Prognostic markers of the outcome in severe head injuries

Introduction

Neuronal-specific enolase (NSE) is a subunit of the enolase group specific for the central neural system, found in the neurons and the neuroendocrine tissue of the brain. NSE is released as a result of leakage across the injured neuronal membrane; elevations of serum NSE are due to neuronal injury and increased permeability of the blood–brain barrier. Protein S-100 (especially the B subunit) is a calcium binding protein found in high concentrations specifically in neurogliar and Schwann cells. Procalcitonin (PCT) is the precursor of calcitonin and under normal conditions it is not detected in the plasma (0–0.5 ng/ml). PCT is elevated in microbial sepsis and trauma.

Objective

To investigate the validity of outcome prediction after severe head injury using the serum levels of protein S-100 B, of NSE and of PCT.

Materials and methods

Over a period of 24 months (2003–2004) 42 patients with severe head injury older than 18 years treated in the ICU of KAT General Hospital, intubated and mechanically ventilated, were prospectively included in the study. The study protocol was approved by the local ethics committee. Informed consent was obtained from the next of kin of all patients. The patients were 20 men and 12 women, without other injuries, mean age 34 years and mean admission GCS 6. None of the patients had spinal cord injury or any other previous neurological disease. Venous blood samples were taken on admission (first day) and consecutively on the second and third days. The immunoluminometric assay was used for the specimens. We tried to correlate the S-100 B, NSE and PCT serum concentrations with the CT scan intracerebral pathology as well as with the age, gender and ICU outcome.

Results

All patients on admission had elevated S-100 B and NSE serum concentrations but PCT was very little increased. There were a gradual reduction from the first towards the third day of ICU stay. The first day the mean values of S-100B were 3.74 μg/l and the third day they were 1.8 μg/l (P < 0.001). The first day the mean values of NSE were 21.7 μg/l and the third day they were 18.2 μg/l (P < 0.05). The first day the mean values of PCT were 1.38 ng/ml and the third day they were 0.49 ng/ml (P = NS). Protein S-100B levels and NSE were higher in patients who died (P < 0.001). There was no strong correlation between the initial serum S-100 B and NSE values, the CT scan findings, the GCS on admission, the age of patients and the gender.

Conclusion

The protein S-100 B and NSE are biochemical markers that seem to be elevated during the first days after injury in patients with severe head trauma. They could be used as markers of the severity of the injury and with great probability as prognostic markers of patient outcome. On the contrary, the PCT levels seem to have no prognostic value in isolated severe head trauma, although the PCT seems to increase in polytrauma patients.