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Neonatal focal lesions are associated with long-term morbidity. They have often been used as a paradigm for exploring the relationship between cerebral structures and different aspects of function, and the possible mechanism of plasticity of the neonatal brain in response to an early insult. These studies have explored several aspects of function, mainly focusing on motor performance, language development, or specific aspects of cognitive ability.

Despite the large number of papers published on this topic, our understanding of cognitive outcome following neonatal focal lesions is still limited. While several studies have provided clear information on motor outcome and on the risk of developing hemiplegia or other motor sequelae (both in preterm and term infants with different patterns of focal lesions), the data on cognitive outcome are still controversial.

Cognitive findings in childhood are mixed, ranging from normal results to a much higher risk of developing cognitive impairment.[1, 2] This is largely due to the different inclusion criteria used in the various studies. Some of these studies focused on cerebral arterial infarctions occurring in term infants, while others investigated focal haemorrhagic lesions occurring in preterm infants. In the older papers the lesions were mainly identified on cranial ultrasound or on late computed tomography or magnetic resonance imaging (MRI) performed in symptomatic children. Other factors that contribute to the variability of the cognitive data available are related to the tests used and to the age of the child when these were administered, with many of the previous studies only assessing neurodevelopmental outcome in the first years after birth.

The article by van Buuren et al.[3] methodically addresses these shortcomings by reporting on children with neonatal periventricular haemorrhagic infarction and perinatal arterial ischemic stroke separately (all detected by neonatal MRI), and by describing longitudinal neurodevelopmental and cognitive assessments.

The use of neonatal MRI not only provided the possibility to define the details of the lesions and to have a neat classification that was associated with different outcomes, but also helped to identify possible factors associated with a higher risk of cognitive involvement. The involvement of the basal ganglia and thalami (reported in previous studies to be one of the cofactors determining hemiplegia in perinatal arterial infarcts[4]) appears to also play a role in cognitive function, as suggested by the linear regression used in the study. These findings provide further evidence of the possible role of the basal ganglia in modulating brain plasticity at the time of perinatal lesions.

The longitudinal study uses both early neurodevelopmental assessments and school-age cognitive tests in children with perinatal arterial infarcts to provide evidence of a decline in cognitive function over time, probably related to difficulties with higher-level cognitive skills that only become obvious at school age. These findings help to clarify the apparent discrepancy between previous studies reporting little evidence of cognitive difficulties in young and preschool children and others showing evidence of cognitive impairment in children assessed at different ages.

The study also suggests that postnatal factors, such as epilepsy and/or antiepilepetic drugs, may also influence the risk of developing cognitive difficulties.

In summary, the study improves our knowledge on the mechanisms underlying cognitive difficulties in neonatal brain focal lesions, suggesting that the type and the site of lesions, the age at assessment, and postnatal factors (such as epilepsy or antiepileptic drugs) may all contribute to cognitive difficulties. Further studies in larger cohorts allowing multivariate analysis will help to establish the effect of each of these variables and the possible co-dependence of some of these factors (e.g. thalamic lesions and epilepsy).

References

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  2. References
  • 1
    Ricci D, Mercuri E, Barnett A, et al. Cognitive outcome at early school age in term-born children with perinatally acquired middle cerebral artery territory infarction. Stroke 2008; 39: 40310.
  • 2
    Westmacott R, MacGregor D, Askalan R, deVeber G. Late emergence of cognitive deficits after unilateral neonatal stroke. Stroke 2009; 40: 20129.
  • 3
    van Buuren LM, van der Aa NE, Dekker HC, et al. Cognitive outcome in childhood following unilateral perinatal brain injury. Dev Med Child Neurol DOI: 10.1111/dmcn.12187.
  • 4
    Boardman JP, Ganesan V, Rutherford MA, Saunders DE, Mercuri E, Cowan F. Magnetic resonance image correlates of hemiparesis after neonatal and childhood middle cerebral artery stroke. Pediatrics 2005; 115: 3216.