METHODS OF ANEURYSM REPAIR Direct clipping of the aneurysm neck is the optimal method of treatment and prevents further rupture; aneurysm clips rarely slip after application. The operating microscope and improved anaesthetic techniques have considerably lowered mortality and morbidity. Careful dissection of arachnoid tissue around the neck of the aneurysm enables accurate positioning of the clip.
Wrapping: If the width of the aneurysm neck or its involvement with adjacent vessels prevents clipping then muslin gauze may be wrapped around the fundus. This provides some protection but rebleeding can still occur.
Balloon embolisation: Inflating a balloon introduced through a special angiographic catheter within the aneurysm sac has had very limited success. The technique carries a risk of causing immediate aneurysm rupture or of allowing balloon fragments to pass into the distal circulation causing an embolic stroke. Results have shown that even apparent successful balloon occlusion does not necessarily prevent rebleeding in the long term. Using a balloon to occlude the neck of an aneurysm along with the parent vessel e.g. for a 'giant' ophthalmic 'artery aneurysm', should produce a permanent repair provided the patient can tolerate the occlusion (see below).
Coil embolisation: In recent years, radiologists have succeeded in inserting single or multiple helical platinum coils into the aneurysm sac to induce thrombosis. Although this is still an experimental technique, results are encouraging.
A tracker catheter is guided through the aneurysm neck. The coil, attached to the end of a delivery wire, is inserted through the catheter into the aneurysm fundus. After accurate placement, the passage of an electric current causes electrochemical release from the delivery wire.
Complications may still occur during the procedure and unless the fundus is completely obliterated, rebleeding may still follow, The wider the aneurysm neck and the larger the size, the smaller the chance of producing complete obliteration. Without this, rebleeding can occur.
Unfortunately early work suggests that aneurysms that surgeons find difficult to clip also pose difficulty to the radiologist. Whether or not coil embolisation will improve the results obtained by direct clipping will take many years to evaluate.
Trapping: clipping of proximal and distal vessels is the only possible treatment for some aneurysms, e.g. 'giant' and intracavernous aneurysms. This prevents rebleeding but carries a high risk of producing an ischaemic deficit. A bypass procedure - superficial temporal to middle cerebral anastomosis, prior to trapping - may help minimise the risk of this complication (see page 287).
Basilar bifurcation aneurysm before coil embolisation after coil embolisation showing complete obliteration.
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