The document discusses the surgical anatomy of the third ventricle, highlighting its complex structure and relation to surrounding neural elements, which presents challenges for access during interventions. It describes the anatomical features, including walls and connections to neighboring ventricles, as well as common lesions and various surgical approaches with their respective advantages and disadvantages. Specific concerns regarding possible collateral damage to critical structures during approaches to the third ventricle are also noted.

1. SURGICAL ANATOMY OF THIRD
VENTRICLE
DR PARTHA SARATHI MONDAL
SENIOR RESIDENT
NEUROSURGERY

2. CONCERNS
• IT IS LOCATED AT THE CORE OF THE CRANIUM
AND DIFFICULT TO ACCESS.
• IT IS SURROUNDED BY CRITICAL NEURAL
ELEMENTS.
• LESIONS OF THIRD VENTRICLE ARE NOT
UNCOMMON

3. VENTRICULAR SYSTEM

4. GROSS ANATOMY
• Funnel shaped unilocular
narrow midline cavity.
• Connected laterally to lateral
ventricles by means of
Foramen of Monro and
caudally to 4th ventricle by
means of Aqueduct of sylvius.
• Possesses a roof, a floor,
anterior wall, posterior wall
and two lateral walls.

5. RELATIONS
• Anterior wall
-Foramen of Monro
-Anterior Commissure
-Lamina Terminalis
-Optic chiasma
• Posterior wall
-Suprapineal rescess(4)
-Habenular commissure
-Pineal recess(5) & gland
-Posterior commissure
-Aqueduct of sylvius

6. RELATIONS-cont
• Floor
-Optic Chiasma & recess
- Infundibulum & recess
-Pituitary gland
-Tuber cinereum
-Mamillary bodies
-Posterior perforated subs
Tegmentum of midbrain
• Roof
-Body of fornix
-Tella choroidea
-Crura of fornix
- Hippocampal commissure

7. LATERAL WALLS
• Stria medullaris thalami
• Medial surface of
thalamus and
hypothalamus with
hypothalamic sulcus in
between.
• Interthalamic
adhesions(seen in 75%)

8. MICROSURGICAL ANATOMY

9. ROOF
-Extending from foramen of Monro anteriorly to
suprapineal recess posteriorly.
-Consists of four layers: fornix, outer tela ch,
vascular layer, inner tela ch from out to inward
-Tela ch- thin translucent membranes derived from
pia
- Vascular layer enclosed in a space called velum
interpositum in between two layers of tela. It
contains posterior choroidal artery with its
branches and internal cerebral veins with its
tributaries.

10. • Left lateral ventricle -Viewed from above after
removal of upper frontal lobe exposing Foramen of
Monro and adjoining parts of Rt lateral and 3rd
ventricle.Dissection done through Tenia fornicis

11. Floor
• Extends from optic chiasm anteriorly to aqueduct
posteriorly.
• Anterior half-formed by diencephalic structures,
anterior to posterior , optic chiasm, infundibulum of
the hypothalamus, tuber cinereum, mamillary bodies
posterior perforated substance.
• Tuber cinereum forms an internal elevation called
median eminence whereas mamillary bodies form
paired elevations just posterior to infundibular recess.
• Posterior half is formed by part of the tegmentum of
the midbrain

12. Floor

13. Anterior wall
• Extends from Foramen of Monro above to optic
chiasma below.
• Upper 1/3rd hidden behind rostrum of corpus
callosum and externally exposed lower 2/3 rd is
formed by lamina terminalis and optic chiasm.
• Lamina terminalis is a thin sheet of grey and pia
mater filling the gap(approx 10mm) between optic
chiasma and anterior commissure.
• From anterosuperior to posteroinferiorly, floor is
formed by , columns of fornix, foramen of Monro,
anterior commissure, lamina terminalis, optic recess
and chiasm.

14. • Saggital section through 3rd ventricle showing right
lateral wall and anterior wall from left side.

