Diagnostic Approach to Macrocephaly in Children

Macrocephaly and Finger Changes: A Narrative Review

Macrocephaly, characterized by an abnormally large head circumference, often co-occurs with distinctive finger changes, presenting a diagnostic challenge for clinicians. This review aims to provide a current synthetic overview of the main acquired and genetic etiologies associated with macrocephaly and finger changes. The genetic cause encompasses several categories of diseases, including bone marrow expansion disorders, skeletal dysplasias, ciliopathies, inherited metabolic diseases, RASopathies, and overgrowth syndromes. Furthermore, autoimmune and autoinflammatory diseases are also explored for their potential involvement in macrocephaly and finger changes. The intricate genetic mechanisms involved in the formation of cranial bones and extremities are multifaceted. An excess in growth may stem from disruptions in the intricate interplays among the genetic, epigenetic, and hormonal factors that regulate human growth. Understanding the underlying cellular and molecular mechanisms is important for elucidating the developmental pathways and biological processes that contribute to the observed clinical phenotypes. The review provides a practical approach to delineate causes of macrocephaly and finger changes, facilitate differential diagnosis and guide for the appropriate etiological framework. Early recognition contributes to timely intervention and improved outcomes for affected individuals.

Diagnostic Pitfalls of Macrocephaly and Intracranial Dural Arteriovenous Fistulas: Connecting the Dots With the Red Flags

Macrocephaly is defined as an abnormal increase in head circumference greater than two standard deviations above the mean for a given age and sex. We present the case of a 16-month-old boy with congenital progressive macrocephaly, who was referred to our hospital for a ventriculoperitoneal shunt placement for external hydrocephalus diagnosed at 13 months of age. The patient had a febrile seizure 12 hours after the shunt was placed and the emergency CT exam revealed collapsed ventricles and a right frontal subdural collection, suggestive of an over-drainage and intracranial hypotension. A subsequent electroencephalogram (EEG) revealed some anomalies, but the patient was discharged two days later due to having no neurological symptoms after being placed on anticonvulsants. The patient returned to the hospital one week later due to recurrent seizures. Further clinical examination revealed prominent and tortuous veins of the skull, palpated in the left occipital region. A thrill and a left carotid murmur were heard during auscultation. A subsequent brain MRI with MR arteriography and venography was performed in search of an explanation for hydrocephaly. The sequences were suggestive of a dural arteriovenous fistula, which was confirmed and then treated using coils during an interventional angiography. A second procedure was performed two months later to complete the embolization, with subsequent imaging follow-ups showing the procedure to have been successful. The measurement of the cranial circumference, its regular evaluation, and its evolution allow a hierarchical diagnosis strategy by distinguishing primary and secondary macrocephaly, progressive or not. Dural arteriovenous fistulas (DAVF) are an under-appreciated cause of macrocephaly, with which they are associated in 35% of cases. Intracranial DAVFs are pathologic shunts between dural arteries and dural venous sinuses, meningeal veins, or cortical veins. Patients with DAVFs may be completely asymptomatic. Symptoms, when present, may range from neurological deficits, seizures, and hydrocephaly to fatal hemorrhage. The symptoms depend on the location and venous and drainage patterns of the DAVF. They can be difficult to identify on routine MRIs unless specifically searched for, especially in cases of technically suboptimal examinations. We aim to give a practical approach to identify the clinical clues that warrant further investigation. Several specific protocols exist regarding the management of macrocephaly and should be followed carefully once a diagnosis has been reached, but further studies are needed to integrate more clinical and neuroimaging findings to permit an early diagnosis.

Fetal macrocephaly: Pathophysiology, prenatal diagnosis and management

Macrocephaly means a large head and is defined as a head circumference (HC) above the 98th percentile or greater than +2SD above the mean for gestational age. Macrocephaly can be primary and due to increased brain tissue (megalocephaly), which in most cases is familial and benign or secondary. The latter may be due to various causes, including but not limited to communicating or non-communicating hydrocephalus, cerebral edema, focal and pericerebral increased fluid collections, thickened calvarium and brain tumors. Megalocephaly can be syndromic or non-syndromic. In the former, gyral and structural CNS anomalies are common. It is important to exercise caution when considering a diagnosis of megalocephaly due to limitations in the accuracy of HC measurement, lack of nomograms for specific populations, inconsistencies between prenatal and postnatal HC growth curves and progression over time. The degree of macrocephaly is important, with mild macrocephaly ≤2.5SD carrying a good prognosis, especially when one of the parents has macrocephaly and normal development. Cases in which the patient history and/or physical exam are positive or when parental HC are normal are more worrisome and warrant a neurosonogram, fetal MRI and genetic testing to better delineate the underlying etiology and provide appropriate counseling.

