The document provides an overview of the anatomy of the third ventricle and surgical approaches. It begins with a brief historical review of discoveries related to the ventricles from ancient Greek physicians to the 20th century. It then describes in detail the structures that make up the walls, roof, and floor of the third ventricle. Several surgical approaches for accessing lesions in the third ventricle are outlined, including transventricular, transcallosal, and transcortical approaches. Endoscopic third ventriculostomy is discussed as a treatment for obstructive hydrocephalus, with the optimal entry point and perforation location described. Potential complications of approaches to the third ventricle are also mentioned.

1. ANATOMY OF THIRD VENTRICLE
AND
SURGICAL APPROACHES
DR PRAVEEN K TRIPATHI

2. HISTORICAL REVIEW
 HEROPHILUS(335-280 B.C):First to describe
ventricles
 GALEN(129-200A.D):Described ventricles in
detail,studied the symtoms and signs of
hydrocehalus
 LEONARDO DA VINCI(1452-1519):First wax
casting of ventricles
 WALTER DANDY(1886-1946):First
pneumoencephalography

3. HISTORICAL REVIEW
 First successful endoscopic third ventriculostomy
(ETV) was performed in 1923 by william J. Mixter .
 In 1947, mcnickle described a modified technique of
performing a percutaneous third ventriculostomy
utilizing a 19-gauge needle to puncture the floor of
the third ventricle.
 In 1952, Nulsen and Spitz first reported creation of a
shunt diverting cerebrospinal fluid (csf) from the
ventricular system to the jugular vein.
 1990 Jones Etal reported successful ETV in 24 pt.

4. Third ventricle is a narrow slit-like cavity whose lateral walls are formed by
the thalamus and hypothalamus on either side. At the rostral margin of the
midbrain, the cerebral aqueduct opens into the third ventricle.
4

5. Third Ventricle -ventriculus
tertius
 The third ventricle is a narrow, funnel-shaped,
unilocular midline cavity.
 Slit-like space, lying in the sagittal plane
 It communicates at its anterosuperior margin with
each lateral ventricle through the foramen of monro
and posteriorly with the fourth ventricle through the
aqueduct of sylvius.

6. Neural tube

7. Third Ventricle
 Comprises of:
Anterior wall
Two side walls
Floor
Roof

10. Third Ventricle
 Anterior wall:
lamina terminalis
anterior commissure
 Two side walls:
Thalamus Interthalamic adhesion (60% of
brains)
Hypothalamus Supraoptic nucleus – ADH
Paraventricular nucleus –
Vasopressin/Oxytocin
Subthalamus Subthalamic nucleus

11. The lamina terminalis has been opened.
The chiasmatic recess is located between the lower part of the
lamina terminalis and the posterior part of the optic chiasm.
Anterior wall of the third ventricle

12. The anterior communicating artery commonly passes in front of
the lamina terminalis. Perforating arteries arise from a precallosal
branch of the anterior communicating artery and penetrate the
anterior wall of the third ventricle to reach the columns of the
Anterior wall of the third ventricle

13. The roof
 The roof extends from the foramen of Monro
anteriorly to the suprapineal recess posteriorly
 constituted superiorly to inferiorly by five layers
 the fornix
 the superior membrane of the tela choroidea
 vascular layer located in a space between the
superior and inferior membranes of the tela
choroidea called the velum interpositum
 the inferior membrane of the tela choroidea
 the choroidal plexus of the third ventricle

14. Roof of the third ventricle through a
transchoroidal approach.
1, Head of the caudate nucleus and anterior caudate vein;
2, rostrum of the corpus callosum;
3, column of the fornix;
4, anterior septal vein;
5, foramen of Monro;
6, body of the fornix;
7, thalamostriate vein;
8, inferior membrane of the tela choroidea and choroid plexus of
the third ventricle (the superior membrane of the tela has been
removed);
9, body of the caudate nucleus and thalamostriate vein;
10, dorsal surface of the thalamus;
11, internal cerebral vein and medial posterior choroidal artery;
12, splenium of the corpus callosum.

