Fetal intracranial hemorrhage: role of fetal MRI

Congenital infectious encephalopathies from the intrapartum period to postnatal life

Congenital infections are a common but often underrecognized cause of fetal brain abnormalities, as well as fetal-neonatal morbidity and mortality, that should be considered by all healthcare professionals providing neurological care to fetuses and newborns. Maternal infection with various pathogens (cytomegalovirus, Toxoplasmosis, Rubella virus, Parvovirus B19, lymphocytic choriomeningitis virus, syphilis, Zika virus, varicella zoster virus) during pregnancy can be transmitted to the developing fetus, which can cause multisystem dysfunction and destructive or malformative central nervous system lesions. These can be recognized on fetal and neonatal imaging, including ultrasound and MRI. Imaging and clinical features often overlap, but some distinguishing features can help identify specific pathogens and guide subsequent testing strategies. Some pathogens can be specifically treated, and others can be managed with targeted interventions or symptomatic therapy based on expected complications. Neurological and neurodevelopmental complications related to congenital infections vary widely and are likely driven by a combination of pathophysiologic factors, alone or in combination. These include direct invasion of the fetal central nervous system by pathogens, inflammation of the maternal-placental-fetal triad in response to infection, and long-term effects of immunogenic and epigenetic changes in the fetus in response to maternal-fetal infection. Congenital infections and their neurodevelopmental impacts should be seen as an issue of public health policy, given that infection and the associated complications disproportionately affect woman and children from low- and middle-income countries and those with lower socio-economic status in high-income countries. Congenital infections may be preventable and treatable, which can improve long-term neurodevelopmental outcomes in children.

The association between fetal intracranial hemorrhages detected on MRI and neurodevelopment

PURPOSE

Fetal intracranial hemorrhage is rarely identified in prenatal imaging. When identified, sparse data regarding neurodevelopmental outcomes worsens prenatal dilemmas. This MRI-based study aimed to assess prenatal characteristics and neurodevelopmental outcomes of fetal intracranial hemorrhage.

METHODS

A historical cohort study which identified fetal intracranial hemorrhage in 22 individual fetal MRI scans, as part of the assessment of abnormal prenatal sonographic findings. Severity was graded by the grading system commonly used in neonates, with modifications. Prenatal data was collected. Neurodevelopmental outcome was assessed clinically by Vineland-II Adaptive Behavior Scales.

RESULTS

Eight fetuses had intraventricular hemorrhage grade I-II, twelve had intraventricular hemorrhage grade III-IV, and two had infratentorial hemorrhage. The most prevalent risk factors were maternal chronic diseases and chronic use of medications. There was male predominance. Pregnancy was terminated in eleven cases. No surviving child who participated in the Vineland assessment had a grade IV hemorrhage. Vineland scores were normal in 9/11 children and moderately low in 2/11. The mean composite score of the cohort was not different from the mean score expected for age. Clinically, one child had hypotonia.

CONCLUSIONS

Prognosis for fetuses with ICH without parenchymal involvement is potentially more favorable than expected from the intraventricular hemorrhage grading-scale adopted from the preterm neonates. Parenchymal involvement may predict a worse outcome, but it is not the sole predicting feature. This information may be valuable during prenatal counseling.

Longitudinal MRI in the context of in utero surgery for open spina bifida: A descriptive study

INTRODUCTION

Fetal surgery for open spina bifida (OSB) requires comprehensive preoperative assessment using imaging for appropriate patient selection and to evaluate postoperative efficacy and complications. We explored patient access and conduct of fetal magnetic resonance imaging (MRI) for prenatal assessment of OSB patients eligible for fetal surgery. We compared imaging acquisition and reporting to the International Society of Ultrasound in Obstetrics and Gynecology MRI performance guidelines.

MATERIAL AND METHODS

We surveyed access to fetal MRI for OSB in referring fetal medicine units (FMUs) in the UK and Ireland, and two NHS England specialist commissioned fetal surgery centers (FSCs) at University College London Hospital, and University Hospitals KU Leuven Belgium. To study MRI acquisition protocols, we retrospectively analyzed fetal MRI images before and after fetal surgery for OSB.

