Cerebral Aneurysm Surgery

What is a Cerebral Aneursym?

A cerebral aneurysm occurs at a weak point in the wall of a blood vessel (artery) that supplies blood to the brain. Because of the flaw, the artery wall bulges outward and fills with blood. This bulge is called an aneurysm. An aneurysm can rupture, spilling blood into the surrounding body tissue. A ruptured cerebral aneurysm can cause permanent brain damage, disability, or death. Cerebral aneurysms most commonly arise around the Circle of Willis at the base of the brain at arterial branch points where the flow of blood is turbulent and traumatic to the inner arterial lining. More information can be seen in the "Anatomy and Causes" section of this web site.

What are the treatment options?

Aneurysm surgery is most commonly done on patients with a clinical presentation (symptoms and signs) of subarachnoid hemorrhage from an aneurysm demonstrated on a cerebral vascular imaging study (cerebral angiogram). Some aneurysms are found in patients without subarachnoid hemorrhage. Surgery is most frequently done on aneurysms that have ruptured. Surgery on unruptured aneurysms is, in general, simpler, safer, and easier than on aneurysms that have ruptured and filled the subarachnoid space with blood.

Alternatives to surgery are Neurointerventional procedures (coiling, embolization, etc).

Unruptured aneurysm treatment

If an aneurysm has not ruptured and is not causing any symptoms, it may be left untreated. Because there is a 1-2% chance of rupture per year, the cumulative risk over a number of years may justify surgical treatment. However, if the aneurysm is small or in a place that would be difficult to reach, or if the person who has the aneurysm is in poor health, the surgical treatment may be a greater risk than the aneurysm. Risk of rupture is higher for people who have more than one aneurysm. Unruptured aneurysm would probably be treated with a surgical procedure called the clip ligation, as described below.

Ruptured aneurysm treatment

The primary treatment for a ruptured aneurysm involves stabilising the victim's condition, treating the immediate symptoms, and promptly assessing further treatment options, especially surgical procedures. The patient may require mechanical ventilation, oxygen, and fluids. Medications may be given to prevent major secondary complications such as seizures, rebleeding, and vasospasm (narrowing of the affected blood vessel). Vasospasm decreases blood flow to the brain and causes the death of nerve cells. A drug such as nimodipine (Nimotop) may help prevent vasospasm by relaxing the smooth muscle tissue of the arteries. Even with treatment, however, vasospasm may cause stroke or death.

To prevent further hemorrhage from the aneurysm, it must be removed from circulation. In general, surgical procedures should be performed as soon as possible to prevent rebleeding. The chances that aneurysm will rebleed are greatest in the first 24 hours, and vasospasm usually does not occur until 72 hours or more after rupture. If the patient is in poor condition or if there is vasospasm or other complication, surgical procedures may be delayed. The preferred surgical method is a clip ligation in which a clip is placed around the base of the aneurysm to block it off from circulation. Surgical coating, wrapping, or trapping of the aneurysm may also be performed. These procedures do not completely remove the aneurysm from circulation, however, and there is some risk that it may rebleed in the future. Newer techniques that look promising include balloon embolization, a procedure that blocks the aneurysm with an inflatable membrane introduced by means of a catheter inserted through the artery.

Subarachnoid Haemorrhage

The Clip Ligation Operation

Preparation

The patient is usually positioned on their back, then a general anesthetic is given. The position of the head is determined by the location of the aneurysm and the approach to be used to reach it. The prepping and draping for clip ligation of a cerebral aneurysm is the same as for any craniotomy. The back will also be prepped if a lumbar drain is to be used.

Incision

The location, length, and configuration of the skin incision for intracerebral aneurysms depends on the location of the aneurysm. Most aneurysms of the anterior circulation are currently done using the pterional approach with its associated incision. Posterior circulation aneurysms may be approached using temporal and/or suboccipital incisions.

Dissection

Special techniques for aneurysm clipping include sphenoid drilling, where the wing of the sphenoid bone in the skull base must be drilled to give a better exposure and line of sight to the anterior carotid artery complex.

