The vulnerability of thalamocortical circuitry to hypoxic-ischemic injury in a mouse model of periventricular leukomalacia

Impaired glymphatic system revealed by DTI-ALPS in cerebral palsy due to periventricular leukomalacia: relation with brain lesion burden and hand dysfunction

PURPOSE

Preterm children with cerebral palsy (CP) often have varying hand dysfunction, while the specific brain injury with periventricular leukomalacia (PVL) cannot quite explain its mechanism. We aimed to investigate glymphatic activity using diffusion tensor image analysis along the perivascular space (DTI-ALPS) method and evaluate its association with brain lesion burden and hand dysfunction in children with CP secondary to PVL.

METHODS

We retrospectively enrolled 18 children with bilateral spastic CP due to PVL and 29 age- and sex-matched typically developing controls. The Manual Ability Classification System (MACS) was used to assess severity of hand dysfunction in CP. A mediation model was performed to explore the relationship among the DTI-ALPS index, brain lesion burden, and the MACS level in children with CP.

RESULTS

There were significant differences in the DTI-ALPS index between children with CP and their typically developing peers. The DTI-ALPS index of the children with CP was lower than that of the controls (1.448 vs. 1.625, P = 0.003). The mediation analysis showed that the DTI-ALPS index fully mediated the relationship between brain lesion burden and the MACS level (c' = 0.061, P = 0.665), explaining 80% of the effect.

CONCLUSION

This study provides new insights into the neural basis of hand dysfunction in children with CP, demonstrating an important role of glymphatic impairment in such patients. These results suggest that PVL might affect hand function in children with CP by disrupting glymphatic drainage.

Dystonia in individuals with spastic cerebral palsy and isolated periventricular leukomalacia

AIM

To determine the prevalence of dystonia in individuals with periventricular leukomalacia (PVL) and spastic cerebral palsy (CP), but without basal ganglia and thalamic injury (BGTI) on brain magnetic resonance imaging (MRI).

METHOD

This was a retrospective study of individuals with spastic CP and PVL on MRI evaluated between 2005 and 2018 in a CP center. Individuals with non-PVL brain lesions on MRI, including BGTI, were excluded. Dystonia was assessed via blinded review of neurological exam videos by pediatric movement disorders specialists.

RESULTS

Eighty-five participants (45 males, 40 females; mean age at videotaping 12 years [standard deviation 5 years 6 months], range 4-26 years) met inclusion and exclusion criteria. Of these participants, 50 (59%) displayed dystonia in their exam videos. The most common locations of dystonia were the fingers and hip adductors. The prevalence of dystonia was unaffected by the gestational age or severity of PVL, and was affected by Gross Motor Function Classification System level.

INTERPRETATION

Dystonia is common in individuals with spastic CP and PVL, even without BGTI on MRI. Our findings suggest vigilance for dystonia in individuals with spastic CP should remain high, even without MRI evidence of BGTI.

WHAT THIS PAPER ADDS

Individuals with spastic cerebral palsy and isolated periventricular leukomalacia on magnetic resonance imaging commonly display dystonia. Common sites of dystonia are in the fingers and hip adductors.

Interaction between Preterm White Matter Injury and Childhood Thalamic Growth

OBJECTIVE

The purpose of this study was to determine how preterm white matter injury (WMI) and long-term thalamic growth interact to predict 8-year neurodevelopmental outcomes.

METHODS

A prospective cohort of 114 children born at 24 to 32 weeks' gestational age (GA) underwent structural and diffusion tensor magnetic resonance imaging early in life (median 32 weeks), at term-equivalent age and at 8 years. Manual segmentation of neonatal WMI was performed on T1-weighted images and thalamic volumes were obtained using the MAGeT brain segmentation pipeline. Cognitive, motor, and visual-motor outcomes were evaluated at 8 years of age. Multivariable regression was used to examine the relationship among neonatal WMI volume, school-age thalamic volume, and neurodevelopmental outcomes.

RESULTS

School-age thalamic volumes were predicted by neonatal thalamic growth rate, GA, sex, and neonatal WMI volume (p < 0.0001). After accounting for total cerebral volume, WMI volume remained associated with school-age thalamic volume (β = -0.31, p = 0.005). In thalamocortical tracts, fractional anisotropy (FA) at term-equivalent age interacted with early WMI volume to predict school-age thalamic volumes (all p < 0.02). School-age thalamic volumes and neonatal WMI interacted to predict full-scale IQ (p = 0.002) and adverse motor scores among those with significant WMI (p = 0.01). Visual-motor scores were predicted by thalamic volumes (p = 0.04).

