BACKGROUND: The primary objective of this study was to characterize changes in cerebral blood flow measured using transcranial Doppler in children with central nervous system infections. We hypothesized that children with central nervous system infections have abnormal cerebral blood flow, associated with a greater frequency of complications and poor neurological outcome. METHODS: We conducted a single-center, retrospective study of children admitted to the neonatal or pediatric intensive care unit with central nervous system infection and undergoing transcranial Doppler as part of routine care between March 2011 and July 2015. RESULTS: A total of 20 children with central nervous system infection underwent 35 transcranial Dopplers. The mean age was 8.2 +/- 6.3 years, including 12 boys and eight girls. The most common infection was meningitis (n = 11, 55%), with the remainder comprising encephalitis (15%), meningoencephalitis (20%), and abscess or empyema (10%). Bacterial (n = 10, 50%) and viral (n = 6) sources were common with only one (5%) fungal infection and three (15%) unknown but presumed viral etiology. The patients underwent transcranial Doppler 4 +/- 9 days after intensive care unit admission. Mean cerebral blood flow velocities were overall increased compared with reference values for age (healthy children and critically ill children) mostly because of hyperemia (n = 21, 60%) and vasospasm (6%). Hypoperfusion (cerebral blood flow velocity <1 S.D. of normal value) in at least one vessel was associated with morbidity (intubation, vasoactive medications, neurosurgery, cardiac arrest) (P = 0.04) and mortality (P = 0.03). Two patients had increased intracranial pressure and hyperventilation was safely achieved with transcranial Doppler monitoring to avoid ischemia. Serial transcranial Dopplers were used to guide blood pressure management. CONCLUSIONS: Transcranial Doppler can be used in children with central nervous system infection as a tool to assess cerebral blood flow. In this retrospective study, cerebral hypoperfusion was associated with increased morbidity and mortality. If transcranial Doppler is to guide medical therapy and management of cerebral blood flow in children with central nervous system infections, these results will need to be validated in prospective studies with a more homogenous population of children with encephalitis or meningitis.