Opening the Sylvian fissure

The Sylvian fissure is a cerebrospinal fluid (CSF)-filled space located between the frontal and temporal lobes. Access to a large portion of the anterior Circle of Willis -- where many anterior circulation aneurysms are located. The arachnoid membrane overlying the temporal and frontal lobes is continuous across the Sylvian fissure. To retract the frontal and temporal lobes away from one another to access the anterior Circle of Willis the arachnoid must be divided between the frontal and temporal lobes. The width of the Sylvian fissure (and, therefore of the arachnoid membrane spanning it) is normally only a few millimeters. A sharp micro-instrument is used to puncture the arachnoid a few centimeters proximal (away from the base of the fissure). The tip of a micro-scissor is then inserted and the membrane cut from the opening downwards along towards the Sylvian fissure base. Several tiny veins cross the fissure between the frontal and temporal lobes. These vessels must be either avoided or coagulated and cut (bleeding from these tiny vessels is difficult to control, and even small amounts of blood in the surgical field quickly obscure and make further dissection difficult and even dangerous.

Clipping the Aneurysm

Once the aneurysm is exposed, the neck of the aneurysm is the usual optimal site for clip placement. The dome of the aneurysm is the usual site of intraoperative hemorrhage from the aneurysm. To decrease bleeding in the event of an intraoperative rupture temporary clipping of arteries feeding the aneurysm is an important technique.

Under microscope control, the neck of the aneurysm is clipped with 1 to 5 clips, depending on the size of the aneurysm. These clips will remain in place premanently.

Closure

Closure of a craniotomy for clipping of an intracranial aneurysm is the same as for closure of any craniotomy.
A craniotomy with aneurysm clip ligation takes approximately 3 to 4 hours in total.

What happens afterwards?

After craniotomy for aneurysm clipping the patient is usually taken to the Recovery ward. Immediately post operatively the patient is monitored in the Intensive Care Unit (ICU) for one or more days.

Patient recovery from aneurysm surgery should not be longer than for any uncomplicated craniotomy provided the aneurysm had not ruptured pre-operatively. The prolonged recovery following aneurysm surgery in patients who have had a subarachnoid hemorrhage is due to the effects of the hemorrhage. Following craniotomy for an unruptured aneurysm skin staples or sutures can usually be removed on the 7th post operative day.

Rehabilitation

Rehabilitation is sometimes indicated following craniotomy and aneurysm clipping. Most patients who have aneurysms clipped have had a subarachnoid hemorrhage preoperatively. The Hunt and Hess ("H and H") Scale grades the clinical condition of patients who have had a subarachnoid hemorrhage according to their neurologic condition at the time of their presentation. Patients who have a higher "H and H" grade are in worse condition than those with a lower grade. Patients with a higher "H and H" grade going into craniotomy for aneurysm clip ligation are more likely to need physical, occupational, and cognitive (speech) therapy and/or rehabilitation, coming out.

Follow up

A follow up angiogram may be indicated in patients who did not have an intraoperative angiogram to confirm clip placement.

After discharge from the post surgical unit (home, long term care facility, etc.) the patient following craniotomy for clip ligation of aneurysm should be seen by a member of the surgical team within 7 to 10 days.

Reoperation

Re-operation following clip ligation of a cerebral aneurysm is most frequently for:

1. Problem with the clip
2. Problem with the closure

Patients who develop hydrocephalus as a complication of a subarachnoid hemorrhage (frequently the clinical manifestation of an aneurysm) may require ventriculoperitoneal (VP) shunt insertion (usually done as a separate procedure after clip ligation).

Complications

The risks and complication of clip ligation of a cerebral aneurysm are greater for aneurysms that are very large, are located in along the posterior circulation (vertebral or basilar artery and their branches), and have a dome pointing towards the surgeon as he approaches it during dissection.

Risks and complications aneurysm clipping include: intra-operative aneurysm rupture, injury to a major artery, injury to a perforating artery, retraction injury, vasospasm, injury to the optic nerve (with clinoid drilling), and movement of the aneurysm clip. Infection of the craniotomy bone is also a risk.

Click here for a Patient Information Sheet on Cerebral Aneurysms

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