meningitis

A 3-year-old boy is brought to the emergency department by his parents due to a high fever and irritability. He has had a runny nose and cough for the past two days. On examination, he is lethargic and has a bulging fontanelle. A lumbar puncture is performed, and the cerebrospinal fluid (CSF) analysis shows elevated protein, low glucose, and a high white cell count with a predominance of neutrophils. What is the most likely diagnosis?

A 25-year-old man presents to the emergency department with a 2-day history of severe headache, photophobia, and neck stiffness. He has no significant past medical history and is not on any medications. On examination, he is febrile with a temperature of 39°C, and there is a positive Brudzinski's sign. What is the most appropriate initial investigation to confirm the diagnosis?

A 32-year-old woman presents to the emergency department with sudden onset of severe headache, nausea, and photophobia. She has no significant past medical history and is not on any medications. On examination, she is alert but in distress due to the headache. Her vital signs are stable, and there is no neck stiffness. A CT scan of the head is performed and shows no abnormalities. What is the most appropriate next step in the management of this patient?

A 35-year-old man, recently arrived from a country with a high burden of tuberculosis, presents to the emergency department with a 2-week history of worsening headache, low-grade fever, and general malaise. Over the past 48 hours, he has become increasingly drowsy and confused. He denies cough, weight loss, or night sweats. His past medical history is unremarkable, and he is not on any regular medications. On examination, he is febrile (38.5°C), drowsy but rousable, with a Glasgow Coma Scale (GCS) of 13/15 (E3 V4 M6). His neck is stiff, and Kernig's sign is positive. Fundoscopy is normal. Chest auscultation is clear. Neurological examination reveals no focal deficits. Initial blood tests show a mild lymphocytosis, normal electrolytes, and normal renal and liver function. A non-contrast CT scan of the brain shows subtle basal meningeal enhancement. A lumbar puncture is performed. CSF Results: * Appearance: Slightly turbid * Opening pressure: 25 cm H2O (elevated) * White cell count: 150 cells/µL (normal <5), 80% lymphocytes * Red cell count: 5 cells/µL * Protein: 1.5 g/L (normal 0.15-0.45) * Glucose: 1.8 mmol/L (normal 2.5-4.5), simultaneous blood glucose 5.5 mmol/L Given the clinical presentation and investigation findings, what is the most appropriate immediate next step in management?