Ppt for neurosurgery resident , vascular neurosurgery, aneurysm anatomy, definition, epidemiology and etiology, treatment considerations

1. BY
DR. HIMANSHU RAVAL
R1 NEUROSURGERY

2. Aneurysm :
It’s permanent abnormal dilation of blood vessel occurring due to congenital / acquired weakening
or destruction of vessel wall.
Classification:
1> depending upon composition of wall
- True: involving all layers
- False: due to trauma
2> depending upon shape
- Saccular
- Fusiform
- Cylindrical
- Serpentine
- Racemose
3>based on pathogenic mechanism
- Atherosclerotic
- Syphilitic
- Dissecting
- Mycotic
- berry

3. • Incidence of aneurysm difficult to estimate
• Prevalence 0.2-7.9 %
• Half of the aneurysms ruptures
• Incidence of aneurysmal rupture is 6-12 /
100,000

4. • Overall mortality at 6 months: 40% - 50%
• 15% of patients expire before reaching the
Hospital
• 25% die within 24 hours
• Only one third of those who survive have
functional independent lives.
• Re bleed has a catastrophic morbidity : 48% to
78%

5. • Congenital predisposition
• Atherosclerotic/ hypertensive
• Embolic
• Infectious
• Traumatic

7. • Anterior circulation (85-95%)
• Posterior circulation (5-15%)
• Multiple site (20-30%)

8. ANTERIOR CIRCULATION ANEURYSMS 85-95% OF
TOTAL ANEURYSM
— A com and DACA(30-35%)
— MCA (20-25%)
— P com(25-30%)
— ICA bifurcation (5-7%)

9. • Major rupture
— SAH
— ICH
— IVH
— Subdural blood
• Mass effect
— cranial nerve palsy:
3rd nerve in PCOM
Chiasmal syndrome - ophthalmic, Acom
— giant aneurysm compressing brainstem
— Endocrine disturbance: sellar and suprasellar

10. • headache
• Minor haemorrhage
• Seizures
• Incidental finding

11. • ADPKD
• Fibromuscular Dysplasia
• ED syndrome
• Marfan Syndrome
• Coarctation of Aorta
• Atherosclerosis
• MEN
• NF type1
• Bacterial endocarditis

12. • Gold standard :80-85% sensitivity
• Surgical information:
— Cerebrovascular anatomy, aneurysm location & source of bleeding
— Aneurysm size/shape/orientation of dome and neck
— Relation to the parent/perforating arteries
• May be useful to evaluate for possible cerebral vasospasm
• 3-D reconstruction:
— dome-to-neck ratio
— parent artery or branch orientation to neck
— enhances surgical view for clip placement and vessel reconstruction

13. • Reported to detect aneurysms larger than 3 mm
• Sensitivity of 95% and 83% specificity.
• Provide sufficient anatomic detail especially relation to
near by bony structure

14. • Can detect aneurysms >3 mm with 86% sensitivity
• Useful for evaluating relation with soft tissue structures

15. • Risk of SAH is 0.05-6 % each year
• 50 % rupture : fatal
• Increase in size >1 cm increases the risk 11 fold

16. • Aneurysm arise at branching point of parent artery.
• Saccular aneurysm arise at curve of artery on convex site.
• Aneurysm sac direction is toward the direction of blood flow.
• There is constantly occurring perforators situated at each aneurysm site
that need to be protected.
• If aneurysm arise on non branching part it is directed longitudnally and of dissecting type.

