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You are seeing a 12 year old child that presents with altered mental status, fever, and history of headache and vomiting before the decline in mental status. The patient has a seizure on arrival to the ED, which resolve with lorazepam IV. The CT scan shows evidence of a subdural fluid collection. The lumbar puncture results show a neutrophilic pleocytosis with an elevated protein. Gram stain is negative. 

Which of the following is true of subdural empyema?