Glucose, Spinal Fluid

Glucose enters the cerebrospinal fluid (CSF) from the plasma by both diffusion and active transport. The concentration and duration of plasma glucose influence the CSF level. Typically, spinal fluid glucose concentration is 60 to 70% of plasma glucose and lags behind the plasma level by 30 to 90 minutes. An increase in spinal fluid glucose means the patient was hyperglycemic 30 to 90 minutes before and is not clinically significant.

Spinal fluid glucose may be decreased by bacterial, fungal, and tuberculous meningitis; primary and metastatic cancer, subarachnoid hemorrhage; and hypoglycemia. CSF glucose is decreased in 60 to 80% of bacterial meningitis cases. Viral meningitis and neurosyphilis usually do not affect spinal fluid glucose concentration.  

Decreased CSF glucose is usually seen in:

• Bacterial (60-80% of cases), fungal, and tuberculous meningitis
• Primary or metastatic meningeal malignancies
• Subarachnoid hemorrhage 
• Hypoglycemia

Normal glucose level is usually seen in:

• Viral meningitis
• Brain abscess
• Neurosyphilis

Reference range for CSF glucose is 40 to 70 mg/dL.

Specimen requirement is 1 mL of spinal fluid.