Cranial vault reduction cranioplasty for severe macrocephaly due to holoprosencephaly and subdural hygroma: a case report

BACKGROUND

Severe macrocephaly can still be found in developing countries. This condition is usually caused by neglected hydrocephalus and can cause a lot of morbidities. Cranial vault reconstruction cranioplasty is the main treatment option for severe macrocephaly. Holoprosencephaly is often seen with features of microcephaly. Hydrocephalus should be considered as the main cause in HPE patients with features of macrocephaly. In this report, we present a rare case of cranial vault reduction cranioplasty procedure in patient with severe macrocephaly due to holoprosencephaly and subdural hygroma.

CASE DESCRIPTION

A 4-year-10-month-old Indonesian boy was admitted with head enlargement since birth. He had a history of VP shunt placement when he was 3 months old. But the condition was neglected. Preoperative head CT showed massive bilateral subdural hygroma that compressed brain parenchyma caudally. From the craniometric calculation, the occipital frontal circumference was 70.5 cm with prominent vertex expansion, the distance between nasion to inion was 11.91 cm and the vertical height was 25.59 cm. The preoperative cranial volume was 24.611 cc. The patient underwent subdural hygroma evacuation and cranial vault reduction cranioplasty. The postoperative cranial volume was 10.468 cc.

CONCLUSION

Subdural hygroma can be a rare cause of severe macrocephaly in holoprosencephaly patients. Cranial vault reduction cranioplasty and subdural hygroma evacuation is still the main treatment option. Our procedure successfully reduces significant cranial volume (57.46% volume reduction).

The Key Aspects of Neonatal and Infant Neurological Examination: The Ballard Score, the Infant's Head with Hydrocephalus and Assessment in a Clinical Setting

The physical examination of the newborn is essential in diagnosing neurological or neurosurgical conditions in the newborn. This article focuses on three clinical assessments of newborns and infants that are especially important if neurological problems are suspected: The Ballard score, the examination of the head in a baby with (suspected) hydrocephalus, and the neurological and developmental evaluation of an infant in an ambulatory setting. A textual description and a link to a video describe each assessment.

Recognizing and managing hydrocephalus in children

ABSTRACT

Hydrocephalus is one of the most common indications for pediatric neurosurgical intervention and is associated with the need for lifelong monitoring. All clinicians should be familiar with the complications that may arise throughout life in these patients so that they can provide timely intervention. This article focuses on the assessment of hydrocephalus, the appropriate diagnostic workup and differential diagnoses, and evidence-based surgical treatments and associated outcomes.

Clinical Manifestations and Outcomes of 20 Korean Hypochondroplasia Patients with the FGFR3 N540K variant

BACKGROUND

Hypochondroplasia is a skeletal dysplasia caused by activating pathologic variants of FGFR3. The N540K variant accounts for 60-70% of reported cases and is associated with severe manifestations. Here, we analyze the clinical manifestations and outcomes of Korean patients with hypochondroplasia harboring the FGFR3 N540K variant.

METHODS

Medical records of 20 unrelated patients with genetically confirmed N540K-related hypochondroplasia were retrospectively reviewed. All individuals were diagnosed with hypochondroplasia by Sanger sequencing for FGFR3, or target-panel sequencing for skeletal dysplasia. The effectiveness of growth hormone therapy was analyzed in 16 patients treated with growth hormones.

RESULTS

Among 20 patients (7 men, 13 women), the mean age at first visit was 3.5±1.0 years, and the mean follow-up duration was 6.8±0.6 years. The patients presented with a short stature and/or short limbs. Genu varum, macrocephaly, and developmental delay were observed in 11 (55.0%), 9 (45.0%), and 5 (25.0%) patients, respectively. Of the 12 patients who underwent neuroimaging, five (41.7%) showed abnormal findings (one required operation for obstructive hydrocephalus). Among 16 growth-hormone-treated patients (two were growth-hormone deficient), the increase in height standard deviation scores was significant after a mean 5.4±0.7 years of treatment (+0.6 and+1.8 using growth references for healthy controls and achondroplasia children, respectively). Four patients underwent surgical limb lengthening at a mean age of 8.8±3.3 years.

CONCLUSIONS

Neurodevelopmental abnormalities are frequently observed in patients with N540K-related hypochondroplasia. Close monitoring of skeletal manifestations and neurodevelopmental status is necessary for hypochondroplasia.

