2. Introduction
- Posterior circulation aneurysm ~10-15% of all
aneurysms (basilar apex > SCA > PICA)
- First surgical clipping described by Gillingham in 1958
and Drake in 1961
- Both surgeons used a subtemporal approach with
modest success
3. Arises from the
confluence of the two
VA's at the
pontomedullary junction
Ascends in the central
gutter (sulcus basilaris)
Divides into PCA's and
SCA's just inferior to the
pituitary stalk.
BA Anatomy
6. Interpeduncular Fossa
Boundaries
- Anterior: clivus and posterior clinoid processes
- Lateral: mesial aspects of the temporal lobes and
tentorial edges
- Posterior: the cerebral peduncles
- Superior: mamillary bodies and posterior perforated
substance
7. Relative indications for surgery
1. Unfavorable coiling anatomy
2. Thick cistern clot?
3. Symptoms attributable to brainstem
compression (Giant aneurysms)
8. Choosing the Right Surgery
① obtain the shortest trajectory to
the lesion
② Adequate bone removal for
minimal brain retraction
③ Skeletonization & protection of
CN and vascular structure
9. selection of surgical approach based on
location
Site of Aneurysm Skull base Approach
Vertebral artery Far-lateral
Low Basilar Far-lateral
Midbasilar artery Petrosal,
Subtemporal?
High basilar artery Pterional +/- OZ
transyslvian
Subtemporal
10. Basilar Apex
Two pure approaches
1. Trans-sylvian approach +/- Modifcations
2. Subtemporal approach
15. Trans-sylvian approach
Assets Liabilities
• familiar
• prox. control
• exposure of both P1
• wide exposure
• Less temp. lobe
retraction than subtemporal
approach
• “Low” bifurcation BA
• Poor visualization of
peroforators
• ant. or post. directed
aneurysm
27. Anatomic triangles
providing access to the
basilar bifurcation:
1 optic-carotid triangle
2 carotid-oculomotor triangle
3 supracarotid triangle
The carotid-oculomotor
triangle is the one used most
commonly for basilar bifurcation
aneurysms.
28. Identify the Pcomm and CN III
Open the membrane of Liliequist along CN III
34. SUMMARY
Sylvian dissection: freeing of
the frontal and temporal lobe
Open the cisterns
Open the membrane of
Liliequist along CN III
Dissect along the Pcomm
until P1 is seen and then
follow to BA
36. Subtemporal approach
transsylvian app.
- below the middle depth of the
sella turcica
- posterior projection
- allows to dissect the perforators
of the posterior wall of aneurysm
- large aneurysm
right-sided approach : left III nerve
palsy, right hemiparesis
left-side approach
37. Subtemporal approach
Assest Liabilities
• prox. control
• dissection of perforators
• tentorial division widens
exposure
• Good visualization of clip
• ant. or post. directed
aneurysm
• narrow field
• contralat. P1 control
• temporal lobe injury
• CN III palsy
• bleeding control
