Microsurgical repair is a time-honoured means of securing an aneurysm and has a safety record similar to endovascular treatment in expert hands and for appropriately selected cases. Some aneurysms will still be treated most simply and effectively by direct surgery. At our unit each case is discussed by a multidisciplinary team consisting of a specialist neurovascular surgeon and interventional Neuroradiologist before recommending a treatment plan.
Types of Surgical Repair
Clipping
In appropriately selected cases microsurgical repair has the lowest likelihood of aneurysm recurrence and for needing retreatment of the techniques currently available. It lends itself to the definitive treatment of aneurysms with broad necks or complex shapes. It also avoids the need for blood-thinning medication when that is an issue.
Getting to the Aneurysm
A craniotomy is a door which is fashioned in the skull bone to allow access to the brain. At the end of the procedure this bone is replaced and the wound closed to look natural again. The bone door is rigidly fixed in place so that over time it will usually heal solidly with the rest of the skull bone.
A range of incisions are used and tailored to the needs of the individual case. The access is freuqently of a keyhole type and designed to disturb the brain itself as little as possible. It is also important to make the scar as cosmetically satisfactory as possible. In most cases it will be near invisible to someone not already alert to its presence.
The surgery is carried out under general anaesthesia to provide the controlled operating conditions necessary for operating on such delicate structures. The anaesthetist plays a crucial role in enabling the surgery to be safely conducted and also sees the patient can wake comfortably afterwards.
Minimally Invasive Approaches
For selected cases the term mini-craniotomy is used to describe approaches where the full range of the surgical exposure is not necessary to safely treat the aneurysm. This will often allow for faster recovery with some able to return home 24 hours after surgery.
Many aneurysms can now be approached though very small incision utilising a "keyhole' approach as demonstrated in the video above. This is made possible by advanced visualisation technologies that allow circumferential inspection of the aneurysms within a very confined space while retaining the capacity to control bleeding and manage a complication should that occur.
High-definition cameras in endoscopes may introduced and manipulated that allow the surgeon to look at multiple perspectives without having to retract the brain. An injection of dye into a vein (indocyanine videoangiography) allows flow in the blood vessels within the brain to be seen preventing inadvertent occlusions that might cause stroke. Augmented reality technology allows the injection of digitally processed angiographic images into the surgeons eyepieces.
Reconstructing the Blood Vessel
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The aneurysm is most usually secured by placing a metal clip around its base. This permanently prevents blood from entering the aneurysm and removes the risk of bleeding. Modern clips are non-magnetic and come in a range of shapes and sizes to allow complex reconstructions of the blood vessels. `
They do not have to prevent future MRI scans and will not lead to difficulty when passing through airports.
Rarely treated cotton may be applied to the wall of the aneurysm with the goal of causing scarring that will reinforce the wall over time. Although not as reliable as clp occlusion it can provide a useful additional treatment in the most difficult cases. Its use was more commonplace in the past and there is a small risk of an exaggerated inflammatory reaction to the material affecting surrounding neurological structures resulting in seizures or pressure effects.
Revascularisation
Occasionally it is not possible to reconstruct an aneurysmal blood vessel by surgical or endovascular means. To secure the aneurysm requires that the vessel be closed permanently. It may be that other blood vessels can assume the responsibilities of this vessel (collateral circulation) but in the event that it is not capable, stroke will result from the vessel's closure. It is possible to surgically reconstruct or create a new circulation to replace that which is removed.
Broadly speaking there are four strategies deployed. The first, rarely applicable is to excise the aneurysm while reconstructing its wall using tiny stitches- primary repair. The second is to utilise a donor artery from the scalp - usually the superficial temporal artery or occipital artery. By joining these donor arteries to blood vessels within the brain one creates an external carotid (the scalp circulation) to internal carotid (the brain's circulation)- EC-IC bypass.
An EC-IC bypass can also be constructed using a conduit to connect arteries in the neck to blood vessels within the brain- an interposition graft. Veins from the leg or the radial artery retrieved from the forearm provide such conduits. This type of bypass provides a higher blood flow than might be possible from the scalp vessels.
The fourth strategy is to join elements of the brain's circulation together- internal bypass for example by joining the anterior cerebral arteries or posterior inferior cerebellar arteries together.
This type of surgery is complex and rarely required, usually to treat giant (>25mm) aneurysms or fusiform aneurysms. Revascularisation techniques are also used to treat conditions that impair blood flow to areas of the brain, in particular MoyaMoya disease and similar conditions. It is rarely indicated for narrowing caused by hardening of the arteries (atherosclerosis) resulting in reduced blood flow producing transient ischaemic symptoms or stroke. In fact prospective clinical trials to date have shown no additional benefit for that particular indication to date. It may also be used when a tumour has so encased a blood vessel its removal is required along with the growth around it.
Risks Associated with Surgical Treatment
As with any treatment of a brain aneurysm there exists a small risk to life and a risk of stroke resulting in disability. Your treating specialists will discuss those risks as they pertain to your individual circumstances.
There is usually no requirement for longer term anti-platelet medication after surgical treatment. It is our usual practice to re-image to confirm the aneurysms been secured as planned but thereafter further imaging follow-up may not be required in many cases.
There are risks particular to surgery which should be considered:
Seizures- Any disturbance to the surface of the brain may trigger a seizure. With modern microsurgical technique this is increasingly rare. For an elective operation on an unruptured aneurysm now it would be estimated at 2% or less. This is sufficiently low that the UK Driver Vehicle Licensing Authority no longer mandates a driving ban if no seizures occur preoperatively. It is however higher than with endovascular procedures.
Wound Infection- as with any surgical procedure where an incision in the skin is made infections will occasionally develop. These are usually the result of bacteria already resident on the skin. Thankfully infections are rare complicating 1% of procedures and they are usually amenable to treatment with a short course of antibiotic. There are very rare cases (1:1000) where bone may become involved requiring its removal and later reconstruction.
Cosmesis- Your well-being benefits if you still "look" like yourself after surgery. Once healed in most cases the surgical scar will very difficult to see to the untrained eye. Minimal (if any) hair removal is necessary for planned surgery.
Most aneurysm surgeries require an approach in the region of the temple. Occasionally the chewing muscle at the side of the head may shrink a little producing asymmetry which if noticeable can be addressed by cosmetic methods. Rarely the nerves that facilitate raising of the eye-brow may be weakened and occasionally that results in permanent asymmetry in movement of the eyebrow. Great care is taken to make the appearances of any any incision unobtrusive.
