Presented at the Neonatal Society 2006 Widdowson Meeting.
Logitharajah P1, Counsell S2, Allsop J2, Rutherford M2, Cowan F1
1 Department of Paediatrics, Imperial College London, Hammersmith hospital, UK
2 Department of Imaging Sciences, Imperial College London, Hammersmith hospital, UK
Background: Hypoxic-ischaemic encephalopathy (HIE) is difficult to define in the preterm infant; there is only one study of five infants assessing brain imaging patterns of injury in this patient group [1] and no studies assessing outcome beyond infancy.
Aims: To establish the antenatal and intrapartum antecedents, neonatal brain magnetic resonance (MR) imaging patterns of injury and outcome at two years in preterm infants with clinical evidence of HIE and to assess the prognostic value of neonatal brain MR imaging.
Patients and Methods: 63 preterm infants (GA median 35 wks range 26-37) born at or referred to the Hammersmith Hospital presenting with an early signs and symptoms consistent with perinatal asphyxia, an early encephalopathic illness and at least one MR brain scan were studied. Infants with metabolic or genetic problems were excluded. Infants were categorised into three groups: HIE only (HIE and brain MRI < 4 weeks from birth, n=41), HIE and infection (HIE and brain MRI < 4th week, maternal chorioamnionitis/postnatal infant sepsis, n=11) and HIE and late scan (HIE and brain MRI > 4th week, n=11). Antenatal, perinatal, and outcome at a minimum of two years were collected. Ethical approval was obtained from the Hammersmith hospital REC.
Results: Antecedents: Placental abruptions were the single commonest aetiology in both the HIE only and HIE and late scan subgroups, occurring in 40% and 45% of cases respectively.
Brain Injury Patterns: Injury patterns for the 3 subgroups were similar so results for the HIE only subgroup are provided. Basal ganglia and thalamic (BGT) lesions were seen in 76% of infants, 61% of which were severe; 88% of infants had white matter (WM) lesions, mostly mild and diffuse; WM abnormality was seen in 94% of infants with BGT lesions. Brainstem injury, seen in 44%, was mostly diffuse and associated with severe BGT injury. Cortical highlighting, seen in 61%, was mostly mild and focal. The median GA of infants with cortical injury was higher than that of infants without (p=0.0489).
Outcome: HIE only: 28% died, 28% developed cerebral palsy (CP) (23% quadriplegic, 5% diplegic), and 33% were normal. HIE and infection: 45% died, 18% developed CP (9% quadriplegic, 9% diplegic), and 36% were normal. HIE and late scan: 60% developed CP (50% quadriplegic,10% athetoid) and 30% were normal.
Injury patterns and outcome: Injury pattern and outcome associations were similar for all 3 subgroups so results for the entire cohort have been considered together. 95% of infants with severe BGT and brainstem injury died or developed spastic/dystonic CP. 43% of infants with mild/moderate BGT and WM lesions but normal brainstems died or developed spastic/dystonic CP; however 29% had a normal outcome. Isolated WM lesions were associated with a normal outcome in 78% and all infants with normal or only mildly abnormal scans had normal outcomes at 2 years.
Conclusions: HIE in the preterm infant is often preceded by placental abruption and may result in severe brain injury, with high incidences of brainstem and severe BGT lesions and diffuse but mild WM involvement. Cortical injury is a feature of the more mature preterm infant. Prognosis at two years is poor, with high incidences of death and quadriplegic cerebral palsy in our cohort. As with the term born infant, neonatal brain MR imaging provides a useful means of predicting outcome.
References
1. Barkovich AJ, Sargent SK 1995; AJNR, 16(9):1837-46