Subarachnoid haemorrhage

Question 1

what is the definition of SAH?

Answer 1

Spontaneous bleeding into the subarachnoid space - between the arachnoid layer of the meninges and the pia mater

Question 2

what is the epidemiology of SAH?

Answer 2

• Typical age 35-65
• Account for some 5% of strokes
• Most common cause is rupture of Berry aneurysm

Question 3

what is the aetiology of SAH?

Answer 3

Rupture of saccular aneurysms (80%) e.g. berry aneurysms:
• Rupture of the junction of the posterior communicating artery with the internal carotid or of the anterior communicating artery with the anterior cerebral artery - in the circle of Willis
• 15% are multiple i.e. multiple aneurysms
• Associated with; polycystic kidney disease and coarctation of the aorta (narrowing of aorta where ductus arteriosus is)
Arteriovenous malformation (AVM) (10%):
• Vascular developmental malformation often with a fistula between arterial and venous systems causing high flow through the AVM and high-pressure arterialisation of draining veins
No cause found (15%)
Rare:
• Bleeding disorder
• Mycotic aneurysms - endocarditis
• Acute bacterial meningitis
• Tumours

Question 4

what are the risk factors of SAH?

Answer 4

• Hypertension
• Known aneurysm
• Family history
• Disease that predispose to aneurysm: Polycystic kidney disease, Ehlers Danlos syndrome (hyper-mobile joints with increased skin elasticity), Coarctation of aorta
• Smoking, bleeding disorders, post-menopausal decreased oestrogen

Question 5

what is the pathophysiology of SAH?

Answer 5

• Most common cause is ruptured aneurysm which leads to tissue ischaemia (since less blood can reach tissue) as well as rapid raised ICP as the blood (fast flowing since arterial), acts like a space-occupying lesion, puts pressure on the brain, resulting in deficits if not resolved quickly

Question 6

what are the key presentations of SAH?

Answer 6

Sudden onset ‘worst ever headache’, occipital in legion, described as being kicked in the head
Vomiting , collapse, seizures, coma
Neck stiffness
Kernig’s sign - lack of knee extension when thigh is flexed
Brudzinski’s sign - knee and hip flexion when neck is flexed
Vision problems
Fixed dilated pupils - CN3 palsy in posterior communicating artery aneurysm
Increased BP
Warning headache a few days before
Reduced GCS
irritates the meninges
irritates cerebral vessels and causes vasospasm > hypoxic injury
may track back into the ventricular system > hydrocephalus

Question 7

what are the signs of SAH?

Answer 7

Kernig’s sign - lack of knee extension when thigh is flexed
Brudzinski’s sign - knee and hip flexion when neck is flexed
Vision problems
Fixed dilated pupils - CN3 palsy in posterior communicating artery aneurysm
irritates the meninges
irritates cerebral vessels and causes vasospasm > hypoxic injury
may track back into the ventricular system > hydrocephalus

Question 8

what are the symptoms of SAH?

Answer 8

Sudden onset ‘worst ever headache’, occipital in legion, described as being kicked in the head
Vomiting , collapse, seizures, coma
Neck stiffness

Question 9

what are the first line and gold standard investigations for SAH?

Answer 9

(Arterial blood gas - exclude hypoxia)
Acute fresh blood hyperdense on CT (bright white) 
Blood in fissures and cisterns 
Star shaped lesions 
CT angiogram 
Lumbar puncture

Question 10

what are the differential diagnoses for SAH?

Answer 10

Migraine (SAH tends to be more sudden onset and associated with neck stiffness)
Meningitis
ICH

Question 11

how is SAH managed?

Answer 11

Neurosurgeon referral
IV fluids to lower blood pressure and maintain perfusion
Ca2+ blocker to reduce vasospasm (IV nimodipine)
Andovascular coiling
Intracranial stents and balloon remodelling

Question 12

what are the complications of SAH?

Answer 12

Rebleeding, cerebral ischaemia, hydrocephalus, hyponatraemia

Question 13

what is the prognosis of SAH?

Answer 13

Poor