Second trimester fetal MRI of the brain: Through the ground glass

Fetal MRI is an important tool for the prenatal diagnosis of brain malformations and is often requested after second-trimester ultrasonography reveals a possible abnormality. Despite the immature state of the fetal brain at this early stage, early suggestive signs of the presence of brain malformations can be recognized. To differentiate between the normal dynamics of the growing brain and the developing pathological conditions can be challenging and requires extensive knowledge of normal central nervous system developmental stages and their neuroradiological counterparts at those different stages. This article reviews the second-trimester appearances of some commonly encountered brain malformations, focusing on helpful tricks and subtle signs to aid in the diagnosis of such conditions as rhombencephalosynapsis, various causes of vermian rotation, molar tooth spectrum anomalies, diencephalic-mesencephalic junction dysplasia, ganglionic eminence anomalies, and the most common malformations of cortical development.

Subdural Lesions Linking Additional Intracranial Spaces and Chronic Subdural Hematomas: A Narrative Review with Mutual Correlation and Possible Mechanisms behind High Recurrence

The purpose of this study was two-fold. The first was to investigate the pathologic mechanisms underlying the formation of subdural fluid collection, an umbrella term referring to a condition commonly seen in the clinical setting. Accumulation of the cerebrospinal fluid (CSF) in the subdural space can be referred to in this disease category, disregarding the underlying source of the subdural fluid. However, in these two clinical situations, especially after trauma or brain surgery, fluid collection from the subarachnoid space (subdural hygroma) or from the ventricle to the subarachnoid space and infusion into the subdural space (external hydrocephalus), surgical management of critical patients may adopt the strategies of burr-hole, subduroperitoneal shunt, or ventriculoperitoneal shunt, which present distinctly different thoughts. Crucially, the former can be further transformed into chronic subdural hematoma (CSDH). The second significant theme was the pathogenesis of CSDH. Once the potential dural border cell (DBC) layer is separated such as if a wound is formed, the physiological mechanisms that seem to promote wound healing will resume in the subdural space as follows: coagulation, inflammation, fibroblast proliferation, neovascularization, and fibrinolysis. These aptly correspond to several key characteristics of CSDH formation such as the presence of both coagulation and fibrinolysis signals within the clot, neomembrane formation, angiogenesis, and recurrent bleeding, which contribute to CSDH failing to coagulate and absorb easily. Such a complexity of genesis and the possibility of arising from multiple pathological patterns provide a reasonable explanation for the high recurrence rate, even after surgery. Among the various complex and clinically challenging subdural lesions, namely, CSDH (confined to the subdural space alone), subdural hygroma (linked in two spaces), and external hydrocephalus (linked in three spaces), the ability to fully understand the different pathological mechanisms of each, differentiate them clinically, and devote more interventional strategies (including anti-inflammatory, anti-angiogenic, and anti-fibrinolysis) will be important themes in the future.

Establishment of a murine model of congenital toxoplasmosis and validation of a qPCR assay to assess the parasite load in maternal and fetal tissues

Toxoplasma gondii is the causative agent of toxoplasmosis, a disease that affects warm-blooded animals and one third of the human population worldwide. Pregnant women who have never been exposed to the parasite constitute an important risk group, as infection during pregnancy often leads to congenital toxoplasmosis, the most severe form of the disease. Current therapy for toxoplasmosis is the same as it was 50 years ago and has little or no effect when vertical transmission occurs. Therefore, it is urgent to develop new strategies to prevent mother-to-fetus transmission. The implementation of experimental animal models of congenital toxoplasmosis that reproduces the transmission rates and clinical signs in humans opens an avenue of possibilities to interfere in the progression of the disease. In addition, knowing the parasite load in maternal and fetal tissues after infection, which may be related to organ abnormalities and disease outcome, is another important step in designing a promising intervention strategy. Therefore, we implemented here a murine model of congenital toxoplasmosis with outbred Swiss Webster mice infected intravenously with tachyzoites of the ME49 strain of T. gondii that mimics the frequency of transmission of the parasite, as well as important clinical signs of human congenital toxoplasmosis, such as macrocephaly, in addition to providing a highly sensitive quantitative real-time PCR assay to assess parasite load in mouse tissues. As the disease is not restricted to humans, also affecting several domestic animals, including companion animals and livestock, they can also benefit from the model presented in this study.

