22 wk EGA with “possible proboscis and ACC” by U/S.
Slides 2-3: In addition to the exophytic lesion extending anteriorly between the orbits, there was a prominent csf space posterior to the fully formed cerebellum and ventriculomegaly within the supratentorial compartment.
Slides 4-5: The corpus callosum was present, the globes were small and there was hypertelorism.
Dx: frontonasal cephalocele (info below is from StatDx)
Congenital herniation of meninges, CSF ± brain tissue through mesodermal defect in anterior skull/skull base
Heterogeneous, mixed density mass (variable amounts CSF & parenchyma) extending intracranially through bony defect
Midline frontal: Frontonasal type (FNCeph)
Intranasal: Nasoethmoidal type (NECeph)
Inferomedial orbital: Nasoorbital type (NOCeph)
The ventriculomegaly is most likely due to aqueductal stenosis and there is an arachnoid cyst of the posterior fossa.
General Features – Frontoethmoidal cephaloceles
Prior to 8th week of gestation, 2 potential spaces present
Fonticulus frontalis: Between frontal, nasal bones
Prenasal space: Between nasal bones, developing cartilaginous nasal septum
Anterior neuropore runs in prenasal space, communicating with anterior cranial fossa via foramen cecum
Dural diverticulum protruding through defects may fail to regress
FNCeph: Protrudes through unobliterated fonticulus frontalis
NECeph: Protrudes through foramen cecum into prenasal space
NOCeph: Protrudes into inferomedial orbit through defect in lacrimal/frontal process of maxillary bones
Additional info on Frontoethmoidal cephaloceles
Not linked to neural tube defects like occipital cephaloceles
Siblings have 6% incidence of congenital CNS abnormalities
Intracranial abnormalities (~ 80%)
Callosal hypogenesis & interhemispheric lipomas
Neuronal migration anomalies
Aqueductal stenosis & hydrocephalus
Colloid or arachnoid cysts
Midline craniofacial dysraphisms & hypertelorism