INTERPRETATION

In very preterm-born children, neonatal thalamic growth and WMI volume predict school-age thalamic volumes. The emergence at term of an interaction between FA and WMI to impact school-age thalamic volume indicates dysmaturation as a mechanism of thalamic growth failure. Cognition is predicted by the interaction of WMI and thalamic growth, highlighting the need to consider multiple dimensions of brain injury in these children. ANN NEUROL 2021;90:584-594.

Multimodal pathophysiological dataset of gradual cerebral ischemia in a cohort of juvenile pigs

Ischemic brain injuries are frequent and difficult to detect reliably or early. We present the multi-modal data set containing cardiovascular (blood pressure, blood flow, electrocardiogram) and brain electrical activities to derive electroencephalogram (EEG) biomarkers of corticothalamic communication under normal, sedation, and hypoxic/ischemic conditions with ensuing recovery. We provide technical validation using EEGLAB. We also delineate the corresponding changes in the electrocardiogram (ECG)-derived heart rate variability (HRV) with the potential for future in-depth analyses of joint EEG-ECG dynamics. We review an open-source methodology to derive signatures of coupling between the ECoG and electrothalamogram (EThG) signals contained in the presented data set to better characterize the dynamics of thalamocortical communication during these clinically relevant states. The data set is presented in full band sampled at 2000 Hz, so the additional potential exists for insights from the full-band EEG and high-frequency oscillations under the bespoke experimental conditions. Future studies on the dataset may contribute to the development of new brain monitoring technologies, which will facilitate the prevention of neurological injuries.

Measurement(s)	EEG with persistent abnormal rhythmic activity • electrocardiogram • Electrothalamogram • cerebral blood flow measurement • positive regulation of heart rate involved in baroreceptor response to decreased systemic arterial blood pressure • cerebral metabolic rate of oxygen • cerebral perfusion pressure
Technology Type(s)	electrophysiology assay • extracellular electrophysiology recording assay • fluorescent colormicrospheres • Electrophysiology
Factor Type(s)	sedation • cerebral ischemia • recovery
Sample Characteristic - Organism	Sus scrofa
Sample Characteristic - Environment	laboratory environment

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.13251176

Regional Brain Growth Trajectories in Fetuses with Congenital Heart Disease

OBJECTIVE

Congenital heart disease (CHD) is associated with abnormal brain development in utero. We applied innovative fetal magnetic resonance imaging (MRI) techniques to determine whether reduced fetal cerebral substrate delivery impacts the brain globally, or in a region-specific pattern. Our novel design included two control groups, one with and the other without a family history of CHD, to explore the contribution of shared genes and/or fetal environment to brain development.

METHODS

From 2014 to 2018, we enrolled 179 pregnant women into 4 groups: "HLHS/TGA" fetuses with hypoplastic left heart syndrome (HLHS) or transposition of the great arteries (TGA), diagnoses with lowest fetal cerebral substrate delivery; "CHD-other," with other CHD diagnoses; "CHD-related," healthy with a CHD family history; and "optimal control," healthy without a family history. Two MRIs were obtained between 18 and 40 weeks gestation. Random effect regression models assessed group differences in brain volumes and relationships to hemodynamic variables.

RESULTS

HLHS/TGA (n = 24), CHD-other (50), and CHD-related (34) groups each had generally smaller brain volumes than the optimal controls (71). Compared with CHD-related, the HLHS/TGA group had smaller subplate (-13.3% [standard error = 4.3%], p < 0.01) and intermediate (-13.7% [4.3%], p < 0.01) zones, with a similar trend in ventricular zone (-7.1% [1.9%], p = 0.07). These volumetric reductions were associated with lower cerebral substrate delivery.

INTERPRETATION

Fetuses with CHD, especially those with lowest cerebral substrate delivery, show a region-specific pattern of small brain volumes and impaired brain growth before 32 weeks gestation. The brains of fetuses with CHD were more similar to those of CHD-related than optimal controls, suggesting genetic or environmental factors also contribute. ANN NEUROL 2021;89:143-157.

