Brain Ventricular and Cistern Anatomy

Overview

This lecture covers the anatomy of the brain’s ventricular system and identifies major subarachnoid cisterns, focusing on their location, structure, and clinical importance.

Ventricular System Anatomy

• The brain has four ventricles: two lateral, one third, and one fourth ventricle.
• Lateral ventricles are the largest and divided into anterior horn, body, atrium/trigone, occipital horn, and temporal horn.
• The septum pellucidum is a thin membrane separating the lateral ventricles.
• Lateral ventricles connect to the third ventricle via the interventricular foramen (of Monro).
• The third ventricle lies between the thalami and hypothalamus.
• The interthalamic adhesion may be present in some patients, connecting the two thalami.
• The third ventricle connects to the fourth ventricle via the cerebral aqueduct.
• The fourth ventricle is bordered by the pons (anterior) and cerebellum (posterior); it has a diamond shape.
• The fourth ventricle drains into the central canal of the spinal cord and into subarachnoid space via lateral (foramina of Luschka) and median (foramen of Magendie) apertures.

Clinical Relevance of Ventricles

• Abnormal ventricle size can indicate mass effect, increased intracranial pressure, or hydrocephalus.
• Ventricle enlargement in elderly patients often reflects brain atrophy (ex vacuo dilatation).
• Lesion localization near ventricles aids diagnosis.
• Interventricular blood often accumulates in gravity-dependent horns, visible on scans.

Choroid Plexus & CSF Flow

• Cerebrospinal fluid (CSF) is produced by the choroid plexus, found in the temporal horns, body, and third and fourth ventricles.
• No choroid plexus in the anterior or occipital horns.
• CSF circulates from lateral ventricles → third ventricle → fourth ventricle → subarachnoid space → absorbed via arachnoid granulations.

Subarachnoid Cisterns

• Cisterns are expanded subarachnoid spaces where arachnoid peels away from brain surface, often at brain folds.
• Named cisterns facilitate anatomical localization.
• Major cisterns include:
  • Cistern of lamina terminalis (anterior to third ventricle)
  • Suprasellar/chiasmatic cistern (above pituitary/optic chiasm)
  • Interpeduncular cistern (between cerebral peduncles)
  • Ambient cisterns (lateral to midbrain)
  • Quadrigeminal cistern (posterior to midbrain tectum)
  • Superior cerebellar cistern (above cerebellum)
  • Prepontine cistern (anterior to pons)
  • Cerebellopontine cistern (between cerebellum and pons)
  • Pre-medullary and cerebellomedullary cisterns (around medulla)
  • Cisterna magna (largest, near foramen magnum)

Key Terms & Definitions

• Ventricle — fluid-filled cavity in the brain.
• Interventricular foramen (of Monro) — channel connecting lateral to the third ventricle.
• Septum pellucidum — thin partition between lateral ventricles.
• Choroid plexus — tissue producing cerebrospinal fluid.
• Cistern — enlarged subarachnoid space filled with CSF.
• Arachnoid granulation — structure for CSF absorption into the venous system.

Action Items / Next Steps

• Review brain MRI scans to practice identifying ventricles and cisterns.
• Study diagrams showing CSF flow and major cistern locations.
• Prepare questions on ventricular or cistern anatomy for next session.