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. A range of incisions are used and tailored to the needs of the individual case. The access is often of the "key-hole" type and designed to minimally disturb the brain itself. It is also important to make the scar as cosmetically satisfactory as possible. In most cases it will be invisible to an untrained observer.
The aneurysm is 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.
The surgery is carried out under general anesthesia 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.
Rarely it is necessary to construct an alternative pathway for blood to reach the brain thus bypassing the aneurysm completely- a cerebrovascular bypass. This is accomplished by using a donor vessel to carry blood from the large arteries in the neck directly to those in the brain. This donor vessel may be an artery from the scalp itself or the radial artery in the arm may be used. Alternatively a vein may be taken from the leg, similar to the the procedure used in coronary artery bypass grafting.
The risks of surgical repair can include:
The decision as to what treatment is offered will be considered by specialist interventional neuroradioologists as well as neurosurgeons. It may be appropriate that you meet both neuroradiologist and neurosurgeon to discuss the pros and cons of each approach and have your questions answered. The details of your operation will be discussed with you in detail by your surgeon and the risks specific to your operation explained. We will endeavour to answer any questions you have and encourage you to ask them.
In the photos on the right is an example of what a surgeon sees through the operating microscope as they approach a cerebral aneurysm. In this case the patient has suffered a subarachnoid haemorrhage from an anterior communicating artery aneurysm. The complex shape of this aneurysm has made us favour microsurgical treatment for it. There are blood vessels emerging close to the neck of the aneurysm that quickly give origin to small branches which supply oxygen to important parts of the brain. Injuring vessels in this region can affect movement and sensation in the legs, behaviour, speech, memory, concentration and the ability to control body chemistry.
In the photo you wll also notice that part of the aneurysm appears a yellow colour. This is an atherosclerotic plaque. Atherosclerosis is a degenerative process of blood vessels. The word derives form a Greek word Ather- meaning a type of gruel or porridge. As a result of atherosclerosis blood vessels are hardened by the deposition of plaques made up of fatty material and calcium in their walls. The process is accelerated by smoking.
An incision is made behind the hairline and the scalp reflected forward so that the surgeon has access to the area just above the eye. A small opening (craniotomy) is fashioned and the blood vessels at the base of the brain approached using a powerful operating microscope. The blood vessels that allow blood into the aneurysm are carefully identified and controlled before approaching the aneurysm itself. Should the aneurysm rupture again the bloodflow may therefore be temporarily arrested while the surgeon completes the repair.
The aneurysm is made secure by placing a small titanium clip across its base. This will effectively prevent it from bleeding again. We use a variety of clips in different shapes and sizes to reconstruct the original blood vessel while attempting to preserving the flow through blood vessels some of which are the thickness of a human hair. Occasionally the wall of the aneurysm may be re-enforced by wrapping the aneurysm in a material designed to form a scar on the aneurysm wall. Typically treated cotton is used for this purpose.
There are various tools used to demonstrate sufficent blood in the vessels once the repair has been completed. These include ultrasound probes and a a type of real-time angiography called Indocyanine Green Videoangiography (ICG-VA). ICG-VA is carried out by injecting a green dye intravenously. Light is shone on the blood vessels within the brain from the microscope and the surgeon views them through a special filter and able to see the dye fluoresce as it passes through the arteries. Images form the surgery to repair this relatively complex aneurysm are shown below. The tiny but vital branches arising around the aneurysm are seen to fill with blood and this patient woke up without any adverse consequences. If necessary the clips are replaced and adjusted to optimise the blood flow to the brain. Once surgery is completed the lining of the brain is sutured closed and the craniotomy replaced before closing the wound.
For scheduled repairs of unruptured aneurysms the recovery time after an operation is generally a little longer than with endovascular treatment. The patient may expect to remain in hospital for about 4-5 days. For scheduled endovascular treatment of unruptured aneurysms it is usually 1-3 days. Patients suffering an aneurysmal subarachnoid haemorrhage will remain in hospital for 10-14 days on average irrespective of how the aneurysm is secured.
The rules relating to driving in the United Kingdom formerly distinguished between undergoing a craniotomy and having endovascular treatment to secure an aneurysm. The advice relating to driving after craniotomy are more relaxed than they once were. As of November 2014 DVLA guidance states that the patient may resume driving on a Type 1 Driving licence once clinically recovered from the procedure providing they have not suffered a seizure and no other disbarring disability is present. This includes after craniotomy for middle cerebral artery aneurysm. For type 2 (commercial licences) there will be a 12 to 24 month disbarment from driving dependent on the location of the aneurysm and the severity of any disability resulting from the subarachnoid haemorrhage. Read the full DVLA guidance here or visit the DVLA website.