, and hepatitis E.