Plasticity of Interhemispheric Temporal Lobe White Matter Pathways Due to Early Disruption of Corpus Callosum Development in Spina Bifida

Assessment of longitudinal brain development using super-resolution magnetic resonance imaging following fetal surgery for open spina bifida

OBJECTIVES

Prenatal surgery is offered for selected fetuses with open spina bifida (OSB) to improve long-term outcome. We studied the effect of fetal OSB surgery on brain development using advanced magnetic resonance imaging (MRI) techniques to quantify the volume, surface area and shape of cerebral structures and to analyze surface curvature by means of parameters that correspond to gyrification.

METHODS

We compared MRI data from 29 fetuses with OSB before fetal surgery (mean gestational age (GA), 23 + 3 weeks) and at 1 and 6 weeks after surgery, with that of 36 GA-matched control fetuses (GA range, 21 + 2 to 36 + 2 weeks). Automated super-resolution reconstruction provided three-dimensional isotropic volumetric brain images. Unmyelinated white matter, cerebellum and ventricles were segmented automatically and refined manually, after which volume, surface area and shape parameter (volume/surface area) were quantified. Mathematical markers (shape index (SI) and curvedness) were used to measure gyrification. Parameters were assessed according to lesion type (myelomeningocele vs myeloschisis (MS)), postoperative persistence of hindbrain herniation (HH) and the presence of supratentorial anomalies, namely partial agenesis of the corpus callosum (pACC) and heterotopia (HT).

RESULTS

Growth in ventricular volume per week and change in shape parameter per week were higher at 6 weeks after surgery in fetuses with OSB compared with controls (median, 2500.94 (interquartile range (IQR), 1689.70-3580.80) mm3 /week vs 708.21 (IQR, 474.50-925.00) mm3 /week; P < 0.001 and 0.075 (IQR, 0.047-0.112) mm/week vs 0.022 (IQR, 0.009-0.042) mm/week; P = 0.046, respectively). Ventricular volume growth increased 6 weeks after surgery in cases with pACC (P < 0.001) and those with persistent HH (P = 0.002). During that time period, the change in unmyelinated white-matter shape parameter per week was decreased in OSB fetuses compared with controls (0.056 (IQR, 0.044-0.092) mm/week vs 0.159 (IQR, 0.100-0.247) mm/week; P = 0.002), particularly in cases with persistent HH (P = 0.011), MS (P = 0.015), HT (P = 0.022), HT with corpus callosum anomaly (P = 0.017) and persistent HH with corpus callosum anomaly (P = 0.007). At 6 weeks postoperatively, despite OSB fetuses having a lower rate of change in curvedness compared with controls (0.061 (IQR, 0.040-0.093) mm-1 /week vs 0.094 (IQR, 0.070-0.146) mm-1 /week; P < 0.001), reversing the trend seen at 1 week after surgery (0.144 (IQR, 0.099-0.236) mm-1 /week vs 0.072 (IQR, 0.059-0.081) mm-1 /week; P < 0.001), gyrification, as determined using SI, appeared to be increased in OSB fetuses overall compared with controls. This observation was more prominent in fetuses with pACC and those with severe ventriculomegaly (P-value range, < 0.001 to 0.006).

CONCLUSIONS

Following fetal OSB repair, volume, shape and curvedness of ventricles and unmyelinated white matter differed significantly compared with those of normal fetuses. Morphological brain changes after fetal surgery were not limited to effects on the circulation of cerebrospinal fluid. These observations may have implications for postnatal neurocognitive outcome. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Evaluation of the height of the corpus callosum body region in fetal meningomyelocele malformation

PURPOSE

To investigate height of the corpus callosum (CC) in order to describe the corpus callosum anomalies in fetuses with meningomyelocele (MMC) and compare these findings with the corpus callosum of healthy fetuses.

METHODS

In this study, fetal MRI examinations were performed on 44 fetal MMC malformation cases. As the control group, 34 fetal MRI examinations, which were anatomically normal, were evaluated retrospectively. In the study group, lateral ventricle diameter, the level and diameter of the MMC defect, and CC height were measured. In the control group, CC height and lateral ventricular diameter were measured.

