Cerebellar hypoplasia of prematurity: Causes and consequences

Cerebellar hemorrhages in very preterm infants: presence, involvement of the dentate nucleus, and cerebellar hypoplasia are associated with adverse cognitive outcomes

OBJECTIVE

Impaired cognition is a frequent complication of prematurity, closely related to patients' outcomes. Imaging features of cerebellar hemorrhages (CBH) related to impaired cognition are not well studied. This study evaluated the relationship between cMRI-derived CBH characteristics and clinical risk factors for adverse cognition.

METHODS

Our analysis is threefold: (1) We included very preterm infants (2009-2018) undergoing cMRI, and compared clinical and cMRI findings between infants with and without CBH. (2) In the CBH cohort, we associated clinical and imaging findings with cognitive outcomes (Bayley Score of Infant Development at two years corrected age, impaired outcomes: < 85) using uni- and multivariable logistic regression analyses. (3) We conducted a matched pair case-control analysis (CBH vs. no CBH) matching for gestational age (GA) and supratentorial injury.

RESULTS

Among the 507 infants (52% male; mean GA 26.8 ± 2.7 weeks), 53 (10.5%) presented with CBH. Cognition was impaired in those with CBH (case-control: 88 (IQR: 75-110) vs. 105 (IQR: 90-112), p < 0.001), even in those with CBH < 5 mm (case-control: 95 (IQR: 77.5-115) vs. 105 (IQR: 91-113), p = 0.037). In infants with CBH, red-blood-cell-transfusion requirement (odds ratio (OR) 1.32, 95% CI: 1.01-1.72, p = 0.037), dentate nucleus involvement (OR 17.61, 95% CI: 1.83-169.83, p = 0.013) and moderate-to-severe cerebellar hypoplasia (OR 26.41, 95% CI: 1.11-626.21, p = 0.043) were independent predictors of impaired cognition. Adding dentate nucleus involvement to cerebellar hypoplasia increased the discriminatory capacity (AUC 0.85 vs. 0.71, p = 0.004).

CONCLUSION

CBH (even < 5 mm) impact cognitive outcomes of very preterm infants, underlining the cerebellum's importance for cognition. In infants with CBH, involvement of the dentate nucleus and moderate-to-severe cerebellar hypoplasia are independent structural risk factors for impaired cognition.

KEY POINTS

Question The cerebellum is important for cognition. Cerebellar hemorrhages are common in preterm infants, but the imaging features related to impaired cognition are not well studied. Findings Even small cerebellar hemorrhages affected cognition. Involvement of the dentate nucleus and moderate-to-severe cerebellar hypoplasia were identified as new structural risk factors for adverse cognition. Clinical relevance Cerebral MRI enables precise diagnosis of cerebellar hemorrhages and the detection of structural risk factors for adverse cognition like dentate nucleus involvement and cerebellar moderate-to-severe hypoplasia. This knowledge facilitates risk estimation, structured follow-up, and interventions after prematurity.

Cerebellar Development and the Burden of Prematurity

The role of the cerebellum in the neurodevelopmental outcomes of preterm infants has often been neglected. However, accumulating evidence indicates that normal cerebellar development is disrupted by prematurity-associated complications causing cerebellar injury and by prematurity itself. This hampers not only the normal development of motor skills and gait, but also cognitive, language, and behavioral development, collectively referred to as "developmental cognitive affective syndrome." In this comprehensive narrative review, we provide the results of an extensive literature search in PubMed and Embase to summarize recent evidence on altered cerebellar development in premature infants, focusing on neuroimaging findings, its causative factors and its impact on long-term neurodevelopmental outcomes.

Fetal Intraparenchymal Hemorrhage Imaging Patterns, Etiology, and Outcomes: A Single Center Cohort Study

OBJECTIVE

This study examines associations among fetal brain magnetic resonance imaging (MRI) injury patterns, etiologies, and outcomes in fetal intraparenchymal hemorrhage (IPH).

METHODS

This is a retrospective, single-center cohort study of IPH diagnosed on fetal MRI (1996-2022). IPH and associated abnormalities were categorized by 2 pediatric neuroradiologists; electronic medical records were reviewed by 2 pediatric neurologists to classify etiology and outcomes including cerebral palsy, epilepsy, developmental delay, and death.

