A 28-year-old male presents to the emergency department with…
A 28-year-old male presents to the emergency department with a headache and generalized malaise. His family reports that “it is hard to keep him awake” at home. He has a history of tobacco use, marijuana use, and HSV-2 “fever blisters”. Exam: He is lethargic but awakens to voice. He is oriented to himself and his family but disoriented to situation and time. Neck exam reveals a positive Kernig’s sign. No focal motor or sensory deficits are noted, and no rash is appreciated. Vital signs: Temp 102.3°F, HR 110 bpm, BP 100/50 mmHg, SpO₂ 96% on room air. Diagnostics: CT head without contrast: No acute intracranial findings. CSF studies (via lumbar puncture): Opening pressure: 150 mm H₂O (normal) Appearance: Clear WBC: 500/mm³ (elevated) Total protein: 45 mg/dL (normal) Glucose: 60 mg/dL (normal) Which of the following is the most likely diagnosis?