| What are the results for treating aneurysms? |
Unruptured intracranial aneurysms
Treatment by watching and progress radiology.
Unruptured asymptomatic aneurysms have been studied in a multi-centre trial (ISUIA) demonstrating that over a short period of 8 years the chance of aneurysm rupture is very dependent on location and size. The risk varies from as low as 0.1% per year for small aneurysms less than 7 mm to 17% in the first year and then 2% per year for aneurysms greater than 25 mm in diameter. For certain aneurysm locations (such as the basilar artery) these risks are higher. The long-term risks are unknown but from post-mortem studies it has been estimated that half of all aneurysms bleed at some stage during a persons life. Another suggested concern is that the irregularly shaped aneurysm may be more likely to bleed even at a small size.
If an aneurysm is followed until it ruptures there is a 66% chance of death and a significant chance of permanent neurological dysfunction.
Treatment by microsurgery.
Risks of surgery are dependent on aneurysm size, aneurysm location, the presence of calcification at the base of the aneurysm, age of the patient, and coincidental medical problems. The most common complications leading to an adverse outcome are the blockage of small or large arteries at the time of surgery and bleeding. In more than 1,750 aneurysms treated by Professor Morgan half have been for aneurysms that have not ruptured. For these cases the potential for some adverse result from treatment are close to a 1% risk per mm diameter of the aneurysm. Therefore, a 7 mm aneurysm approximates a 7% risk of treatment and a 25 mm aneurysm a 25% chance of adverse outcome. These adverse outcomes include may be mild, neurological deficits that do not interfere with independent function (half of all patients with an adverse outcome), or severe including death and major disability (half of all patients with adverse outcomes). Of the more than 600 small unruptured aneurysms in the anterior circulation treated by Professor Morgan the severe adverse outcomes are uncommon (less than 1%). These aneurysms, when effectively treated, have not bled following surgery.
Treatment by coil insertion.
The most common complications of treatment is failure to cure, rupture of the aneurysm, blockage of small or large arteries at the time of treatment, and re-opening of the aneurysm at some later date. As with microsurgery, these risks are very dependent on aneurysm size and location. Whilst we can estimate the risks from series to be about 5-9% chance of some adverse effect occurring (from rupture or blocking an artery) at the time of the procedure the number of aneurysms that are not cured at the initial treatment varies depending on the cases selected. When only certain aneurysm locations are considered, the opening into the aneurysm measures less than 4 mm and the body of the aneurysm is at least twice the size as the opening the immediate chance of preventing blood entering the aneurysm approaches 95%. However, when more difficult aneurysms are coiled the chance of preventing blood entering the aneurysm falls well below 95%. Of greater uncertainty is the chance of the aneurysm from re-opening. In certain locations this has been reported as often as 20% of cases within the first 2 years (longer follow-up data is not yet reliable). The difference between why aneurysms might re-open after coiling and less so after surgery is likely to be because of the fundamental difference in treatments (i.e. that clipping closes off the mouth into the aneurysm whereas coiling packs the open mouth of the aneurysm).
Choosing between methods of management.
In general, for aneurysms less than 6 mm that are asymptomatic without any irregular features in the anterior circulation unassociated with a previous history of ruptured aneurysm the usual recommendation is to watch and monitor the patient. For very young patients this may not be appropriate and for older patients any asymptomatic aneurysm (irrespective of size) may be inappropriate to treat.
Ruptured intracranial aneurysms.
Outcome for treating aneurysmal subarachnoid haemorrhage is dependent on the severity and damage caused by the initial bleed (or re-bleeding) and complications from treatment (such as surgery, coiling or medical management in intensive care)(see endovascular surgery and microsurgery). The overall results from Royal North Shore and Dalcross Hospitals from 1992 until 2003 (in excess of 500 aneurysmal subarachnoid haemorrhage patients treated by Professor Morgan) have found at 3 months following the subarachnoid haemorrhage that 65.5% of patients are normal, 15% have a neurological deficit but are independent for activity of daily living, 14% are alive but have a significant neurological deficit that renders them dependent on others for some aspects of activities of daily living, and 5.5% are dead.
In those who are neurologically normal on admission a normal outcome is expected in 93% with the remaining cases divided equally between those that are neurologically abnormal but independent for activities of daily living and those with loss of independence (death in this group is very unusual). 41.7% of those with a focal neurological deficit or decrease in level of consciousness at time of admission are normal at three months, 25% are abnormal but independent for activities of daily living, 23.1% have a loss of independence and 10.2% are dead. The effect of vasospasm has been minimised and does not currently have a significant negative impact on outcome. Having said this, the intensive care management and radiological interventions necessary to treat vasospasm are very complex with the potential for significant risks (see vasospasm).
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