Visual and neurological outcome of infants with periventricular leukomalacia

Prevalence of the Infantile Strabismus Complex in Premature Children With and Without Periventricular Leukomalacia

PURPOSE

To determine whether rates of strabismus and associated visuomotor deficits differed among children with different severities of periventricular leukomalacia (PVL).

DESIGN

Retrospective, case-control study.

METHODS

Brain magnetic resonance images (MRI) obtained from 98 children aged ≥2 years were analyzed using a standardized scoring system: 67 of 98 had PVL (mean GA 31 weeks) and 31 of 98 did not have PVL (mean GA 29 weeks). Severity of PVL was scored as degree of damage to the posterior optic radiations and the splenium of the corpus callosum on MRI. Ophthalmologic examination data were collated to assess the prevalence of visuomotor deficits and the relationship to PVL severity (grades 1-3, mild to severe).

RESULTS

Infantile strabismus was documented in 61% of children with mild, 74% with moderate, and 88% with severe PVL (esotropia: exotropia ratio 3.5:1). Associated ocular motor deficits also increased systematically with PVL severity: latent ("fusion maldevelopment") nystagmus (20%, 47%, and 40%, respectively), dissociated vertical deviation (13%, 28%, and 30%), and nasotemporal pursuit/optokinetic nystagmus asymmetry (23%, 38%, and 54%). Additionally, the prevalence of retrograde optic neuropathy increased with PVL severity (5%, 26%, and 38%). The prevalence of each of these signs was substantially lower in children who had no PVL.

CONCLUSIONS

Children who suffer PVL are likely to develop the deficits of the infantile strabismus complex. The deficits tend to increase systematically as a function of PVL severity. These findings provide evidence that infantile strabismus is linked to perinatal damage to cerebral vergence and gaze pathways.

INCREASED FOVEAL GANGLION CELL AND INNER PLEXIFORM LAYER THICKNESS IN CHILDREN AGED 6.5 YEARS BORN EXTREMELY PRETERM

PURPOSE

To analyze the ganglion cell layer and inner plexiform layer (GCL+) thickness in children born extremely preterm and control children.

METHODS

A study of 6.5-year-old children born before the gestational age of 27 weeks and age-matched controls. The GCL+ thickness and foveal depth (FD) were analyzed in a single optical coherence tomography B-scan. Association with neonatal risk factors and sex was investigated. Extremely preterm was divided into no, mild, and severe retinopathy of prematurity, retinopathy of prematurity treatment, and no, mild, and severe intraventricular hemorrhage.

RESULTS

Adequate measurements were obtained from 89 children born extremely preterm and 92 controls. Extremely preterm children had increased total (5 µm, P < 0.001) and central (21 µm, P < 0.001) GCL+ thickness and reduced FD (-53 µm, P < 0.001) compared with controls. Extremely preterm children receiving retinopathy of prematurity treatment had increased GCL+ thickness and reduced FD compared with other subgroups. Sex and gestational age were associated with increased central GCL+ thickness and reduced FD. Reduced total GCL+ thickness was associated with severe intraventricular hemorrhage.

CONCLUSION

Extremely preterm birth can cause incomplete extrusion of the GCL+ and reduced FD. Retinopathy of prematurity treatment, gestational age, and male sex were associated to increased central GCL+ thickness and reduced FD, while severe intraventricular hemorrhage was associated with reduced total GCL+ thickness.

Visual function in preterm infants: visualizing the brain to improve prognosis

Considerable development of the visual system occurs in the third trimester of life, a time when very preterm-born infants are in a neonatal intensive care unit (NICU). Their very early birth during a period of rapid and marked neurodevelopment and their clinical course makes them a very high-risk population. A range of different events impacts brain development and the visual system, leading to significant long-term visual dysfunction. Improved neuroimaging techniques provide an important window on the early brain and visual system development of these vulnerable infants. Greater understanding of the etiology of visual impairment subsequent to preterm birth and the timing of critical processes will allow early recognition and the earlier implementations of interventions. In the longer term, this will help clinicians optimize NICU practice to reduce the incidence of visual dysfunction in these children.

An analysis of neonatal risk factors associated with the development of ophthalmologic problems at infancy and early childhood: a study of premature infants born at or before 32 weeks of gestation

BACKGROUND

To determine the frequency of ophthalmologic problems and the risk factors that affect the occurrence of these problems in premature newborns with a gestational age of 32 weeks or less.

METHODS

Premature newborns observed at a neonatal intensive care unit between January 2002 and March 2006 were included. A control visit including an ophthalmologic examination was performed at 10 months of age or later. Primary ocular morbidities were studied, and the association between these parameters and prenatal, perinatal, and neonatal characteristics were evaluated.

RESULTS

A total of 169 premature newborns were included in the study, and they were examined at a mean age of 25.85 ± 11.79 months (range: 10 to 42 months). There was complete vision loss (blindness) in 1 (0.6%) case, strabismus in 15 (8.9%) cases, and refractive errors in 10 (5.9%) cases. Twenty (77%) cases with any abnormality and 50 (35%) cases with a normal examination at follow-up had a history of retinopathy of prematurity (ROP) at any stage during the neonatal period (P = .001). Short gestational age (P = .018), low birth weight (P = .002), and the presence of ROP requiring retinal surgery during the neonatal period (P = .007) were determined to be significant risk factors for the development of vision loss, strabismus, and refractive errors.

CONCLUSION

Neonates with a gestational age of 32 weeks or less, especially those younger than 30 weeks, should not only be screened for ROP in the neonatal period, but should also have regular follow-up examinations to check for the development of other ophthalmologic problems during infancy and early childhood.

