Anatomy Atlas

Ventricular system and CSF

Systema ventriculare
Also: Lateral ventricles · Third ventricle · Fourth ventricle · Cerebrospinal fluid · CSF · Hydrocephalus · Normal pressure hydrocephalus · Choroid plexus
Space / regionHigh-yielddraftMSK

Four interconnected cavities in the brain that produce and circulate cerebrospinal fluid. Blockage or impaired absorption causes hydrocephalus, including normal pressure hydrocephalus in older adults.

Core anatomy

Location

Within the brain — two lateral ventricles in the cerebral hemispheres, the third ventricle between the thalami, the cerebral aqueduct through the midbrain and the fourth ventricle between the pons/medulla and cerebellum.

Boundaries
lateral ventricles
Frontal horn, body, occipital horn and temporal horn (the hippocampus lies in its floor); the caudate forms the lateral wall of the body
third ventricle
Thalami (lateral walls), hypothalamus (floor), lamina terminalis (front)
fourth ventricle
Pons and medulla (floor, rhomboid fossa), cerebellum (roof)
Contents
  • CSF — about 150 mL total, produced at about 500 mL/day (replaced 3–4 times daily), mainly by the choroid plexus (lateral, third and fourth ventricles)
  • Choroid plexus (ependymal cells over capillaries)
Communications

Lateral ventricles → interventricular foramina (of Monro) → third ventricle → cerebral aqueduct (of Sylvius) → fourth ventricle → median aperture (Magendie) and two lateral apertures (Luschka) → subarachnoid space and cisterns (and the central canal of the cord) → absorbed through arachnoid granulations into the superior sagittal sinus (see dural venous sinuses, cranial meninges and intracranial hemorrhage).

Notes

CSF cushions the brain (buoyancy), removes metabolites and maintains a stable chemical environment. Normal opening pressure on lumbar puncture is about 6–20 cm H₂O (lateral decubitus). verify

Mentioned in

Generated automatically from links in other entries.

Flow of cerebrospinal fluid and the causes of hydrocephalusCerebrospinal fluid is made mainly by the choroid plexus, about 500 mL a day. It flows from the lateral ventricles through the interventricular foramina of Monro into the third ventricle, through the cerebral aqueduct into the fourth ventricle, and out through the median aperture of Magendie and the lateral apertures of Luschka into the subarachnoid space and cisterns. It is absorbed through the arachnoid granulations into the superior sagittal sinus and drains via the transverse and sigmoid sinuses to the internal jugular vein. A block within the ventricular system causes noncommunicating hydrocephalus: a colloid cyst at the foramen of Monro, aqueductal stenosis, or a posterior fossa tumor, Chiari II or Dandy–Walker malformation at the fourth ventricle. Failed absorption at the arachnoid granulations, after subarachnoid hemorrhage or meningitis or in normal pressure hydrocephalus, causes communicating hydrocephalus.Choroid plexusmakes about 500 mL a dayLateral ventriclesThird ventricleFourth ventricleSubarachnoid spaceand cisterns (and central canal)Superior sagittal sinusInternal jugular veinvia the transverse and sigmoid sinusessecretes intoInterventricular foramina (Monro)Cerebral aqueduct (Sylvius)Median (Magendie) and lateral (Luschka) aperturesArachnoid granulationsdrains toColloid cyst of the third ventricle(positional headache, drop attacks)Aqueductal stenosis: lateral and thirdventricles dilated, fourth normalPosterior fossa tumor, Chiari II,Dandy–WalkerAfter subarachnoid hemorrhage ormeningitis; normal pressure hydrocephalusNoncommunicating (obstructive)block inside the ventriclesCommunicatingabsorption fails✕ = where hydrocephalus starts

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Flow of cerebrospinal fluid. Lateral ventricles → foramina of Monro → third ventricle → cerebral aqueduct → fourth ventricle → Magendie and Luschka → subarachnoid space → arachnoid granulations → superior sagittal sinus. A block anywhere inside the ventricles causes noncommunicating (obstructive) hydrocephalus, with the ventricles dilated upstream of the block; failed absorption at the granulations causes communicating hydrocephalus.
Original schematic, created for this atlas.
Cast of the ventricles showing the lateral ventricle with its horns, the interventricular foramen, third ventricle, cerebral aqueduct and fourth ventricle
Cast of the ventricles: lateral, third and fourth ventricles and the cerebral aqueduct.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 736. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))
Lateral view of the brain with the lateral and third ventricles, cerebral aqueduct and fourth ventricle projected onto it
The ventricles projected onto the surface of the brain.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 734. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))

Clinical correlations

Hydrocephalus PANCE

Mechanism / lesion

Noncommunicating (obstructive) — blockage within the ventricles: aqueductal stenosis, tumors (posterior fossa, colloid cyst of the third ventricle), Chiari II/Dandy–Walker. Communicating — impaired absorption at the arachnoid granulations: after subarachnoid hemorrhage or meningitis; normal pressure hydrocephalus.