RESULTS

Forty-four fetuses with IPH were identified (34 singleton and 10 twin gestations) with MRI at median 24 weeks gestation (interquartile range [IQR] = 22-28 weeks). IPH was commonly supratentorial (84%) and focal (50%) or focal with diffuse injury (43%) and was often associated with germinal matrix hemorrhage (GMH; 75%) and/or intraventricular hemorrhage (IVH; 52%). An etiology was identified in 75%, including twin-twin transfusion syndrome (TTTS, n = 10), COL4A1/2 variants (n = 8), or other fetal/maternal conditions (n = 15). COL4A1/2 variants were associated with focal IPH and the presence of hemorrhagic porencephaly, and intrauterine transfusion was associated with infratentorial hemorrhage. Twenty-two fetuses were liveborn, and 18 pregnancies were terminated. Among those with follow-up ≥ 12 months (median = 7 years), 12 of 13 had cerebral palsy, 6 of 13 had developmental delay, and 5 of 13 had epilepsy.

INTERPRETATION

An etiology for fetal IPH with or without GMH-IVH is identified in most cases in our cohort and is commonly TTTS, COL4A1/2 variants, or other maternal/fetal comorbidities. Pattern of fetal IPH on MRI is associated with etiology. Cerebral palsy and neurodevelopmental impairment were common in liveborn infants. Genetic studies should be considered in cases of fetal IPH without an otherwise apparent cause. ANN NEUROL 2024;96:1137-1147.

A Simple MRI Score Predicts Pathological General Movements in Very Preterm Infants with Brain Injury-Retrospective Cohort Study

BACKGROUND/OBJECTIVES

Very preterm infants are at increased risk of brain injury and impaired brain development. The Total Abnormality Score and biometric parameters, such as biparietal width, interhemispheric distance and transcerebellar diameter, are simple measures to evaluate brain injury, development and growth using cerebral magnetic resonance imaging data at term-equivalent age. The aim of this study was to evaluate the association between the Total Abnormality Score and biometric parameters with general movements in very preterm infants with brain injury.

METHODS

This single-center retrospective cohort study included 70 very preterm infants (≤32 weeks' gestation and/or <1500 g birth weight) born between January 2017 and June 2021 in a level-three neonatal intensive care unit with brain injury-identified using cerebral magnetic resonance imaging data at term-equivalent age. General movements analysis was carried out at corrected age of 8-16 weeks. Binary logistic regression and Spearman correlation were used to examine the associations between the Total Abnormality Score and biometric parameters with general movements.

RESULTS

There was a significant association between the Total Abnormality Score and the absence of fidgety movements [OR: 1.19, 95% CI = 1.38-1.03] as well as a significant association between the transcerebellar diameter and fidgety movements (Spearman ρ = -0.269, p < 0.05).

CONCLUSIONS

Among very preterm infants with brain injury, the Total Abnormality Score can be used to predict the absence of fidgety movements and may be an easily accessible tool for identifying high-risk very preterm infants and planning early interventions accordingly.

Fibrinogen inhibits sonic hedgehog signaling and impairs neonatal cerebellar development after blood-brain barrier disruption

Cerebellar injury in preterm infants with central nervous system (CNS) hemorrhage results in lasting neurological deficits and an increased risk of autism. The impact of blood-induced pathways on cerebellar development remains largely unknown, so no specific treatments have been developed to counteract the harmful effects of blood after neurovascular damage in preterm infants. Here, we show that fibrinogen, a blood-clotting protein, plays a central role in impairing neonatal cerebellar development. Longitudinal MRI of preterm infants revealed that cerebellar bleeds were the most critical factor associated with poor cerebellar growth. Using inflammatory and hemorrhagic mouse models of neonatal cerebellar injury, we found that fibrinogen increased innate immune activation and impeded neurogenesis in the developing cerebellum. Fibrinogen inhibited sonic hedgehog (SHH) signaling, the main mitogenic pathway in cerebellar granule neuron progenitors (CGNPs), and was sufficient to disrupt cerebellar growth. Genetic fibrinogen depletion attenuated neuroinflammation, promoted CGNP proliferation, and preserved normal cerebellar development after neurovascular damage. Our findings suggest that fibrinogen alters the balance of SHH signaling in the neurovascular niche and may serve as a therapeutic target to mitigate developmental brain injury after CNS hemorrhage.