Visual performance and brain structures in the developing brain of pre-term infants

The presence of abnormal visual function has been related to overt lesions in the thalami, peritrigonal white matter (such as cavitational-necrotic periventricular leucomalacia) and optic radiations, and also to the extent of occipital cortex involvement. The normal development of visual function seems to depend on the integrity of a network that includes not only optic radiations and the primary visual cortex but also other cortical and subcortical areas, such as the frontal or temporal lobes or basal ganglia, which have been found to play a topical role in the development of vision. Therefore, the complex functions and functional connectivity of the developing brain of premature infants can be studied only with highly sophisticated techniques such as diffusion tensor tractography. The combined use of visual tests and neonatal structural and functional neuroimaging, which have become available for newborn infants, provides a better understanding of the correlation between structure and function from early life. This appears to be particularly relevant considering the essential role of early visual function in cognitive development. The identification of early visual impairment is also important, as it allows for early enrolment in intervention programmes. The association of clinical and functional studies to newer imaging techniques, which are being increasingly used also in neonates, are likely to provide further information on early aspects of vision and the mechanisms underlying brain plasticity, which are still not fully understood. Early exposure to a difficult postnatal environment together with early and unexpected removal from a protective milieu are exclusive and peculiar factors of prematurity that interfere with the normal development of the visual system in pre-term babies. The problem is further compounded by the influence of different perinatal brain lesions affecting the developing brain of premature babies. Nevertheless, in the last few decades, there have been considerable advances in our understanding of the development of vision in pre-term infants during early infancy. This has mainly been due to the development of age-specific tests assessing various aspects of visual function, from ophthalmological examination to more cortical aspects of vision, such as the ability to process orientation or different aspects of visual attention [1-7]. Improvements in understanding very early and specific neurological impairments in neurological functions have been reported in pre-term infants, known to be at risk of developing visual and visual-perceptual impairment. These impairments are due not only to retinopathy, a common finding in premature infants, but also to cerebral (central) visual impairment, secondary to brain lesions affecting the central visual pathway.

The assessment of visual acuity in children with periventricular damage: a comparison of behavioural and electrophysiological techniques

It has been controversial whether electrophysiology offers better precision than behavioural techniques in measuring visual acuity in children with brain damage. We investigated the concordance between sweep VEPs and Acuity Cards (AC) in 29 children with periventricular leukomalacia (PVL), the most common type of brain damage in preterm infants. An overall good correlation was shown but with relatively better behavioural acuity values. VEP/AC ratio was significantly correlated to corpus callosum posterior thinning. We propose that this result reflects the efficacy of the compensatory mechanisms following early brain damage which may differentially affect the two methods.

White-matter injury is associated with impaired gaze in premature infants

Periventricular leukomalacia is a risk factor for visual impairment in children born prematurely. The impact of diffuse white-matter injury, as detected on magnetic resonance imaging, on early visual function is unknown. We developed two 5-point visual-gaze scores to analyze the association between this clinical assessment and white-matter injury in 93 premature neonates <34 weeks of gestational age at birth. Older postmenstrual age was associated with higher values of the two gaze scores. Infants with moderate or severe white-matter injury had lower scores than their peers without white-matter injury (0.41 points, 95% confidence interval of 0.13-0.69 for visual fixation score; and 0.70 points, 95% confidence interval of 0.30-1.10 for conjugate score, P < 0.005). Using the results from both scales, a score of >or=9 in an infant examined at >or=36 weeks postmenstrual age predicted normal white matter on magnetic resonance examination, with a sensitivity of 84% and a specificity of 100%. These preliminary findings suggest that white-matter injury affects visual function even before term equivalent postmenstrual age.

The development of vision

Disorders of visual function are common findings in children with neonatal brain lesions of antenatal and perinatal onset. In the last few years the development of age appropriate batteries for assessing visual function in the first years and the combined use of neuroimaging and neurophysiological techniques have allowed to achieve better understanding of the mechanisms underlying development of vision in low risk infants and in those with brain lesions. We will review the main models of visual development and the tests available to assess visual function in infancy, focusing on the recently described battery of tests for assessing early visual abilities in preterm and full term infants.

Children born weighing less than 1701 g: visual and cognitive outcomes at 11-14 years

BACKGROUND AND OBJECTIVE

Few studies of low birthweight children have explored the relationship between later visual morbidity and neuropsychological function. This study evaluated these outcomes using a geographically defined cohort.

METHODS

Prospective study of retinopathy of prematurity (ROP) in infants born weighing <1701 g, undertaken in 1985-7. 254 of the survivors consented to ophthalmic examination at 10-13 years. Four children were severely disabled and could not complete the tests. 198 of the remaining agreed to neuropsychological assessment at 11-14 years (British Ability Scales II (BAS), Movement Assessment Battery (ABC), Neale Analysis of Reading Ability).

RESULTS

At 10-13 years, 99/198 children had an adverse ophthalmic outcome (AOO) (reduced acuity n=48, myopia n=40, strabismus n=36, colour defect n=2, field defect n=1). There were no significant differences between children with AOO and those with a normal ophthalmic outcome with regard to sex, gestation, birth weight, neonatal cranial scan appearances and social class. 106/198 had ROP; 98 had mild ROP with no increased risk of AOO in later childhood. All eight children with severe ROP had an AOO in later childhood. Children with an AOO performed worse on the BAS, ABC and reading ability tests.

CONCLUSIONS

At age 10-13, 50% of children born <1701 g have an AOO. These children are not simply those with earlier gestations, lower birth weight or ROP. Children with AOO have a worse neuropsychological outcome. The next step is to determine whether there are visual interventions which can improve ophthalmic outcome and whether a better neuropsychological outcome follows.

