Subarachnoid haemorrhage

Question 1

What is a subarachnoid haemorrhage?

Answer 1

A subarachnoid haemorrhage (SAH) is an intracranial haemorrhage that is defined as the presence of blood within the subarachnoid space, i.e. deep to the subarachnoid layer of the meninges.

Question 2

What is the most common cause of SAH?

Answer 2

The most common cause of SAH is head injury and this is called traumatic SAH.
In the absence of trauma, SAH is termed spontaneous SAH.

Question 3

What are the causes of SAH?

Answer 3

Intracranial aneurysm* (saccular ‘berry’ aneurysms): this accounts for around 85% of cases. Conditions associated with berry aneurysms include adult polycystic kidney disease, Ehlers-Danlos syndrome and coarctation of the aorta

Arteriovenous malformation

Pituitary apoplexy

Arterial dissection

Mycotic (infective) aneurysms

Perimesencephalic (an idiopathic venous bleed)

Question 4

What are the risk factors for SAH?

Answer 4

The bigger the aneurysm, the more likely it is to bleed.
Hypertension
Smoking
Cocaine use is a risk factor and is also associated with a worse outcome
Excessive alcohol intake roughly doubles the risk
Although no single gene has been isolated, genetic factors also play a part and account for around 10%
Linked genetic disorders include autosomal dominant adult polycystic disease, Ehlers-Danlos syndrome type IV and neurofibromatosis type 1. Berry aneurysms are found in 10% of patients with autosomal dominant adult polycystic kidney disease and represent 2% of cases of SAH.
Marfan’s syndrome has also been linked to SAH through the presence of berry aneurysms.

Question 5

Where do berry aneurysms most commonly occur?

Answer 5

Most berry aneurysms under 7 mm do not rupture, but they grow unpredictably.
85% occur in the Circle of Willis.
Multiple aneurysms are seen in 30% of patients.
Most are saccular aneurysms. These are not congenital but develop over the course of life, being rare in children

Question 6

What are the presenting features of SAH?

Answer 6

Headache: typically sudden-onset (‘thunderclap’ or ‘baseball bat’), severe (‘worst of my life’) and occipital
Nausea and vomiting
Meningism (photophobia, neck stiffness)
Coma
Seizures
Sudden death
ECG changes including ST elevation may be seen

Question 7

What are sentinel bleeds?

Answer 7

There may be warning symptoms in the three weeks prior to SAH that represent small leaks. These are called sentinel bleeds or expansion of the aneurysm.

These are usually headaches with the characteristics of SAH but which resolve by themselves without further symptoms.

Question 8

What are the signs and symptoms that may accompany sentinel bleeds?

Answer 8

The most common symptoms are headache (48%), dizziness (10%), orbital pain (7%), diplopia (4%) and visual loss (4%).
Signs may accompany these sentinel bleeds: sensory or motor disturbance (6%), seizures (4%), ptosis (3%), bruits (3%) and dysphasia (2%).

Question 9

What is seen in the examination of a patient presenting with SAH?

Answer 9

Decreased conscious level
Neck stiffness may occur due to meningeal irritation by blood.
Ophthalmoscopy may show intraocular haemorrhages.
Focal neurological signs suggestive of a stroke.

Question 10

What is the cause of SAH in a person known to have seizures?

Answer 10

Arteriovenous malformation

Question 11

What are the differentials of SAH?

Answer 11

Other causes of stroke.
Meningitis (rarely features thunderclap headache).
Trauma.
Thunderclap headache of other aetiology.
Primary sexual headache.
Cerebral venous sinus thrombosis.
Cervical artery dissection.
Carotid artery dissection.
Hypertensive emergency (severely raised blood pressure).
Pituitary apoplexy (infarction or haemorrhage of the pituitary gland).

Question 12

What are the investigations done in a person presenting in a px with SAH?

Answer 12

Every patient in whom SAH is suspected should have a CT scan at the earliest opportunity.

This should be done immediately if the patient presents with a sudden severe headache, and as soon as possible in all other cases.

Cerebral panangiography
LP
ECG

Question 13

What does the CT show in SAH?

Answer 13

If SAH is suspected, CT scanning (without contrast) is the first line in investigation because of the characteristically hyperdense appearance of blood in the basal cisterns.
CT without contrast will correctly identify 95-98% of cases, particularly if performed within 24 hours of onset.
The distribution of blood can give some indication of the location of the aneurysm.