17. • Inter hemispheric bleed and intra ventricular bleed
• DSA view

18. The most common aneurysm site on the anterior cerebral artery is at the level of the
anterior communicating artery. The segment of the anterior cerebral artery between
the internal carotid and anterior communicating arteries is referred to as theA1 segment,
and the segment between the anterior communicating artery and the rostrum of the
corpus callosum is referred to as A2 segment. Aneurysms usually occur in the setting where
one A1 segment is hypoplastic and the dominant A1 gives rise to both A2s. The aneurysm
arises at the point where the dominant A1 segment bifurcates at the level of the
anterior communicating artery to give rise to both the left and right A2 segments. These
aneurysms usually point away from the dominant segment toward the opposite side.
The direction in which the fundus points is determined by the course of the anterior
cerebral arteries proximal to their junction with the anterior communicating artery.
Tortuosity of the arteries may create a situation in which the hemodynamic thrust varies,
so that these aneurysms may project not only to the opposite side, but also in the
anterior, posterior, or inferior direction.

20. The anterior cerebral artery gives rise to numerous perforating branches. The branches
arise from two sources. First, the A1 segment gives rise to branches that pass directly
to the anterior perforated substance; and second, the A1 and the proximal part of the
A2 segments give rise to the recurrent artery. The recurrent branch of the anterior cerebral
artery is the largest and longest of the branches directed to the anterior perforated substance.
It may be the first artery seen on elevating the frontal lobe to approach the
anterior communicating aneurysm. It is unique among arteries in that it doubles back on
its parent vessel, passing above the carotid bifurcation, and accompanying the
middle cerebral artery into the sylvian fissure before entering the anterior perforated substance
If the A1 segment is hypoplastic, the recurrent artery on that side may be as large as the
hypoplastic A1 segment and might even be confused with it, since both will be passing
along the area between the carotid bifurcation and interhemispheric fissure.
The recurrent artery may lie in any direction from the A1 segment. Its origin may adhere
to the wall of the anterior communicating aneurysms. The inverting adventitia of A1
may so obscure the recurrent artery that inadvertent occlusion by a clip may easily occur,
even under the operating microscope.

22. The recurrent artery pursues a long, redundant path,looping forward on the
gyrus rectus or the posterior part of the orbital surface of the frontal lobe
where it could be damaged and occluded in removing the posterior 1 or 2 cm of the
gyrus rectus, as in exposing anterior communicating aneurysms.
It may arise from a common stem with the frontopolar artery. Ischemia in the
area supplied by Heubner's artery may cause hemiparesis with
facial and brachial predominance, because of compromise of the branch
supplying the anterior limb of the internal capsule, and may cause aphasia
if the artery is on the dominant side.
The anterior communicating artery is the site of origin of as many as
four perforating branches to the dorsal surface of the optic chiasm and
suprachiasmatic area. These perforating branches perfuse the fornix, corpus callosum,
and septal region.

23. SURGICAL APPROACHES
ACOM
• Pterional craniotomy
— GOLD STANDARD
• Subfrontal approach
— useful for superiorly pointing aneurysm when
there is a large amount of frontal blood clot
• Anterior interhemispheric approach
— contraindicated for anteriorly/superiorly pointing aneurysms
as the dome is approached first
• Transcallosal approach

24. Usually right pterional craniotomy used with following exception:
• Large Acom pointing to right.
• Dominant left A1 feeder to aneurysm with no filling from Right A1
• Additional left sided aneurysm
*Pterional approach

25. Microsurgical dissection:
1>dissect down sylvian fissure> exposure of olfactory nerve> optic nerve
2>Open arachnoid over carotid and optic cistern
3>elevation of temporal tip and expose ICA
4>follow ICA distally and look for origin of A1
*Ways to increase exposure
1>gyrus rectus resection
2>fronto-temporal-orbital-zygoma removal
3> spliiting entire sylvian fissure
4>ventricular drainage
*critical branches that needed to be preserved
- Recurrent branch of heubner

26. Anterior Interhemispheric approach
• Involves minimal brain retraction, suitable for
aneurysm pointing anteriorly
• A transverse incision on lower forehead
with craniotomy in midline
just above glabella
• Rectangular dural opening with flap
hinged on SSS.
• Approximate depth to aneurysm is 6cm.
Proximal control is difficult.

