MCA aneurysm

Technical stages

MCA
3 pins
Drapped and clean
Head turn
Curvilinear incision down to just above galea
Rannies inserted
Monopolar thru the temporalis muscle down to bone
Elevate temporalis off the bone from the root towards the superior temporal line
Temporalis elevated off until the root of the zygoma and the frontal ridge
3x burrholes made at just above zygoma, don't go too posterior and inferior jnto the mastoid air cells, just under the superior temporal line and keyhole
Drill holes along the frontal and parietal bone on the bone flap and skull itself to allow sutures to go thru. Sutures are clipped and cut
Elevate the dura off the anterior skull base and middle skull base. Go down until half of the sphenoid wing. Use a silver 6 cutting burr to drill off the sphenoid wing. Use the yansen to bite off the sphenoid wing.
Use doppler to check location of MCA.
Dura opened in a U shaped manner and cut radially to flip dura down to zygomatic root to prevent bleeding from entering field. Of course place strip of Surgicel around bone Edge
Look for the olfactory nerve at the base of the frontal lobe and follow it to find the optic nerve and the ICA going under the sphnoid wing. Let csf out until you can see the temporal please falling off the middle fossa.
Placed Doro buddy
Microscope in
Open the slyvian fissure: using a arachnoid knife dissection the arachnoid sharply off the slyian vein. The slyvian vein is supposed to go to the frontal lobe side. Start the dissection superficially in the posterior slyvian then go deep anteriorly

What are we trying to achieve with head position?

Allows a better exposure of the important neuro-vascular structures eg the parent vessels: carotid, M1, A1
Trying to bring the sylvian fissure into optimal view
Facilitates the visualization of the aneurysm’s neck and its main related arteries.
A straight forward approach with less brain retraction and less manipulation of nearby structures eg frontal lobe, sylvian fissure
Improves the procedure success.

Anatomical considerations for head position

Extension beyond 20° must be avoided because it brings the orbital roof towards the surgeon’s angle of view.

Head extension places the sylvian fissure more superficial to the surgeon, and allows direct vision down the fissure.

Make the maxillary eminence the highest point

Trying to bring the sylvian fissure SF into optimal view MCA

Rotation of more than 30° may obstruct fissure dissection by rotating the temporal opercula onto the angle of fissure dissection

Over rotation above 10° deepens the proximal portion of the SF, making the dissection of the carotid and M1 cisterns more difficult

Head position for anterior circulation aneurysms

First group

Aneurysms along the ICA

Aneurysms located at the ophthalmic, posterior communicating and anterior choroidal segments of ICA

Head in neutral extension

15° of rotation

Second Group

MCA, anterior communicating segment of ACA, and ICA bifurcation

Head at 15 degrees of extension

With minimal rotation

Tilt head not contralateral shoulder gives more space for surgeon to work

A number of different head positions for ACom surgery have been described in the literature

Meyer et al suggested that the head must be rotated a maximum of 30° toward the opposite side and that this angle should not be exceeded.
Yasargil and Roux and Winn emphasized the need to position the head rotated at 30°.
Tamargo et al stated that Acom surgery required an angle between 30° and 45°.
Sekhar et al and Samson and Batjer suggested head positions of 45° and 60°, respectively.

Keep clamps horizontal so that the clamp would not come into way when operating

Sphenoid wing

Why do you drill sphenoid wing

Try to make anterior fossa and middle fossa as one

Stop at superior orbital fissure

Drilling the sphenoid wing

How much do you drill?

Perforators

While dissecting the MCA and ACA and its branches, the surgeon should stay along the anterior and anterolateral surface of the vessel

Lenticulostriate perforators arise from the posterior and medial surfaces.

Recurrent artery of Heubner from proximal A2.

Do not damage them while dissecting

Perforators run posterior medial surface of vessels → dissect in the anterior lateral

Distal or proximal approach

It is imperative to get proximal control of the parent vessel.
Proximal approach

Aneurysms with SAH or haematoma, especially when the dome points towards the Sylvian approach.