Question 14

When is a false positive diagnosis of SAH on CT possible?

Answer 14

A false positive diagnosis of SAH on CT is possible in the presence of generalised brain oedema, which causes venous congestion in the subarachnoid space.

Question 15

What is the gold standard investigation for the detection of ruptured aneurysms in the brain?

Answer 15

Cerebral panangiography continues to be the gold standard for detection, demonstration and localisation of ruptured aneurysms.

After an SAH is confirmed, its origin needs to be determined. If the bleeding is likely to have originated from an aneurysm, the choice is between cerebral angiography (injecting radiocontrast through a catheter to the brain arteries) and CT angiography (visualising blood vessels with radiocontrast on a CT scan) to identify aneurysms.

Question 16

Which method of angiography offers a possibility of coiling the aneurysm?

Answer 16

Catheter angiography also offers the possibility of coiling an aneurysm.

Question 17

When should a LP be performed in a px presenting with SAH?

Answer 17

Lumbar puncture to remove a CSF sample from the lumbar sac should ideally take place over 12 hours after the onset of the headache because if there are red cells in the CSF, sufficient lysis will have taken place during that time for bilirubin and oxyhaemoglobin to have formed.

Question 18

What is used to diagnose SAH in an LP sample?

Answer 18

Spectrophotometry should be used to examine the CSF, to permit the detection of small amounts of xanthochromia (yellow discolouration of the spinal fluid). The ‘three tube test’ (a decrease in red cells in consecutive tubes on visual inspection) is notoriously unreliable.

Question 19

What is the early management of SAH?

Answer 19

Initial management of SAH aims to prevent further bleeding and to reduce the rate of secondary complications, such as cerebral ischaemia or hydrocephalus.

Re-bleeding is the most imminent danger; a first aim is therefore occlusion of the aneurysm. Endovascular obliteration by means of platinum spirals (coiling) is now the preferred mode of treatment, but some patients require a direct neurosurgical approach (clipping).

Question 20

What is nimodipine used for in the management of SAH?

Answer 20

Another complication is delayed cerebral ischaemia due to vasospasm; the risk is reduced with oral nimodipine and probably by maintaining circulatory volume.

Question 21

What is the supportive management of SAH?

Answer 21

Every patient should be referred to a specialist unit, usually neurosurgical, for investigation and, if appropriate, definitive treatment. This transfer should take place within 24 hours if appropriate.

Patients should be under continuous observation in an intensive care unit, or in an intermediate care facility of a stroke or neurovascular unit.

Staff should be experienced in assessing swallowing function to prevent pneumonia, a frequent complication after SAH and independent risk factor for poor outcome.

All necessary supportive care should be provided. This often includes intubation and ventilation in patients with depressed conscious level, together with nasogastric feeding. For most patients this will mean an intensive care bed.

Analgesia and antiemetics are needed for conscious patients.

Question 22

Apart from nimodipine, what can be used to prevent vasospasm?

Answer 22

Nitroprusside (a potent vasodilator) and labetolol may be employed to treat hypertension; the level should be low enough to prevent re-bleeding whilst high enough to maintain cerebral perfusion.

Patients should not be given an antifibrinolytic agent or steroids.

Question 23

What is coiling?

Answer 23

Coiling is performed through femoral catheterisation with platinum coils that obliterate the aneurysm by causing a blood clot to form in it.

Question 24

What is clipping?

Answer 24

Clipping requires a craniotomy followed by the placement of clips around the neck of the aneurysm.

Question 25

Why is the treatment of hydrocephalus important in SAH?

Answer 25

Hydrocephalus may complicate SAH both in the short and in the long term. Relief of hydrocephalus can cause an enormous improvement in a patient’s clinical status.

Hydrocephalus might cause gradual obtundation in the first few hours or days; it can be treated by lumbar puncture or ventricular drainage, dependent on the site of obstruction.

Question 26

What is involved in the secondary prevention of SAH?

Answer 26

All surviving patients should be advised on secondary prevention, especially on treatment for hypertension and the need to stop smoking.

10-15% of patients with SAH do not survive as far as hospital.

Any patient with residual impairment after investigation and treatment should be referred to an appropriate specialist rehabilitation service.

Patients with a strong family history (one other affected first-degree relative and/or with a history of polycystic kidney disease) should be advised that their immediate family may be at greater risk of SAH, and a referral made to a neurovascular specialist for up-to-date information and advice.