Neurosurg Focus 29 (5):E2, 2010

Role of the S100B serum biomarker in the treatment of children suffering from mild traumatic brain injury

Ar i s t o t e l i s S. Fi l i p p i d i s , M.D.,1 Di m i t r i o s C. Pa p a d o p o u l o s , M.D.,2 Ef t y c h i a Z. Ka p s a l ak i , M.D., Ph.D., 3 a n d Ko s t a s N. Fo u n t a s , M.D., Ph.D.1 Departments of 1Neurosurgery and 3Diagnostic Radiology, University Hospital of Larissa, School of Medicine, University of Thessaly; and 2Department of Critical Care Medicine, General Hospital of Larissa, Greece

Object. The aim of this study was to provide a systematic update of the current literature regarding the clinical role of the S100B serum biomarker in the initial evaluation of children who have sustained a mild traumatic brain injury (TBI). Methods. Searches in MEDLINE were defined with the keywords “mild TBI children S100,” “mild TBI pedi- atric S100,” and “children S100 brain injury.” From the pool of obtained studies, those that had the inclusion criteria of mild TBI only or mixed types of TBI but including detailed information about groups of children with mild TBI were used. Results. Few studies were identified and fewer included more than 100 cases. The prospective studies showed that the S100B biomarker levels could be influenced by patient age and the time frame between head injury and blood sampling. Moreover, extracranial sources of S100B or additional injuries could influence the measured levels of this biomarker. A normal value of S100B in children with mild TBI could rule out injury-associated abnormalities on CT scans in the majority of reported cases. Conclusions. The vulnerability of S100B serum levels to the influences of patient age, blood sampling time, and extracranial S100B release limits the biomarker’s role in the initial evaluation of children with mild TBI. The application of S100B in pediatric mild TBI cases has an elusive role, although it could help in selected cases to avoid unnecessary head CT scans. (DOI: 10.3171/2010.8.FOCUS10185)

Ke y Wo r d s • biomarker • children • mild traumatic brain injury • S100B biomarker

r a u m a t i c brain injury is one of the leading causes cian, since the decision for a hospital admission to obtain of death and morbidity in children.1,4,8,20 Patients imaging studies is not easy and significantly raises the with mild TBI demonstrate heterogeneity in clini- cost of treatment. The physician’s experience is the key Tcal presentation with or without loss of consciousness factor dictating the management plan given that there are or posttraumatic amnesia and with GCS scores ranging currently no guidelines for the treatment of mild TBI in from 13 to 15.23 The different age groups and commu- children.1,4,8,20 nication difficulties in pediatric patients may sometimes The above considerations in pediatric cases of mild present further obstacles in obtaining a detailed injury TBI create a need to design a diagnostic tool that would history and identifying TBI symptoms in an accurate combine diagnostic performance, ease of use, minimal and timely manner. The neurological examination in pe- invasiveness, cost effectiveness, and outcome prediction diatric patients, especially in the very young ones, may in a timely and efficient manner.6,20 For years, imaging be quite challenging, and the patient’s initial clinical studies have been used as supplemental tools in diagnos- picture and injury history may frequently be unreliable. ing and managing pediatric TBI cases. However, these Their evaluation requires time and patience, which un- studies are not always feasible because of their prohibi- fortunately can be difficult to find in a chaotic and busy tive use due to high costs, time requirements, and dif- emergency room. In addition, pediatric cases of mild TBI ficult application. The necessity of finding an optimal can impose a diagnostic dilemma on the managing physi- biomarker from the blood or CSF that could establish a TBI diagnosis, accurately measure its severity, and pre- Abbreviations used in this paper: GCS = Glasgow Coma Scale; dict its outcome is more than apparent.6,20 Protein S100B, TBI = traumatic brain injury. neuron-specific enolase, and glial fibrillary acidic protein

