Protein S-100B as biochemical marker of brain ischemic damage after treatment of carotid stenosis

Abstract

Background: S-100 protein is a family of low molecular weight proteins found in vertebrates characterized by two calcium binding sites of the helix-loop-helix ("EF-hand type") conformation. There are at least 21 different types of S-100 proteins. The name is derived from the fact that the protein is 100% soluble in ammonium sulfate at neutral pH. Protein S-100B was investigated as a marker of brain ischemic damage after treatment of carotid stenoses.

Methods: Between December 1, 2009 and December 1, 2010, S-100B protein was monitored in 76 patients after carotid artery stenting (CAS) and in 24 patients after carotid endarterectomy (CEA). In each patient, multiple samples were taken: before the procedure (basal sample), immediately after CAS or CEA, 60 minutes after CAS or CEA, and daily during the hospital stay. Evaluation of S-100B was carried out by blind assessment. Patients underwent pre- and postoperative diffusion-weighted magnetic resonance imaging or computed tomographic scan.

Results: An S-100B coefficient of variation higher than the established cut-off was detected in 16 patients: three affected by postoperative stroke, two patients with minor stroke, and one patient with fatal stroke; 12 patients presented with uneventful neurological outcome and positive brain imaging; and there was one false positive case. No false negative cases occurred. The postoperative protein S-100B level lowered to basal level in 15 patients: within 24 hours in the 12 patients with the uneventful outcome (and positive brain imaging) and in the false positive case; and after 120 and 144 hours, respectively, in the two patients with minor stroke. In the patient with fatal stroke, protein S-100B never returned to the preoperative level.

Conclusions: In patients with an increased S-100B coefficient of variation, the diffusion-weighted magnetic resonance imaging was positive for ischemic brain lesions, except for one patient who was reported as a false positive case. The postoperative S-100B protein level decreased within 24 hours in the uneventful neurological cases and in the false positive case, whereas long-lasting postoperative increased values of the S-100B protein were observed in patients with poor neurological outcomes.