The fourth ventricle is a midline cavity located between the cerebellum and brainstem. It has a roof, floor, and two lateral recesses. The roof is tent-shaped and expands laterally, consisting of superior and inferior parts formed by neural and membranous structures respectively. The floor is rhomboid-shaped and formed by the brainstem. It is divided into pontine, junctional, and medullary parts by sulci. Choroid plexuses project into the ventricle from its walls.

1. THE FOURTH VENTRICLE
Dr Sreenath
Dept of Neurosurgery

2. Structures of Post fossa

3. 4th v
• broad, tent-shaped midline
cavity
• between the cerebellum
and the brainstem
• connected rostrally through
the aqueduct with the third
ventricle
• caudally through the
foramen of Magendie with
the cisterna magna
• laterally through the
foramina of Luschka with
the cerebellopontine
angles.

5. • roof, a floor, and two lateral
recesses.
• ventral to the cerebellum
• dorsal to the pons and
medulla
• medial to the cerebellar
peduncles.
• roof is tent-shaped, expands
laterally and posteriorly.
• superior and inferior parts.
• inferior part is formed largely
by thin membranous layers
• superior part is formed by
thicker neural structures.

6. • The three fissures formed by the
embryological folding of the cerebellum
around the brainstem
• 1.the cerebellomesencephalic fissure.
• 2.the cerebellopontine fissure.
• 3.the cerebellomedullary fissure.
Each fissure communicates with the adjacent
fissure.

7. cerebello mesencephalic fissure

8. cerebellomedullary fissure

9. cerebellopontine fissure

10. • A major cerebellar artery and vein course in
each fissure.
1.The superior cerebellar artery (SCA) and the
vein course within the cerebello
mesencephalic fissure
2.the anteroinferior cerebellar artery (AICA) and
the vein related to the cerebellopontine
fissure
3.the posteroinferior cerebellar artery (PICA)
and the vein cerebellomedullary fissure

12. Upper ventricular roof
• A single median and two lateral parts
• The median part- superior medullary velum
• The lateral parts (also referred to as the lateral
walls)- the inner surface of the cerebellar
peduncles.
• The superior medullary velum is a thin lamina
of white matter

13. Lower roof

14. Roof

15. LATERAL RECESS
• narrow, curved pouches
formed by the union of
the roof and the floor.
• extend laterally below
the cerebellar
peduncles and open
through the foramina of
Luschka into the
cerebellopontine angles

17. CHOROID PLEXUS
• composed of two inverted L-shaped fringes that
arise on the ventricular surface of the tela
choroidea and are located on each side of the
midline
• letter T, the vertical limb is double.
• Each medial segment is subdivided into rostral or
nodular part and a caudal or tonsillar part
• Each lateral segment is subdivided into a medial
or peduncular part and a lateral or floccular part.

20. FLOOR
• brainstem forms the fourth ventricular floor.
• composed of the mesencephalon, pons, and medulla
• The floor has a rhomboid shape
• rostral two-thirds of the floor is posterior to the pons
and the caudal one-third is posterior to the medulla.
• Its cranial apex is at the level of the cerebral aqueduct;
its caudal tip, the obex, is located at the rostral end of
the remnant of the spinal canal, anterior to the foramen
of Magendie; and its lateral angles open through the
lateral recesses and foramina of Luschka into the
cerebellopontine angles.

21. • three parts:
• a superior or pontine
part,
• an intermediate or
junctional part,
• and an inferior or
medullary part.

22. • symmetrical halves by the median sulcus.
• The sulcus limitans divides each half of the
floor into a raised median strip, called the
median eminence and a lateral region called
the vestibular area.
• feather or pen nib configuration- the calamus
scriptorius.