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Unauthenticated | Downloaded 10/01/21 10:09 AM UTC A. S. Filippidis et al. are the most commonly studied biomarkers, while protein can be found in very low levels in human CSF and se- S100B has been studied the most in the field of pediatric rum, and normal levels of this protein have been strongly TBI.1,3–7,14,18,20 correlated with the absence of any intracranial injuries.21 The aim of our study was to assess the role of S100B Low basal levels of S100B in human serum suggest that as a clinical biomarker in pediatric cases of mild TBI and sharp increases in the concentrations of this protein are to systematically review the pertinent literature. sensitive indicators of brain injury. Cerebral lesions cause immediate leaking of S100B from damaged glial cells 19 Methods into the blood or CSF. The precise mechanism of the increased serum concentration of S100B in cases of TBI We accessed the MEDLINE database to gather the remains uncertain. The S100B could be directly released required data and information for this review article. Our by damaged cells, but it is also secreted into the extracel- search strategy involved 3 different search sessions us- lular space by activated glial cells. It may enter the serum ing the keywords “mild TBI children S100,” “mild TBI through a transient disruption of the blood-brain barrier pediatric S100,” and “children S100 brain injury.” We or via the CSF circulation.20 It has been shown that se- included only those articles published in the English lan- rum S100B levels correlate well with a patient’s clinical guage. After obtaining the first pool of studies, a second condition and imaging findings as well as their outcome filter procedure followed. The inclusion criteria isolated scores in cases of TBI. It has been postulated that S100B studies with pediatric cases of mild TBI only. Whenever protein is the most promising marker for evaluating the studies with mixed types of TBI or mixed populations severity of TBI in patients suffering from mild injuries.10 (adult and pediatric) were encountered, we tried to extract It has also been shown that in patients with severe TBI, information specific to pediatric cases of mild TBI. serum S100B concentrations higher than 1.13 ng/ml are associated with increased death and morbidity.24 Thus, Results this protein has been proposed as a potential biomarker indicating the severity of neuronal injury and the disrup- Profile of S100B tion of the blood-brain barrier and predicting a patient’s 22 The S100 calcium binding protein B, or S100B, be- outcome. On the other hand, it has been demonstrated longs to the S-100 protein family and is characterized by that there is a poor correlation between CSF and serum 2 calcium-binding sites of the helix-loop-helix conforma- S100B levels; this is because the intact blood-brain bar- tion. The S100 proteins are located in the cytoplasm and rier is not permeable to S100B. It has been postulated that nucleus of a wide range of cells and are involved in the an increase in serum concentration may be indicative of blood-brain barrier disruption rather than irreversible regulation of a number of cellular processes, such as cell 6 cycle progression and differentiation. Specifically, S100B neuronal damage. Furthermore, increased S100B serum regulates cellular homeostasis and enzyme activity and levels have been described in cases of and he- patic, renal, and/or intestinal ischemia, probably due to inhibits protein kinase C phosphorylation of growth-as- 17 sociated protein 43, which is involved in axonal growth the presence of S100B in other nonglial cells. In addi- and synaptogenesis during development, synaptic remod- tion, the use of S100B as a neuronal injury biomarker has 13 been questioned because its concentration was increased eling, and long-term potentiation. It also plays a sig- 2 nificant role in the stabilization of tau and microtubule- in trauma patients with no head injuries. 26 associated protein 2 (MAP-2). The S100 genes include Clinical Studies of S100B in Children With Mild TBI at least 13 members, which are located as a cluster on 1q21. There are at least 21 different types of Most of the clinical studies concerning mild TBI and S100 proteins.25 The name of this protein group derives S100B serum levels in children included a limited number from its solubility in ammonium sulfate, which is 100% of patients, and thus no statistically powerful conclusions at a neutral pH. can be extracted. Interestingly, very few studies included The S100B protein was first identified in 1965 by more than 100 patients. Geyer et al.8 conducted a prospec- Moore.15 It is a low-molecular-weight protein (10–12 kD) tive clinical study involving 148 children with mild TBI. composed of 2 subunits, alpha and beta, with the aa The biomarkers S100B and neuron-specific enolase were subtype found mostly in striated muscles, heart, and kid- measured within 6 hours of injury. Two diagnostic groups neys; the ab subtype, in glial cells; and the bb subtype, were studied. The first one, called the “mild TBI group” in high concentrations in astroglia.9 The S100 proteins included children with GCS scores of 13–15 and signs of and especially S100B can act as a cancer biomarker in concussion. The second one, called the “head contusion malignant melanoma. It has a serum half-life of 60–120 group,” included children with a GCS score of 15 and no minutes and is eliminated by renal clearance.11,12 Al- signs or symptoms of concussion. The authors found that though S100B is glial-specific and expressed primarily patient age and the time frame between injury and blood by and Schwann cells, it is also found in sev- withdrawal significantly influence the serum S100B con- eral non–nervous system cells, such as adipocytes (white centrations. The levels of S100B in the mild TBI and head and brown fat), chondrocytes, skin, and glioblastoma and contusion groups did not significantly differ. Moreover, melanoma cells.27 However, it is not expressed by all as- there was no significant difference between the levels of trocytes. It has been shown that S100B is only expressed S100B in patients with GCS Scores 15 or 14. These au- by a subtype of mature astrocytes, which are in proximity thors concluded that S100B demonstrates low sensitivity to blood vessels, and also by NG2-expressing cells.25 It in mild TBI cases in children (Table 1).