Extremely Preterm Infants with a Near-total Absence of Cerebellum: Usefulness of Quantitative Magnetic Resonance in Predicting the Motor Outcome

This study aims to evaluate in extremely premature infants the severity of brain structural injury causing total absence or near-total absence of cerebellar hemispheres by using MRI visual and volumetric scoring systems. It also aims to assess the role of the score systems in predicting motor outcome. We developed qualitative and quantitative MRI scoring systems to grade the overall brain damage severity in 16 infants with total absence or near-total absence of cerebellar hemispheres. The qualitative scoring system assessed the severity of macrostructural abnormalities of cerebellum, brainstem, supratentorial gray and white matters, ventricles while the quantitative scoring system weighted the loss of brain tissue volumes, and gross motor function classification system (GMFCS) was used to assess motor function at 1- and 5-year follow-ups.Positive correlations between both MRI scores and GMFCS scales were detected at follow-ups (p > 0.05), but only the volumetric score could identify those infants developing higher levels of motor impairment.Brain volumetric MRI offers an unbiassed assessment of prenatal brain damage. The quantitative scoring system, performed at term equivalent age, can be a helpful tool for predicting the long-term motor outcome in extremely preterm infants with a near-total absence of cerebellum.

Divergent neurodevelopmental profiles of very-low-birth-weight infants

BACKGROUND

Advanced perinatal medicine has decreased the mortality rate of preterm infants. Long-term neurodevelopmental outcomes of very-low-birth-weight infants (VLBWIs) remain to be investigated.

METHODS

Participants were 124 VLBWIs who had in-hospital birth from 2007 to 2015. Perinatal information, developmental or intelligence quotient (DQ/IQ), and neurological comorbidities at ages 3 and 6 years were analyzed.

RESULTS

Fifty-eight (47%) VLBWIs received neurodevelopmental assessments at ages 3 and 6 years. Among them, 15 (26%) showed DQ/IQ <75 at age 6 years. From age 3 to 6 years, 21 (36%) patients showed a decrease (≤-10), while 5 (9%) showed an increase (≥+10) in DQ/IQ scores. Eight (17%) with autism spectrum disorder or attention-deficit hyperactivity disorder (ASD/ADHD) showed split courses of DQ/IQ, including two with ≤-10 and one with +31 to their scores. On the other hand, all 7 VLBWIs with cerebral palsy showed DQ ≤35 at these ages. Magnetic resonance imaging detected severe brain lesions in 7 (47%) of those with DQ <75 and 1 (18%) with ASD/ADHD.

CONCLUSIONS

VLBWIs show a broad spectrum of neurodevelopmental outcomes after 6 years. These divergent profiles also indicate that different risks contribute to the development of ASD/ADHD from those of cerebral palsy and epilepsy in VLBWIs.

IMPACT

Very-low-birth-weight infants (VLBWIs) show divergent neurodevelopmental outcomes from age 3 to 6 years. A deep longitudinal study depicts the dynamic change in neurodevelopmental profiles of VLBWIs from age 3 to 6 years. Perinatal brain injury is associated with developmental delay, cerebral palsy and epilepsy, but not with ASD or ADHD at age 6 years.

Cerebellar injury in preterm infants less than 28 weeks gestational age

BACKGROUND

Cerebellar injury is one of the perinatal complications in preterm infants. Recent studies have highlighted the effect of perinatal complications on neurological morbidity. We investigated the perinatal risk factors and morbidity for cerebellar injury in extremely premature infants.

METHODS

This retrospective cohort study included 285 infants born between April 2009 and December 2020 at gestational age <28 weeks at our institution. The infants were divided into two groups based on magnetic resonance imaging findings: those with and without cerebellar injury. We performed a statistical analysis of the perinatal background and short-term morbidity of the two groups.

