MRI infant prognosis unaffected by hypothermia

By Lynda Williams

Magnetic resonance imaging (MRI) is prognostic for newborn infants with hypoxic-ischemic encephalopathy (HIE) regardless of treatment with hypothermia, research shows.

The results of the Infant Cooling Evaluation trial found the ability of MRI to identify abnormalities associated with a poor long-term outcome in infants with HIE did not significantly differ between the 66 patients randomly assigned to receive hypothermia and the 61 patients who were not.

"This finding is important for clinicians because hypothermia is now widely used to treat moderate to severe HIE," explain Jeanie Cheong (Royal Women's Hospital, Parkville, Victoria, Australia) and co-authors.

The infants, aged an average of 6 days old, with a gestational age of at least 35 weeks and moderate-to-severe HIE, showed significantly fewer moderate and severe white matter or cortical gray matter abnormalities on T1- and T2-weighted MRI when treated with whole-body hypothermia than with normothermia (odds ratio [OR]=0.29 and 0.41, respectively).

Furthermore, T1- and T2-weighted MRI abnormalities were significantly associated with the likelihood for death or major disability at age 2 years, with the strongest predictions found for abnormalities in the posterior limb of the internal capsule (OR=4.10), and basal ganglia and thalamus (OR=10.09). Similar patterns were found with diffusional MRI for the two regions, with ORs of 4.81 and 9.38, respectively.

"The finding that diffusion abnormalities on MRI at the end of the first week after birth are predictive of death or significant sensorineural disability at 2 years is of clinical and practical importance," the authors note in the Archives of Pediatric and Adolescent Medicine.

Hypothermia, defined as a target temperature of 33.5°C (range, 33-34°C), was initiated within 6 hours of birth and continued for 72 hours in infants with clinical encephalopathy and peripartum HI cerebral injury, defined as an Apgar score of 5 or less at 10 minutes, mechanical ventilation at 10 minutes, and/or metabolic acidosis within an hour of birth.

"The reduction in brain injury in the hypothermia-treated group compared with the normothermia-treated group found in this study further supports hypothermia as a treatment for moderate to severe HIE in terms of reducing the incidence of white and cortical gray matter abnormality," Cheong et al conclude.

" Moreover, these results have shown that conventional and diffusion MRI of the brain are important biomarkers of long-term outcome in newborns with HIE, with or without hypothermia treatment."

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