ИСТИНА

Brain stem blood flow in traumatic brain injury: the exploratory multivariate analysis Introduction: Since the introduction of perfusion computerized tomography (PCT) into clinical practice, it was rarely used for brain stem blood flow evaluation in traumatic brain injury (TBI). The aim of this study was to assess a complex relationship between brain stem blood flow (BBF) and pathophysiological/clinical manifestations of TBI using classic data analysis and advanced data mining toolbox. Methods: CT-perfusion data were obtained for 81 patients with mild to severe TBI between 2005 and 2014 The regions of interest were set in right and left cerebral peduncles and midbrain tegmentum at one section. We analysed cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) related to level of consciousness (Glasgow Coma Scale), motor response to pain, vestibulo-ocular, corneal, pupillary, vertical gaze, cough, pharyngeal, palatal reflexes, anisocoria, strabismus, hemodynamic failure as well as cerebral blood flow autoregulation (by pressure reactivity index [PRx]). Brain stem lesions were verified by advanced MRI modalities. Statistical analysis and data mining was performed using R software. Results: The majority of patients were severely injured (81.5%) in road-traffic accidents (65%). The average values of BBF were 27-29 ml/100g/min, ranging significantly in severely injured patients (Table 1). The average level of brain stem blood flow was lower compared to hemispheric (26-28 ml/100 g/min, p < 0.05). The lowest BBF values were found inside the hemorrhagic lesions (4.0 ml/100 g/min). Oppositely, we explored that the high BBF (up to 76 ml/100 g/min) was related to cerebral circulation autoregulation failure (p <0.05), which, in turn, was accompanied by intracranial hypertension. Multivariate time series classification was used to distinguish the patterns of intracranial pressure (ICP) leading to autoregulation disturbance. The key factor for disregulation was ICP > 15 mmHg which appeared to be lower than the accepted ICP threshold of 25 mmHg for surgical interventions. To analyze the connection between BBF and neurologic dysfunction each patient was examined right ahead of perfusion CT. We proposed a scoring system to quantify each neurologic sign. We found that one and the same blood flow level was accompanied by diverse neurological manifestations. The linear relation between neurological signs and BBF was rarely observed in our study. Conclusion: Brain stem blood flow in TBI varies in a wide range depending on brain stem damage and cerebral circulation autoregulation. Brain stem clinical dysfunction is accompanied by multivariate blood flow patterns. Brain stem CBF is typically low inside (not necessarily outside) the hemorrhagic lesions, however, autoregulation failure may lead to extremely high CBF levels. A multicenter randomized controlled study in patients undergoing decompressive craniectomy is required to test the clinical utility of brain stem CT perfusion.