Ascending Aorta Size at Birth Predicts White Matter Microstructure in Adolescents Who Underwent Fontan Palliation

Background In neonates with single ventricle, smaller ascending aorta diameter is associated with cerebral white matter ( WM ) microstructural abnormalities. We sought to determine whether this association persists into adolescence. Methods and Results Ascending aorta Z scores were obtained from first postnatal echocardiogram. Brain magnetic resonance imaging with diffusion tensor imaging was acquired in adolescence and used to obtain fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity in 33 WM tract regions of interest. Partial Pearson correlation coefficients were evaluated for associations between ascending aorta Z scores and WM microstructure measures, adjusting for sex, age at magnetic resonance imaging, scanner field strength, and Norwood status. Among 42 single ventricle patients aged 10 to 19 years, 31 had undergone the Norwood procedure as neonates. Lower ascending aorta Z scores were associated with lower fractional anisotropy in bilateral pontine crossing tracts ( P=0.02), inferior fronto-occipital fasciculus ( P=0.02), and inferior longitudinal fasciculus ( P=0.01); left cingulum-cingulate bundle ( P=0.01), superior longitudinal fasciculus ( P=0.04), and superior longitudinal fasciculus-temporal component ( P=0.01); and right cingulum-hippocampal bundle (P=0.009) and inferior cerebellar peduncle ( P=0.01). Lower ascending aorta Z scores were associated with higher radial diffusivity and mean diffusivity in a similar regional pattern but not with axial diffusivity. Conclusions In adolescents with single ventricle, smaller aorta diameter at birth is associated with abnormalities of WM microstructure in a subset of WM tracts, mostly those located in deeper brain regions. Our findings suggest that despite multiple intervening medical or surgical procedures, prenatal cerebral blood flow may have a lasting influence on WM microstructure in single-ventricle patients.

Enhancing Oligodendrocyte Myelination Rescues Synaptic Loss and Improves Functional Recovery after Chronic Hypoxia

To address the significance of enhancing myelination for functional recovery after white matter injury (WMI) in preterm infants, we characterized hypomyelination associated with chronic hypoxia and identified structural and functional deficits of excitatory cortical synapses with a prolonged motor deficit. We demonstrate that genetically delaying myelination phenocopies the synaptic and functional deficits observed in mice after hypoxia, suggesting that myelination may possibly facilitate excitatory presynaptic innervation. As a gain-of-function experiment, we specifically ablated the muscarinic receptor 1 (M1R), a negative regulator of oligodendrocyte differentiation in oligodendrocyte precursor cells. Genetically enhancing oligodendrocyte differentiation and myelination rescued the synaptic loss after chronic hypoxia and promoted functional recovery. As a proof of concept, drug-based myelination therapies also resulted in accelerated differentiation and myelination with functional recovery after chronic hypoxia. Together, our data indicate that myelination-enhancing strategies in preterm infants may represent a promising therapeutic approach for structural/functional recovery after hypoxic WMI.

MRI Differences Associated with Intrauterine Growth Restriction in Preterm Infants

BACKGROUND

Preterm infants are at risk for neurodevelopmental impairment. Intrauterine growth restriction (IUGR) further increases this risk. Brain imaging studies are often utilized at or near term-equivalent age to determine later prognosis.

OBJECTIVE

To evaluate the association between intrauterine growth and regional brain volume on MRI scans performed in preterm infants at or near term-equivalent age.

METHODS

This is a retrospective case-control study of 24 infants born at gestational age ≤30 weeks and cared for in a large, inner-city, academic neonatal intensive-care unit from 2012 to 2013. Each IUGR infant was matched with 1-2 appropriate for gestational age (AGA) infants who served as controls. Predischarge MRI scans routinely obtained at ≥36 weeks' adjusted age were analyzed for regional brain volumetric differences. We examined the association between IUGR and thalamic, basal ganglion, and cerebellar brain volumes in these preterm infants.

RESULTS

Compared to AGA infants, IUGR infants had a smaller thalamus (7.88 vs. 5.87 mL, p = 0.001) and basal ganglion (8.87 vs. 6.92 mL, p = 0.002) volumes. There was no difference in cerebellar volumes between the two study groups. Linear regression analyses revealed similar trends in the associations between IUGR and brain volumes after adjusting for sex, gestational age at birth, and postconceptual age and weight at MRI.

CONCLUSIONS

Thalamus and basal ganglion volumes are reduced in growth-restricted preterm infants. These differences may preferentially impact neurodevelopmental outcomes. Further research is needed to explore these relationships.