15. The roof of the ventricle is formed by pia-ependyma, which spans
between the two striae medullaris thalami, situated along the
dorsomedial border of the thalamus.
15

16. In the rostral part of the third ventricle lies an aperture, the
interventricular foramen or foramen of Monro, which is located
between the column of the fornix and the anterior pole of the thalamus.
16

17. Cont..

18. The floor
The floor extends from the
 Anteriorly-optic chiasm
 Posteriorly- to the orifice of the aqueduct of
Sylvius
From anterior to posterior
 The optic and infundibular recesses,
 The tuber cinereum,
 The mamillary bodies,
 The posterior perforated substance,
 The midbrain, and the aqueduct

19. THIRD VENTRICLE

20. CHOROIDAL FISSURE AND CHOROID PLEXUS
 The choroidal fissure is the narrow C shaped
cleft between the fornix and the thalamus along
which the choroid plexus is attached
 The fissure extends from the foramen of Monro
to the choroidal point along the surface of
thalamus
 Choroid plexus continues as two parallel strands
of plexus in the roof of third ventricle

21. Cont..
 Choroidal arteries arise from internal carotid
and posterior cerebral arteries and enter the
ventricles through the choroidal fissure
 Choroid plexus is divided into body,atrial and
temporal parts

22. LESIONS WITHIN THIRD
VENTRICLE
Anterior third ventricle
1. colloid cyst
2. sellar mass
3. sarcoidosis
4. aneurysm
5. hypothalamic glioma
6. histiocytosis
7. meningioma
8. optic glioma
Posterior third ventricle
1. pinealoma
(dysgerminoma)
2. meningioma
3. arachnoid cyst
4. vein of Galen aneurysm

23. (A, foramen of Monro; B, anterior third
ventricle;
C, posterior third ventricle) and relevant
Schematic representation highlighting common
tumor locations

24. THIRD VENTICLE-APPROACHES

25. THIRD VENTRICLE -
APPROACHES

26. THIRD VENTRICLE -
APPROACHES

27. COMBINED TRANSLAMINAR
TRANSCORTICAL

28. Indications
 Transventricular (Wegen’s)–Tumors arising in
corpus callosum and extending to third
ventricle
 Transcallosal (Dandy’s)–Tumor extending to
splenium
 Occipital‐transtentorial ( Popen’s) –Tumor
extending to medial wall of ventricle and in
occipital lobe
 Supracerebellar infratentorial (krause’s) –
Pineal region tumors

29. Approach to Ant. TV tumors
 Subfrontal
 Frontotemporal
 Anterior transcallosal
 Anterior transcortical
 Transsphenoidal

30. Corridors
 Interoptic
 Opticocarotid
 Lamina terminalis
 Transfrontal‐transsphenoidal
 Lamina terminalis‐rostrum of callosum
approach

31. THIRD VENTRICLE -
APPROACHES

32. Corridors For Transcallosal
Approach

33. THIRD VENTRICLE -
APPROACHES

34. Transcortical approach to the
lateral
and third ventricles.
A, the scalp incision
(solid line) and bone flap
(dotted line) are centered
over the middle frontal
gyrus.
B, The cortical opening
exposes the right lateral
ventricle.
C, the third ventricle has
been exposed by opening
the choroidal fissure
along the site of the
attachment of the choroid
plexus to the fornix. This
exposes the internal
cerebral veins and medial
posterior choroidal
arteries in the roof of the

35. TRANSCORTICAL VS
TRANSCALLOSAL PROS

36. TRANSCORTICAL VS
TRANSCALLOSAL CONS

38. Subfrontal approach
 Supine position with head extension
 Coronal flap incision
 Quadrangular craniotomy flush with
 orbital margins
 Frontal sinus exteriorized and packed
 Olfactory nerve divided if necessary

39. Frontotemporal or subtemporal
approach
 Frontotemporal craniotomy
 Dura reflected on sphenoid ridge
 Tumor approached through corridor between
third nerve and carotid.
 Temporal pole can be elevated or resected.