Cognitive profiles and visuoperceptual abilities in preterm and term spastic diplegic children with periventricular leukomalacia

Although relations between the extent of periventricular leukomalacia and neuropsychological performance in preterm children with spastic diplegia have been extensively investigated, studies on term children with spastic diplegia are rare. The authors examined 15 preterm children and 9 term children with spastic diplegia, all of whom had periventricular leukomalacia as a main magnetic resonance imaging (MRI) finding (excluding full-term spastic diplegic children with other MRI findings). Cognitive abilities (Griffith scale) and visuoperceptual abilities (Developmental Test of Visual Perception) were compared in the 2 groups and related to periventricular leukomalacia severity. Cognitive performance was substantially similar in the 2 groups. However, the overall Developmental Test of Visual Perception scores were below normal in the preterm and were normal in the term children; furthermore, visuoperceptual abilities were differentially affected in the preterm children, with visuomotor abilities more compromised than nonmotor visuoperceptual abilities. These children had similar cognitive performance and MRI findings, so the greater visuoperceptual compromise in the preterm group suggests a direct influence of prematurity, which may have adversely influenced the reorganization of visual centers and pathways following the initial developmental insult. The strabismus present in most preterm children would also have contributed to their greater visuoperceptual compromise. The authors conclude that the management of preterm and term children should differ, with concentration on visuoperceptual skills and rehabilitation in the former.

Thalamic atrophy in infants with PVL and cerebral visual impairment

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.

A clinical and etiologic profile of spastic diplegia

To identify the clinical and etiologic profile of children with spastic diplegia, the medical records of patients with spastic diplegia in a single practice over a 12-year period were systematically and retrospectively reviewed. Clinical factors and possible etiology based on investigations were identified. Univariate and binomial logistical regression analyses were undertaken to identify factors correlating with an etiologic determination. Chart review identified 54 children with spastic diplegia. There were 31 (57.4%) preterm children and 23 (42.6%) term children. Periventricular leukomalacia was diagnosed in 24 (44.4%) children (26.1% of term children, 58.1% of preterm children). An etiology was not identified in 25 (46.3%) children: 14 (60.9%) term children and 11 (35.5%) preterm children. Periventricular leukomalacia among all children correlated with a birth weight less than 2000 gm (P = 0.037), history of neonatal resuscitation (P = 0.004), and gestation less than 33 weeks (P = 0.001). Factors specifically associated with periventricular leukomalacia in term children were a problematic perinatal history (P = 0.011), a history of neonatal resuscitation (P = 0.011), and a history of neonatal respiratory distress (P = 0.046). Regression analysis revealed a correlation between an abnormal perinatal history and an etiology of periventricular leukomalacia among term children (odds ratio 8.67, 95% confidence interval 2.51-29.97, P = 0.001). Approximately half of all children with spastic diplegia encountered in clinical practice will have an etiology identified.

Ophthalmic impairment at 7 years of age in children born very preterm

AIMS

To determine the prevalence of ophthalmic impairments in very preterm compared with term infants, the relation between impairments and cerebral ultrasound appearances and retinopathy, and the correlation with visual perception and motor and cognitive measures.

SUBJECTS

279 children at 7 years of age born before 32 weeks gestation within Liverpool during 1991-92 and attending mainstream schools, and 210 term controls.

METHODS

Visual acuity was assessed by Snellen chart, and strabismus by the cover test. Stereopsis was determined using the TNO random dot test, and contrast sensitivity using the Cambridge low contrast gratings. Visual and motor abilities were assessed using the Developmental test of motor integration (VMI) and the Movement ABC. Intelligence was measured with the Wechsler intelligence scale for children UK. Perinatal cranial ultrasound and retinopathy data were extracted from clinical records.

RESULTS

Children born preterm were significantly more likely to wear glasses, to have poor visual acuity, reduced stereopsis, and strabismus than term controls, but they showed no significant decrease in contrast sensitivity. Ophthalmic impairments were significantly related to poorer scores on the VMI, Movement ABC, and Wechsler IQ tests, but were not significantly related to neonatal cranial ultrasound appearances. Stage 3 retinopathy was related to poorer subsequent acuity.

CONCLUSIONS

Children born very preterm and without major neurodevelopmental sequelae have an increased prevalence of ophthalmic impairments at primary school age which are associated with visual perceptional, motor, and cognitive defects. The cause may be a generalised abnormality of cortical development rather than perinatally acquired focal lesions of the brain.

Hemorrhagic-ischemic cerebral injury in the preterm infant: current concepts

PV-IVH and adjacent white matter injury remains a significant problem in the premature infant. The potential mechanisms contributing to injury are complex and involve factors related to blood flow and its regulation, as well as cellular mediators including cytokines, free radical formation, and excitotoxin release. Although a reduction in the occurrence of severe IVH can be achieved with indomethacin, it does translate into long-term neurodevelopmental benefit. This reinforces the concept of a more diffuse injury to brain in sick premature infants than is apparent from the appearance of current neuroimaging techniques.

Preterm birth and visual development

Visual impairment, oculomotor abnormalities, and refractive error are prevalent among children with a history of preterm birth. These conditions may result from exposure of the immature visual system to early visual stimulation, from nutritional deficits that occur following the abrupt loss of placental maternal-to-fetal transfer of essential nutrients, and as secondary effects of systemic disease or complications associated with preterm birth. This chapter provides an overview of the structural and functional maturation of the visual system of the healthy preterm infant and of several forms of visual impairment that are prevalent in the low birth weight population.