27. • Inter hemispheric bleed and intra ventricular bleed
• DSA view

28. OPERATIVE APPROACH
(DACA)
• Pterional craniotomy with partial gyrus rectus resection
for aneurysm up to 1cm from A com
• Frontal craniotomy(extending to contralateral side) with
interhemispheric approach for aneurysm >1cm distal to
A com up to genu of corpus callosum
• Para saggital craniotomy with interhemispheric approach for
aneurysm distal to genu of corpus callosum

29. • Sylvian fissure bleed
• Angiographic view

30. The middle cerebral artery is one of the most common sites of saccular
aneurysms. They most commonly arise at the level of the first major bifurcation or
trifurcation of the artery. The angulation with which the bifurcating trunks arise from
the main trunk forms the turn or curve. These aneurysms usually point laterally in the
direction of the long axis of the prebifurcation segment of the main trunk.
The middle cerebral artery is divided into four segments, M1 to M4.
Saccular aneurysms arise on junction of the M1 and M2 segment.
The small cortical branches arising from the M1 segment proximal to the bifurcation,
called early branches, may be the site of origin of aneurysms. The early
branches are directed to the frontal and temporal lobes.

31. The middle cerebral artery branches to the anterior perforated substance are called
the lenticulostriate arteries. On average, there are 10 (range, 1-20) lenticulostriate arteries
per hemisphere. Eighty percent of lenticulostriate arteries arise from the prebifurcation
part. An aneurysm may infrequently arise at the origin of a large lenticulostriate branch.
The lenticulostriate arteries are divided into medial, intermediate, and lateral
groups. All three groups are encountered in splitting the sylvian fissure and following the
artery medially.

32. OPERATIVE APPROACH
(MCA)
*Pterional craniotomy/ craniectomy
• Lateral trans-sylvian approach
For the unruptured and uncomplicated MCA bifurcation aneurysm
Exposes the dome first
• Medial trans-sylvian approach
For patients with short M1 segment, aneurysm arises from the
proximal M1 trunk or have a
complicated configuration with increased risk of rupture
• Superior temporal Gyrus approach
For aneurysms A/W ICH
The aneurysm is exposed through the hematoma
cavity in the sup temporal gyrus

33. • Female > male
• SAH in a lateral suprasellar and ambient cistern
• Intraparenchymal haemorrhage into the uncus of the temporal lobe,
intraventricular haemorrhage into the temporal horn or
haemorrhage into the subdural space can also occur
• Dome usually directed lateral, posterior and inferiorly.

35. The posterior communicating and anterior choroidal arteries arise from the
posterior wall on convex curve as the carotid artery passes upward toward its bifurcation.
The most common carotid aneurysm arises at the carotid-posterior communicating artery
junction. These aneurysms arise from the posterior wall of the carotid artery near the
apex of this turn, immediately above the distal edge of the origin of the posterior
communicating artery.
Another important relationship in this area is that of the oculomotor nerve to the
internal carotid artery. Aneurysms arising at the origin of the posterior communicating
artery point downward and backward and may compress the oculomotor nerve at its
entrance into the dural roof of the cavernous sinus.
The posterior communicating artery is usually found inferomedial and the
anterior choroidal artery superior or superolateral to the neck of the aneurysm.
In exposing the carotid artery beyond the origin of the ophthalmic artery, the surgeon
often sees the anterior choroidal artery before the posterior communicating artery.

36. The posterior communicating artery, which forms the lateral boundary of the
circle of Willis, arises from the posteromedial surface of the internal carotid
artery and sweeps backward above the sella turcica and above and medial
to the oculomotor nerve to join the posterior cerebral artery.
If the posterior communicating artery is of small or normal size, it courses
posteromedially to join the posterior cerebral artery medial to the oculomotor
nerve, but if it is of a fetal type, it courses posterolaterally above or above
and lateral to the oculomotor nerve.

