In cerebrospinal fluid (CSF), which level of glucose is indicative of septic meningitis and other serious conditions?

In cerebrospinal fluid (CSF), levels below 40 mg/dL of glucose are indicative of septic meningitis and other serious conditions. Septic meningitis leads to an inflammatory response, which often results in the consumption of glucose by both the bacteria causing the infection and the immune cells responding to the infection. As a result, patients with septic meningitis typically present with a significant decrease in the CSF glucose concentration, commonly falling below the threshold of 40 mg/dL.

Monitoring glucose levels in CSF is a critical aspect of diagnosing various types of meningitis. In contrast, a CSF glucose level equal to the plasma glucose level would not necessarily indicate an infection, as this is often seen in viral meningitis or benign conditions. A hyperglycorrhachia state, which refers to elevated glucose levels in the CSF, is also not indicative of septic meningitis, since it suggests higher availability of glucose, potentially seen in conditions like diabetes or in cases of malignant infiltration. Similarly, if the CSF glucose is greater than the plasma glucose level, it usually points to other processes that are not consistent with septic meningitis. Thus, levels below 40 mg/dL are the hallmark of serious infectious processes in the central nervous system.