Periventricular leukomalacia: an important cause of visual and ocular motility dysfunction in children

The immature visual system in infants born preterm is vulnerable to adverse events during the perinatal period. Periventricular leukomalacia affecting the optic radiation has now become the principal cause of visual impairment and dysfunction in children born prematurely. Visual dysfunction is characterized by delayed visual maturation, subnormal visual acuity, crowding, visual field defects, and visual perceptual-cognitive problems. Magnetic resonance imaging is the method of choice for diagnosing this brain lesion, which is associated with optic disk abnormalities, strabismus, nystagmus, and deficient visually guided eye movements. Children with periventricular leukomalacia may present to the ophthalmologist within a clinical spectrum from severe cerebral visual impairment in combination with cerebral palsy and mental retardation to only early-onset esotropia, normal intellectual level, and no cerebral palsy. Optimal educational and habilitational strategies need to be developed to meet the needs of this group of visually impaired children.

Correlation between visual function, neurodevelopmental outcome, and magnetic resonance imaging findings in infants with periventricular leucomalacia

AIM

To evaluate the correlation between visual function and neurodevelopmental outcome in children with periventricular leucomalacia at 1 and 3 years.

METHOD

Visual acuity, visual field, ocular motility, and optokinetic nystagmus were tested in 29 infants with periventricular leucomalacia by brain magnetic resonance imaging. All infants also had a structured neurological examination and a Griffiths developmental assessment.

RESULTS

21 of the infants showed at least one abnormality of visual function. The degree of visual impairment-that is, the number of visual tests showing abnormal results-correlated well with the results on developmental assessment at both ages.

CONCLUSION

Multivariate analysis showed that visual impairment was the most important variable in determining the neurodevelopmental scores of these infants, more than their motor disability and the extent of their lesions on magnetic resonance imaging.

Risk factors for strabismus in children born before 32 weeks' gestation

AIM

To investigate risk factors associated with strabismus in children born prematurely.

METHODS

Prospective study of all children born before 32 weeks' gestation between 1 January 1990 and 31 December 1991 in a geographically defined population of approximately 3 million in the Northern Region of the United Kingdom. All children were examined aged 2 years by the same ophthalmologist and paediatrician.

RESULTS

558 children (98.6% of study group) were examined. Logistic regression showed an increased risk of strabismus in children with cicatricial retinopathy of prematurity (p=0.02), refractive error (p=0.003), family history of strabismus (p<0.0001), and poor neurodevelopmental outcome (p<0.0001), in particular impaired locomotor skills (p=0.008) and hand-eye coordination (p=0. 001). Gestational age and regressed acute ROP were not independent risk factors for strabismus (p=0.92 and 0.85 respectively).

CONCLUSIONS

This study has identified factors which are independently related to strabismus (although not necessarily causative) and others which are related only indirectly. This may contribute both to the management of children born prematurely and to future studies of the aetiology of strabismus.

White matter injury in the preterm infant: an important determination of abnormal neurodevelopment outcome

Periventricular white matter injury, specifically cystic periventricular leukomalacia (PVL) and ipsilateral hemorrhage into white matter associated with periventricular-intraventricular hemorrhage (PV-IVH), contribute significantly to neonatal mortality and long-term neurodevelopmental deficits in the premature infant. The first lesion PVL occurs in approximately 3-4% of infants of birth weight (BW) < 1500 grams. It manifests either as a focal or diffuse lesion within white matter. Although the pathogenesis of PVL is complex and likely multifactorial, principle contributors include vascular factors which markedly increase the risk for ischemia during periods of systemic hypotension and the intrinsic vulnerability of the oligodendrocyte to neurotoxic factors such as free radicals or cytokines. Clinical associations with PVL include a history of chorioamnionitis, prolonged rupture of membranes, asphyxia, sepsis, hypocarbia, etc. The vast majority of infants exhibit long-term neurodevelopmental deficits that affect motor, cognitive and visual function. The second lesion, the ipsilateral hemorrhage into white matter lesion associated with PV-IVH, occurs in approximately 10-15% of infants of BW < 1000 grams. The white matter injury appears to be a venous infarction with hemorrhage occurring as a secondary phenomenon. Prevention of this lesion has to include prevention of the associated PV-IVH. In this regard, the antenatal administration of glucocorticoids has been associated with a significant reduction in the sonographic incidence of severe IVH and the associated white matter involvement. The postnatal administration of indomethacin to high risk infants appears to hold the most promise at the current time in preventing this lesion. The neurodevelopmental outcome with extensive white matter injury is universally poor, affecting long-term motor and cognitive deficits; the long-term outcome is more favorable with lesser involvement. A clearer understanding of pathogenesis of both conditions is essential so as to provide targeted preventative strategies.

West syndrome with periventricular leukomalacia: a morphometric MRI study

A morphometric magnetic resonance imaging study was performed, and the results were compared among three groups (group 1, periventricular leukomalacia patients with West syndrome; group 2, periventricular leukomalacia patients without West syndrome; and group 3, control patients) to clarify the characteristics and cause of West syndrome. This study included 21 infants (11 males and 10 females, 7 months to 2 years 8 months old) born at 24-32 weeks of gestation and weighing 625-1,908 gm. The Evans ratio, ratio of the posterior horns, Cella media index, width of the third ventricle, and the areas of the midbrain, pons, and medulla oblongata were measured and compared among the three groups. There were no differences of gestation or birth weight among the three groups. The Evans ratio, ratio of the posterior horns, Cella media index, and width of the third ventricle were larger in group 1 than in groups 2 and 3. The ratio of the posterior horns and Cella media index were larger in group 2 than in group 3, although the width of the third ventricle was not. Myelination was delayed in all patients in group 1 and in two patients in group 2. In group 1 the areas of the midbrain and pons were smaller than in groups 2 and 3 and the medulla oblongata was smaller than in group 3, although there were no differences in midbrain, pons, and medulla oblongata between groups 2 and 3. Although the infants with periventricular leukomalacia and West syndrome frequently demonstrated marked ventricular dilatation and delayed myelination, the atrophy of midbrain and pons was the most characteristic, and the damage may cause West syndrome.