Classic presentation

Adults: headache (worse in the morning), vomiting, papilledema, declining consciousness, CN VI palsy. Infants: enlarging head circumference, bulging fontanelle, splayed sutures, "sunset eyes" (upgaze palsy). Treat with a ventriculoperitoneal shunt or endoscopic third ventriculostomy; acute cases need an external ventricular drain.

Normal pressure hydrocephalus PANCE

Mechanism / lesion

Communicating hydrocephalus in older adults, often idiopathic; normal opening pressure on LP.

Classic presentation

Triad "wet, wobbly and wacky": urinary incontinence, gait apraxia (magnetic, shuffling, wide-based gait — usually first), and dementia. CT/MRI: ventricles enlarged out of proportion to atrophy. Improvement after large-volume lumbar puncture predicts benefit from a VP shunt — a reversible dementia.

Colloid cyst of the third ventricle

Mechanism / lesion

Benign cyst near the foramen of Monro that can intermittently block CSF outflow.

Classic presentation

Positional headaches, drop attacks and sudden death from acute hydrocephalus.

High-yield PANCE pearls

  • Gait apraxia + incontinence + dementia → NPH → large-volume LP → VP shunt.
  • Infant with rapidly enlarging head, bulging fontanelle and sunset eyes → hydrocephalus → ultrasound through the fontanelle.
  • Hydrocephalus after SAH or meningitis → communicating (arachnoid granulations).
  • CSF path: lateral → Monro → third → aqueduct → fourth → Luschka/Magendie → subarachnoid → arachnoid granulations → superior sagittal sinus.

Imaging anatomy

CT

Noncontrast CT — ventricular size, periventricular edema (transependymal flow), shunt problems.

MRI

MRI — cause of obstruction (aqueductal stenosis, tumor), CSF flow studies, NPH (enlarged ventricles, narrow high-convexity sulci).

Ultrasound

Cranial ultrasound through the anterior fontanelle in infants.

Key views & landmarks
  • Shunt series (X-rays along the tubing) for suspected shunt malfunction

Physical exam

Surface landmarks

Lumbar puncture below the conus — at L3–L4 or L4–L5 (the iliac crests mark about L4; see spinal meninges and spaces).

Strength / function testing

Head circumference (plot on growth charts), fontanelle, fundi (papilledema), gait (NPH: timed walk before and after LP), cognition; examine for shunt malfunction (headache, vomiting, lethargy).

Self-quiz

Q1.

A 74-year-old man has had progressive urinary urgency and incontinence, forgetfulness, and a slow, shuffling gait in which his feet seem stuck to the floor. CT shows enlarged ventricles without proportional sulcal widening. What is the most appropriate next step?

Show answer

B

This is normal pressure hydrocephalus (wet, wobbly, wacky). Clinical improvement after large-volume CSF removal supports a VP shunt, which can reverse symptoms.

Q2.

An MRI shows dilated lateral and third ventricles and a normal-sized fourth ventricle. Where is the obstruction most likely?

Show answer

B

Dilation proximal to the aqueduct (lateral and third ventricles) with a normal fourth ventricle localizes the block to the cerebral aqueduct (aqueductal stenosis).

Q3.

Where is most cerebrospinal fluid produced?

Show answer

C

CSF (about 500 mL/day, about 150 mL at a time) is made mainly by the choroid plexus of the lateral, third and fourth ventricles and absorbed through arachnoid granulations into the superior sagittal sinus.

Q4.

Hydrocephalus after subarachnoid hemorrhage or meningitis is usually caused by what?

Show answer

D

Blood or pus impairs absorption at the arachnoid granulations, causing communicating hydrocephalus. Blocks within the ventricular system cause noncommunicating hydrocephalus.

Q5.

Which finding in an infant suggests hydrocephalus?

Show answer

B

Infant hydrocephalus causes rapidly enlarging head circumference, a bulging fontanelle, splayed sutures and "sunset eyes" (upgaze palsy). Ultrasound through the fontanelle is the first test.

Flashcards

See also