RESULTS

Significant differences (p < 0.05) were observed between the groups with respect to the perinatal background, especially gestational weeks, birthweight, and hemoglobin values at birth. In the short-term morbidity, significant differences (p < 0.05) were observed in the incidence of respiratory distress syndrome, chronic lung disease, hydrocephalus, severe intraventricular hemorrhage (IVH), and cerebellar hemorrhage. Extensive cerebellar lesions, such as cerebellar agenesis or global cerebellar hypoplasia, accounted for 11 of the 22 cases of cerebellar injury; seven of the 11 cases had severe IVH in addition to cerebellar hemorrhage.

CONCLUSIONS

Gestational age was significantly lower in the cerebellar injury group. The combination of severe IVH and cerebellar hemorrhage may promote cerebellar injury.

What risk factors for Developmental Language Disorder can tell us about the neurobiological mechanisms of language development

Language is a complex multidimensional cognitive system that is connected to many neurocognitive capacities. The development of language is therefore strongly intertwined with the development of these capacities and their neurobiological substrates. Consequently, language problems, for example those of children with Developmental Language Disorder (DLD), are explained by a variety of etiological pathways and each of these pathways will be associated with specific risk factors. In this review, we attempt to link previously described factors that may interfere with language development to putative underlying neurobiological mechanisms of language development, hoping to uncover openings for future therapeutical approaches or interventions that can help children to optimally develop their language skills.

Neonatal subarachnoid hemorrhage disrupts multiple aspects of cerebellar development

Over the past decade, survival rates for extremely low gestational age neonates (ELGANs; <28 weeks gestation) has markedly improved. Unfortunately, a significant proportion of ELGANs will suffer from neurodevelopmental dysfunction. Cerebellar hemorrhagic injury (CHI) has been increasingly recognized in the ELGANs population and may contribute to neurologic dysfunction; however, the underlying mechanisms are poorly understood. To address this gap in knowledge, we developed a novel model of early isolated posterior fossa subarachnoid hemorrhage (SAH) in neonatal mice and investigated both acute and long-term effects. Following SAH on postnatal day 6 (P6), we found significant decreased levels of proliferation with the external granular layer (EGL), thinning of the EGL, decreased Purkinje cell (PC) density, and increased Bergmann glial (BG) fiber crossings at P8. At P42, CHI resulted in decreased PC density, decreased molecular layer interneuron (MLI) density, and increased BG fiber crossings. Results from both Rotarod and inverted screen assays did not demonstrate significant effects on motor strength or learning at P35-38. Treatment with the anti-inflammatory drug Ketoprofen did not significantly alter our findings after CHI, suggesting that treatment of neuro-inflammation does not provide significant neuroprotection post CHI. Further studies are required to fully elucidate the mechanisms through which CHI disrupts cerebellar developmental programming in order to develop therapeutic strategies for neuroprotection in ELGANs.

Associations of preterm and early-term birth with suspected developmental coordination disorder: a national retrospective cohort study in children aged 3-10 years

BACKGROUND

This study analyzed the motor development and suspected developmental coordination disorder of very and moderately preterm (< 34+0 gestational age), late preterm (34+0-36+6 gestational week), and early-term (37+0-38+6 gestational week) children compared to their full-term peers with a national population-based sample in China.

METHODS

A total of 1673 children (799 girls, 874 boys) aged 3-10 years old were individually assessed with the Movement Assessment Battery for Children-second edition (MABC-2). The association between gestational age and motor performance of children was analyzed using a multilevel regression model.

RESULTS

The global motor performance [β =  - 5.111, 95% confidence interval (CI) =  - 9.200 to - 1.022; P = 0.015] and balance (β =  - 5.182, 95% CI =  - 5.055 to - 1.158; P = 0.003) for very and moderately preterm children aged 3-6 years old were significantly lower than their full-term peers when adjusting for confounders. Late preterm and early-term children showed no difference. Moreover, very and moderately preterm children aged 3-6 years had a higher risk of suspected developmental coordination disorder (DCD) (≤ 5 percentile of MABC-2 score) when adjusting for potential confounders [odds ratio (OR) = 2.931, 95% CI = 1.067-8.054; P = 0.038]. Late preterm and early-term children showed no difference in motor performance from their full-term peers (each P > 0.05).

CONCLUSIONS

Our findings have important implications for understanding motor impairment in children born at different gestational ages. Very and moderately preterm preschoolers have an increased risk of DCD, and long-term follow-up should be provided for early detection and intervention.