Visual behaviours of neurologically impaired children with cerebral visual impairment: an ethological study

BACKGROUND/AIMS

Visual functions of neurologically impaired children with permanent cerebral visual impairment (CVI) can be difficult to determine. This study investigated the behavioural profile of CVI children by means of ethological observations in order to gain a better understanding of their visual functions.

METHODS

Video registrations of nine subjects who were unable to undergo more orthodox methods of visual function testing were observed and analysed by an ethologist.

RESULTS

A series of behaviours (direct signs) and supportive or confirming behavioural elements (indirect signs) indicating some visual perception in the children were found.

CONCLUSION

Detailed ethological observations of visual behaviour were shown to be useful for analysing visual functions of children with permanent CVI.

Brain injury in the premature infant: overview of clinical aspects, neuropathology, and pathogenesis

Brain injury in the premature infant is an extremely important problem, in part because of the large absolute number of infants affected yearly. The two principal brain lesions that underlie the neurological manifestations subsequently observed in premature infants are periventricular hemorrhagic infarction and periventricular leukomalacia. The emphases of this article are the neurology, neuropathology, and pathogenesis of these two lesions. Recent work suggests that the ultimate goal, prevention of the lesions, is potentially achievable. Periventricular hemorrhagic infarction may be preventable by prevention of germinal matrix/intraventricular hemorrhage, and periventricular leukomalacia, by detection of impaired cerebrovascular autoregulation, prevention of impaired cerebral blood flow, and interruption of the cascade to oligodendroglial cell death by such agents as free-radical scavengers.

Electroencephalographic coherence abnormalities in preterm diplegia

Twelve patients with spastic diplegia (SD) and visuoperceptual impairments from preterm birth were evaluated for electroencephalogram (EEG) spectral power density, interhemispheric (ICoh) and intrahemispheric (HCoh) coherence, and asymmetry of coherence between the right and left hemispheres in and compared with normal children under resting conditions. There were no significant differences in EEG spectral power density. The SD group revealed lower ICoh at the occipital pair for the alpha band (P = .0034) and a higher value at the frontal pair for the theta band (P = .0047). Higher HCoh in SD was pronounced in the left hemisphere for the delta, theta, and beta bands (P < .01). There were no higher values in the control group. Higher HCoh asymmetry was exhibited in the left hemisphere in the control group, while very little asymmetry was found in the SD group. In both groups 91.7% were classified correctly by discriminant analysis. We suggest that these neurophysiologic abnormalities in preterm SD children correspond neuroanatomically to the callosal thinning and neuropsychologically to the visuoperceptual impairments.

Brain injury in the premature infant--from pathogenesis to prevention

Brain injury in the premature infant is an extremely important problem, in part because of the large absolute number of infants affected yearly. The two principal brain lesions that underlie the neurological manifestations subsequently observed in premature infants are periventricular hemorrhagic infarction and periventricular leukomalacia. The emphases of this article are the neurology, neuropathology and pathogenesis of these two lesions. Recent work suggests that the ultimate goal, prevention of the lesions, is potentially achievable. Periventricular hemorrhagic infarction may be preventable by prevention of germinal matrix-intraventricular hemorrhage, and periventricular leukomalacia, by detection of impaired cerebrovascular autoregulation, prevention of impaired cerebral blood flow and interruption of the cascade to oligodendroglial cell death by such agents as free radical scavengers.

Cerebral visual impairment in preterm infants with periventricular leukomalacia

Neonatal brain lesions are the main cause of cerebral visual impairment in infancy, i.e., of a visual deficit caused by damage to posterior visual pathways. Visual outcome of preterm infants with periventricular leukomalacia (PVL) was investigated in 14 subjects affected by severe cystic PVL, another 34 with moderate PVL (prolonged periventricular echodensities), and 18 control preterm infants. All cases with significant ocular abnormalities (such as retinopathy of prematurity state III or upwards, optic nerve atrophy, or major refraction problems) were excluded. Visual acuity, visual field, eye alignment, fixation and following, optokinetic nystagmus, and visual threat were tested at 1 year of corrected age. A high incidence of cerebral visual impairment, consisting mainly of low visual acuity, severe oculomotor disorders, and reduced visual field, was found in infants with severe PVL. Visual defects were less frequent and less severe in the moderate PVL group, and very rare in the control group. The results of neuroimaging, and especially of magnetic resonance imaging, correlated with the visual outcome and indicate lesions at the level of optic radiations as the main anatomic substrate of the visual impairment. All infants with PVL need a visual follow-up, from the first months of life, the results of which are important both for visual and motor rehabilitation of these cases and for their daily care.

Constructional dyspraxia in preterm diplegia: isolation from visual and visual perceptual impairments

OBJECTIVE

To evaluate ophthalmological profiles, visual perception and constructional function in preterm children with spastic diplegia (SD) and to clarify their neuropsychological deficits in comparison with a control group.

METHODS

Thirty-five SD and 34 control children were investigated for visual acuity, eye position, stereoacuity, depth perception, visual perception, visuo-spatial construction and constructional praxis. Each of the results was compared among the four groups as SD with and without strabismus, and control with and without strabismus.

