Subarachnoid haemorrhage

Clinical History

The patient collapsed at work with a severe headache of sudden onset.

Imaging Findings

The patient collapsed at work with a severe headache of sudden onset. She became drowsy and was taken by ambulance to hospital. On examination she was photophobic, with minimal neck stiffness, GCS was 13/15 and there was no focal neurology.

An urgent CT scan of the brain was obtained.

Discussion

Acute subarachnoid haemorrhage (SAH) occurs most commonly as a result of rupture of a saccular aneurysm at the base of the brain. These are not thought to be congenital but develop during the course of life. The aneurysms occur commonly at sites of arterial bifurcation and their precise aetiology is unclear. Approximately 85% of intracerebral aneurysms arise from the anterior aspect of the circle of Willis, whereas 15% arise in the vertebrobasilar territory. Common locations include the anterior communicating artery (33%), middle cerebral artery (30%), posterior communicating artery (25%) and the basilar artery (10%). Approximately 15% of cases of SAH result from other causes such as non-aneurysmal peri-mesencephalic haemorrhage, bleeding from arteriovenous or other vascular malformations, arterial dissection, septic aneurysms or coagulopathy.

The classic presentation of acute SAH is with sudden onset of severe headache ("thunderclap headache"), which is often described as "the worst headache of my life". A period of unresponsiveness occurs in up to half of patients and focal signs develop in approximately one-third. Nausea, vomiting and neck stiffness can occur and sub-hyaloid haemorrhages may be identified with fundoscopy. Seizures may also be a feature of SAH.

Smoking, hypertension and heavy drinking are significant risk factors for SAH. An increased incidence of intracerebral aneurysm formation is associated with specific inherited disorders of connective tissue (such as Ehlers-Danlos disease and Marfan's syndrome) and with autosomal dominant polycystic kidney disease.

The initial investigation of choice in patients with suspected SAH is unenhanced cerebral CT scan. This may identify blood, which is seen as high attenuation in the cerebral subarachnoid spaces. Haemorrhage may also be seen intracerebrally. The pattern of the haemorrhage often suggests the location of the bleeding. A negative CT scan does not exclude SAH however. Up to 14% of patients with SAH may have a negative CT scan and many will require lumbar puncture in order to look for red cells and blood products from cell lysis (pigments that cause a yellow tinge or xanthochromia) in the CSF. Catheter angiography can identify and localise aneurysms and is seen as the 'gold standard' for diagnosis. However this technique does have associated risks and is time consuming. Many patients with SAH are now investigated with CT or MR angiography (CTA or MRA) in order to identify aneurysms. These techniques are becoming more popular because of their non-invasive nature and as CT and MRI techniques improve producing better vascular imaging.

SAH is associated with a high morbidity and mortality and a significant proportion of patients who survive are left with disablity. Vasospasm can occur in association with SAH resulting in cerebral ischaemia and possibly infarction which worsens the prognosis.

Treatment options include surgical clipping of the aneurysm, interventional endovascular coil embolisation, and combinations of the two.

Differential Diagnosis List

Final Diagnosis

Subarachnoid haemorrhage

URL:	https://www.eurorad.org/case/1603
DOI:	10.1594/EURORAD/CASE.1603
ISSN:	1563-4086