15. Posterior wall
• Posterior wall extends from suprapineal recess
above and aqueduct of sylvius below.
• From above downward it consists of suprapineal
recess, habenular commissure, pineal body & its
recess, posterior commissure &aqueduct of sylvius.

16. • Pineal gland is
projected to
quadrigeminal cistern
from a stalk with a
recess inside
enclosed by upper
and lower lamina.
Upper and lower
laminiae crossed by
habenular and
posterior
commissure
respectively.
• At lower most part
,aqueduct connects
the 3rd ventricle with
4th ventricle
Internal structures of posterior
wall seen from above

17. Common lesions of 3rd Ventricle
Congenital lesions Acquired lesions
Aqueductal Stenosis Anterior mass- Seller-supraseller mass
Chiasmatic-hypothalamic mass
Cavum Veli Interpositi Cyst Posterior mass-pineal sol, tectal sol, Inferior
thalamic sol
Congenital Intraventricular Cysts Inferior mass- Hypothalamic hamartoma ,
Arachnoid cyst
Mass near Foramen of Monro- Colloid cyst ,
SEGA, Subependymoma
Intraventricular SOL- Choroid plexus
neoplasm(Primary or Secondary), Congenital
intraventricular cyst, Vascular malformation of
choroid plexus

18. SURGICAL APPROACHES

19. APPROACH TO THIRD
VENTRICLE
ANTERIOR
ANTERIOR
TRANSCALLOSAL
TRANSCORTICAL
(THROUGH MIDDLE
FRONTAL GYRUS)
SUBFRONTAL
POSTERIOR
TRANSCALLOSAL TRANSCORTICAL
INFRATENTORIAL
SUPRACELEBELLAR

20. Anterior transcallosal approach
• Basically a transcallosal-transventricular approach.
• Indications-Anterosuperior lesion or lateral ventricular
extension.
• Advantages-access to both lateral ventricles as well, less neural
incision, possible in nondilated ventricles.
• Corridor to entry into 3rd ventricle-Transforaminal,
transforniceal, transchoroidal.
• Nearby critical structures susceptible to injury-
1)Genu of internal capsule(in transforaminal)-Hemiplegia
2)Fornix-memory disturbance
3)Thalamostriate vein-drowsiness, hemiplegia, mutism.
4)Dorsomedial Nucleus of Thalamus-emotional disturbance

21. Caudate nucleus
Tenia choroidea
Internal cerebral vein
Thalamus

22. Other Approaches to 3rd ventricle
Approaches Suitable for Advantage Disadvantage Collateral damage
Anterior
transcortical
Predominantly
lateral
ventricular
tumor with 3rd
ventricluar
extension
Easy access to c/l
ventricle through
septum pellucidum
if required
Mandatory
cortical
(MFG)incision.
Difficult in
nondialted
ventricles.
Risk of speech
deficit in case of
dominant
hemisphere.
Anterior
subfrontal
Anteroinferior
lesion
No cortical incision. Requires more
brain retraction,
working around
vessels.
Perforator vessel
injury(ACOM in
particular)
Posterior
transcortical
(through
sup parietal
lobule)
Posterior 3rd
ventricle and
roof
Good access to
quadrigeminal
cistern and also to
pineal gland.
Less spacious
exposure,
Needs cortical
incision.
Optic
radiation,visuospatia
l defect, aphasia.

23. Approaches Suitable for Advantage Disadvantage Collateral damage
Posterior
transcallosal
Posterosuper
ior 3rd
ventricular
sol
Working around
great veins,
higher chance of
memory
disturbance
Injury to tectal plate,
cerebellar arteries,
trochlear nerve.
Occipital
transtentorial
Pineal
tumors with
no C/L or
posterior
fossa
extension
No cortical
incision.
Deep venous
system hinders
easy access.
Injury to tectal plate,
cerebellar arteries,
trochlear nerve,
lateral & medial
posterior choroidal
artery
Infratentorial
supracerebellar
Pineal
tumors with
posterior
fossa
extension
Deep venous
system doesn’t
hinder easy access.
More chance of
injury to tectal
plate
tectal plate

24. Thank you