RESULTS

MRI for fetal OSB was accessible with appropriate specialists available to supervise, perform, and report scans. The average time to arrange a fetal MRI appointment from request was 4 ± 3 days (range, 0-10), the average scan time available was 37 ± 16 min (range, 20-80 min), with 15 ± 11 min (range, 0-30 min) extra time to repeat sequences as required. Specific MRI acquisition protocols, and MRI reporting templates were available in only 32% and 18% of units, respectively. Satisfactory T2-weighted (T2W) brain imaging acquired in three orthogonal planes was achieved preoperatively in all centers, and 6 weeks postoperatively in 96% of FSCs and 78% of referring FMUs. However, for T2W spine image acquisition referring FMUs were less able to provide three orthogonal planes presurgery (98% FSC vs. 50% FMU, p < 0.001), and 6 weeks post-surgery (100% FSC vs. 48% FMU, p < 0.001). Other standard imaging recommendations such as T1-weighted (T1W), gradient echo (GE) or echoplanar fetal brain and spine imaging in one or two orthogonal planes were more likely available in FSCs compared to FMUs pre- and post-surgery (p < 0.001).

CONCLUSIONS

There was timely access to supervised MRI for OSB fetal surgery assessment. However, the provision of images of the fetal brain and spine in sufficient orthogonal planes, which are required for determining eligibility and to determine the reversal of hindbrain herniation after fetal surgery, were less frequently acquired. Our evidence suggests the need for specific guidance in relation to fetal MRI for OSB. We propose an example guidance for MRI acquisition and reporting.

Cerebral Lateral Ventricular Asymmetry: Normal Variant or an Indicator of Underlying Pathology

INTRODUCTION

Isolated lateral ventricular asymmetry has been associated with a favorable prognosis; however, prenatal evaluations in existing studies have been conducted using ultrasonography (US). This study aimed to describe the magnetic resonance imaging (MRI) findings, progression of ventricular asymmetry, and perinatal outcomes in fetuses prenatally diagnosed with isolated ventricular asymmetry.

METHODS

This retrospective study included patients who underwent MRI for isolated fetal ventricular asymmetry at a tertiary center between January 2012 and January 2020. Information, including pregnancy history, US, MRI findings, and perinatal outcomes, was obtained from medical records.

RESULTS

The study cohort included 17 women with fetal ventricular asymmetry but without ventriculomegaly at the time of index US. Mild ventriculomegaly subsequently developed in 13 patients; 12 of them showed spontaneous resolution before delivery. MRI identified low-grade intraventricular hemorrhage (IVH) in 13 fetuses. Postnatally, 12 newborns underwent neonatal cranial US where two of them showed evidence of germinal matrix hemorrhage. Both newborns appeared normal at birth without neonatal complications.

CONCLUSION

MRI identified low-grade IVH in most fetuses with isolated ventricular asymmetry. These fetuses were also likely to develop mild ventriculomegaly with spontaneous resolution. Although perinatal outcomes appeared good, careful follow-up in both prenatal and postnatal periods is warranted.

Pregnancy and Child Outcomes Following Fetal Intracranial Hemorrhage

BACKGROUND

The prenatal and early postnatal outcomes of fetal intracranial hemorrhage (ICH) prenatally diagnosed by fetal magnetic resonance imaging (MRI) have not been well described.

METHODS

A retrospective study of cases with fetal ICH diagnosed by fetal MRI at Children's National Hospital, Washington, DC, from 2012 to 2020 was conducted. Maternal characteristics, prenatal imaging, pregnancy outcome, and child developmental outcomes were recorded. Abnormal outcomes were categorized as mild for required physical/occupational therapy without other delays, moderate for intermediate multidomain developmental delays, and severe if nonambulatory, nonverbal, or intellectual disability.

RESULTS

Fifty-seven cases with fetal ICH were included. The mean (S.D.) maternal age was 31.1 (6.9) years, gestational age at fetal evaluation was 28.1 (5.3) weeks, and gestational age at birth was 38.2 (1.3) weeks. Pregnancy outcomes were 75% (n = 43) live birth, 14% (n = 8) termination of pregnancy, and 11% (n = 6) intrauterine demise (IUD). Live births decreased from 90% to 33% and IUD increased 10% to 22% when comparing unilateral intraventricular hemorrhage with more extensive hemorrhages. Among the 37 live-born infants with clinical follow-up to age 1.8 (1.6) years, neurodevelopmental outcome was normal in 57%, mildly abnormal in 24%, moderately abnormal in 14%, and severely abnormal in 5%. In five cases, an etiology was identified: two had placental pathologies, two had genetic findings (fetal neonatal alloimmune thrombocytopenia and COL4A1 mutation), and one had congenital cytomegalovirus infection.