37. Treatment aspect:
• Pterional approach
• Sylvian dissection
• Careful dissection of carotid at
posterior margin
• Ant choroidal A must be preserved
during clipping

38. • SAH in carotid cistern
• may present with
Intraparenchymal haemorrhage
into the basal ganglia simulating the
hypertensive bleed
• may enlarge to giant size and
compressthe optic apparatus

39. These aneurysms arise at the apex of the T-shaped bifurcation. They point
upward in the direction of the long axis of the prebifurcation segment of the
artery toward the anterior perforated substance. The perforating branches
arising from the choroidal segment of the internalcarotid and the proximal
part of the anterior and middle cerebral arteries are stretched around the
back side ofthe neck and wall of the aneurysm and should be dissected
free of the aneurysm.

42. Treatment aspect:
Pterional approach
30° head rotation from vertical plane
dissect down sylvian fissure> exposure of olfactory nerve> optic nerve
Open arachnoid over carotid and optic cistern
Usually it is pointing superiorly

43. 3 types:
• Cavernous segment
• Clinoidal segment
• Supra-clinoid segment
•Female : male = 9:1
•5-6 th decade
•incidental lesions/ mass effect
•multiplicity

44. • Most clinically significant
aneurysms arise from the
horizontal segment and
project forward and
laterally toward the SOF
below the ACP
• cavernous sinus syndrome

45. • Anterolateral variant (can resemble opthalmic artery aneurysm):
erode ACP ¢ Monocular visual loss
Large ones can compress optic chiasm
• Medial variant (can resemble superior Hypophyseal
artery aneurysm ):
Enlargement into the pituitary fossa Hypopituitarism,
may simulate Pituitary apoplexy, epistaxis

47. The clinoid segment is located at the junction of the intracavernous and subarachnoid
segments of the artery, between the dural folds coming off the upper and lower margins
of the anterior clinoid process. The dura that extends medially from the top of the anterior
clinoid process forms the upper dural ring around the carotid artery. The dura that extends
medially from the lower margin of the anterior clinoid surrounds the artery to form the
lower dural ring, which marks the lower margin of the clinoid segment.
The layer that extends medially to form the lower dural ring separates the lower
Margin of the clinoid process from the upper surface of the oculomotor nerve. The upper
ring forms a tight collar around the artery, but inspection under the operating microscope
reveals that there is often a narrow depression in the dura at the site at which the ring hugs
the anteromedial aspect of the artery, called the carotid cave. The cave, the short
downward pouching, extends a variable distance below the level of the upper dural ring
and is most prominent on the anteromedial side of the artery, where it may extend down
to near the lower ring. Carotid cave aneurysms are distinct from clinoid segment
aneurysms, which arise from the clinoid segment.

48. • Opthalmic artery aneurysm
Project superiorly compressing the Optic nerve
• Superior Hypophyseal artery aneurysm
Arise from the inferomedial surface, projects medially
• Dorsal variant
Ophthalmic segment aneurysm

50. Aneurysms arising at the carotid-ophthalmic artery junction commonly arise from the
superior wall of the carotid artery at the distal edge of the origin of the ophthalmic artery
at or above the roof of the cavernous sinus, where the superiorly directed intracavernous
segment turns posteriorly. At this turn, the maximal hemodynamic thrust is directed toward
the superior wall of the carotid artery just distal to the ophthalmic artery, and the aneurysm
projects upward toward the optic nerve.
The origin of the ophthalmic artery is difficult to expose because of its short
intradural length and its location under the optic nerve. It arises from the carotid
artery below the optic nerve and reaches the orbit by one of three routes. It usually passes
through the optic canal to enter the orbit. In a few cases it will arise in the cavernous sinus
and enter the orbit through the superior orbital fissure. The least common course is for it to
penetrate a foramen in the bony strut that separates the optic foramen and the superior
orbital fissure. Aneurysms arising in the region of the origin of the ophthalmic artery and
the anterior clinoid process are among the most complicated aneurysms because
of the variable origin and course of the ophthalmic artery.

