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Background

Subarachnoid haemorrhage (SAH) refers to extravasation of blood (bleeding) into subarachnoid space (where cerebrospinal fluid is housed) between pia mater and arachnoid mater (usually secondary to head trauma)
Nontraumatic (spontaneous) SAH occurs in the setting of a ruptured cerebral saccular (berry) aneurysm or arteriovenous malformation (AVM)
Prehospital mortality rates from acute SAH have been reported to be 22% to 26% and the course of symptoms is very rapid
Patients complain of “worst headache of their life” or “thunderclap headache”
Rupture of an aneurysm can result from an acute trigger, such as physical exertion or can occur in the absence of an acute trigger, such as in sleep

	Extradural hemorrhage	Subdural hemorrhage	Subarachnoid hemorrhage
Location	Between the skull bone and the dura mater	between the dura and the arachnoid mater	Between the arachnoid and pia mater
Pathophysiology	Rupture of middle meningeal artery on the temporal surface of the skull	rupture of bridging cranial veins	Rupture of a berry aneurysm
Clinical presentation	history of trauma Skull fracture Lucid interval, followed by unconsciousness	History of trauma Older patients Alcohol misuse Child, non-accidental injury Gradual deterioration	History of trauma Rupture of berry aneurysm Thunderclap headache Sudden onset of symptoms
CT findings	Convex shaped	Concave/crescent	Hyper-attenuation around the circle of Willis

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Risk factors for SAH

For alert patients >15 years of age with new severe non-traumatic headache reaching maximum intensity within 1 hour. Patients require additional investigation for SAH if they meet any of the following criteria.
1	Age >40 years
2	Neck pain or stiffness
3	Witnessed loss of consciousness
4	Onset during exertion
5	Thunderclap headache (instantly peaking pain)
6	Limited neck flexion on examination

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Characteristics	Risk factors
Rerupture
Residual aneurysm	Incomplete aneurysm occlusion results in a higher risk of rerupture. However, even completely obliterated aneurysms carry a risk of rerupture in the long term
Coiled aneurysm	Coiled aneurysms have a higher rate of incomplete occlusion and recurrence and therefore have a higher risk of rerupture
De novo
Formation	Risk factors for de novo aneurysm in patients with ruptured aneurysm include younger age, family history, and multiple aneurysm
Growth and rupture	Risk factors for growth and rupture of de novo aneurysm include female sex, shorter interval to formation of the de novo aneurysm, multiple aneurysms and large size

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Sudden onset of severe headache often described as “the worst headache of my life”
Nausea and vomiting (secondary to increased intracranial pressure)
Signs of meningeal irritation (nuchal rigidity)
Photophobia and visual changes
Focal neurological deficits
Seizures

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CT head without contrast (hyperdensities in the suprasellar cisterns extending peripherally)
When CT head without contrast is normal and there is still high suspicion for SAH (over 6 hours from onset of symptoms, lumbar puncture (LP_ is indicated
LP shows xanthromia (bloody or yellow)

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Arterial vasospasm can occur due to blood breakdown or rebelled 3-10 days after haemorrhage (prevented by nimodipine)
Communicating and/or obstructive hydrocephalus
Hyponatremia (secondary to development of SIADH)

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Medical (nimodipine as a prophylaxis to reduce the risk of vasospasm and delayed cerebral ischemia)
Surgical (Aneurysmal repair)

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Overview of Subarachnoid Hemorrhage
Clinical features	Most commonly due to ruptured arterial saccular (berry) aneurysm Severe headache at onset of neurological symptoms Meningeal irritation (e.g., neck stiffness) Focal deficits uncommon
Complications	Rebleeding (first 24 hours) Vasospasm (after 3 days) Hydrocephalus/increased intracranial pressure Seizures Hyponatremia (usually secondary to SIADH)
Diagnosis	Noncontrast head CT scan is >90% sensitive Lumbar puncture required to definitively rule out SAH Xanthochromia in cerebrospinal fluid confirms diagnosis (usually seen 6 hours after onset) Cerebral angiography to identify bleeding source
Treatment	Angiographic procedure to stabilize aneurysm by coiling or stenting (endovascular therapy) Nimodipine and hyperdynamic therapy to reduce vasospasm

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