CONCLUSION

Perinatal and early child outcomes following fetal ICH have a wide spectrum of outcomes. Fetal MRI description of ICH location may aid in pregnancy and postnatal outcome prediction.

Perinatal Stroke in Fetuses, Preterm and Term Infants

Perinatal stroke is a well-defined heterogenous group of disorders involving a focal disruption of cerebral blood flow between 20 weeks gestation and 28 days of postnatal life. The most focused lifetime risk for stroke occurs during the first week after birth. The morbidity of perinatal stroke is high, as it is the most common cause of hemiparetic cerebral palsy which results in lifelong disability that becomes more apparent throughout childhood. Perinatal strokes can be classified by the timing of diagnosis (acute or retrospective), vessel involved (arterial or venous), and underlying cause (hemorrhagic or ischemic). Perinatal stroke has primarily been reported as a disorder of term infants; however, the preterm brain possesses different vulnerabilities that predispose an infant to stroke injury both in utero and after birth. Accurate diagnosis of perinatal stroke syndromes has important implications for investigations, management, and prognosis. The classification of perinatal stroke by age at presentation (fetal, preterm neonatal, term neonatal, and infancy/childhood) is summarized in this review, and includes detailed descriptions of risk factors, diagnosis, treatment, outcomes, controversies, and resources for family support.

Fetal MRI Neuroradiology: Indications

Fetal MRI is a safe, noninvasive examination of the fetus and placenta, a complement to ultrasonography. MRI provides detailed CNS evaluation, including depicting parenchymal architecture and posterior fossa morphology, and is key in prenatal assessment of spinal dysraphism, neck masses, and ventriculomegaly. Fetal MRI is typically performed after 22 weeks gestation, and ultrafast T1 and T2-weighted MRI sequences are the core of the exam, with advanced sequences such as diffusion weighted imaging used for specific questions. The fetal brain grows and develops rapidly, and familiarity with gestational age specific norms is essential to MRI interpretation.

Contribution of fetal magnetic resonance imaging in the evaluation of neurosonographically detected cases of isolated mild and moderate cerebral ventriculomegaly

AIM

This study aimed to present the contribution of prenatal magnetic resonance imaging (MRI) in the diagnosis of fetuses that were previously identified as isolated mild and moderate cerebral ventriculomegaly (VM) by ultrasound (US).

METHODS

The data between February 2013 and August 2020 were collected for women who were diagnosed with isolated mild or moderate fetal VM by US and subsequently underwent a fetal MRI.

RESULTS

Among 321 women, 21 (6.5%) had a clinically important additional finding after MRI. Twelve of 276 (4.3%) fetuses with mild VM and 9 of 45 (20%) with moderate VM had turned out to have additional central nervous system abnormalities. Additional findings were detected more in fetuses with moderate VM, mothers with an anterior-located placenta, and mothers with higher body mass indexes (BMIs) with statistical significance (p = 0.001, p = 0.013, p = 0.036, respectively). The most common additional MRI finding was grade 3 or 4 germinal matrix hemorrhage, which was detected in 11 of 21 fetuses (52.3%).

CONCLUSIONS

Considering the countries' health policies, prenatal MRI would contribute mostly to the diagnosis of fetuses with moderate VM, pregnancies with anterior-located placenta, and mothers with high BMIs. According to our data, we believe that MRI will be valuable, especially in the diagnosis of grade 3 and 4 intracranial hemorrhage group.

Magnetic resonance neuroimaging after laser for twin-twin transfusion syndrome with single fetal demise

BACKGROUND

Neurologic injury in the surviving twin is a risk after single fetal demise in a monochorionic pregnancy.

OBJECTIVE

This study aimed to describe fetal magnetic resonance neuroimaging findings in pregnancies complicated by single fetal demise after laser photocoagulation for twin-twin transfusion syndrome.

