Ventriculomegaly (VM) is the fetal central nervous system (CNS) anomaly most commonly represented in prenatal imaging. It is defined as a lateral ventricle of dimensions greater than or equal to 10 mm; it can be unilateral or bilateral. More generally, hydrocephalus is defined as an imbalance between brain parenchyma and cerebrospinal fluid (CSF) due to an abnormal increase of the latter within the ventricles in an almost bilateral manner. To identify ventriculomegaly and categorize its severity, the appropriate imaging and measurement methods are crucial. Clinical outcomes vary greatly because of the wide differential diagnosis. Furthermore, there is a significant chance that these causes may recur in subsequent pregnancies. Pregnancy care and counseling depend on a precise diagnosis of the underlying cause. We retrospectively reviewed our institutional fetal MR imaging database (4568 examinations) from 2005 until 2024. We focused on obstructive hydrocephalus and, according to rigorous inclusion/exclusion criteria (Table 1), we enrolled 201 cases. We analyzed isolated aqueduct stenosis (36.3%); hemorrhagic events (30.3%); rhombencephalosynapsis (7.5%); dural sinus malformation (6%); midline cysts (5.4%); diencephalic-mesencephalic junction (DMJ) dysplasia (3.5%); infectious lesions (3%); tumors (2.5%); Chiari 1 (1.5%); Walker Warburg disease (1%); not otherwise specified (3%). We discuss the different etiologies of obstructive hydrocephalus in our population and propose an etiology-based approach that allows the clinician and radiologist to reach the correct differential diagnosis and provide an indication for possible fetal surgery. Hydrocephalus arises from embryological abnormalities or acquired insults, requiring precise neuroimaging for diagnosis and management. A thorough imaging approach aids in etiological diagnosis, surgical planning, and essential counseling.

Cerebellar infarct resembling Lhermitte-Duclos disease (LDD) is a rare case scenario. LDD being a rare, slowly growing cerebellar tumor is generally characterized by headaches, ataxia, cranial nerve palsies, and impaired cerebellar symptoms. Primarily diagnosed with a magnetic resonance imaging, the lesion has several differential diagnoses, including vascular malformation with cerebellar venous congestion, rhombencephalosynapsis, cerebellar dysplasia, and medulloblastoma. In unusual instances, a cerebellar stroke may mimic LDD, potentially leading to a delay in management. We present a case of a 49-year-old female with complaints of headache and vomiting for 5 days with no previous similar history. Based on the initial impression and classical imaging findings, LDD was diagnosed, and she was managed conservatively. Even though the majority of patients with LDD develop the disease over a course of time, some cases have been reported to show acute presentation. However, on worsening of symptoms, with extension of lesion on repeat imaging, an emergency craniotomy was performed, and biopsy revealed an acute infarct with hemorrhagic transformation. Various neurological conditions can imitate LDD and vice versa. We recommend that a cerebellar stroke should be ruled out when encountering with a radiological diagnosis of LDD, to avoid critical delays in the management of stroke.

CEBALID syndrome (Craniofacial defects, dysmorphic Ears, Brain Abnormalities, Language delay, and Intellectual Disability) is caused by C-terminal truncated transcriptional activator MN1. This novel syndrome characterized by neurodevelopmental delay, craniofacial anomalies, and partial rhombencephalosynapsis was recently identified in 2020. Since then, less than 30 cases have been reported worldwide. None of the reported cases described an association of arthrogryposis with CEBALID syndrome. Below we present the first reported case in Lebanon with an associated arthrogryposis at birth. A case of a late preterm newborn girl admitted to the neonatal intensive care unit for multiple joint contractures and facial dysmorphology. In addition, the patient had poor extra-uterine cardiopulmonary adaptation that required mechanical ventilation, and feeding difficulties were noted with hypotonicity. The maternal history revealed two prior abortions. Brain magnetic resonance imaging (MRI) was done for the newborn and revealed polymicrogyri, agenesis of the genu of the corpus callosum and rhombencephalosynapsis. Whole exome sequencing confirmed the diagnosis of CEBALID syndrome which was the underlying cause of the complex of malformations, with novel presentation as arthrogryposis. Genetic counselling was recommended for the parents for future pregnancies and supportive medical care was given to the patient. Multiple congenital anomalies, along with repetitive abortions that were present in the maternal history, suggested the presence of genetic background. Multi-disciplinary approach is very important in cases with complex malformations and whole exome sequencing helped establish the diagnosis. Rarity of the case led to absence of clear guidelines in management which made supportive treatment the best approach available.

Fetal neurology addresses counselling parents on the clinical significance of brain anomalies encountered in their fetus, including disruptive lesions (i.e. stroke, periventricular haemorrhagic infarction, and infection), and genetically based cortical (i.e. hemimegalencephaly, lissencephaly, cobblestone malformation, polymicrogyria, heterotopia) or posterior fossa anomalies (i.e. cerebellar agenesis and hypoplasia, rhombencephalosynapsis, Dandy-Walker syndrome, mega cisterna magna, Blake's pouch cyst). Unlike paediatric neurologists, fetal neurologists cannot examine the infant directly so they diagnose and prognosticate using imaging and other diagnostic studies. The integration of fetal neurologists into fetal multidisciplinary teams is essential for providing expert counselling and cohesive care. This review emphasizes the need for specialized training, multidisciplinary collaboration, and the development of comprehensive service designs to ensure consistent and effective care for families. Additionally, it emphasizes the critical role of fetal neurologists in identifying brain anomalies early and providing thorough counselling to parents, helping them to understand the prognosis, potential interventions, and long-term outcomes for their unborn child.

Mesencephalosynapsis is characterized by a failure of the dorsal brainstem colliculi to separate into distinct lateral masses (non-cleavage, a.k.a. "fusion"). It is linked to ventriculomegaly and aqueductal stenosis but other associations have not been systematically examined. We reviewed a large cohort of fetal hydrocephalus cases to explore associations of aqueductal stenosis, mesencephalosynapsis, and other pathologies. Among 115 cases of fetal obstructive hydrocephalus (15-41 weeks gestation), mesencephalosynapsis was seen in 44 cases (38.3%). We graded the wide range of abnormal aqueductal histology; mesencephalosynapsis was associated with 67% of severe, 35% of mild, and 10% of borderline aqueductal pathologies. In 75% of cases, it was associated with other CNS anomalies, including rhombencephalosynapsis, holoprosencephaly, hemifacial microsomia, and amniotic rupture sequence. We also identified 2 cases of aqueductal stenosis associated with brainstem tegmental injury, probably ischemic in origin, without mesencephalosynapsis. Clinical and genetic associations of mesencephalosynapsis included diabetic embryopathy, amniotic rupture sequence, chromosomal abnormalities, and mutations in TBCD132, FRAS1, and NECTIN1. This is the largest review of the histology of fetal aqueductal stenosis to date. We conclude that mesencephalosynapsis points to a defect in embryonic brainstem patterning and may be isolated, associated with other malformations, and that it is found in heritable and non-heritable conditions.