This document discusses the surgical management of middle cerebral artery (MCA) aneurysms. Key points include: - MCA aneurysms are most commonly located at the MCA bifurcation and trifurcation. They can grow quite large before detection and present challenges for endovascular treatment. - Surgical preparation involves cerebrospinal fluid drainage and a pterional craniotomy for exposure. The Sylvian fissure is opened to access the aneurysm. - For clipping, the aneurysm is dissected away from surrounding branches and temporarily clipped before applying definitive clips in parallel to branches to avoid remnants. Complex aneurysms may require multiple clips or fenestrated clips. - Giant or fusiform

1. Surgical Management of
Middle Cerebral Artery Aneurysms
Alexander M. Mason , C. Michael Cawley , Daniel L. Barrow
2/02/59

2. • May grow to 20 mm or larger before detection
• More likely to present with an
intraparenchymal clot
• More likely to cause symptoms of mass
effect than most other intracranial aneurysms
• More challenging to treat with endovascular
techniques than other aneurysms within the
intracranial circulation
MCA aneurysm

3. Anatomy

4. • Sylvian fissure
– deep component
• anterior (sphenoidal) compartment
– M1 segment
• posterior (operculoinsular) compartment
– M2 and M3 segments
– superficial component
Anatomy

5. • M1 (sphenoidal)
– lateral lenticulostriate arteries
• caudate nucleus
– anterior temporal artery
• temporal tip
• M2 (insular)
• M3 (opercular)
• M4 (cortical)
• MCA candelabra : duplication of MCA
Anatomy

6. • Morphology
– Saccular aneurysms : most common
– Fusiform aneurysms
– Blister aneurysms : less common
– Extremely dysmorphic or distal aneurysms are usually
infectious : M4 branches
• Size
– small (<5 mm)
– medium (5 to 10 mm)
– large (11 to 25 mm)
– giant (>25 mm)
Classification

7. Classification
• Location
– MCA bifurcation and trifurcation aneurysm 90%
• Surgical consideration
– Proximal MCA aneurysm
• Superior wall type :
– aneurysms arise at the origins of the
lenticulostriate arteries
– project into the frontal lobe posterosuperiorly
• Inferior wall type :
– aneurysms arise at the origin of the anterior
temporal artery or the temporopolar artery
– project toward the temporal lobe in an anterolateral
projection

8. • Location
– Distal MCA aneurysms
• most uncommon of the MCA aneurysms
• either infectious or, less frequently, traumatic
• often small and can be challenging to identify
Classification

9. Classification
• Etiology
– Saccular Aneurysms(berry)
• at sites of arterial curves or branching
• hemodynamic forces
– Infectious Aneurysms(mycotic)
• most commonly found along the distal branches of the
cerebral arteries
• secondary to infectious emboli
• bacterial endocarditis, idiopathic bacterial or fungal
sources
• neoplastic disease, such as choriocarcinoma and atrial
myxoma

10. • Etiology
– Fusiform Aneurysms
• most frequently seen in the posterior circulation
– Dissecting Aneurysms
• rare
• may be associated with infection, connective tissue diseases
such as Marfan’s syndrome, cystic medial degeneration, and
fibromuscular dysplasia
• present with ischemia or SAH
– Traumatic Aneurysms
• uncommon
• most often associated with the ACA
• most frequently distal on M3 and M4 segments and often
present with
Classification

11. • Because of their propensity to become quite large
before detection, they may occasionally become
symptomatic without SAH
• Seizures in giant aneurysm
• Lack of blood necessitates a lumbar puncture (LP) if
the history is suggestive of an aneurysm rupture
• CT
– SAH
– ICH
Presentation and evaluation

12. • MCA aneurysms are preferentially clipped at
most cerebrovascular centers
– frequently broad-based configuration
– the relatively small caliber of surrounding branches
often precludes the use of stents
– their classic bifurcation location makes recurrence
more likely
Surgical treatment

13. • Cerebrospinal fluid drainage
– indicated in patients with acute hydrocephalus after
aneurysmal SAH
– relaxed brain makes surgery safer in ruptured
aneurysm surgery
– patients with unruptured aneurysms generally do not
have preoperative placement of a lumbar drain
• Position
– head is turned about 30 degrees to the opposite
side with the vertex slightly extended
Preparation

14. Craniotomy
• Pterional incision
• Preserve STA
• Temporalis muscle splitting
with leaving cuff of muscle
• 2 burr holes
– Key hole
– Superior to zygoma

15. • Dura is stripped from the cranium with a Penfield
No. 3
• Pterional craniotomy flap is created with a high-
speed drill with footplate
• The lesser wing of the sphenoid is flattened to
the level of the superior orbital fissure
• Dural tack-up sutures
• Dura is opened in a curvilinear fashion
Craniotomy

16. • Microscope
• Sylvian fissure is opened sharply with an
arachnoid knife or a No. 11 knife blade
• After a 3-4 mm, microscissors are used to
continue to open the superficial arachnoid
over the fissure
• Inside out technique or open opticocarotid
cistern
Fissure dissection

17. Fissure dissection

18. • Unruptured aneurysm or a small, laterally
pointing ruptured aneurysm of the bifurcation
– first distally and then ultimately on the medial surface
(undersurface) of the bifurcation to access the M1
segment, gaining proximal control without opening the
proximal fissure first
• larger or ruptured aneurysm or uncertain
anatomy
– fissure dissection should be wide and include
proximal control, initially at the opticocarotid cistern,
and then working distally until the proximal M1 is
identified
Aneurysm Dissection and Clipping

19. • Sharp dissection,clear aneurysm neck
• Beware small branches adherence to dome
• Temporary clip
• Clips should be applied parallel to the branch
vessels to avoid possible small remnants and to
reestablish normal anatomic flow
Aneurysm Dissection and Clipping

20. • Multilobed aneurysms
– require more than one clip and often imaginative clip
constructs
• Large, multilobulated aneurysms often also
have calcified or atheromatous walls
– closure of clips tricky
– tandem clipping technique
– fenestrated clip through the distal neck and then
completing the proximal neck occlusion with a
nonfenestrated clip
Aneurysm Dissection and Clipping

21. Aneurysm Dissection and Clipping

22. • Giant MCA aneurysms
– visualization of branches or small lenticulostriate
arteries is often poor
– usually calcification or atheroma
– large sacs contain intraluminal thrombus that must be
removed before clip application
• Temporary trapping and opening of the sac
to evacuate the thrombus
• Brain ischemic protection
– modest hypothermia
– induced hypertension
– barbiturates
Aneurysmorrhaphy

23. Temporary Occlusion
• occlusion times of less than 10 minutes are
preferable
• no consensus in the literature regarding specific
cerebroprotective agents

24. Bypass
• Fusiform and giant aneurysms
• STA-MCA bypass
• M2 side to side