Results of brain imaging studies (head computed tomography, brain magnetic resonance imaging, and brain magnetic resonance venogram) were normal. The results of routine blood tests were normal; the levels of glycated hemoglobin, thyrotropin, and B12 were normal as well. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were elevated at 3.9 mg/dL and 48 mm/h, respectively (to convert CRP to nanomoles per liter, multiply by 9.524). Lumbar puncture opening pressure was 175 mm H2O. Cerebral spinal fluid (CSF) had an elevated white blood cell count (10 000/μL) (to convert to ×109/L, multiply by 0.001), with a differential cell count of 2% polymorphonuclear leukocytes, 64% lymphocytes, 0% eosinophils, 0% basophils, and 34% macrophages (to convert all the percentages to a proportion of 1.0, multiply by 0.01). Red blood cell count (9.0×109/L) (to convert to ×1012/L, multiply by 1.0) and protein (29 mg/dL) (to convert to grams per liter, multiply by 10.0) and glucose (61 mg/dL) (to convert to millimoles per liter, multiply by 0.0555) levels were within normal limits. A chest radiograph was normal and tuberculosis skin test (purified protein derivative) was nonreactive. Results of serum angiotensin-converting enzyme, antinuclear antibody (ANA), anti–neutrophil cytoplasmic antibodies (pANCA or cANCA), and human immunodeficiency virus testing were negative. Serologic results for serum rapid plasma reagin, Lyme, Borrelia, and toxoplasmosis antibody titers were all negative, as were CSF culture, VDRL test, polymerase chain reaction for Bartonella and Lyme DNA, and multiple sclerosis (CSF) panel (myelin basic protein, oligoclonal bands, IgG index).