Sub-arachnoid haemorrhage Flashcards
How common is it?
Accounts for 5% of strokes. Incidence of 6 per 100,000 per annum.
Who does it affect?
The mean age of patient presentation is 50.
What causes it?
Spontaneous arterial bleeding into the subarachnoid space. This can be caused by:
- Saccular ‘berry’ aneurysms in 70% of cases. These are acquired lesions that are most commonly located at the branching points of the major arteries coursing through the subarachnoid space at the base of the brain (Circle of Willis)
- Congenital arteriovenous malformations (10%)
- In 20% of cases no lesion can be found.
What risk factors are there?
Probably everything for hypertension.
How does it present?
Most intracranial aneurysms remain asymptomatic until they rupture and cause an SAH.
Some however, become symptomatic because of a mass effect, and the most common symptom is a painful third nerve palsy.
The typical presentation of a SAH is the sudden onset of a severe headache, often occipital, that reaches its maximum intensity immediately or within minutes (worst ever, absence of similar headaches in the past). It is often accompanied by nausea and vomiting, and sometimes a LOC.
Signs on examination?
May be signs of meningeal irritation (neck stiffness and a positive kernings sign), focal neurological signs and a sunbhyaloid haemorrhages (between the retina and vitreous membrane) with or without papilledema. Some patients experience a warning headache a few days before the bleed.
Investigations
Immediate CT
Lumbar puncture is indicated if there is a strong clinical suspicion of a SAH but the CT scan is normal. An increase in pigments (bilirubin and/or oxyhaemoglobin released from lysis and phagocytosis of RBCs) is the key finding to support SAH. Must be performed at least 12 hours after onset. Can be detected for 2 weeks after onset. Sample should be protected from light.
MR angiography is usually performed to establish the source of bleeding in all patients potentially fit for surgery.
Treatment
Cautious control of hypertension, bed rest and supportive management.
Nimodipine, a calcium channel blocker can be given to reduce cerebral artery spasm.
Obliteration of the aneurysm by surgical clipping or insertion of a fine wire coil under radiological guidance prevents re-bleeding.
Surviving patients should be advised on lifestyle changes.
50% die suddenly, and 10-20 die in the early weeks in hospital. If you have a good GCS when you come in you are likely to do alright (>12)
Conditions that would present similarly
Other types of strokes.
Hypoglycaemia.
Conditions which cause dizziness, faintness or disturbed balance.
Migraine.
Neurological abnormalities (e.g. MS, focal neuropathy, previous stroke).
Mass lesions.
Postictal states and seizures.
Hyperglycaemia.
Hyponatraemia and hepatic encephalopathy.
Facitious stroke (functional hemiparesis).
Anxiety. Physical trauma.
