FIGURE 72.1 Diagnostic approach to seizures The most common causes are in bold type An LP with analysis of the cerebrospinal fluid (CSF) is the only way to make the diagnosis of meningitis and should be performed when meningitis is being considered An elevated CSF protein, CSF pleocytosis, and a low CSF glucose level are all suggestive of CNS infection CSF cultures, Gram stain, latex studies, and polymerase chain reaction may identify a specific agent Ideally, CSF cultures should be obtained before antibiotic therapy is initiated However, in the critically ill or unstable patient, antibiotics should not be withheld until an LP is performed Furthermore, in cases in which a potential metabolic disease is being considered, CSF lactate, pyruvate, and/or amino acid level determinations can be used to diagnose a specific metabolic disorder In these cases, it is often helpful to