Aneurysms that arise from a short segment M1

IF fresh bleed its is better to get proiximal control early

Distal sylvian approach

Unruptured aneurysms

Longer M1, aneurysm is more distal

The Sylvian fissure

The most consistent and distinct landmark of the lateral hemispheric surface of the brain. It is formed by the anatomical relationship between the frontoparietal operculum, the temporal operculum, and the insula. The arachnoid membrane covers the fissure creating the Sylvian cistern, a subarachnoid space that contains important vascular structures surrounded by cerebrospinal fluid. The splitting of the Sylvian fissure, opening the arachnoid layer between the opercula, exposes the superficial Sylvian vein, the middle cerebral artery, the deep middle cerebral vein, and the insula.

If you have two veins in the fissure go between them

If you have one vein go towards the frontal lobe side of it

Anterior communicating artery aneurysms: Which side to approach

Dominant A1 aneurysms

Better control for intra operative rupture

Away from the dome

Go on the side of the dominant A1

Go away from the dome of the aneuyrsm

In this region five blood vessels must be confirmed before neck clipping of the aneurysm, namely, the bilateral A1 and A2 and the Acomm. In some cases it may be difficult to dissect the neck of the aneurysm completely. May need to go through the gyrus rectus to access the aneurysm.

The recurrent artery of Heubner runs in the reverse direction along the A1 around the Acomm or from the origin of the A2.

Principles of aneurysm clipping

Calm
View of the neck of the aneurysm, associated branches, and perforators while avoiding the dome
The surgeon needs to see both sides of the neck and the two clip blades at the time of application
When the neck of the aneurysm is squeezed shut by the clip blades, the diameter of the neck increases by about 50%. Hence, the clip blades should be that much longer (1.5 times the neck diameter)
Temporary clipping of the parent artery can soften the aneurysm

Temporary clipping of the parent vessel or branches

Many surgeons advocate almost routine use of temporary clips on the parent vessel.
Ruptured aneurysms, before final dissection and placement of the permanent clip.
The temporary clip softens the aneurysm and makes the neck more pliable, aiding in dissection of adherent vessels.
Reduces the risk of massive blood loss and obscuration of the operative field in the event of a rupture.
A particular situation where one might consider avoiding temporary clip application is when the vessels are very atherosclerotic.
However, a few surgeons avoid routine placement of temporary clips and reserve its use only when there is an intraoperative aneurysmal rupture.

Intra operative aneurysm rupture

It’s a tense time, and can happen suddenly and unexpectedly

Be prepared: anticipate

Temporary clip loaded, suction/s working and bottles not to full

Head up

Clear the blood if possible

Place a temporary clip across the parent vessel. ? Safe time period

Dome clipping. (remove or stack clips)

Bipolar the defect for small bleeds

Permanently clip the aneurysm

No safe time for temprary clipping

2.5 mins -5 mins on Motor evoked potential
But it depends vasospasms, age of patient
Can instead you dome clips just over the perforated part

Permanent clip placement principles

Rhoton's rules of aneurysm formation while understanding the fundamental principles of clip application.

(i) Aneurysms arise at the branching sites on the parent artery (side branch or bifurcation)

(ii) Aneurysms arise at turns or curves in the outer wall of the artery where hemodynamic stress is the greatest

(iii) Aneurysms point in the direction that blood would have gone if the curve at the aneurysm site was not present

(iv) Each aneurysm is associated with a set of perforating arteries that needs to be preserved

Clip application

Hence, according to rule 1, clips should be applied perpendicular to the afferent artery and parallel to the efferent branches with bifurcation aneurysms

Simple clipping, multiple clipping, fenestrated clipping and vessel reconstruction. It is important to place the blades of the clip parallel to the branches.

Checking the clip

Can hear transmitted vessel

No sounds when a vessel is kinked

ICG angiography

Disadvantages

Inability to visualize areas outside the field of the microscope
Difficulty visualizing of arteries at the depth of the surgical field
Residual neck in calcified and thrombosed aneurysms

Advantages

Provides real-time information regarding aneurysmal exclusion from the circulation
Patency of parent and branch vessels
Clip repositioning can be performed within minutes given the immediate visual feedback of ICG.