Cerebral Autoregulation and Conventional and Diffusion Tensor Imaging Magnetic Resonance Imaging in Neonatal Hypoxic-Ischemic Encephalopathy

Abstract

Background Deviation of mean arterial blood pressure (MAP) from the range that optimizes cerebral autoregulatory vasoreactivity (optimal MAP) could increase neurological injury from hypoxic-ischemic encephalopathy (HIE). We tested whether a global magnetic resonance imaging (MRI) brain injury score and regional diffusion tensor imaging (DTI) are associated with optimal MAP in neonates with HIE. Methods Twenty-five neonates cooled for HIE were monitored with the hemoglobin volume index. In this observational study, we identified optimal MAP and measured brain injury by qualitative and quantitative MRIs with the Neonatal Research Network (NRN) score and DTI mean diffusivity scalars. Optimal MAP and blood pressure were compared with brain injury. Results Neonates with blood pressure within optimal MAP during rewarming had less brain injury by NRN score (P = 0.040). Longer duration of MAP within optimal MAP during hypothermia correlated with higher mean diffusivity in the anterior centrum semiovale (P = 0.008) and pons (P = 0.002). Blood pressure deviation below optimal MAP was associated with lower mean diffusivity in cerebellar white matter (P = 0.033). Higher optimal MAP values related to lower mean diffusivity in the basal ganglia (P = 0.021), the thalamus (P = 0.006), the posterior limb of the internal capsule (P = 0.018), the posterior centrum semiovale (P = 0.035), and the cerebellar white matter (P = 0.008). Optimal MAP values were not associated with the NRN score. Conclusions The NRN score and the regional mean diffusivity scalars detected injury with mean arterial blood pressure deviations from the optimal MAP. Higher optimal MAP and lower mean diffusivity may be related because of cytotoxic edema and limited vasodilatory reserve at low MAP in injured brain. DTI detected injury with elevated optimal MAP better than the NRN score.

Neonatal cerebrovascular autoregulation

“…Maintaining blood pressure within optimal ABP is associated with less brain injury in MRI and improved 2-year neurodevelopmental outcomes in neonatal HIE. 76–80 Traumatic brain injury and preterm neonatal studies also support using optimal MAP as a hemodynamic goal.…”

Diffusion tensor imaging in neonatal encephalopathy: a systematic review

“…In all, 19 studies were included in our final list for review, which included DTI data from 557 NE infants and 112 healthy controls 15–33. These studies all met the guidelines outlined in the STROBE statement13 in regard to quality and bias.…”

“…Usually myelinated at term, the PLIC can be seen as a low intensity signal on a T2-weighted scan in the healthy term infant. Loss of low signal or increased T2 signal within the PLIC may indicate evidence of NE, and in fact, several of the studies reviewed included this as part of their diagnostic criteria 17 18 21 22 29…”

Neonatal Hypoxic-Ischemic Encephalopathy Yields Permanent Deficits in Learning Acquisition: A Preclinical Touchscreen Assessment

“…Thus, the utilization of this testing paradigm allows for insight into specific characterization of cognitive deficits observed followed HIE in a preclinical model. We predicted that mice subject to HIE would have cognitive deficits as adults, defined by deficits in reversal learning, specifically the learning or later portion, reflective of the structural brain injury extensively published in this model (13,(17)(18)(19)(20)(27)(28)(29)(30)(31)(32).…”