Neonatal Subarachnoid Hemorrhage Disrupts Multiple Aspects of Cerebellar Development

Over the past decade, survival rates for extremely low gestational age neonates (ELGANs; <28 weeks gestation) has markedly improved. Unfortunately, a significant proportion of ELGANs will suffer from neurodevelopmental dysfunction. Cerebellar hemorrhagic injury (CHI) has been increasingly recognized in the ELGANs population and may contribute to neurologic dysfunction; however, the underlying mechanisms are poorly understood. To address this gap in knowledge, we developed a novel model of early isolated posterior fossa subarachnoid hemorrhage (SAH) in neonatal mice and investigated both acute and long-term effects. Following SAH on postnatal day 6 (P6), we found significant decreased levels of proliferation with the external granular layer (EGL), thinning of the EGL, decreased Purkinje cell (PC) density, and increased Bergmann glial (BG) fiber crossings at P8. At P42, CHI resulted in decreased PC density, decreased molecular layer interneuron (MLI) density, and increased BG fiber crossings. Results from both Rotarod and inverted screen assays did not demonstrate significant effects on motor strength or learning at P35-38. Treatment with the anti-inflammatory drug Ketoprofen did not significantly alter our findings after CHI, suggesting that treatment of neuro-inflammation does not provide significant neuroprotection post CHI. Further studies are required to fully elucidate the mechanisms through which CHI disrupts cerebellar developmental programming in order to develop therapeutic strategies for neuroprotection in ELGANs.

Cerebellar development after preterm birth

Preterm birth and its complications and the associated adverse factors, including brain hemorrhage, inflammation, and the side effects of medical treatments, are the leading causes of neurodevelopmental disability. Growing evidence suggests that preterm birth affects the cerebellum, which is the brain region involved in motor coordination, cognition, learning, memory, and social communication. The cerebellum is particularly vulnerable to the adverse effects of preterm birth because key cerebellar developmental processes, including the proliferation of neural progenitors, and differentiation and migration of neurons, occur in the third trimester of a human pregnancy. This review discusses the negative impacts of preterm birth and its associated factors on cerebellar development, focusing on the cellular and molecular mechanisms that mediate cerebellar pathology. A better understanding of the cerebellar developmental mechanisms affected by preterm birth is necessary for developing novel treatment and neuroprotective strategies to ameliorate the cognitive, behavioral, and motor deficits experienced by preterm subjects.

CNS Malformations in the Newborn

Structural brain anomalies are relatively common and may be detected either prenatally or postnatally. Brain malformations can be characterized based on the developmental processes that have been perturbed, either by environmental, infectious, disruptive or genetic causes. Fetuses and neonates with brain malformations should be thoroughly surveilled for potential other anomalies, and depending on the nature of the brain malformation, may require additional investigations such as genetic testing, ophthalmological examinations, cardiorespiratory monitoring, and screening laboratory studies.

Cerebellar injury in premature neonates: Imaging findings and relationship with outcome

Cerebellar hemorrhagic injury (CHI) is a common complication of preterm birth. There are now many studies that have investigated the developmental consequences of CHI. This review summarizes the present state of evidence regarding the outcomes of prematurity related CHI, with a particular focus on the neuroimaging characteristics associated with adverse outcomes. Studies published to date suggest that the severity of functional deficits is dependent on injury size and topography. However, the unique contribution of the CHI to outcomes still needs to be further investigated to ensure optimal prognostic counseling.

Maturation of Purkinje cell firing properties relies on neurogenesis of excitatory neurons

Preterm infants that suffer cerebellar insults often develop motor disorders and cognitive difficulty. Excitatory granule cells, the most numerous neuron type in the brain, are especially vulnerable and likely instigate disease by impairing the function of their targets, the Purkinje cells. Here, we use regional genetic manipulations and in vivo electrophysiology to test whether excitatory neurons establish the firing properties of Purkinje cells during postnatal mouse development. We generated mutant mice that lack the majority of excitatory cerebellar neurons and tracked the structural and functional consequences on Purkinje cells. We reveal that Purkinje cells fail to acquire their typical morphology and connectivity, and that the concomitant transformation of Purkinje cell firing activity does not occur either. We also show that our mutant pups have impaired motor behaviors and vocal skills. These data argue that excitatory cerebellar neurons define the maturation time-window for postnatal Purkinje cell functions and refine cerebellar-dependent behaviors.

