Subarachnoid haemorrhage and CSF xanthochromia analysis Flashcards
What is the Subarachnoid space?
- Sits between the pia mater (inner) and the arachnoid (outer) mater
- Contains CSF as a protective layer around the brain
- Arteries and veins reside in the subarachnoid space before penetrating the surface of the brain
What is a Subarachnoid Haemorrhage?
Escape of blood from a cerebral artery into the subarachnoid space
What are causes of Subarachnoid Haemorrhage?
- Most SAH are due to rupture of a cerebral aneurysm
- Protruding lesion caused by haemodynamic stress at a weak spot in a blood vessel, often at bifurcation points/bends
What are causes of SAH?
- Congenital defects
- Injury or infection of the vessel
- Medical conditions such as arteriovenous malformations and connective tissue disorders
An aneurysm may be unsuspected until rupture occurs. Physical exertion may trigger a rupture but most aneurysmal SAH occur without an identifiable trigger
What are symptoms of Subarachnoid haemorrhage?
- Severe headache of acute onset (“thunderclap headache”), classically occipital
- Vomiting
- Altered level of consciousness, coma unusual
- Blurred vision (retinal haemorrhage)
- Neck pain
What are causes of the symptoms in subarachnoid haemorrhages?
- Meningeal irritation
- Hydrocephalus: blood in the subarachnoid space affects the flow and absorption of CSF, may lead to increased intracranial pressure
- Vasospasm of cerebral blood vessels leads to: release of substances during lysis of blood clots causes endothelial damage and smooth muscle contractionrestricts blood supply to parts of the brain, may cause cerebral ischaemia.
What are other differential diagnosis when consider Subarachnoid Haemorhage?
- Spontaneous intracranial hypotension
- Pituitary apoplexy
- Ischaemic stroke
- Acute hypertensive crisis
- Infections (eg acute complicated sinusitis)
What are epidemiological statistics surround SAH?
Incidence of SAH from ruptured aneurysms is approximately 12 cases per 100,000 people per year in North America and Europe
Mean age for SAH is 50 years
Hypertension, cigarette smoking and family history are the most consistently observed risk factors
Of patients with aneurysmal SAH:
- ~25% die within 24hrs
- ~45% die within 30 days
- ~50% re-bleed within 6 months
What are survivors of SAH afflicted with?
Survivors commonly experience deficits in:
- •Memory
- •Cognition
- •Language
These may be further compounded by depression, anxiety, fatigue and sleep disturbance
How is SAH acutely managed?
- Discontinue antithrombotic/anticoagulant therapy
- Manage increased intracranial pressure: physically (drain or shunt) and medically (diuresis)
- Consider antiepileptic drugs to prevent seizures (evidence of benefit is unclear)
- Prevention of vasospasm (Nimodipine (calcium channel blocker))
- Maintain euvolaemia (IV fluids): hypovolaemia is a risk factor for ischaemic complications
What are forms of aneurysm repair?
Clipping
- A clip is placed across the neck of the aneurysm, preventing blood flow
- Surgical intervention
- Requires craniotomy
Coiling
- A platinum wire is fed through a catheter into the aneurysm
- A small thrombosis forms around the coil, preventing blood flow
- Can be done as an extension of angiography
- Generally better outcomes than clipping
How is SAH diagnosed and the advanatges of using CT scans?
High resolution CT scan without contrast within 48 h of initial bleed will detect ~95% of SAH. Highest sensitivity within 6-12 h
Advantages
- Location of ruptured aneurysm
- Condition of ventricles
- Overall blood load
- Presence of cerebral infarction
Late presenting cases
- Within 48hrs of bleed, 5% patients with SAH show no evidence on CT
- After 1 week, 50% patients with SAH show no evidence on CT
- After 2 weeks, 70% patients with SAH show no evidence on CT
May fail to detect small SAH
- Especially if imaging is performed several days post-bleed
- CT scans are affected by patient motion; sedation may be necessary to obtain satisfactory diagnostic images
What is angiography for SAH?
Positive CT scan – proceed to angiogram
- Catheter inserted into major artery & threaded through circulatory system
- Contrast agent injected to visualise blood vessels
What are benefits and disadvantages of Angiography?
- Determine location of aneurysm & relationship with surrounding blood vessels
- Resource intensive
- Invasive procedure with (small) risk of morbidity and mortality