This is a follow up to my previous blog post, What should we really know about cerebral aneurysms? In that post, I discussed the nature and presentations of cerebral aneurysms. In this post I will look at the two major treatments for cerebral aneurysms, exploring their pros and cons, and looking at some emerging challenges to the conventional wisdom.
The first question to answer regarding treatment of aneurysms is whether they need any treatment at all. In other words, are they best left well alone? In principle, aneurysms that have ruptured require treatment, irrespective of their size. On the other hand, aneurysms that are discovered incidentally, before they rupture, may not need surgical treatment unless they are large (usually 7mm or more in diameter), or they are associated with high-risk features/locations. Low-risk aneurysms that do not require treatment however need long-term surveillance with intermittent brain imaging. To limit the growth of such aneurysms, people harbouring them are advised to stop smoking, and if they have hypertension, to ensure that this is well-controlled.
There are two treatment approaches to ruptured aneurysms and high-risk unruptured aneurysms. The first is invasive and neurosurgical; the cranium is opened, the aneurysm located, and a surgical clip is put around its neck, sequestering it from its parent vessel. In this way, with its wing literally clipped, the aneurysm is disarmed, its potential for growth and rupture severely restricted.
The other procedure, younger and safer than clipping, is endovascular coiling or coil embolisation. This procedure, performed by an interventional neuroradiologist, involves tunnelling a fine wire or coil through blood vessels until it reaches the aneurysm. The aneurysm space is then filled up with the coil until it is totally obliterated. Unable to fill up with blood or expand, the aneurysm is rendered impotent. Both coiling and clipping however carry a small failure risk, resulting in aneurysm recurrence or re-rupture.
By 77giallo77 – Own work, CC BY-SA 4.0, Link
This is the conventional wisdom of cerebral aneurysm treatment. But there are advocates out there who are pushing the case for clipping over coiling. One reason they put forward is the emerging observation that clipping results in better recovery of function of the third cranial or oculomotor nerve. The oculomotor nerve is critical to the movement of the eye and eyelid, and it is vulnerable to compression by the posterior communicating artery (PCOM) aneurysm. A compressed third cranial nerve results in a droopy eyelid (ptosis) and double vision (diplopia); recovery of function of the oculomotor nerve is therefore an important goal in the treatment of aneurysms.
There are now at least four systematic reviews and/or meta-analyses that show that recovery of the oculomotor nerve function is better achieved by clipping than by coiling. These are:
- Is clipping better than coiling in the treatment of patients with oculomotor nerve palsies induced by posterior communicating artery aneurysms?, published in the journal Clinical Neurology and Neurosurgery in 2017.
- Clipping versus coiling in the management of posterior communicating artery aneurysms with third nerve palsy: a systematic review and meta-analysis published in World Neurosurgery in 2016.
- Clipping versus coiling for ruptured intracranial aneurysms: a meta-analysis of randomized controlled trials, published in World Neurosurgery in 2019.
- Endovascular coiling versus neurosurgical clipping for aneurysmal subarachnoid hemorrhage: a systematic review and meta-analysis, published in Cereus in 2019.
Another meta-analysis, titled Clinical outcome after surgical clipping or endovascular coiling for cerebral aneurysms, goes further to argue that clipping results in better chances of survival and independent living than coiling.
These may be the last-gasp attempts of clippers to have one up over coilers, but the consensus still remains dominantly in favour of endovascular coiling. We however need to keep a close eye on this pendulum-it may just swing back unexpectedly.
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