Is MRI still cool after hypothermia?

Prognostic Value of Brain Magnetic Resonance Imaging in Neonatal Hypoxic-Ischemic Encephalopathy: A Meta-analysis

OBJECTIVE

To quantify the prognostic value of neonatal brain magnetic resonance imaging (MRI) in neonatal hypoxic-ischemic encephalopathy.

METHODS

Meta-analysis of studies with ≥35-week neonates with hypoxic-ischemic encephalopathy who underwent brain MRI within age 4 weeks and had neurodevelopmental follow-up for at least 12 months.

RESULTS

An abnormal neonatal brain MRI was more frequent among patients with unfavorable neurodevelopmental outcome: odds ratio = 18.2 (95% confidence interval: 9.4-34.9), P <.0001. The prognostic value of neonatal brain MRI in moderate hypoxic-ischemic encephalopathy had an odds ratio of 17.7 (95% confidence interval: 5.3-59.3) and in severe hypoxic-ischemic encephalopathy, the odds ratio was 125.0 (95% confidence interval: 2.0-7917.1). Therapeutic hypothermia did not change the prognostic value of neonatal brain MRI (odds ratio for hypothermia, 14.0 [95% confidence interval: 3.1-63.6], vs no hypothermia, 18.1 [95% confidence interval: 10.0-33.1], P = .7525).

CONCLUSION

Neonatal brain MRI provides prognostic information on outcome beyond early infancy in hypoxic-ischemic encephalopathy and therapeutic hypothermia does not change its prognostic value.

Evolution of Apparent Diffusion Coefficient and Fractional Anisotropy in the Cerebrum of Asphyxiated Newborns Treated with Hypothermia over the First Month of Life

The objective of this study was to assess the evolution of diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) over the first month of life in asphyxiated newborns treated with hypothermia and to compare it with that of healthy newborns. Asphyxiated newborns treated with hypothermia were enrolled prospectively; and the presence and extent of brain injury were scored on each MRI. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured in the basal ganglia, in the white matter and in the cortical grey matter. Sixty-one asphyxiated newborns treated with hypothermia had a total of 126 ADC and FA maps. Asphyxiated newborns developing brain injury eventually had significantly decreased ADC values on days 2-3 of life and decreased FA values around day 10 and 1 month of life compared with those not developing brain injury. Despite hypothermia treatment, asphyxiated newborns may develop brain injury that still can be detected with advanced neuroimaging techniques such as DWI and DTI as early as days 2-3 of life. A study of ADC and FA values over time may aid in the understanding of how brain injury develops in these newborns despite hypothermia treatment.

MRI obtained during versus after hypothermia in asphyxiated newborns

OBJECTIVE

To assess whether the brain MRI results obtained during hypothermia identify the later brain injury observed in asphyxiated newborns after therapy is completed.

PATIENTS AND METHODS

Asphyxiated newborns treated with hypothermia were prospectively enrolled in this study if they had at least one MRI performed during hypothermia treatment and then another MRI performed around day 10 of life.

RESULTS

A total of 129 MRI scans were obtained from 43 asphyxiated newborns treated with hypothermia. Sixty per cent developed brain injury; all the brain injuries observed on the late scans were already present on day 2-3 of life during hypothermia, and the extent of injury was similar between the early and late scans. The brain MRI on day 2-3 of life had a sensitivity of 100% (95% CI 84% to 100%) and a specificity of 100% (95% CI 77% to 100%) to identify the presence and extent of later brain injury.

CONCLUSIONS

The brain MRIs performed during hypothermia already permit an accurate definition of the presence and extent of brain injury that later develop in asphyxiated newborns despite treatment. These results may have research and clinical implications for the care of these newborns.

Detecting brain injury in neonatal hypoxic ischemic encephalopathy: closing the gap between experimental and clinical research

