Laboratory studies disclosed the following values: ABGs, pH, 7.67; PaCO2, 8 mm Hg; and PaO2, 129 mm Hg; hematocrit, 33.3%, white blood cell count, 10 900×103/μL; neutrophils, 81%; erythrocyte sedimentation rate, 40 mm/h; sodium, 134 mEq/L; potassium, 4.2 mEq/L; chloride, 105 mEq/L; bicarbonate, 14 mEq/L; serum urea nitrogen; 37 mg/dL (17 mmol/L), creatinine, 1.3 mg/dL (114 μmol/L); and glucose, 112 mg/dL (6.2 mmol/L). Liver function test results, including those from the ammonia test, were normal; the carcinoembryonic antigen level was slightly elevated at 4.5 ng/mL; and protein electrophoresis and urinalysis results were normal. Lumbar puncture opening pressure was 13 cm. Cerebrospinal fluid (CSF) contained the following values: 6 white blood cells, 44% neutrophils, 33% lymphocytes, 6% monocytes, and 16% “other” cells; the CSF protein level was 26 mg/dL; glucose level, 52 mg/dL (3 mmol/L); and pH, 7.32. Cytologic examination of CSF showed rare, atypical, nucleated cells. Repeat CSF analysis 5 days after hospital admission showed a white blood cell count of 0, protein level of 24 mg/dL, and glucose level of 95 mg/dL (5 mmol/L).