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TABLE 1: Literature review of studies on pediatric patients with mild TBI*

Parameter Geyer et al., 2009 Castellani et al., 2009 Morochovic et al., 2009 Akhtar et al., 2003 Berger et al., 2005 sample size 148 109 102 17 12† type of population pediatric pediatric pediatric & adult‡ pediatric pediatric % males 57.4 67 ND ND ND age range 6 mos–15 yrs 5 mos–17.5 yrs 12–84 yrs 6–15 yrs ND GCS score >12 >12 >12 § 15 time point of S100B sampling (hrs) ≤6 ≤6 ≤6 ≤6, ≤12¶ ≤12 imaging modality none CT CT CT & MRI CT

* No outcome measurements (Glasgow Outcome Scale or neuropsychological tests) were used in any of the studies. Abbreviation: ND = no data. † Extracted data of 12 patients with mild TBI (from a total of 168). ‡ Extracted pediatric data used in the paper. § Traumatic brain injury patients with negative CT. ¶ First sample, second sample.

In a prospective study, Castellani et al.4 tried to re- concussion. In that cohort, 67% of the children demonstrat- veal whether S100B levels in 109 children with mild TBI ed increased serum levels of S100B. The authors concluded (GCS Scores 13–15 at admission and clinical symptoma- that S100B could be a more sensitive biomarker than CT or tology present) were related to their CT findings. The in- MR imaging in cases of pediatric TBI.3 The high levels clusion criteria were as follows: 1) children who required of S100B could potentially reflect CNS damage that was a CT scan during hospitalization and 2) whose S100B lev- undetected with imaging modalities (Table 1).3 els had been determined within 6 hours of the traumatic event. Blood sampling had also occurred within 6 hours after the injury event. An interesting finding was the in- Discussion creased serum S100B levels in patients with an abnormal The application of serum S100B protein as a clinical CT scan as compared with levels in children with non- biomarker and outcome-predicting factor in pediatric cas- diagnostic findings on CT, and this difference was sta- es of mild TBI meets several obstacles given that numer- tistically significant. However, no statistically significant ous factors can influence baseline serum S100B concentra- difference in the serum S100B concentrations was found tions and many pathological conditions other than TBI can between the different GCS subgroups (patients with GCS cause elevated S100B levels. Patient age is one of the most scores of 13 vs 14 vs 15), after the adjustment of p values influential factors in determining normal baseline serum for pairwise analysis. When CT findings were used as a levels of S100B. The effect is significant in the pediatric factor to assess serum S100B marker performance, sensi- population, which expresses highly varying growth factors tivity was 1.00, specificity 0.42, positive predictive value at different developmental stages and produces a variety of 0.46, and negative predictive value 1.00 with an area un- proteins to meet everyday growth demands. This observa- der the curve of 0.68. All children with normal serum 8 S100B values had no injury-related abnormalities on head tion has been confirmed by Geyer et al. in their pediatric study of mild TBI as well as in other clinical studies.5,7,20 CT scans. This finding can be used in routine clinical 7 practice to avoid unnecessary CT scans in children with Gazzolo et al. evaluated the normal levels of S100B in se- normal S100B values. It should be noted that children rum in 1004 children to create a reference curve and found with head and other systemic injuries had higher mean that there are 2 peaks, 1 in children younger than 1 year of S100B levels than those with isolated head injuries. This age and another occurring in adolescents. The changes in S100B reference levels in children of different ages were difference reached the levels of statistical significance in 5 their study (Table 1).4 also confirmed in the study by Castellani et al. All of these Akhtar et al.1 tried to assess the significance of serum studies show that S100B is definitely an age-dependent S100B levels in 17 children who had sustained a TBI and protein, and any future S100B TBI studies should use ref- had been screened with brain MR imaging. All children erence levels for specific age groups. in their study had a negative CT scan. Unfortunately, there Another source of variability in the S100B levels in were no details regarding the admitting GCS scores. The cases of TBI is the presence of additional injuries.1,2,8,20 S100B biomarker did not efficiently identify TBI patients Although S100B can be found at high levels in astroglia with positive or negative MR imaging studies. Moreover, and neurons, the lack of specificity of this biomarker for additional systemic injuries affected the serum levels of the CNS may create a distorted image in cases of mild S100B, so that children with concomitant injuries had TBI associated with multiple injuries. Concomitant sys- consistently higher S100B serum concentrations than the temic injuries, such as long bone fractures and extensive children with head injury only (Table 1).1 skin injuries, adipose tissue injuries, and muscle or joint Berger et al.3 reported their experience with 12 chil- injuries, can become a source of additional S100B release dren who had sustained TBIs, with admitting GCS scores in the serum and thus perplex its diagnostic accuracy in of 15, normal head CT scans, and no clinical evidence of TBI cases.27