Cerebellum and Prematurity: A Complex Interplay Between Disruptive and Dysmaturational Events

The cerebellum plays a critical regulatory role in motor coordination, cognition, behavior, language, memory, and learning, hence overseeing a multiplicity of functions. Cerebellar development begins during early embryonic development, lasting until the first postnatal years. Particularly, the greatest increase of its volume occurs during the third trimester of pregnancy, which represents a critical period for cerebellar maturation. Preterm birth and all the related prenatal and perinatal contingencies may determine both dysmaturative and lesional events, potentially involving the developing cerebellum, and contributing to the constellation of the neuropsychiatric outcomes with several implications in setting-up clinical follow-up and early intervention.

Complex neurodevelopmental disorder in a preterm child with unilateral cerebellar hemorrhage

BACKGROUND

Cerebellar hemorrhage (CBH) represents the main form of direct cerebellar injury in preterm infants. Most CBHs occur bilaterally, while isolated unilateral hemorrhages are less frequent and often associated with focal atrophy. Limited and heterogeneous data exist on preterm birth, unilateral CBH and consequent long-term neurodevelopmental and non-motor outcomes.

CASE REPORT

This is the case of a six-year-old child, born preterm, diagnosed with a complete atrophy of the right cerebellar hemisphere through brain MRI and presenting mild social atypies, visuo-perceptive and pragmatic language impairment, but only minor neurological signs.

DISCUSSION

Despite the large extension of the patient's CBH neurological sequelae were mild, likely due to cerebellar plasticity, and only specific deficits in non-motor, behavioral and social skills were shown. Evidence exists on cerebellar contribution to dynamic visual information processing and to perceptual signals detection and prediction, that might explain the presence of non-motor signs.

Diagnostic Approach to Cerebellar Hypoplasia

Cerebellar hypoplasia (CH) refers to a cerebellum of reduced volume with preserved shape. CH is associated with a broad heterogeneity in neuroradiologic features, etiologies, clinical characteristics, and neurodevelopmental outcomes, challenging physicians evaluating children with CH. Traditionally, neuroimaging has been a key tool to categorize CH based on the pattern of cerebellar involvement (e.g., hypoplasia of cerebellar vermis only vs. hypoplasia of both the vermis and cerebellar hemispheres) and the presence of associated brainstem and cerebral anomalies. With the advances in genetic technologies of the recent decade, many novel CH genes have been identified, and consequently, a constant updating of the literature and revision of the classification of cerebellar malformations are needed. Here, we review the current literature on CH. We propose a systematic approach to recognize specific neuroimaging patterns associated with CH, based on whether the CH is isolated or associated with posterior cerebrospinal fluid anomalies, specific brainstem or cerebellar malformations, brainstem hypoplasia with or without cortical migration anomalies, or dysplasia. The CH radiologic pattern and clinical assessment will allow the clinician to guide his investigations and genetic testing, give a more precise diagnosis, screen for associated comorbidities, and improve prognostication of associated neurodevelopmental outcomes.

Insights From Genetic Studies of Cerebral Palsy

Cohort-based whole exome and whole genome sequencing and copy number variant (CNV) studies have identified genetic etiologies for a sizable proportion of patients with cerebral palsy (CP). These findings indicate that genetic mutations collectively comprise an important cause of CP. We review findings in CP genomics and propose criteria for CP-associated genes at the level of gene discovery, research study, and clinical application. We review the published literature and report 18 genes and 5 CNVs from genomics studies with strong evidence of for the pathophysiology of CP. CP-associated genes often disrupt early brain developmental programming or predispose individuals to known environmental risk factors. We discuss the overlap of CP-associated genes with other neurodevelopmental disorders and related movement disorders. We revisit diagnostic criteria for CP and discuss how identification of genetic etiologies does not preclude CP as an appropriate diagnosis. The identification of genetic etiologies improves our understanding of the neurobiology of CP, providing opportunities to study CP pathogenesis and develop mechanism-based interventions.