Review of the MRI brain findings of septo-optic dysplasia

Prenatally Diagnosed Absent Septum Pellucidum and Septo-Optic Dysplasia: A Narrative Review and Practical Recommendations for Pediatric Neurologists

Evaluation of the cavum septum pellucidum is required in standard second-trimester screening fetal anatomy ultrasound scans. The absence of septum pellucidum triggers further evaluation and referral for subspecialty counseling. Absence of septum pellucidum is linked to other midline anomalies including septo-optic dysplasia. The purpose of this narrative review on absent septum pellucidum and septo-optic dysplasia is to discuss the literature, including pre- and postnatal management and neurodevelopmental outcome, provide practical recommendations, and outline research gaps to advance this nascent field.

Sonographic visualization and measurement of the fetal optic chiasm and optic tract and association with the cavum septum pellucidum

OBJECTIVES

To assess the sonographic visualization of the fetal optic chiasm (OC) and optic tracts (OTs), establish mid-trimester reference values, and assess the relationship between OC and OT dimensions and cavum septum pellucidum (CSP) measurements.

METHODS

This prospective cross-sectional study included 154 morphologically normal fetuses between 19 and 23 weeks of gestation. The diameters of the fetal OC and OTs were measured using two-dimensional transabdominal ultrasound in a transventricular axial section angled approximately 20-40° caudally. CSP length as well as anterior, middle, and posterior widths were measured by placing the cursor on the inner surfaces in the transventricular section. The average CSP width was included in the analysis.

RESULTS

The OC and OTs were successfully visualized in 109 fetuses and included in the analysis. Visualization success in transabdominal axial sections at 19-23 weeks was 70.8 %, with high intraobserver and interobserver reproducibility. Additionally, visualization rates were higher in advanced gestational weeks and in fetuses with breech presentation (p=0.007 and p=0.017, respectively). OC and OT dimensions were positively correlated with CSP length and width, biparietal diameter (BPD), head circumference (HC), and gestational age (p<0.05, for all).

CONCLUSIONS

The OC and OTs were successfully visualized transabdominally in axial sections with high intraobserver and interobserver reproducibility. Additionally, OC and OT dimensions were positively correlated with gestational age, as well as with BPD, HC, and CSP measurements.

Septo-optic dysplasia plus: A case report for reviewing and recognizing this condition

Septo-optic dysplasia is a congenital neurological condition with multifactorial etiology, characterized by septum pellucidum agenesis and/or corpus callosum dysgenesis, hypoplasia of the chiasm or optic nerves, and hormonal dysfunction with pituitary or hypothalamic alterations. Diagnosis requires two of these criteria and magnetic resonance is the imaging test of choice. Most cases present with abnormalities of cortical development in the form known as septo-optic dysplasia plus. While seizures and neurodevelopmental disorders are the dominant neurological manifestations, this entity is highly heterogeneous and has multiple clinical and radiological findings to consider. We present the case of a 35-year-old man with a history of cranioencephalic trauma in childhood and remission for refractory focal epilepsy associated with cognitive deficit. During the initial examination, the simple cranial tomography showed septum pellucidum agenesis and corpus callosum dysgenesis. Brain magnetic resonance imaging revealed agenesis of the septum pellucidum, irregularity and anomalous thickening of the cerebral cortex in frontal lobes and perisylvian region, heterotopic gray matter in frontal lobes and left fronto-insular region, mild supratentorial ventriculomegaly, atypical appearance of the corpus callosum rostrum, and hypoplasia of the chiasm and optic nerves. Although agenesis of the septum pellucidum was the key finding in this case, it is not present in all patients. The relevance of magnetic resonance imaging for the detailed evaluation of other involved structures, highlighting optic nerve hypoplasia, is fundamental in the radiologist’s diagnostic workup and this entity recognition.

Optic Nerve Hypoplasia - Case Report

The case report of a young myope (born in 1997) who was diagnosed with bilateral concentric narrowing of the visual field to 15-20 degrees in 2021 is presented. On eye fundus, the findings were normal with central excavation c/d=0.5 and 0.4, respectively. OCT showed loss of retinal nerve fiber layer - in both vertical quadrants, including a reduction in the ganglion cell complex. Electrophysiological examination (PERG) showed normal retinal responses. Visual evoked responses (PVEP) after stimulation squared a 1 degree decrease in amplitudes, with no prolongation of P100 latency. When stimulated with 15-minute squares, responses were normal (see Supplementary Figure). Magnetic resonance imaging of the brain showed a narrowing of the chiasm. In conclusion, optic chiasm hypoplasia may not always have distinct morphological and functional manifestations. In addition to imaging methods, electrophysiological examination of the visual analyser was of great help for its verification.