STUDY DESIGN

This was a single-center retrospective analysis of a cohort of prospectively collected patients in a monochorionic twin registry who had fetoscopic laser photocoagulation for twin-twin transfusion syndrome with single fetal demise at follow-up. Magnetic resonance neuroimaging was offered 3 to 4 weeks after the demise to assess for potential neurologic sequelae. Magnetic resonance images were interpreted by 2 board-certified neuroradiologists and classified as normal, mildly abnormal, or severely abnormal. The groups were compared on the basis of recipient vs donor demise using the Fisher exact test and Mann-Whitney U test. Multivariate logistic regression was performed to determine risk factors for abnormal magnetic resonance neuroimaging.

RESULTS

In 378 laser photocoagulation procedures, 64 cases (16.9%) of single demise were identified (36 in the donor group and 28 in the recipient group). Of note, 6 patients had rupture of membranes with nonviable delivery (3 from each group). Moreover, 40 patients (69%) underwent magnetic resonance imaging. Of those patients, 12 (30%) had abnormal findings: 10 (83%) were associated with mild changes, and 2 (17%) were associated with severe findings. Abnormal magnetic resonance neuroimaging was seen in 3 of 22 patients (14%) after donor demise and 9 of 18 patients (50%) after recipient demise (P=.02). Logistic regression revealed that recipient vs donor demise was an independent risk factor for abnormal magnetic resonance imaging. In addition, 2 pregnancies with severe magnetic resonance imaging findings had complicated courses.

CONCLUSION

Mildly abnormal magnetic resonance neuroimaging findings were common after laser photocoagulation for twin-twin transfusion syndrome complicated by single fetal demise and were more common in cases of recipient demise than donor demise. Severe magnetic resonance neuroimaging findings in this series were limited to patients with complicated peri- or postoperative courses.

Diagnostic Value of Sylvian Fissure Hyperechogenicity in Fetal SAH

BACKGROUND AND PURPOSE

Fetal SAH is an intracranial malformation. The typical diagnostic features of fetal SAH in ultrasound have not been reported. This study aimed to evaluate the diagnostic value of Sylvian fissure hyperechogenicity by prenatal ultrasound in fetuses with SAH.

MATERIALS AND METHODS

The features on ultrasound and MR imaging of 10 fetuses with SAH were reviewed and summarized. The diagnostic value of the Sylvian fissure in fetal SAH by prenatal ultrasound was evaluated.

RESULTS

The typical and most obvious manifestations of SAH during the prenatal period were hyperechogenicity in the subarachnoid cavity, especially in the Sylvian fissure; all 10 cases (10/10) had such manifestations. Other manifestations included a hyperecho in other sulci (6/10), especially in the subfrontal sulcus, superior temporal sulcus, or parieto-occipital sulcus; a hyperecho in the cisterns (8/10), especially in the suprasellar cistern, posterior cranial fossa, cisterna ambiens, or quadrigeminal cistern; and a hyperecho around the anterior and posterior longitudinal fissures (2/10). Combined hemorrhage in the parenchymal layer or ventricles (9/10) was found. In addition, Doppler ultrasound showed that the peak flow velocity in the MCA increased in 6 cases (6/10).

CONCLUSIONS

The homogeneous hyperechogenicity of the Sylvian fissure is an important clue for detecting and diagnosing fetal SAH by prenatal ultrasound. A diagnostic approach has been proposed for fetal SAH, which has great significance in further prognosis.

Prenatal Evaluation of Intracranial Hemorrhage on Fetal MRI: A Retrospective Review

BACKGROUND AND PURPOSE

The evaluation and characterization of germinal matrix hemorrhages have been predominantly described on postnatal head sonography in premature neonates. However, germinal matrix hemorrhages that are seen in premature neonates can be also seen in fetuses of the same postconceptual age and are now more frequently encountered in the era of fetal MR imaging. Our aim was to examine and describe the MR imaging findings of fetuses with intracranial hemorrhage.

MATERIALS AND METHODS

A retrospective review of diagnostic-quality fetal MRIs showing intracranial hemorrhage from January 2004 to May 2020 was performed. Images were reviewed by 2 radiologists, and imaging characteristics of fetal intracranial hemorrhages were documented. Corresponding postnatal imaging and clinical parameters were reviewed.