51. The anatomy of ophthalmic
aneurysms varies depending on the
site of origin and course. If the aneurysm
arises on the upper surface of the carotid
artery above the upper ring, it will project
upward into the optic nerve. If the
ophthalmic artery has an even longer
subarachnoid segment superomedial
side of the carotid artery, the aneurysm
may project medially under the optic
nerve. The variant of the ophthalmic
aneurysm is one that is associated with
an ophthalmic artery that arises within the
cavernous sinus and passes through the
superior orbital fissure to reach the orbit.
This aneurysm will point upward,
but almost immediately encounters the
lower margin of the anterior clinoid process.

52. The ophthalmic artery usually arises from the medial third of the superior surface of
the carotid in the area below the optic nerve. The ophthalmic artery, after exiting the carotid,
may immediately enter the optic canal, but in most cases, there is a 2- to 5-mm preforaminal
segment. Exposure of the neck of this aneurysm may be facilitated by the removal of the
anterior clinoid process and adjacent part of the lesser sphenoid wing, by removing the roof
of the optic foramen and adjacent part of the orbital roof to allow some mobilization of the
optic nerve, and by incision of the falciform process, a thin fold of dura mater that extends
medially from the anterior clinoid process to the tuberculum sellae and covers the segment
of the optic nerve immediately proximal to the optic foramen.
Ophthalmic aneurysms typically arise on the upper anterior wall of the
carotid artery and point upward away from the perforating branches arising from
the ophthalmic segment. The risk of damaging the adjacent perforating branches is less in
clipping an ophthalmic aneurysm because ophthalmic aneurysms typically point upward,
away from these perforating branches.

53. Treatment aspect
• Cut falciform fold for
decompression of optic nerve
• Extradural approach for
unruptured aneurysm
• Drill off anterior clinoid
• Side angle clip placed
parellal to parent artery

54. The segment of the carotid artery just distal to the origin of the ophthalmic artery,
and from which the superior hypophyseal artery arises, has a medially convex curve in the
area lateral to the pituitary stalk. It is on this medially convex curve that the superior
hypophyseal aneurysm arises. The aneurysm arises at the distal edge of the origin of the
superior hypophyseal artery and points medially into the area between the lower surface of
the optic chiasm and the diaphragma sellae. The aneurysms are often confused,
on lateral angiograms, with intracavernous aneurysms, because they frequently project
below the level of the anterior clinoid process, although they are located in the subarachnoid
space below the optic chiasm.
The superior hypophyseal arteries are small branches, usually two, that arise from
the medial or posterior aspect of the ophthalmic segment. One branch often predominates.
These arteries pass medially to reach the floor of the third ventricle, optic nerves, and
the chiasm and pituitary stalk.

55. They arise below the plane of the ACP.
As the lesion expands and fills the
suprasellar space, it may venture
across the midline.
• treatment aspect
pterional approach
Exposing ica
Clinoid removal
Clipping preferred

56. • Age and condition of patient
• Anatomy of aneurysm and associated vasculature
• Availability of endovascular instruments
• Therapies that do not directly address the aneurysm
-control of hypertension
-vasospasm Mx
-stool softeners
-nutrition
-electrolyte balance
• Therapies directed towards aneurysm
- Open surgical techniques
- endovascular

57. Clipping:
• Gold standard
• Placement across the neck to discontinue aneurysm from parent vessel
without occluding it
Wrapping:
• For fusiform aneurysm involving basilar trunk, cavernous ICA
• Available material: muscle/ cotton or muslin/ Teflon/ fibrin glue/ plastic resin

58. • Thrombosis of aneurysm
- Coiling
- Onyx HD500
- Flow diversion
• Trapping

59. Factors to be considered
• Availability of equipment
• Skill set and experience of neurosurgeon
• Dome/neck ratio
• Associated Haemorrhages
• Mass effect
• Patient’s age
• Clinical profile of patient
*ISAT trial: coiling> clipping

60. *prepared from Greenberg, Rhoton, youmans and online material