RESULTS

The mean CC body height was 1.36 mm in the study group, and 2.48 mm in the control group. The height of the CC body region of the study population was inclined to be thinner compared with the control population (p<0.001).

CONCLUSIONS

The fact that the height of the CC body region was found to be thinner in fetal MRI in cases of MMC compared with normal fetuses suggests that various callosal anomalies are uncertain, investigation of additional callosal anomalies may be beneficial in the decision for the continuation of pregnancy, and termination or intrauterine surgery in cases with MMC. Further large case group studies are needed.

Fetal MRI prior to intrauterine surgery of open neural tube defects: What does the radiologist need to know

The management of myelomeningocele study trial showed significant prognostic improvement in fetal repair before 26 weeks of gestation. Hence, surgery in utero represents the best treatment option for open-neural tube defects (NTDs). Fetal surgery of open-NTDs has specific inclusion and exclusion criteria, which can be adequately studied with fetal MRI. The main concern: the spine (spinal defects other than Myelomeningocele and Myeloschisis, the level of the lesion higher than T1 or lower than S1 and the degree of kyphosis ≥ 30°), the skull/brain (no cerebellum herniation and Chiari II malformation and the presence of any intracranial abnormality unrelated to open NTDs), the uterus (cervix length less than 2 cm, multiple gestations and placental and uterine abnormalities) and any other fetal abnormality not attributed to spinal defect. In this review, we describe the fundamental role of fetal MRI in supporting therapeutic decisions in pre-surgery intrauterine planning through the accurate and comprehensive description of findings, providing a proposal of a structured report. In addition, we describe how post-surgical MRI is important in investigating the effectiveness of surgery and detecting repairing complications.

The Role of Neuroplasticity in Improving the Decision-Making Quality of Individuals With Agenesis of the Corpus Callosum: A Systematic Review

Although individuals with agenesis of corpus callosum (ACC) possess intelligence coefficients within regular parameters, current studies have demonstrated decision-making compromise and potential negative social consequences. Furthermore, alternative pathways regarding brain connectivity in acallosal patients combined with cognitive therapy that would potentially mitigate such difficulties. Therefore, this study aimed to examine the current state of the art regarding brain foundations in the role of neuroplasticity by improving the decision-making quality in ACC.

A systematic revision of literature was performed including studies conducted on non-syndromic ACC individuals and analyzing the impact of the potential role of neuroplasticity on the decision-making published to date. Studies with patients who underwent callosotomy were excluded. Experimental studies performed on animal models were included.

During this period, 849 studies were identified; among them, 11 were eligible for qualitative analysis. Despite the paucity of evidence on this matter, patients with ACC present considerable decision-making difficulties mainly due to the functional connectivity impairment in the frontal lobes. Moreover, neuroplasticity was characterized by increased anterior commissure width as compared with controls. Notwithstanding, no studies were conducted on cognitive therapists managing this type of disease.

Although the reorganization of inter-hemispheric bundles on anterior commissure has demonstrated the main natural neuroanatomic strategy in ACC, further evidence will be needed to clarify whether cognitive stimulus could improve the decision-making quality.

Prevalence of supratentorial anomalies assessed by magnetic resonance imaging in fetuses with open spina bifida

OBJECTIVES

To determine the prevalence of brain anomalies at the time of preoperative magnetic resonance imaging (MRI) assessment in fetuses eligible for prenatal open spina bifida (OSB) repair, and to explore the relationship between brain abnormalities and features of the spinal defect.

METHODS

This was a retrospective cross-sectional study, conducted in three fetal medicine centers, of fetuses eligible for OSB fetal surgery repair between January 2009 and December 2019. MRI images obtained as part of the presurgical assessment were re-evaluated by two independent observers, blinded to perinatal results, to assess: (1) the type and area of the defect and its anatomical level; (2) the presence of any structural central nervous system (CNS) anomaly and abnormal ventricular wall; and (3) fetal head and brain biometry. Binary regression analyses were performed and data were adjusted for type of defect, upper level of the lesion (ULL), gestational age (GA) at MRI and fetal medicine center. Multiple logistic regression analysis was performed in order to identify lesion characteristics and brain anomalies associated with a higher risk of presence of abnormal corpus callosum (CC) and/or heterotopia.

