CSF and ECF glutamate concentrations in head injured patients

Excitatory Amino Acids (EAAs) release has been considered to be neurotoxic in traumatic brain injury patients. Microdialysis samples of extracellular space (ECS) and high glutamate concentrations in cerebrospinal fluid (CSF) following Traumatic Brain Injury (TBI) have been documented. The objective of this study was to determine the correlation between EAA release in ECS and CSF in focal and diffuse injury. Head injury patients (GCS < or = 8, n = 16) admitted to Medical College of Virginia Hospital were instrumented for microdialysis collection of ECS samples. CSF samples were collected through the external ventricular drainage catheter at four hour intervals for the first four days following injury. As a control group, CSF was collected from normal pressure hydrocephalus patients (n = 6). Elevated glutamate levels were observed in both CSF and ECS following head injury. The average glutamate concentration in CSF (3.20 +/- 3.62 mumol/l) was significantly increased from control levels (1.13 +/- 0.49 mumol/l, p < 0.05). Comparison of CSF and extracellular fluid (ECF) samples showed that the glutamate concentrations were maximal on the first and second days and gradually decreased on days 3 and 4. On days 4, the level of the glutamate had remained elevated above the normal level.