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The sampling time of S100B in relation to the time of Kapsalaki. Drafting the article: all authors. Critically revising the head injury is also an important factor that may influence article: all authors. Reviewed final version of the manuscript and its serum concentrations and thus make the interpreta- approved it for submission: Fountas. 8,16 tion of any S100B increases inconclusive in TBI cases. References Delayed serum measurements of S100B following a head injury may lead to erroneous conclusions regarding the 1. Akhtar JI, Spear RM, Senac MO, Peterson BM, Diaz SM: Detection of traumatic brain injury with magnetic resonance severity and extent of neuronal damage, because of the imaging and S-100B protein in children, despite normal com- relatively short half-life of the S100B protein. Geyer et 8 puted tomography of the brain. Pediatr Crit Care Med 4: al. emphasized the importance of the time span between 322–326, 2003 injury and S100B blood sampling in the accurate mea- 2. Anderson RE, Hansson LO, Nilsson O, Dijlai-Merzoug R, surement of S100B serum levels. It cannot be overempha- Settergren G: High serum S100B levels for trauma patients sized that exact knowledge of blood sampling is manda- without head injuries. Neurosurgery 48:1255–1260, 2001 tory for interpreting serum S100B levels and evaluating 3. Berger RP, Adelson PD, Pierce MC, Dulani T, Cassidy LD, their association with the severity and prognosis of the Kochanek PM: Serum neuron-specific enolase, S100B, and myelin basic protein concentrations after inflicted and nonin- underlying head injury. flicted traumatic brain injury in children.J Neurosurg 103 (1 The role of S100B as a biomarker in children suffer- Suppl):61–68, 2005 ing from mild TBI meets strong criticism in the litera- 4. Castellani C, Bimbashi P, Ruttenstock E, Sacherer P, Stoja- ture. Studies by Geyer et al.,8 Berger et al.,3 and Akhtar et kovic T, Weinberg AM: Neuroprotein S-100B—a useful pa- al.1 demonstrated a low sensitivity for S100B in pediatric rameter in paediatric patients with mild traumatic brain in- cases of mild TBI. In all of these series, serum levels of jury? Acta Paediatr 98:1607–1612, 2009 S100B failed to efficiently identify children with intra­ 5. Castellani C, Stojakovic T, Cichocki M, Scharnagl H, Erwa W, 1,3,8 Gutmann A, et al: Reference ranges for neuroprotein S-100B: cranial pathology on imaging studies. These findings from infants to adolescents. Clin Chem Lab Med 46:1296– agree with those in the mild TBI study by Morochovic et 1299, 2008 16 al., which showed that S100B is an unreliable screen- 6. Dash PK, Zhao J, Hergenroeder G, Moore AN: Biomarkers for ing tool for detecting intracranial pathology in adults and the diagnosis, prognosis, and evaluation of treatment efficacy for children. 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Harpio R, Einarsson R: S100 proteins as cancer biomarkers less, their findings were promising, and the potential role with focus on S100B in malignant melanoma. Clin Biochem of S100B in the triage of children with mild TBI should 37:512–518, 2004 10. Ingebrigtsen T, Romner B: Biochemical serum markers for brain be explored in a large-scale, prospective clinical trial. damage: a short review with emphasis on clinical utility in mild head injury. Restor Neurol Neurosci 21:171–176, 2003 11. Ingebrigtsen T, Romner B: Biochemical serum markers of Conclusions traumatic brain injury. J Trauma 52:798–808, 2002 In summary, the role of the S100B biomarker in the 12. Jönsson H, Johnsson P, Höglund P, Alling C, Blomquist S: initial evaluation of children with mild TBI is still contro- Elimination of S100B and renal function after cardiac sur- gery. J Cardiothorac Vasc Anesth 14:698–701, 2000 versial and remains to be defined. Many factors—includ- 13. Kövesdi E, Lückl J, Bukovics P, Farkas O, Pál J, Czeiter E, ing a patient’s age, the serum sampling time, and the pres- et al: Update on protein biomarkers in traumatic brain injury ence of multiple extracranial injuries—can influence the with emphasis on clinical use in adults and pediatrics. Acta levels of S100B, yielding inadequate or even confusing Neurochir (Wien) 152:1–17, 2010 results. The identification of a more specific biomarker 14. Lumpkins KM, Bochicchio GV, Keledjian K, Simard JM, Mc- for CNS injuries, the use of paired biomarkers in pediat- Cunn M, Scalea T: Glial fibrillary acidic protein is highly cor- ric studies of mild TBI , and the design and performance related with brain injury. J Trauma 65:778–784, 2008 15. Moore BW: A soluble protein characteristic of the nervous of large-scale, prospective clinical studies could provide system. Biochem Biophys Res Commun 19:739–744, 1965 more data and shed more light on the ambiguous role of 16. Morochovic R, Rácz O, Kitka M, Pingorová S, Cibur P, Tom- biomarkers in the evaluation of children with mild closed- ková D, et al: Serum S100B protein in early management head injuries. of patients after mild traumatic brain injury. Eur J Neurol 16:1112–1117, 2009 Disclosure 17. Pelinka LE, Harada N, Szalay L, Jafarmadar M, Redl H, Bah- rami S: Release of S100B differs during ischemia and reper- The authors report no conflict of interest concerning the mate- fusion of the liver, the gut, and the kidney in rats. Shock 21: rials or methods used in this study or the findings specified in this 72–76, 2004 paper. 18. Pelinka LE, Kroepfl A, Leixnering M, Buchinger W, Raabe A, Author contributions to the study and manuscript preparation Redl H: GFAP versus S100B in serum after traumatic brain include the following. Conception and design: Filippidis. Acquisition injury: relationship to brain damage and outcome. J Neuro­ of data: Filippidis. Analysis and interpretation of data: Filippidis, trauma 21:1553–1561, 2004

