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The aetiology of delayed visual maturation: short review and personal findings in relation to magnetic resonance imaging

Neonatal encephalopathy occurs in 2 to 5/1000 live births and is principally related to hypoxic-ischemic injury to the newborn brain in the immediate peripartum period. In the last decade, there have been significant advances in neuroprotection that have been successful in reducing the risk of death and disability in infants who have suffered from a potential hypoxic-ischemic cerebral injury. The advent of therapeutic hypothermia has led to a major focus on the early clinical recognition of infants that may benefit from such therapies. In addition, optimal recognition and therapeutic targeting of neonatal seizures, with other neuroprotective approaches, have been emphasized. This chapter will summarize the clinical presentation, neuropathological correlates, neurodiagnostic evaluation, prognosis, and management of this condition.

The aim of this retrospective study was to establish the presence and severity of cerebral visual impairment in preterm infants with PVL. We also wished to establish whether abnormalities of visual function are related to brain MRI findings and more specifically not only to the involvement of optic radiations and occipital cortex but also to changes in the thalami, that are often affected in infants with PVL.

Twelve infants with cystic PVL were assessed at 1 year (+ 2) corrected age with a battery of tests specifically designed to assess various aspects of visual function in infancy, such as ocular movements, visual acuity, visual fields and fixation shift. All infants also had a brain MRI.

Eleven of the 12 had involvement of the optic radiations: all had some abnormalities of visual function and visual impairment was more severe in infants with more extensive involvement of the optic radiations. The child with normal optic radiations had normal visual function.

Six of the 12 infants also had obvious signs of atrophy of the thalami and all had severe and wide-ranging abnormalities of visual function in all testing domains. Two children had equivocal atrophy of the thalami, both had some abnormalities of visual function.

Four children had normal thalami and had normal visual function or only minor abnormalities on one of the visual tests. Our results suggest that the atrophy of the thalami may play an additional role in the abnormal development of visual function in infants with PVL and abnormal optic radiations.

In the last two decades there has been a considerable increase in the understanding of visual maturation in the young infant and it has been possible to develop methods for testing visual function that are applicable in the neonatal period and early infancy. Several studies have reported that various aspects of visual function, such as visual acuity, visual fields and optokinetic nystagmus are often impaired in infants with brain lesions of antenatal and perinatal onset. We report our experience with such infants and a more general review of the literature on the maturation of visual function in the first years after birth in normal and brain damaged children.