RESULTS

Of 115 fetuses included, 91 had myelomeningocele and 24 had myeloschisis. Anatomical level of the lesion was thoracic in seven fetuses, L1-L2 in 13, L3-L5 in 68 and sacral in 27. Median GA at MRI was 24.7 (interquartile range, 23.0-25.7) weeks. Overall, 52.7% of cases had at least one additional brain anomaly. Specifically, abnormal CC was observed in 50.4% of cases and abnormality of the ventricular wall in 19.1%, of which 4.3% had nodular heterotopia. Factors associated independently with higher risk of abnormal CC and/or heterotopia were non-sacral ULL (odds ratio (OR), 0.51 (95% CI, 0.26-0.97); P = 0.043), larger ventricular width (per mm) (OR, 1.23 (95% CI, 1.07-1.43); P = 0.005) and presence of abnormal cavum septi pellucidi (OR, 3.76 (95% CI, 1.13-12.48); P = 0.031).

CONCLUSIONS

Half of the fetuses assessed for OSB repair had an abnormal CC and/or an abnormal ventricular wall prior to prenatal repair. The likelihood of brain abnormalities was increased in cases with a non-sacral lesion and wider lateral ventricles. These findings highlight the importance of a detailed preoperative CNS evaluation of fetuses with OSB. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

A Systematic Review of Cognitive Function in Adults with Spina Bifida

Background: Though much research has been done on the cognitive profiles of children, the abilities of patients with SBM as they age into adulthood are not well understood.Objective: Determine if adults with SBM have impairments in overall cognition, attention, executive function, and memory compared to typically developing adults or a standardized population mean.Methods: A medical librarian composed a search of spina bifida, adults, and cognitive function. 549 results were screened using title and abstract. Data were extracted using Covidence review software, including risk of bias assessments. 24 studies were included.Results: Memory impairments, notably working and prospective, have been reported. Results in other domains varied. Average VIQ or PIQ did not imply lack of impairment in other specific domains.Conclusion: Memory impairments should be accounted for and neuropsychological testing should be considered when providing care to adults with SBM. Future longitudinal cognitive aging and interventional studies are needed.

Neuropsychological care guidelines for people with spina bifida

While the neuropsychological profile for individuals with Spina Bifida (SB) can vary, often certain patterns of strengths and weaknesses are evident across the lifespan. Understanding variability related to neural structure, genetics, ethnicity, and the environment is key to understanding individual differences in outcomes and can be vital in planning interventions and tracking progress. This article outlines the SB Guideline for the Neuropsychological Care of People with Spina Bifida from the 2018 Spina Bifida Association's Fourth Edition of the Guidelines for the Care of People with Spina Bifida and acknowledges that further research in SB neurocognitive profiles is warranted.

The evolution, formation and connectivity of the anterior commissure

The anterior commissure is the most ancient of the forebrain interhemispheric connections among all vertebrates. Indeed, it is the predominant pallial commissure in all non-eutherian vertebrates, universally subserving basic functions related to olfaction and survival. A key feature of the anterior commissure is its ability to convey connections from diverse brain areas, such as most of the neocortex in non-eutherian mammals, thereby mediating the bilateral integration of diverse functions. Shared developmental mechanisms between the anterior commissure and more evolutionarily recent commissures, such as the corpus callosum in eutherians, have led to the hypothesis that the former may have been a precursor for additional expansion of commissural circuits. However, differences between the formation of the anterior commissure and other telencephalic commissures suggest that independent developmental mechanisms underlie the emergence of these connections in extant species. Here, we review the developmental mechanisms and connectivity of the anterior commissure across evolutionarily distant species, and highlight its potential functional importance in humans, both in the course of normal neurodevelopment, and as a site of plastic axonal rerouting in the absence or damage of other connections.

Long-term neuroimaging and neurological outcome of fetal spina bifida aperta after postnatal surgical repair

OBJECTIVE

Parents faced with the choice between postnatal management and prenatal surgery for spina bifida need to have up-to-date information on the expected outcomes. The aim of this study was to report the long-term physical and neurological outcomes of infants with prenatally diagnosed isolated spina bifida that underwent postnatal surgical repair and were managed by a multidisciplinary team from a large tertiary center.