40. Anterior transcallosal approach
Advantages
 –Short trajectory to third ventricle
 –Can access posterior and basal TV
 –Bilateral exposure of foramina of monro
 –No requirement of ventriculomegaly

41. Maneuvers for TV entry
 transforaminal
 Transchoroidal
 Transfornicial

42. Transforaminal
 Gives access to anterior TV
 Foramen of monro identified
 Initial dilatation can be tried
 Incision is made through one column of fornix
at anteriosuperior edge.

43. Transchoroidal
 Entry into the middle of TV
 Opening through the velum interpositum
 Two approaches:
Suprachoroidal
 •Incision in tinea fornicia
Subchoroidal
 •Incision in teniea choroidea

44. Roof of the third ventricle through a
transchoroidal approach.
1, Head of the caudate nucleus and anterior caudate vein;
2, rostrum of the corpus callosum;
3, column of the fornix;
4, anterior septal vein;
5, foramen of Monro;
6, body of the fornix;
7, thalamostriate vein;
8, inferior membrane of the tela choroidea and choroid plexus of
the third ventricle (the superior membrane of the tela has been
removed);
9, body of the caudate nucleus and thalamostriate vein;
10, dorsal surface of the thalamus;
11, internal cerebral vein and medial posterior choroidal artery;
12, splenium of the corpus callosum.

45. Transfornicial
 Identify the septum pellucidum
 Develop a plane between septa.
 Incision is given in the body of fornix not
exceeding 2 cm behind the FM.

46. Complications
 Fornicial injury–Recent memory disturbances
 Vascular compromise–Basal ganglia infarcts
 Thalamic infarcts–Limbic system ischemia
 Hippocampal syndrome

47. Approaches to the post TV tumors
 Transventricular
 Interhemispheric transcallosal
 Occipital transtentorial
 Infratentorial supracerebellar

48. Endoscopy
 Treatement of choice for malignant third
ventricular tumors
 Biopsy of lesion
 Post operative radiotherapy
 Treatment of hydrocephalus

49. CHOICE OF ENDOSCOPIC
ENTRY POINT

50. Indications -ETV

51. FAVOURABLE FACTORS-ETV

53. A, Oblique view showing the endoscope passing through the lateral ventricle and foramen
of Monro and into the third ventricle. B, Sagittal view depicting the perforation of the floor
of the third ventricle. It is important to understand the close relationship of the floor of the
third ventricle to the anterior structures (optic chiasm, infundibulum, and clivus) and
posterior structures (basilar artery and brainstem) to avoid undesired complications.
Schematics demonstrating the surgical trajectory for ETV using a
rigid endoscope

54. LOCATION OF ETV
The location of the opening is chosen:
A. in the midline
B. in the region of the tuber cinereum
(prominence of the base of the hypothalamus,
extending ventrally into the infundibulum and
pituitary stalk)
C. posterior to the infundibular recess
D. anterior to the mammillary bodies
E. anterior to the tip of the basilar artery

55. . A, View of foramen of Monro from right lateral ventricle. The choroid plexus (center), anterior septal vein (medial), and
thalamostriate vein (lateral) are seen. Care must be taken not to damage these structures when entering the foramen of Monro in
order to prevent hemorrhage or venous infarcts.
B, View of the floor of the third ventricle. From anterior to posterior, the optic chiasm, infundibulum, tuber cinereum, paired
mammillary bodies are clearly seen. The basilar artery can also be seen between the mammillary arteries and must be avoided upon
perforation of the third ventricular floor.
Intraoperative views and corresponding schematic
representations

56. showing the thin area in front of the mamillary bodies (yellow arrow)
through which a third ventriculostomy is completed.
FLOOR OF THIRD VENTRICLE

57. ETV

58. COMPLICATIONS

59. THANK YOU
