On the next day after being taken by influenza a 46-year-old woman presented with intensified headache, dizziness, nausea. Objectively: the patient is conscious, psychomotor excitement is present; there is general hyperesthesia, moderate meningeal syndrome, nystagmus. Tendon teflexes are higher on the right, right extremities display muscle weakness, right-sided pathological Babinski's sign is present. Liquor is transparent, pressure is 220 mm of water column; cytosis is 46/3 with prevailing lymphocytes. What is the most likely diagnosis?