Moderate to severe neonatal hypoxic ischemic encephalopathy remains an important cause of infant death and childhood disability. Early and accurate diagnosis of encephalopathy is difficult but critical for timely intervention. Thus, we have utilized a clinically relevant large animal model of asphyxia in-utero, followed by immediate lamb delivery, resuscitation and clinical care over the next 72h for assessment of potential biomarkers of brain injury. In-utero asphyxia was induced in twelve near-term lambs and outcomes compared with seven controls. Asphyxia resulted in bradycardia (97±12beats/min), hypotension (12.1±1mm Hg) and metabolic acidosis (pH6.9±0.02; base-excess -13.8±0.8mmol/l). 72h following asphyxia, cerebrospinal concentrations of malondialdehyde and S100B were elevated 2-fold and 5-fold, respectively, in asphyxic lambs compared to control lambs. Magnetic resonance spectroscopy (MRS) at 72h showed a significant decrease in n-acetyl aspartate: choline ratio in asphyxia lambs compared to that observed at 12h (0.56±0.23 vs. 0.82±0.15, respectively); lactate:choline ratio was not changed over this time. Marked neuropathology was observed in asphyxia lambs with neuronal degeneration in the hippocampus, thalamus, striatum and cortex. Astrogliosis was observed in the hippocampus and thalamus. Early blood markers of metabolic state showed limited predictive value of histological damage at 72h. MRS outcomes at 72h showed a modest but significant correlation with histological evidence of neuronal brain injury (lactate:N-acetyl aspartate ratio in the thalamus r(2)=0.2, p<0.01). MRS at 72h was best able to detect established brain injury, but a combination of biomarkers over multiple phases of injury may be able to assess the evolution of neonatal brain injury.

Maintenance of whole-body therapeutic hypothermia during patient transport and magnetic resonance imaging

Therapeutic hypothermia has become standard treatment for neonatal hypoxic-ischemic encephalopathy (HIE), with brain MRI commonly performed after the child has been rewarmed. However, early imaging during hypothermia might provide information important in designing clinical trials that refine and personalize therapeutic hypothermia. We tested a protocol to ensure safety and maintenance of hypothermia during in-hospital transport and MRI. MRI during therapeutic hypothermia was performed in 13 newborns on the 2nd-3rd postnatal days. Mean one-way transport time was 20.0 ± 3.3 min. Mean rectal temperatures (°C) leaving the unit, upon arrival at the MR suite, during MRI scan and upon return to the unit were 33.5 ± 0.3 °C, 33.3 ± 0.3 °C, 33.1 ± 0.4 °C and 33.4 ± 0.3 °C, respectively. Using our protocol therapeutic hypothermia was safely and effectively continued during in-hospital transport and MRI without adverse effects.

Relationship between acute kidney injury and brain MRI findings in asphyxiated newborns after therapeutic hypothermia

BACKGROUND

We hypothesized that acute kidney injury (AKI) in asphyxiated neonates treated with therapeutic hypothermia would be associated with hypoxic-ischemic lesions on brain magnetic resonance imaging (MRI).

METHODS

Medical records of 88 cooled neonates who had had brain MRI were reviewed. All neonates had serum creatinine assessed before the start of cooling; at 24, 48, and 72 h through cooling; and then on day 5 or 7 of life. A neonatal modification of the Kidney Disease: Improving Global Outcomes guidelines was used to classify AKI. MRI images were evaluated by a neuroradiologist masked to outcomes. Outcome of interest was abnormal brain MRI at 7-10 d of life.

RESULTS

AKI was found in 34 (39%) of 88 neonates, with 15, 7, and 12 fulfilling criteria for stages 1, 2, and 3, respectively. Brain MRI abnormalities related to hypoxia-ischemia were present in 50 (59%) newborns. Abnormal MRI was more frequent in infants from the AKI group (AKI: 25 of 34, 73% vs. no AKI: 25 of 54, 46%; P = 0.012; odds ratio (OR) = 3.2; 95% confidence interval (CI) = 1.3-8.2). Multivariate analysis identified AKI (OR = 2.9; 95% CI = 1.1-7.6) to be independently associated with the primary outcome.

CONCLUSION

AKI is independently associated with the presence of hypoxic-ischemic lesions on postcooling brain MRI.

Can induced hypothermia be assured during brain MRI in neonates with hypoxic-ischemic encephalopathy?

Until now, brain MRIs in asphyxiated neonates who are receiving therapeutic hypothermia have been performed after treatment is complete. However, there is increasing interest in utilizing early brain MRI while hypothermia is still being provided to rapidly understand the degree of brain injury and possibly refine neuroprotective strategies. This study was designed to assess whether therapeutic hypothermia can be maintained while performing a brain MRI. Twenty MRI scans were obtained in 12 asphyxiated neonates while they were treated with hypothermia. The median difference between esophageal temperature on NICU departure and return was 0.1°C (range: -0.8 to 0.8°C). We found that therapeutic hypothermia can be safely and reproducibly maintained during a brain MRI. Hypothermia treatment should not prevent obtaining an early brain MRI if clinically indicated.