Neonatal watershed brain injury on MRI correlates with verbal IQ at four years

OBJECTIVE We have previously described patterns of neonatal brain injury that correlate with global cognitive and motor outcomes. We now examine, in survivors of neonatal encephalopathy (presumed secondary to hypoxia-ischemia) without functional motor deficits, whether the severity and neuroanatomical involvement on neonatal magnetic resonance imaging (MRI) are associated with domain-specific cognitive outcomes, verbal (VIQ) and performance IQ (PIQ), at four years of age. METHODS In this prospective study, neonatal MRIs of 81 term infants with neonatal encephalopathy were scored for degree of injury in two common patterns: watershed-distribution (WS) and basal ganglia-distribution (BG). Follow-up evaluation at four years of age by examiners blinded to clinical history and MRIs included a five-point neuromotor score and the Wechsler Preschool and Primary Scale of Intelligence – Revised. In 64 subjects with no functional motor impairment, test of trend was used to examine the association of ordered WS and BG MRI scores with mean VIQ and PIQ. RESULTS Lower VIQs and PIQs were seen with increasing degree of injury on both WS and BG scales in univariate analyses (p≤0.05, all four analyses). When each MRI pattern score was adjusted for the other, only the association of decreasing VIQ with increasing WS injury remained significant (p=0.01; VIQ means across WS scores: 105–84). A suggestion of decreasing VIQ with increasing BG injury was also seen in the multivariate model (p=0.06; means across BG scores: 100–80), while no association was seen between PIQ and severity of injury in either MRI pattern. CONCLUSIONS In survivors of neonatal encephalopathy without functional motor deficits at 4 years of age, an increasing severity of watershed-distribution injury is associated with more impaired language-related abilities.