Objectives Vertigo is a common presenting complaint resulting from central or peripheral etiologies. Because central causes may be life-threatening, ascertaining the nature of the vertigo is crucial in the emergency department (ED). With a broad range of potential etiologies, distinguishing central causes from benign peripheral causes is a diagnostic challenge. Cranial magnetic resonance imaging (MRI) is the recommended neuroimaging method when clinical findings are ambiguous. However, MRI scanning for every patient with an uncertain diagnosis may not be efficient or possible. Therefore, to improve ED resource utilization for patients with vertigo, there is a need to identify the subset most likely to have MRI abnormalities. It has previously been shown that S100B protein provides a useful serum marker of stroke, subarachnoid hemorrhage, and traumatic brain injury. This study evaluated whether S100B levels could predict central causes of vertigo as identified by cranial MRI in the ED. Methods This prospective, observational study was conducted with adult patients with acute-onset vertigo (within 6 hours) in the ED of a teaching hospital in Kocaeli, Turkey. Patients with nausea or dizziness complaints without previously known vertigo or cranial pathology, and who agreed to participate in the study, were included. Patients with trauma or with neurologic findings that developed concurrent with their symptoms were excluded. Serum levels of S100B were measured with an electrochemiluminescence immunoassay kit. All subjects underwent cranial MRI. The predictors of positive MRI results were evaluated using logistic regression analysis. Sensitivity and specificity of S100B levels for identifying subjects with central causes of vertigo on MRI were calculated with receiver operating characteristic (ROC) curve. Results Of the 82 subjects included in the study, 48 (58.5%) were female, and the mean (±SD) age was 51 (±16) years. Thirty-one (37.8%) subjects had positive MRI results. Median (with interquartile range [IQR]) serum S100B levels were significantly different between MRI-negative and MRI-positive groups (median = 27.00 pg/mL, IQR = 10.00 to 44.60 vs. median = 60.94 pg/mL, IQR = 38.25 to 77.95, respectively; p = 0.04). In logistic regression analysis, subjective “he or she is spinning” (p = 0.030, odds ratio [OR] = 1.63, 95% confidence interval [CI] = 1.38 to 2.49), systolic blood pressure (sBP; p = 0.045, OR = 1.044, 95% CI = 1.021 to 1.080), and serum S100B level (p = 0.042, OR = 1.22, 95% CI = 1.018 to 1.445) were found to be independent predictors of MRI abnormalities. In the ROC analysis, S100B > 30 pg/mL predicted the clinical outcome with 83.9% sensitivity (95% CI = 66.3% to 94.5%) and 51.0% specificity (95% CI = 36.6% to 65.2%). The area under the ROC curve was 0.774 (95% CI = 0.666 to 0.881). Conclusions To the best of our knowledge this is the first study assessing the utility of serum S100B levels for diagnosis of acute-onset vertigo. Serum S100B levels are associated with the presence of central causes of vertigo on cranial MRI. However, serum S100B levels are not sufficiently sensitive to exclude candidates from cranial MRI. Resumen Objetivos El vertigo es un motivo de consulta frecuente y es consecuencia de una etiologia central o periferica. Debido a que las causas centrales pueden ser de riesgo vital, la determinacion de la naturaleza del vertigo es crucial en el servicio de urgencias (SU). Con un amplio abanico de etiologias potenciales, el distinguir las causas centrales de las perifericas benignas es un reto diagnostico. La resonancia magnetica (RM) craneal es la prueba de neuroimagen recomendada cuando los hallazgos clinicos son ambiguos. Sin embargo, la realizacion de una RM a todo paciente con diagnostico incierto puede no ser posible o eficiente. Por lo tanto, para mejorar la utilizacion de recursos del SU en los pacientes con vertigo, existe la necesidad de identificar el grupo con mayor probabilidad de tener alteraciones en la RM. Se ha demostrado previamente que la proteina S100B es un marcador serico de utilidad para el ictus, la hemorragia subaracnoidea y la lesion cerebral traumatica. Este estudio evaluo si los valores de S100B podrian predecir las causas centrales de vertigo en el SU como las identifica la RM craneal. Metodologia Estudio observacional prospectivo que se llevo a cabo en pacientes adultos con vertigo de inicio agudo (en las 6 primeras horas) en el SU de un hospital universitario en Kocaeli (Turquia). Se incluyeron los pacientes que aquejaban mareo o nauseas, sin historia previa conocida de vertigo o patologia craneal, y que consintieron participar en el estudio. Se excluyeron los pacientes con traumatismo o hallazgos neurologicos desarrollados simultaneamente con sus otros sintomas. Se midieron los valores sericos de S100B con un kit de inmunoensayo de electrofluorescencia. Se realizo RM craneal a todos los sujetos. Se evaluaron los factores predictivos de RM positiva usando un analisis de regresion logistica. Se calculo con la curva de caracteristica operativa del receptor (Receiver Operating Characteristic, ROC) la sensibilidad y la especificidad de los valores de S100B para la identificacion de sujetos con causas centrales de vertigo en la RM. Resultados De los 82 sujetos incluidos en el estudio, 48 (58,5%) fueron mujeres y la media de edad fue de 51 anos. Treinta y un pacientes (37,8%) tuvieron una RM positiva. La mediana (con rango intercuartilico [RIC]) de los valores sericos de S100B fue diferente de forma significativa entre los grupos con RM negativa y RM positiva (mediana 27,00 pg/mL [RIC 10,00 a 44,60] frente a 60,94 pg/mL [RIC 38,25 a 77,95] respectivamente, p = 0,04). En el analisis de regresion logistica, la sensacion subjetiva “que el o ella esta dando vueltas” (OR = 1,63, IC 95% = 1,38 a 2,49; p = 0,030), la presion arterial sistolica (OR = 1,04, IC 95% = 1,02 a 1,08; p = 0,045) y los valores sericos de S100B (OR = 1,22, IC 95% = 1,02 a 1,44; p = 0,042) resultaron ser predictores independientes de alteraciones en la RM. En el analisis ROC, los valores sericos de S100B > 30 pg/ml predijeron el resultado clinico con una sensibilidad de un 83,87% (IC 95% = 66,3% a 94,5%), y una especificidad de 50,98% (IC 95% = 36,6% a 65,2%). El area bajo la curva fue de 0,774 (IC 95% = 0,666 a 0,881). Conclusiones Hasta donde conocemos, este es el primer estudio que evalua la utilidad de los valores sericos de S100B para el diagnostico de vertigo de inicio agudo. Los niveles sericos de S100B se asociaron con la presencia de causas centrales de vertigo en RM craneal. No obstante, los niveles sericos de S100B no son suficientemente sensibles para excluir los candidatos a la RM craneal.