Subarachnoid Haemorrhage Flashcards
What is a subarachnoid haemorrhage (SAH)?
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 (the anatomical space between the arachnoid mater and pia mater).
Briefly describe the anatomy of the meninges
What are the risk factors for SAH?
- Family history
- Female gender
- African descent
- Smoking
- Hypertension
- Excessive alcohol
- Cocaine use
Who is commonly affected by SAH?
They typically occur in patients around 60 yrs old and account for 3% of all strokes.
Subarachnoid haemorrhage is more common in black and female patients.
What conditions are associated wtih SAH?
It is particularly associated with:
- Cocaine use
- Sickle cell anaemia
- Connective tissue disorders (such as Marfan syndrome or Ehlers-Danlos)
- Neurofibromatosis
- Autosomal dominant polycystic kidney disease
How can SAH be classified?
SAH can be classified into either aneurysmal or non-aneurysmal causes:
- Aneurysmal disease (85%) is associated with ADPKD, fibromuscular dysplasia, connective tissue disorders, atherosclerosis and hypertension
- Non-aneurysmal causes for SAH include trauma, arteriovenous malformations, coagulopathies and tumour-related
What is the most common cause of SAH?
The most common cause of SAH is head injury and this is called traumatic SAH.
What are berry aneurysms?
Berry aneurysms are ‘berry-shaped’ true aneurysms that occur at the bifurcation of arteries.
They are typically saccular aneurysms that occur mostly at either the circle of Willis and the bifurcation of the middle cerebral artery.
Unruptured aneurysms occur in around 3% of the adult population; those that present ruptured will be at the age 40-60yrs and can cause either a subarachnoid haemorrhage, cerebral haematoma, or intraventricular haemorrhage.
How do berry aneurysms lead to SAH?
Intracranial aneurysm= saccular ‘berry’ aneurysms.
This accounts for around 85% of SAH cases.
Aneurysmal SAH causes substanital morbidity and mortality. When a cerebral aneurysm ruptures, blood flows into the subarachnoid space, sometims seeping into the brain parenchyma and/ or the ventricles. The sudden increase in intracranial pressure, as well as the destructive and toxic effects of blood on brain parenchyma and cerebral vessles, accounts for most complications.
What conditions have an increased risk of berry aneurysms?
Conditions associated with berry aneurysms include adult polycystic kidney disease, Ehlers-Danlos syndrome and coarctation of the aorta.
What are the clinical features of SAH?
SAH will classically presents with a severe headache, sudden onset (within seconds to minutes), typically in the occipital region (often termed “thunderclap” headaches).
Other features include nausea and vomiting, reduced consciousness, collapse, or seizures, or evidence of meningism (including photophobia, stiff neck, pain on neck flexion, or positive Kernig’s sign).
How will SAH show on a neurological examination?
Examination may reveal focal neurology or evidence of meningism, however may be otherwise unremarkable.
What investigations should be ordered for SAH?
- Non-contrast CT head
- FBC
- Serum electrolytes
- Clotting profile
- Troponin I
- Serum glucose
- ECG
- Lumbar puncture
- Angiography (CT or MRI)
What is the gold standard test for SAH?
CT head is the first line investigation. Immediate CT head is required.
How will SAH present on a CT head?
Blood will cause hyperattenuation in the subarachnoid space therefore hyperdense areas in the subarachnoid space/basal cisterns.
When should a lumbar puncture be performed for diagnosing SAH?
Perform an LP if CT head is negative (2% of patients) or inconclusive but you have a high clinical suspicion of SAH. However, wait for at least 12 hours to pass from the onset of symptoms before performing an LP.
What may a lumbar puncture show in SAH?
CSF can be tested for signs of subarachnoid haemorrhage:
- Red cell count will be raised
- If the cell count is decreasing in number over the samples, this could be due to a traumatic lumbar puncture
- Xanthochromia (the yellow colour of CSF caused by bilirubin)
What is the role of angiography (CT or MRI) in diagnosing SAH?
Request angiography (CT or MRI) in patients with confirmed SAH to identify the causal pathology, define anatomy, and plan the best option to secure the aneurysm related to the haemorrhage.
Briefly describe the immediate treatment of SAH
Patients should be managed by a specialist neurosurgical unit. Patients with reduced consciousness may require intubation and ventilation.
Observe the patient continuously using GCS scoring.
Give nimodipine (orally, or by nasogastric tube if the patient is unable to swallow) as soon as SAH is confirmed to prevent delayed cerebral ischaemia and improve outcomes such as survival and being independent in activities of daily living.
What is the role of nimodipine in treating SAH?
Nimodipine is a calcium channel blocker that is used to prevent vasospasm. Vasospasm is a common complication that can result in brain ischaemia following a subarachnoid haemorrhage.
What is the role of surgery in treating SAH?
Surgical intervention may be used to treat aneurysms. The aim is to repair the vessel and prevent re-bleeding. This can done by coiling, which involves inserting a catheter into the arterial system (taking an “endovascular approach”), placing platinum coils into the aneurysm and sealing it off from the artery. An alternative is clipping, which involves cranial surgery and putting a clip on the aneurysm to seal it.
What are the clinical features of hydrocephalus in SAH?
How is is treated?
Gradually worsening level of arousal with relative preservation of deliberate motor responses, severe headache, vomiting and agitation.
Refer urgently to a neurosurgeon if there are signs/symptoms of acute hydrocephalus. Lumbar puncture or insertion of a shunt may be required to treat hydrocephalus.
What are the complciations of SAH?
- Neuropsychiatric problems
- Over 50% of survivors report cognitive impairment (e.g., mood and memory problems), resulting in a negative impact on functional status, emotional health and quality of life
- Chronic hydrocephalus
What differentials should be considered for SAH?
- Arterial dissection
- Cerebral and cervical arteriovenous malformation (AVM)
- Dural arteriovenous malformations (AVF)
- Vasculitis
What is shown in the image?
SAH
What is shown in the image?
SAH
What is shown in the image?
SAH
Review the various intracranial bleeds
(A) axial
(B) coronal views
EDH = epidural haematoma
SDH = subdural haematoma
SAH = subarachnoid haemorrhage
IPH = intraparenchymal haemorrhage