Rare CNVs and Known Genes Linked to Macrocephaly: Review of Genomic Loci and Promising Candidate Genes

Macrocephaly frequently occurs in single-gene disorders affecting the PI3K-AKT-MTOR pathway; however, epigenetic mutations, mosaicism, and copy number variations (CNVs) are emerging relevant causative factors, revealing a higher genetic heterogeneity than previously expected. The aim of this study was to investigate the role of rare CNVs in patients with macrocephaly and review genomic loci and known genes. We retrieved from the DECIPHER database de novo <500 kb CNVs reported on patients with macrocephaly; in four cases, a candidate gene for macrocephaly could be pinpointed: a known microcephaly gene-TRAPPC9, and three genes based on their functional roles-RALGAPB, RBMS3, and ZDHHC14. From the literature review, 28 pathogenic CNV genomic loci and over 300 known genes linked to macrocephaly were gathered. Among the genomic regions, 17 CNV loci (~61%) exhibited mirror phenotypes, that is, deletions and duplications having opposite effects on head size. Identifying structural variants affecting head size can be a preeminent source of information about pathways underlying brain development. In this study, we reviewed these genes and recurrent CNV loci associated with macrocephaly, as well as suggested novel potential candidate genes deserving further studies to endorse their involvement with this phenotype.

Research models of neurodevelopmental disorders: The right model in the right place

Neurodevelopmental disorders (NDDs) are a heterogeneous group of impairments that affect the development of the central nervous system leading to abnormal brain function. NDDs affect a great percentage of the population worldwide, imposing a high societal and economic burden and thus, interest in this field has widely grown in recent years. Nevertheless, the complexity of human brain development and function as well as the limitations regarding human tissue usage make their modeling challenging. Animal models play a central role in the investigation of the implicated molecular and cellular mechanisms, however many of them display key differences regarding human phenotype and in many cases, they partially or completely fail to recapitulate them. Although in vitro two-dimensional (2D) human-specific models have been highly used to address some of these limitations, they lack crucial features such as complexity and heterogeneity. In this review, we will discuss the advantages, limitations and future applications of in vivo and in vitro models that are used today to model NDDs. Additionally, we will describe the recent development of 3-dimensional brain (3D) organoids which offer a promising approach as human-specific in vitro models to decipher these complex disorders.

Complex Autism Spectrum Disorder with Epilepsy, Strabismus and Self-Injurious Behaviors in a Patient with a De Novo Heterozygous POLR2A Variant

Autism spectrum disorder (ASD) describes a complex and heterogenous group of neurodevelopmental disorders. Whole genome sequencing continues to shed light on the multifactorial etiology of ASD. Dysregulated transcriptional pathways have been implicated in neurodevelopmental disorders. Emerging evidence suggests that de novo POLR2A variants cause a newly described phenotype called ‘Neurodevelopmental Disorder with Hypotonia and Variable Intellectual and Behavioral Abnormalities’ (NEDHIB). The variable phenotype manifests with a spectrum of features; primarily early onset hypotonia and delay in developmental milestones. In this study, we investigate a patient with complex ASD involving epilepsy and strabismus. Whole genome sequencing of the proband−parent trio uncovered a novel de novo POLR2A variant (c.1367T>C, p. Val456Ala) in the proband. The variant appears deleterious according to in silico tools. We describe the phenotype in our patient, who is now 31 years old, draw connections between the previously reported phenotypes and further delineate this emerging neurodevelopmental phenotype. This study sheds new insights into this neurodevelopmental disorder, and more broadly, the genetic etiology of ASD.

Refining the Phenotypic Spectrum of KMT5B-Associated Developmental Delay

The role of lysine methyltransferases (KMTs) and demethylases (KDMs) in the regulation of chromatin modification is well-established. Recently, deleterious heterozygous variants in KMT5B were implicated in individuals with intellectual disability (ID) and/or autism spectrum disorder. We describe three unrelated patients with global developmental delay (GDD) or ID, macrocephaly and additional features. Using whole exome sequencing, each of the probands was found to harbor a distinct de novo heterozygous disease-causing variant in KMT5B: c.541C > G (p.His181Asp); c.833A > T (p.Asn278Ile); or c.391_394delAAAG (p.Lys131GlufsTer6). We discuss herein their clinical presentations, and compare them to those of previously reported patients. Furthermore, using a three-dimensional computational model of the KMT5B protein, we demonstrate the predicted structural effects of the two missense variants. Our findings support the role of de novo missense and nonsense variants in KMT5B-associated GDD/ID, and suggest that this gene should be considered in the differential diagnosis of neurodevelopmental disorders accompanied by macrocephaly and/or overgrowth.