RESULTS

One hundred seventy-seven fetuses with a mean gestational age of 25.73 (SD, 5.01) weeks were included. Germinal matrix hemorrhage was identified in 60.5% (107/177) and nongerminal matrix hemorrhage in 39.5% (70/177) of patients. Significantly increased ventricular size correlated with higher germinal matrix hemorrhage grade (P < .001). Fetal growth restriction was present in 21.3% (20/94) of our population, and there was no significant correlation with germinal matrix grade or type of intracranial hemorrhage. An increased incidence of neonatal death with grade III germinal matrix hemorrhages (P = .069) compared with other grades was identified; 23.2% (16/69) of the neonates required ventriculoperitoneal shunts, with an increased incidence in the nongerminal matrix hemorrhage group (P = .026).

CONCLUSIONS

MR imaging has become a key tool in the diagnosis and characterization of intracranial hemorrhage in the fetus. Appropriate characterization is important for optimizing work-up, therapeutic approach, and prenatal counseling.

Magnetic resonance imaging evaluation of foetal intracranial haemorrhage and the correlation with ultrasound findings and postnatal outcomes

OBJECTIVES

The aim of the study was to compare the magnetic resonance imaging (MRI) findings of intracranial haemorrhage (ICH) in the middle- and late trimesters and to explore the relationship between the MRI features of foetal ICH and postnatal outcomes.

METHODS

This was a retrospective study which recruited foetal ICH diagnosed by MRI in one tertiary centre from 2015 to 2019. The prenatal and postnatal medical records were reviewed.

RESULTS

Of 39 ICH cases, 82.1% (32) had germinal matrix intraventricular haemorrhage (GM-IVH), and 18.9% (7) were diagnosed with non-GM-IVH. The cerebellum, corpus callosum and subdural space were affected in 5, 1 and 1 non-GM-IVH cases, respectively. MRI confirmed possible ICH on sonogram in 10 cases (35.7%) and the remaining 19 added ICH diagnoses that were not obtained on initial ultrasound imaging. Pregnancy outcome data were available in 82.1% of (32) cases, of which 21 were terminated pregnancies, 1 was foetal demise and 10 were delivered. One neonate died after birth and one infant suffered from hearing loss. The remaining eight patients had favourable outcome.

CONCLUSION

In our study, evaluation of the relationship between MRI findings and outcomes remains challenging, depending on the timing of examination and the hematoma itself. MRI was an adjunct to US in diagnosing ICH in utero which helps to assess postnatal development.

Perinatal post-mortem magnetic resonance imaging (MRI) of the central nervous system (CNS): a pictorial review

Central nervous system (CNS) abnormalities cause approximately 32–37.7% of terminations of pregnancy (TOP). Autopsy is currently the gold standard for assessing dead foetuses and stillborn. However, it has limitations and is sometimes subject to parental rejection. Recent studies have described post-mortem foetal magnetic resonance imaging (MRI) as an alternative and even complementary to autopsy for CNS assessment. Radiologists now play a key role in the evaluation of perinatal deaths. Assessment of foetal CNS abnormalities is difficult, and interpretation of foetal studies requires familiarisation with normal and abnormal findings in post-mortem MRI studies as well as the strengths and limitations of the imaging studies. The purpose of this pictorial review is to report our experience in the post-mortem MRI evaluation of the CNS system, including a description of the protocol used, normal CNS findings related to post-mortem status, abnormal CNS findings in our sample, and the correlation of these findings with histopathological results.

Fetal Neuroimaging Update

OBJECTIVES

To review the current imaging techniques available for the evaluation of the fetal brain.

FINDINGS

Ultrasound remains the initial screening modality with routine scanning typically performed at 18-20 weeks gestation. When a central nervous system (CNS) abnormality is noted by ultrasound, MRI is increasingly being used to further clarify findings. Fetal MRI has the unique ability to provide high detailed anatomical information of the entire human fetus with high contrast resolution. This technique has grown due to the development of rapid single shot image acquisition sequences, improvement of motion correction strategies and optimizing shimming techniques.

CONCLUSIONS

The assessment of fetal CNS anomalies continues to improve. Advanced MRI techniques have allowed for further delineation of CNS anomalies and have become a cornerstone in the assessment of fetal brain well-being. Those interpreting fetal studies need to be familiar with the strengths and limitations of each exam and be sensitive to the impact discussing findings can have regarding perinatal care and delivery planning. Collaboration with neurologists, neurosurgeons, geneticists, counselors, and maternal fetal specialists are key in providing the best care to the families we treat.