Prenatal Imaging of Supratentorial Fetal Brain Malformation

This review article provides a comprehensive overview of fetal MR imaging in supratentorial cerebral malformations. It emphasizes the importance of fetal MR imaging as an adjunct diagnostic tool used alongside ultrasound, improving the detection and characterization of prenatal brain abnormalities. This article reviews a spectrum of cerebral malformations, their MR imaging features, and the clinical implications of these findings. Additionally, it outlines the growing importance of fetal MR imaging in the context of perinatal care.

A Novel De novo Heterozygous Mutation in the SON Gene Associated with Septo-optic Dysplasia: A New Phenotype

Septo-optic dysplasia (SOD) syndrome is a rare congenital disorder characterized by a classic triad of optic nerve/chiasm hypoplasia, agenesis of septum pellucidum and corpus callosum, and hypoplasia of the hypothalamic-pituitary axis.Herein, we report the clinical case of 2-year-old boy presenting with psychomotor delay, nystagmus, congenital hypothyroidism, and a clinically relevant growth delay. The neuroradiological examination showed partial segmental agenesis of the corpus callosum, agenesis of the septum pellucidum, optic nerve hypoplasia, and a small pituitary gland with a small median pituitary stalk. A whole-exome sequencing analysis detected a novel heterozygous de novo variant c.1069_1070delAG in SON, predicted as likely pathogenic.To date, SON pathogenic variants have been described as responsible for Zhu-Tokita-Takenouchi-Kim (ZTTK) syndrome, a multisystemic neurodevelopmental disorder mainly characterized by intellectual disability, facial dysmorphisms, visual abnormalities, brain malformations, feeding difficulties, and growth delay. The herein described case is the first recognized clinic-radiological occurrence of SOD syndrome with hypothalamic-pituitary dysfunction in a patient carrying a SON gene variant, considered responsible of ZTTK syndrome, suggesting a possible relationship between SOD and SON gene alterations, never described so far, making the search for SON gene mutations advisable in patients with SOD.

Neuroimaging Features in Children with Optic Nerve Hypoplasia and Septo-Optic-Pituitary Dysplasia

BACKGROUND

Optic nerve hypoplasia (ONH) and septo-optic-pituitary dysplasia (SOD) are common causes of congenital visual impairment. Our primary aim was to investigate the prevalence of abnormal neuroimaging features in patients with these disorders in Manitoba, Canada, and compare them with published reports.

METHODS

A retrospective neuroimaging review was performed in patients resident in Manitoba with ONH/SOD.

RESULTS

There were 128 patients (M = 70) with ONH/SOD who had neuroimaging. Their mean age (SD) at the end of the study was 13.2 (7.5) years. Males were significantly more likely to have bilateral ONH and a small optic chiasm size, while females were more likely to have a left ONH and a small left optic chiasm size on neuroimaging (p = 0.049). ONH and small optic chiasm size were seen in most patients on neuroimaging. Absent septum pellucidum was noted in 40%, small pituitary gland size in 28%, neuronal migration disorders (NMD) in 20% (>1 type and bilateral in 13 cases), corpus callosum abnormalities were present in 9%, while olfactory bulbs-tracts and olfactory sulci were absent in 8.6% of cases. Unilateral ONH was not significantly associated with other structural brain abnormalities, while NMD were significantly associated with other midline brain abnormalities including a symmetrically small optic chiasm size.

CONCLUSION

The prevalence of structural neuroimaging abnormalities in our cohort with ONH/SOD was generally in the same range reported in other studies with corpus callosum abnormalities being relatively less common in our study. Bilateral NMD were relatively common among patients with NMD. The association between sex and ONH laterality requires further study.

Septo-optic dysplasia associated with chromosome 15q13.3 duplication: a case report

Septo-optic dysplasia (SOD) is a rare congenital anomaly that is clinically defined by developmental delay and characteristic brain magnetic resonance imaging findings, including optic nerve hypoplasia, pituitary hormone abnormalities, and midline brain defects. The occurrence of SOD is generally sporadic; however, it can be inherited rarely. Although an association with HESX1, SOX2, and SOX3 mutations has been identified, the detailed etiology is multifactorial and unclear. Here, we present the case of a 7-year-old girl who was clinically diagnosed with SOD and 15q13.3 duplication. Patients with duplication at chromosome 15q13.3 were reported to be diagnosed with autism spectrum disorder, epilepsy, and schizophrenia in previous studies. The relationship between SOD and the microduplication of 15q13.3 has not yet been explored. In this study, we suggest that there may be an association between chromosome 15q13.3 microduplication and SOD.