RESULTS

Strabismic SD showed worse visual acuity, worse stereoacuity and worse depth perception than the other groups. Constructional dyspraxia was detected in 94.1% of SD either with or without strabismus, while it was rare in the control group. There was no significant contribution of visual acuity, eye position, stereoacuity or depth perception to constructional dyspraxia by stepwise multiple linear regression analysis.

CONCLUSION

Strabismic preterm SD children are at high risk for visual dysfunction. Constructional dyspraxia was frequently found in SD children and may be a dysfunction isolated from ophthalmological and visual perceptual dysfunctions.

Neurodevelopmental outcome in very low birth weight infants at 24 months and 5 to 7 years of age: changing diagnosis

We describe the long-term development of 53 very low birth weight premature infants. The children were divided into 2 groups on the basis of ultrasound scan, and classified as: group I, patients with normal ultrasound scan or with uncomplicated hemorrhage; and group II, patients with complicated hemorrhage or only parenchymal lesions. Minor and major sequelae detected at 2 years of age were compared with those observed at 5 to 7 years. Our study confirms that most severely handicapped children are identified by age 2 years. Minor sequelae are more evident at 5 to 7 years and subjects with good outcome, as expressed by a McCarthy General Cognitive Index score > 80, present a discordant cognitive profile with verbal scores higher than performance scores. Therefore, we emphasize the importance of follow-up of very low birth weight premature infants until school age and stress that neonatal ultrasound scan diagnosis of parenchymal damage represents an important diagnostic tool in terms of both short- and long-term neurodevelopmental outcome.

Intellectual status of children with cerebral palsy after elementary education

Using Wechsler Intelligence Tests, we compared the intellectual status of children with cerebral palsy (CP) immediately before and 2 years after entering school. Verbal and performance IQs could be assessed for 23 children with spastic diplegia but only verbal IQs in six children with spastic quadriplegia. Performance IQs were much lower than verbal IQs in both the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) and the Wechsler Intelligence Scale for Children-Revised (WISC-R) in children with spastic diplegia. After schooling, verbal IQ was significantly increased but there was no change in performance IQ, thus, the difference between these IQs became more pronounced. When comparing the school class types, the verbal IQs of children studying in ordinary classes became statistically higher than those of children in special classes. In contrast, since the increases in mean performance IQs were greater in children in special classes, the differences between these IQs became more pronounced in children studying in ordinary classes. We also found that although verbal IQs were lower for quadriplegic children than for diplegic children at preschool age, there was no difference after 2 years of schooling. These results underline the importance and benefits of appropriate education for children with CP.

Grating acuity and visual-field development in children with intraventricular hemorrhage

Visual development was studied in 171 preterm children who had intraventricular hemorrhage (IVH) and in 73 healthy preterm (HPT) children who did not develop IVH. Binocular grating acuity was assessed at age 1 month; monocular grating acuity and binocular visual-field extent were assessed at 4, 8, 12, 17, 24, 30, 36, and 48 months; and monocular H, O, T, V letter recognition acuity was tested at 36 and 48 months. A significantly greater proportion of IVH subjects than HPT subjects had ocular abnormalities. IVH subjects had significantly poorer grating acuity than HPT subjects at 1, 4, 8, 36, and 48 months, poorer recognition acuity than HPT subjects at 36 and 48 months, and smaller average field extent than HPT subjects at 4, 12, and 17 months. Acuity deficits were not related to grade of IVH or to the presence of periventricular leukomalacia, but may have been associated with the presence of ocular abnormalities or cerebral palsy in some IVH subjects.

Long-term grating acuity and visual-field development in preterm children who experienced bronchopulmonary dysplasia

Grating acuity, visual-field extent, and recognition acuity were examined in 77 children who had bronchopulmonary dysplasia (BPD), 101 children who had hyaline membrane disease (HMD), and 77 healthy preterm (HPT) children. None of the subjects had significant retinopathy of prematurity (ROP) or neurological abnormalities. Grating acuity and field extent were tested at 0 to 1, 4, 9, 12, 17, 24, 30, 36, and 48 months corrected age and recognition acuity was tested at 36 and 48 months corrected age. Ophthalmological examinations indicated that a greater proportion of subjects in the BPD group than in the HMD or in the HPT group had strabismus or high refractive error. However, grating acuity and field extent in the BPD group did not significantly differ from the HMD group or from the HPT group at any test age. Recognition acuity was poorer in the BPD and HMD groups than in the HPT group at both 36 and 48 months, but the difference was significant only at 36 months. These results suggest that children who experienced BPD with no significant ROP and no neurological complications show grating acuity and visual-field development comparable to that of healthy preterm children, but that recognition acuity, or the skills required to perform a recognition-acuity task, may be delayed in this BPD population.

Visual fields measured with double-arc perimetry in eyes with threshold retinopathy of prematurity from the cryotherapy for retinopathy of prematurity trial. The CRYO-Retinopathy of Prematurity Cooperative Group

PURPOSE

To measure monocular visual field extent in very-low birth weight children in whom severe (threshold) acute-phase retinopathy of prematurity (ROP) developed in one or both eyes, and who had random assignment of eyes to cryotherapy or no cryotherapy. A control group of very-low birth weight children in whom ROP did not develop also was tested.

METHODS

There were 78 children in the severe ROP group from 5 of 23 centers in the randomized trial of cryotherapy for ROP (CRYO-ROP). The comparison cohort consisted of 75 study participants in whom ROP did not develop. All subjects had birth weights of less than 1251 g. At the 5 1/2-year study examination, visual field size was measured using double-arc kinetic perimetry. Testers were masked to treatment status of each eye. Four meridia were tested: superotemporal (ST), inferotemporal (IT), inferonasal (IN), and superonasal (SN). Target size was 6 degrees.

