Seek urgent local assessment for a sudden severe headache or acute neurological symptoms. Contact your local emergency service. Do not wait for a routine consultation or travel for treatment first.1 2

A headache that needs emergency investigation

A thunderclap headache reaches severe intensity abruptly. Clinicians investigate it because subarachnoid bleeding is one possible cause, alongside other conditions. A person need not describe it using a particular phrase such as “the worst headache of my life” for the problem to merit attention. People may have difficulty describing onset because they are confused, drowsy, in pain or communicating in another language. A witness can help explain what happened without delaying care.1

Bleeding can be accompanied by neck pain or stiffness, nausea, vomiting, sensitivity to light, collapse, a seizure or changes in awareness. Sudden weakness, speech trouble or other new neurological problems also need urgent assessment. This is a description of possible presentations, not a requirement to have every sign. Less dramatic symptoms and a headache that improves do not establish that bleeding is absent.1 2

Many aneurysms are found without warning symptoms

An unruptured aneurysm is often found incidentally on an examination performed for another reason. Some aneurysms can affect nearby nerves or structures, producing problems such as changes in vision or eye movement. An image finding and a symptom still need to be considered together: an aneurysm on a scan is not automatic proof that it caused a chronic headache. New acute changes should not be assigned to a familiar diagnosis without assessment.2 3

Most headaches have causes other than aneurysmal bleeding. That general fact cannot tell an individual reader what caused a new headache. Equally, the absence of pain does not make an incidentally detected aneurysm permanently safe. The planned-care question depends on the aneurysm and the person's circumstances rather than symptoms alone.3

What information helps the assessing team

If possible, describe when symptoms began, how quickly they became severe, what was happening at onset and any change in awareness or movement. Bring available information about earlier aneurysm imaging, procedures and current medicines. These details support clinical assessment; gathering paperwork must not postpone an emergency call.

The clinical team decides what tests are needed and how to interpret them. A negative result has a meaning in a particular context, including the type of test and timing. A screening scan from months earlier is not an assessment of today's acute symptoms. The diagnosis and screening article explains this distinction.1

For a stable incidental finding, prepare a planned discussion using unruptured aneurysms. If bleeding is confirmed, the ruptured aneurysms article describes hospital care. Neither route replaces urgent local assessment when an acute problem is present.

References

National Institute for Health and Care Excellence. NG228. Subarachnoid haemorrhage caused by a ruptured aneurysm: diagnosis and management. 2022. Source ↩
US National Library of Medicine. MedlinePlus: Brain Aneurysm. Updated 30 September 2024. Source ↩
Etminan N et al. European Stroke Journal. 2022;7: LXXXI–CVI. doi:10.1177/23969873221099736. Source ↩