Role of Fetal Magnetic Resonance Imaging in Differentiating Isolated Septal Agenesis from Septo-Optic Dysplasia: Case Study and Review

INTRODUCTION

The detection of absent septi pellucidi (ASP) during obstetric ultrasound is a rare event. However, the clinical implications of this finding are significant. ASP can be associated with severe central nervous system anomalies such as holoprosencephaly, agenesis/dysgenesis of the corpus callosum, schizencephaly, severe ventriculomegaly, and open neural tube defects. In such cases, the prognosis is poor. When no such anomalies are identified, isolated ASP usually carries a good prognosis. However, some fetuses thought to have isolated ASP actually have septo-optic dysplasia (SOD), which is associated with optic nerve hypoplasia, hypothalamic-pituitary dysfunction, and developmental delay.

CASE PRESENTATION

A case in which fetal 3.0 Tesla magnetic resonance imaging (MRI) was considered crucial to definitively diagnose isolated ASP is presented. A review of the literature was conducted and analyzed to determine the role of MRI in the evaluation of fetuses with ASP, with special consideration on the differential diagnosis between isolated ASP and SOD.

CONCLUSION

Differentiating isolated ASP from SOD is imperative for adequate prenatal counseling. Unfortunately, making a prenatal diagnosis of SOD requires visualization and evaluation of the fetal optic nerves, chiasm, and pituitary gland, which is very demanding and not always possible using ultrasound. Fetal MRI has the potential of obtaining high-quality images of the fetal brain, and therefore this technique can be used for establishing the differential diagnosis in utero.

Genetic heterogeneity in corpus callosum agenesis

The corpus callosum is the largest white matter structure connecting the two cerebral hemispheres. Agenesis of the corpus callosum (ACC), complete or partial, is one of the most common cerebral malformations in humans with a reported incidence ranging between 1.8 per 10,000 livebirths to 230–600 per 10,000 in children and its presence is associated with neurodevelopmental disability. ACC may occur as an isolated anomaly or as a component of a complex disorder, caused by genetic changes, teratogenic exposures or vascular factors. Genetic causes are complex and include complete or partial chromosomal anomalies, autosomal dominant, autosomal recessive or X-linked monogenic disorders, which can be either de novo or inherited. The extreme genetic heterogeneity, illustrated by the large number of syndromes associated with ACC, highlight the underlying complexity of corpus callosum development. ACC is associated with a wide spectrum of clinical manifestations ranging from asymptomatic to neonatal death. The most common features are epilepsy, motor impairment and intellectual disability. The understanding of the genetic heterogeneity of ACC may be essential for the diagnosis, developing early intervention strategies, and informed family planning. This review summarizes our current understanding of the genetic heterogeneity in ACC and discusses latest discoveries.

Presentation and diagnosis of childhood-onset combined pituitary hormone deficiency: A single center experience from over 30 years

BACKGROUND

Childhood-onset combined pituitary hormone deficiency (CPHD) has a wide spectrum of etiologies and genetic causes for congenital disease. We aimed to describe the clinical spectrum and genetic etiologies of CPHD in a single tertiary center and estimate the population-level incidence of congenital CPHD.

METHODS

The retrospective clinical cohort comprised 124 CPHD patients (48 with congenital CPHD) treated at the Helsinki University Hospital (HUH) Children's Hospital between 1985 and 2018. Clinical data were collected from the patient charts. Whole exome sequencing was performed in 21 patients with congenital CPHD of unknown etiology.

FINDINGS

The majority (61%;76/124) of the patients had acquired CPHD, most frequently due to craniopharyngiomas and gliomas. The estimated incidence of congenital CPHD was 1/16 000 (95%CI, 1/11 000-1/24 000). The clinical presentation of congenital CPHD in infancy included prolonged/severe neonatal hypoglycaemia, prolonged jaundice, and/or micropenis/bilateral cryptorchidism in 23 (66%) patients; despite these clinical cues, only 76% of them were referred to endocrine investigations during the first year of life. The median delay between the first violation of the growth screening rules and the initiation of GH Rx treatment among all congenital CPHD patients was 2·2 years, interquartile range 1·2-3·7 years. Seven patients harbored pathogenic variants in PROP1, SOX3, TBC1D32, OTX2, and SOX2, and one patient carried a likely pathogenic variant in SHH (c.676G>A, p.(Ala226Thr)).

INTERPRETATION

Our study suggests that congenital CPHD can occur in 1/16 000 children, and that patients frequently exhibit neonatal cues of hypopituitarism and early height growth deflection. These results need to be corroborated in future studies and might inform clinical practice.

FUNDING

Päivikki and Sakari Sohlberg Foundation, Biomedicum Helsinki Foundation, and Emil Aaltonen Foundation research grants.