RESULTS

When blind eyes were assigned a score of 0 degree, the no-ROP, treated, and control eyes had an average visual field extent of 62 degrees, 35 degrees, 27 degrees at ST; 73 degrees, 42 degrees, 35 degrees at IT; 51 degrees, 30 degrees, 21 degrees IN; and 50 degrees, 26 degrees, 22 degrees at SN, respectively. Among 25 children who had bilateral threshold ROP and measurable fields in each eye, values for treated and control eyes were 59 versus 62 at ST, 69 versus 80 at IT, 44 versus 49 at IN, and 41 versus 48 at SN, respectively.

CONCLUSIONS

Overall, visual fields in eyes that reached threshold ROP were smaller than those of eyes that did not develop ROP. When only pairs of sighted eyes were considered, visual fields in the treated eyes were 6.4 degrees smaller than those of control eyes. Therefore, it appears that a small loss of peripheral field occurs when cryotherapy prevents the development of retinal detachment.

Visual impairment in preterm children with periventricular leukomalacia--visual, cognitive and neuropaediatric characteristics related to cerebral imaging

Thirteen preterm children, aged 4 to 14 years, with visual impairment due to periventricular leukomalacia (PVL) were evaluated for visual function, intellectual level, cognitive profile and motor function. Their visual impairment was characterized by low acuity, crowding, visual field defects and ocular motility disturbances. Their cognitive profile was uneven, often with considerably higher scores on verbal than on visual-spatial tasks. Nine children had normal intelligence, three had mild mental retardation and one had severe mental retardation. In all the children, visual impairment was complicated by visual perceptual difficulties, accounting for their greater visual handicap than would be expected from their visual acuities and strabismus alone. Though CT or MRI revealed bilateral PVL in all the children, six had no motor impairment consistent with cerebral palsy, which is an unexpected finding.

Assessment of visuoperceptual disturbance in children with spastic diplegia using measurements of the lateral ventricles on cerebral MRI

The authors estimated perceptual disturbance in children with spastic diplegia from the difference between the visual and performance IQ scores (VIQ-PIQ) on the Wechsler Intelligence Scale for Children-Revised (WISC-R), having found a strong negative correlation between this score and the PQ obtained on the Frostig Developmental Test of Visual Perception (DTVP). The ratio of the areas of the posterior horns to the anterior horns (P/A) correlated negatively with visuoperceptual disturbance. This ratio can therefore be used to assess perceptual disturbance at an early age in children with spastic diplegia.

Vision outcome at age 2 years in a low birth weight population

We assess the prevalence of vision problems in a cohort of low birth weight infants at age 2 years and the relationship of these problems to neonatal brain injury. Data on prenatal and neonatal history and brain injury status were prospectively collected on 721 children weighing 500-2,000 gm at birth enrolled in a multi-center, population-based longitudinal study. Visual acuity was evaluated using the Teller Acuity Card Procedure. Abnormalities of the eye were assessed by a specially trained pediatric nurse practitioner. Failure of the acuity screen occurred in 62 of 699 tested (8.9%). Multiple logistic regression analysis revealed that the only significant independent predictors of failure included presence of disabling cerebral palsy (DCP) (odds ratio [OR] = 14.8) or nondisabling cerebral palsy (NDCP) (OR = 4.0) and Apgar score of less than 5 at 5 minutes (OR = 2.4). Parenchymal brain injury (PEL) was of borderline significance. Strabismus was present in 123 of 702 children (17.5%). Multiple logistic regression analysis disclosed that the joint predictors of strabismus were presence of DCP (OR = 7.2) and length of hospital stay (OR = 1.6). We conclude that low birth weight infants with parenchymal brain lesions leading to cerebral palsy are at particular risk for vision problems early in life and should be carefully evaluated.

Infant peripheral vision: the development of monocular visual acuity in the first 3 months of postnatal life

Quantitative data on the early morphological development of the human retina show that the peripheral region is relatively more mature than the central region. These results have stimulated researchers to compare the development of visual functions in the central and peripheral regions of the visual field. Here, we used preferential looking to evaluate 1-, 2- and 3-month-old infants' central and peripheral (10 degrees and 30 degrees) monocular visual acuity. There were three findings: (i) both central and peripheral acuities were poor at 1 month, improved over the age range tested, but were still about 3 octaves worse than adults' acuity; (ii) at all ages monocular acuity decreased with increasing eccentricity; (iii) 2- and 3-month-olds showed higher acuity for gratings in the temporal than in the nasal visual field at 30 degrees. The implications of these results for issues in visual development are discussed.

Correlation between cerebral visual impairment and magnetic resonance imaging in children with neonatal encephalopathy

To identify brain lesions most often associated with cerebral visual i mpairment (CVI) after neonatal encephalopathy and to evaluate the prognostic value of MRI for visual outcome, the authors reviewed visual assessments and brain MRI of 80 infants and young children with documented perinatal hypoxic-ischaemic and/or haemorrhagic insults. MRIs were classified according to the severity of lesions at the optic radiations and at the visual cortex; visual acuity was tested with the acuity card procedure. Among the 48 children found to have a CVI, 42 had moderate to severe lesions of the optic radiations and 19 had lesions of the visual cortex. In both cases visual acuity was statically correlated with MRI grading, but the damage at the optic radiations was the better predictor. Early detection of abnormal MR findings in the visual cortex and especially, at the optic radiations may indicate which infants with neonatal encephalopthy should receive longitudinal visual assessment and specific rehabilitation and educational management.

