Usually not. A substantial proportion of aneurysms arising in the cerebral arteries remain silent for years and are found incidentally on an MRI or CT performed for some other reason.
How Common Are They?
The prevalence of unruptured cerebral aneurysm in the general population is estimated at approximately 3%.
The belief that “an aneurysm always makes itself known before it bleeds” is therefore mistaken.
Can There Be a Headache Beforehand?
Some patients describe an unaccustomed, severe headache in the days or weeks before an aneurysm bleeds. This is sometimes termed a warning or sentinel headache.
It does not occur in every patient, however, and headache should not be regarded as a reliable early warning system for an aneurysm.
Symptoms Arising from Pressure on Nerves
Larger unruptured aneurysms, or those pressing on adjacent nerves, may give rise to:
- drooping of the eyelid;
- double vision;
- impairment of eye movements;
- marked enlargement of one pupil.
What Is the Headache Like When an Aneurysm Bleeds?
When an aneurysm bleeds — that is, when a subarachnoid hemorrhage occurs — the most characteristic feature is a very severe headache of sudden onset that reaches its greatest intensity within seconds or minutes. Patients sometimes describe it as “the worst headache of my life”.
A headache of sudden onset and unaccustomed severity requires urgent medical assessment, rather than waiting or taking an analgesic in the hope that it will pass.
The headache may be accompanied by:
- nausea and vomiting;
- neck stiffness;
- loss of consciousness;
- seizures;
- neurological disturbance.
The 2023 guideline of the American Heart Association and the American Stroke Association emphasizes that a severe headache of sudden onset of this kind should be assessed promptly for subarachnoid hemorrhage.
Does Every Aneurysm That Is Found Require Treatment?
No. Whether an unruptured aneurysm is treated is not decided merely on the basis that one is present. The following are considered together:
- the size, site and shape of the aneurysm;
- whether it has grown over time;
- the age of the patient;
- factors such as hypertension and smoking.
Where treatment is required, surgical clipping or endovascular methods applied from within the vessel may be used.
In Short
Most cerebral aneurysms give no clear warning before they bleed. Some patients experience headache or symptoms arising from pressure on nerves. One of the most important warning signs is a headache of sudden onset and unaccustomed severity. In such a case urgent assessment is required without delay.
For detailed information on the diagnosis and treatment of cerebral aneurysms, see the Cerebral Aneurysm page.
References
- Hoh et al., Stroke, 2023 — AHA/ASA Guideline for the Management of Aneurysmal Subarachnoid Hemorrhage
- Vlak et al., Lancet Neurology, 2011
- Tawk et al., Mayo Clinic Proceedings, 2021