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19. Petzold A, Keir G, Lim D, Smith M, Thompson EJ: Cerebrospi­ 25. Wang DD, Bordey A: The odyssey. Prog Neurobiol nal fluid (CSF) and serum S100B: release and wash-out pat- 86:342–367, 2008 tern. Brain Res Bull 61:281–285, 2003 26. Whitaker-Azmitia PM, Wingate M, Borella A, Gerlai R, Rod- 20. Sandler SJI, Figaji AA, Adelson PD: Clinical applications of er J, Azmitia EC: Transgenic mice overexpressing the neu- biomarkers in pediatric traumatic brain injury. Childs Nerv rotrophic factor S-100 beta show neuronal cytoskeletal and Syst 26:205–213, 2010 behavioral signs of altered aging processes: implications for 21. Savola O, Pyhtinen J, Leino TK, Siitonen S, Niemelä O, Hill- Alzheimer’s disease and Down’s syndrome. Brain Res 776: bom M: Effects of head and extracranial injuries on serum 51–60, 1997 protein S100B levels in trauma patients. J Trauma 56:1229– 27. Zimmer DB, Cornwall EH, Landar A, Song W: The S100 pro- 1234, 2004 tein family: history, function, and expression. Brain Res Bull 22. Undén J, Astrand R, Waterloo K, Ingebrigtsen T, Bellner J, 37:417–429, 1995 Reinstrup P, et al: Clinical significance of serum S100B levels in neurointensive care. Neurocrit Care 6:94–99, 2007 23. Vos PE, Battistin L, Birbamer G, Gerstenbrand F, Potapov A, Prevec T, et al: EFNS guideline on mild traumatic brain in- jury: report of an EFNS task force. Eur J Neurol 9:207–219, Manuscript submitted July 15, 2010. 2002 Accepted August 23, 2010. 24. Vos PE, Lamers KJB, Hendriks JCM, van Haaren M, Beems Address correspondence to: Kostas N. Fountas, M.D., Ph.D., De­­ T, Zimmerman C, et al: Glial and neuronal proteins in serum partment of Neurosurgery, Build A, Third Floor, Suite #56, Universi­ predict outcome after severe traumatic brain injury. Neurol­ ty Hospital of Larissa, Biopolis, Larissa, Greece. email: fountas@ ogy 62:1303–1310, 2004 med.uth.gr.

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