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Topic

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Fetal lateral ventricle

The fetal lateral ventricles are paired, C-shaped cavities within the cerebral hemispheres that contain cerebrospinal fluid (CSF). They are the largest ventricles of the developing brain and play a key role in fetal neurodevelopment. Their size, symmetry, and morphology are critical markers in prenatal imaging, as abnormalities may reflect hydrocephalus, malformations, or brain injury.

The ventricles are proportionally larger in the fetus than after birth, reflecting the active production and circulation of CSF and the delayed growth of surrounding cerebral parenchyma.

Synonyms

  • Fetal cerebral ventricles

  • Lateral ventricles of the fetal brain

  • Ventricular system (anterior horns/body/temporal horns/occipital horns)

Structure and Development

  • Components: Each lateral ventricle consists of:

    • Frontal (anterior) horn

    • Body

    • Temporal (inferior) horn

    • Occipital (posterior) horn

  • Choroid plexus: Prominent structure within the ventricle, responsible for CSF production

  • Developmentally, ventricles form from the cavity of the neural tube and enlarge during gestation. By mid-gestation, ventricular size stabilizes while brain parenchyma continues to grow.

Relations

  • Medially: Septum pellucidum, corpus callosum, and fornix

  • Laterally: Caudate nucleus (head and body)

  • Inferiorly: Thalamus and hippocampus (at temporal horn)

  • Posteriorly: Occipital lobe white matter

Function

  • Reservoir for cerebrospinal fluid (CSF)

  • Maintains a stable chemical environment for brain development

  • Cushions the developing brain against trauma

  • Reflects brain growth and maturation (ventricle-to-brain ratio is a marker of normal development)

Clinical Significance

  • Ventriculomegaly: Enlargement (>10 mm atrial width) may be isolated or associated with anomalies

  • Hydrocephalus: Progressive dilatation due to obstruction or impaired absorption of CSF

  • Hemorrhage: May occur in germinal matrix, extending into ventricles

  • Infections: TORCH infections may cause ventricular dilatation or intraventricular debris

  • Imaging relevance: Measurement of lateral ventricles is a standard part of fetal neurosonography and MRI

MRI Appearance

T2 HASTE (T2 GRE):

  • CSF within ventricles: very bright hyperintense signal

  • Ventricular walls: thin hypointense margin

  • Choroid plexus: intermediate to hypointense relative to CSF, often appearing as dark frond-like structures inside ventricles

  • Enlarged ventricles: exaggerated bright cavities, easily detected

T1 GRE:

  • CSF: dark/low signal intensity

  • Ventricular walls: thin hypointense line

  • Choroid plexus: intermediate to mildly hyperintense relative to CSF

  • Hemorrhage/proteinaceous debris: bright hyperintense foci within otherwise dark fluid

MRI image

Fetal fourth ventricle MRI image