A Portrait of the Brain Author: Adam Zeman Synopsis How do you sketch a vivid profile of the most perplexing organ in the body? How do you portray the intricate workings of what is, ‘by a very long way, the most complex entity we have yet encountered in the universe‘? (page 36). The author of […]
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.
Why not check out these related blog posts:
Reaching Down the Rabbit Hole Authors: Allan H. Ropper and Brian David Burrell Synopsis This book is about the day-to-day practice of one of the leading neurologists in the world. It explores his challenging work in one of the most prestigious of hospitals, the Brigham and Women’s Hospital– ‘a place where the strangest and challenging […]
The Man Who Mistook His Wife for a Hat Author: Oliver Sacks Synopsis This book is an exhilarating excursion into the world of some the most intriguing neurological disorders. The main theme linking the stories is the detailed narrative of each case study. The author’s trademark is his ingenious capacity for probing beneath the […]
Today is World Brain Day! And we are celebrating with an appropriate series of book reviews. We will be exploring 10 excellent books about the brain. But these are not just any set of brain books. These are books written by those who know it best. As neurologists, neuroscientists, and psychologists, the authors spend, or […]
Cerebral aneurysms are scary things. It is alarming enough that they exist, but it is more spine-chilling that they enlarge with time. The most infamous aneurysm arises from the posterior communicating artery, the so-called PCOM aneurysm. And it signifies its sinister intent when it gradually enlarges and compresses its vascular neighbour, the third cranial nerve, otherwise known as the oculomotor nerve. A dysfunctional third nerve manifests with a droopy eyelid (ptosis) and double vision (diplopia). The reason for the double vision becomes obvious when the neurologist examines the eyes; one eyeball is out of kilter and is deviated downwards and outwards; it is indeed down and out! The pupil is also very widely dilated (mydriasis). These are among the most worrying red flags in medicine, and a very loud call to arms. Cerebral aneurysms however often wave no flags, red or otherwise. Indeed the most malevolent of them will expand quietly until they reach horrendous proportions, and then, without much ado, just rupture. They are therefore veritable time bombs…just waiting to go off.
Cerebral aneurysm however do not need to reach large proportions to rupture; some just rupture when they feel like. Aneurysms under 7mm in diameter however are less prone to rupture. A rupturing aneurysm presents with very startling symptoms. The most ominous is a sudden onset thunderclap headache (TCH), subjects reporting feeling as if they have been hit on the back of the head with a baseball or cricket bat. It is not quite known what non-sporting patients experience-for some reason they never get aneurysms in neurology textbooks! More universally appropriate, a ruptured aneurysm may manifest as sudden loss of consciousness. Both symptoms result from leakage of blood into the cerebrospinal fluid (CSF) space, a condition known as a subarachnoid haemorrhage (SAH).
You may breath a small sigh of relief here because the vast majority of people with thunderclap headaches do not have subarachnoid haemorrhage. Unfortunately, every person who presents with a thunderclap headache must be investigated- to exclude (hopefully), or confirm (ruefully), this catastrophic emergency. The first test is a CT head scan which identifies most head bleeds. The relief of a normal scan is however short-lived because some bleeds do not show on the CT. The definitive test to prove the presence or absence of a bleed is less high tech, but more invasive: the humble spinal tap or lumbar puncture (LP). This must however wait for least 12 hours after the onset of headache or blackout. This is the time it takes for the haemoglobin released by the red blood cells to be broken down into bilirubin and oxyhaemoglobin. These breakdown products are readily identified in the biochemistry lab, and they also impart on the spinal fluid a yellow tinge called xanthochromia. The test may be positive up to 2 weeks after the bleed, but the sensitivity declines after this time. A positive xanthochromia test is startling and sets off an aggressive manhunt for an aneurysm-the culprit in most cases.
Many people with cerebral aneurysms have a family history of these, or of subarachnoid haemorrhage. Some others may have connective tissue diseases such as Ehler’s Danlos syndrome (EDS), adult polycystic kidney disease (APCKD), or the rare Loeys-Dietz syndrome. This family history is a window of opportunity to screen family members for aneurysms. The screening is usually carried out with a CT angiogram (CTA) or MR angiogram (MRA). People are often not born with aneurysms, but tend to develop them after the age of 20 years. Aneurysm surveillance therefore starts shortly after this age, and many experts advocate repeating the screening test every 5-7 years until the age of 70-80 years.
How are aneurysms treated? This will be the subject of a future blog post so watch this space!
Hypertonic saline is superior to mannitol for the combined effect on intracranial pressure and cerebral perfusion pressure burdens in patients with severe traumatic brain injury. Mangat HS, Wu X, Gerber LM, et al. Neurosurgery 2019 (Epub ahead of print). Abstract BACKGROUND: Hypertonic saline (HTS) and mannitol are effective in reducing intracranial pressure (ICP) after severe […]