Grating acuity and visual field development in infants following perinatal asphyxia

Grating acuity and visual fields were assessed in 66 children who had had perinatal asphyxia (ASPH). Also tested were 41 healthy preterm children (H-PT). Subjects were tested at birth to one month, and four, nine, 12, 17, 24, 30 and 36 months corrected age. The mean acuity scores of the ASPH group were lower than those of the H-PT group at most test ages, and significantly so at 30 and 36 months. The mean visual field size of the infants in the ASPH group was significantly smaller than that of the H-PT group at nine, 12, 30 and 36 months. No significant effects were found for preterm vs term birth, gestational age at birth, degree of asphyxia and presence of strabismus. However, central nervous system abnormalities (intraventricular haemorrhage and periventricular leukomalacia) were related to deficits in acuity and visual field size.

Haemorrhagic-ischaemic lesions of the neonatal brain: correlation between cerebral visual impairment, neurodevelopmental outcome and MRI in infancy

The relationship between the degree of cerebral visual impairment, established using the acuity card procedure, and the extent of neurological sequelae was assessed in 65 at-risk neonates in a prospective follow-up study. MRI and CT scans were performed in all infants with severe neurological sequelae. 11 of 12 children with an acuity at or below the 10th centile at 18 months developed cerebral palsy: the underlying condition was extensive cystic leukomalacia in all. An acuity above the 10th centile was no guarantee of normal development, as 10 out of 52 such infants developed cerebral palsy. MRI and CT scans showed that periventricular high signal intensity in the occipital area was a non-specific finding with regard to visual function. Extensive periventricular white matter loss and involvement of the striate/parastriate cortex was found in the most severely visually impaired infants.

Development of grating acuity, letter acuity, and visual fields in small-for-gestational-age preterm infants

Visual acuity and visual field development were assessed longitudinally in 21 preterm children who were born small-for-gestational-age (SGA) and in 51 preterm children who were appropriate-for-gestational-age (AGA). Grating acuity was tested binocularly at 0-1 month and monocularly at 4, 9, 12, 18, 24, 30, 36 and 48 months corrected age, using Teller acuity cards. Visual fields were measured binocularly using kinetic perimetry at the same ages. Recognition (letter) acuity testing was attempted using the crowded HOTV test in all subjects who came in for testing at 36 and 48 months. Children in the SGA group were matched to children in the AGA group by gestational age (+/- 3 weeks) and type of perinatal medical complications. There were no significant differences in grating acuity or binocular visual field size between the SGA and AGA groups. 78% of acuity scores for individual SGA-AGA pairs fell within one octave of perfect agreement. Binocular visual field size for each SGA-AGA pair also showed good agreement. Fewer SGA than AGA subjects were able to perform recognition acuity testing, and those SGA subjects who were able to perform the test, showed consistently poorer recognition acuity than their AGA counterparts. Thus, being SGA does not pose an additional risk for the development of grating acuity or binocular visual field size over the first 4 years of life in preterm children. SGA preterm children may be at risk, however, for acuity deficits when acuity is measured with the more complex targets and the greater test distance used to measure recognition acuity.

A comparative magnetic resonance imaging study of the corpus callosum in neurologically normal children and children with spastic diplegia

To determine the extent of brain damage in children with spastic diplegia, we analyzed the true midsagittal magnetic resonance imaging findings for the corpus callosum in 43 children with spastic diplegia and in 69 neurologically normal children. In the normal children, the thicknesses of the genu, midbody, splenium and the entire corpus callosum were found to increase with age, while the ratios of the thickness of the splenium and of the midbody to the length were constant, regardless of age. Both ratios were significantly reduced in diplegic children and the ratio for the splenium was highly correlated with the extent of motor impairment. Assessment of the morphometric changes in the corpus callosum using magnetic resonance imaging may contribute to the determination of the extent of brain damage in diplegic children.

Patterns of visual impairment associated with lesions of the preterm infant brain

The visual function of 42 children with haemorrhagic and/or ischaemic cerebral lesions acquired before a gestational age of 35 weeks was examined and related to cranial ultrasound in the neonatal period and to MRI and neurodevelopmental status at follow-up. All 37 children with abnormal ultrasound scans and one of the five with normal ultrasound scans showed impairment of one or more aspects of visual function. While impaired acuity was more frequent among infants with MRI evidence of visual pathway damage, this was not an invariable finding. Normal or near-normal visual acuity did not preclude the presence of other functional visual deficits. The authors conclude that preterm cerebral insults may produce a variety of visual difficulties, the pattern and severity of which cannot be predicted on imaging. Each child therefore requires individual assessment of multiple aspects of visual function.

MRI changes and deficits of higher brain functions in preterm diplegia

Forty-one preterm children (29 with spastic diplegia and 12 without motor deficits) who had a normal verbal IQ were studied to clarify the clinical significance of neuroanatomical abnormalities disclosed by T1-weighted and T2-weighted magnetic resonance imaging (MRI). Both types of images clearly showed abnormalities in the frontal corona radiata of the children with spastic diplegia, while there were no abnormalities in the children without motor deficits. We compared the T1-weighted imaging findings with deficits of higher brain functions, evaluated by the performance subtests of the Wechsler Intelligence Scale. Thinning of the parietal and/or occipital white matter was noted in children with visuospatial cognitive deficits. Thus, MRI may be helpful in confirming early clinical suspicions of visuospatial cognitive deficits as well as motor deficits in preterm children, especially those with spastic diplegia.