Cranial ultrasound findings in preterm germinal matrix haemorrhage, sequelae and outcome

Germinal matrix-intraventricular haemorrhage (GMH-IVH), periventricular haemorrhagic infarction (PHI) and its complication, post-haemorrhagic ventricular dilatation (PHVD), are still common neonatal morbidities in preterm infants that are highly associated with adverse neurodevelopmental outcome. Typical cranial ultrasound (CUS) findings of GMH-IVH, PHI and PHVD, their anatomical substrates and underlying mechanisms are discussed in this paper. Furthermore, we propose a detailed descriptive classification of GMH-IVH and PHI that may improve quality of CUS reporting and prediction of outcome in infants suffering from GMH-IVH/PHI.

Fetal MRI for dummies: what the fetal medicine specialist should know about acquisitions and sequences

Fetal MRI is an increasingly used tool in the field of prenatal diagnosis. While US remains the first line screening tool, as an adjuvant imaging tool, MRI has been proven to increase diagnostic accuracy and change patient counseling. Further, there are instances when US may not be sufficient for diagnosis. As a multidisciplinary field, it is important that every person involved in the referral, diagnosis, counseling and treatment of the patients is familiar with the basic principles, indications and findings of fetal MRI. The purpose of the current paper is to equip radiologists and non-radiologists with basic MRI principles and essential topics in patient preparation and provide illustrative examples of when fetal MRI may be used. This aims to aid the referring clinician in better selecting and improve patient counseling prior to arrival in the radiology department and, ultimately, patient care.

Prenatal Diagnosis, Management, and Outcome of Fetal Subdural Haematoma: A Case Report and Systematic Review

BACKGROUND

Fetal subdural haematoma (SDH) is associated with poor prognosis.

OBJECTIVE

The conflicting evidence from the literature presents a challenge in prenatal counselling. We present a case study and systematic review of the literature for the management and outcome of fetal SDH.

METHODS

Systematic search of electronic database.

RESULTS

A total 45 cases were extracted from 39 papers. Prenatal ultrasonographic features were intracranial echogenicity (42%), lateral ventriculomegaly (38%), presence of an intracranial mass (31%), macrocephaly (24%), midline deviation of cerebral falx (20%), and intracranial fluid collection (11%). Further secondary features were noted including reversed diastolic flow in the middle cerebral artery (11%), echogenic bowel (4%), hydrops fetalis (2%), and elevated middle cerebral artery peak systolic velocity (2%) (all highly likely to be associated with fetal anaemia). The rates of termination of pregnancy, stillbirth, and neonatal death were 18% (8/45), 16% (7/45), and 11% (5/45), respectively. Overall, therefore, the fetal and perinatal mortality was 32% (12/37). Amongst the 24 survivors with available neurological outcome, 42% (10/24) and 58% (14/24) had abnormal and normal neurological outcome, respectively. Underlying aetiology of fetal SDH was not identified in 47% (21/45). Fetal SDH with an identifiable underlying aetiology was the only factor associated with a higher chance of normal neurological outcome when compared to fetal SDH without a detectable cause (78.5 vs. 21.4%, p = 0.035).

CONCLUSIONS

Stillbirth and neonatal death occurred in a significant proportion of fetal SDH. 58% of survivors had normal neurological outcome, and better prognosis was seen in SDH with identifiable underlying aetiology.

Research Advances of Germinal Matrix Hemorrhage: An Update Review

Germinal matrix hemorrhage (GMH) refers to bleeding that derives from the subependymal (or periventricular) germinal region of the premature brain. GMH can induce severe and irreversible damage attributing to the vulnerable structure of germinal matrix and deleterious circumstances. Molecular mechanisms remain obscure so far. In this review, we summarized the newest preclinical discoveries recent years about GMH to distill a deeper understanding of the neuropathology, and then discuss the potential diagnostic or therapeutic targets among these pathways. GMH studies mostly in recent 5 years were sorted out and the authors generalized the newest discoveries and ideas into four parts of this essay. Intrinsic fragile structure of preterm germinal matrix is the fundamental cause leading to GMH. Many molecules have been found effective in the pathophysiological courses. Some of these molecules like minocycline are suggested active to reduce the damage in animal GMH model. However, researchers are still trying to find efficient diagnostic methods and remedies that are available in preterm infants to rehabilitate or cure the sequent injury. Merits have been obtained in the last several years on molecular pathways of GMH, but more work is required to further unravel the whole pathophysiology.