A 28-year-old woman is admitted to the hospital with fever, vomiting, and change in mental status over the past 2 days. Her family reports that she has reported a headache for the past 4 weeks and that her symptoms have been progressively worsening. Medical history is significant for type 1 diabetes mellitus. Her only medication is insulin. She does not smoke, drink, or use drugs. She resides in Arizona.
On physical examination, temperature is 38.9 °C (102.0 °F), blood pressure is 110/80 mm Hg, pulse rate is 100/min, and respiration rate is 18/min. BMI is 22. Oxygen saturation breathing ambient air is 97%. She is oriented to person but not place or time. The general medical examination is unremarkable. On neurologic examination, nuchal rigidity is noted, but no additional focal findings are present.
Laboratory studies show a cerebrospinal fluid (CSF) leukocyte count of 1500/µL (1500 × 106/L) with a predominant lymphocytosis but also presence of eosinophils, glucose level of 30 mg/dL (1.7 mmol/L), and protein level of 90 mg/dL (900 mg/L). CSF IgG complement fixation is positive for Coccidioides immitis.
MRI of the brain shows generalized leptomeningeal enhancement.
Which of the following is the most appropriate treatment?