METHODS

This was a retrospective cohort study of all cases of fetal spina bifida managed in a tertiary unit between October 1999 and January 2018. All cases of fetal spina bifida from the local health region were routinely referred to the tertiary unit for further perinatal management. Details on surgical procedures and neonatal neurological outcomes were obtained from institutional case records. Ambulatory status, bladder and bowel continence and neurodevelopment were assessed at a minimum of 3 years.

RESULTS

During the study period, 241 pregnancies with isolated spina bifida were seen in the unit. Of these, 84 (34.9%) women opted to continue with the pregnancy after multidisciplinary counseling by clinicians. Sixty-seven infants underwent postnatal repair of spina bifida aperta and were included in the analysis. After birth, hindbrain herniation was observed in 91.5% of infants with only seven requiring surgical decompression. Ventriculoperitoneal shunt placement was needed in 64.2% of infants, while normal cognitive development or mild impairment was demonstrated in 85.4% of cases with data for this outcome available, at a mean age of 8 years. Cumulatively, 40% of infants were walking independently or using minor support, and normal or mild impairment of bladder and bowel function was reported in 45.5% and 44.4% of infants, respectively.

CONCLUSIONS

Neurodevelopmental and neurological outcomes between prenatal and postnatal repair are similar. As with fetal surgery, conventional postnatal surgery is associated with the reversal of hindbrain herniation. Similarly, postnatal ventriculoperitoneal shunt placement appears to be required mainly in fetuses without evidence of significant fetal ventriculomegaly. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Diagnostic value of Omniview technique on the agenesis of corpus callosum

Objective: This study aimed to discuss the diagnostic value of Omniview technique on the agenesis of corpus callosum. Methods: A total of 43 pregnant women with no obvious structural abnormality and eight pregnant women who diagnosed with agenesis of corpus callosum (ACC) were included in this study. The 2D ultrasonography and the 3D ultrasonography Omniview technique were used to carry out ultrasonic examination on 43 normal fetuses and eight fetuses with agenesis of corpus callosum (as verified through magnetic resonance), respectively. Results: The Omniview technique visually displayed the median sagittal plane of the fetus. The ROC curve of Omniview (0.999) was much higher than that of 2D ultrasonography (0.817). Rating of ACC and normal fetuses showed that the diagnostic efficiency of 3D ultrasonography Omniview technique was much higher than 2D ultrasonography. Conclusion: 3D ultrasonography Omniview technique has certain advantage in the diagnosis of agenesis of corpus callosum, and is of great significance in the prenatal screening of callosum.

How accurate are prenatal tractography results? A postnatal in vivo follow-up study using diffusion tensor imaging

Prenatal detection of abnormal white matter tracts might serve as a structural marker for altered neurodevelopment. As a result of many technical and patient-related challenges, the accuracy of prenatal tractography remains unknown. We hypothesized that characteristics of prenatal tractography of the corpus callosum and corticospinal tracts derived from fetal diffusion tensor imaging (DTI) data are accurate and predictive of the integrity of these tracts postnatally. We compared callosal and corticospinal tracts of 12 subjects with paired prenatal (age: 23-35 gestational weeks) and postnatal (age: 1 day to 2 years) DTI examinations (b values of 0 s/mm² and 700 s/mm², 16 gradient encoding directions) using deterministic tractography. Evaluation for the presence of callosal segments and corticospinal tracts showed moderate degrees of accuracy (67-75%) for the four segments of the corpus callosum and moderate to high degrees of accuracy (75-92%) for the corticospinal tracts. Positive predictive values for segments of the corpus callosum ranged from 50% to 100% and for the corticospinal tracts, 89% to 100%. Negative predictive values for segments of the corpus callosum ranged from 25% to 80% and for the corticospinal tracts, 33% to 50%. The results suggest that when the tracts are not well characterized on the fetal MR, predictions about the postnatal tracts are difficult to make. However, accounting for brain maturation, prenatal visualization of the main projection and commissural tracts can be clinically used as an important predictive tool in the context of image interpretation for the assessment of fetal brain malformations.