Subarachnoid haemorrhage

Subarachnoid haemorrhage

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 most common cause of SAH is head injury and this is called traumatic SAH . In the absence of trauma, SAH is termed spontaneous SAH . The rest of this note focuses on spontaneous SAH.

Causes of spontaneous SAH include:

• intracranial aneurysm (saccular 'berry' aneurysms)
  • accounts for around 85% of cases
  • conditions associated with berry aneurysms include hypertension,adult polycystic kidney disease
    adult polycystic kidney disease
    You've never been tested on this concept
    You've not yet rated this concept.
    , Ehlers-Danlos syndrome
    Ehlers-Danlos syndrome
    You've never been tested on this concept
    You've not yet rated this concept.
    and coarctation of the aorta
• arteriovenous malformation
• pituitary apoplexy
• mycotic (infective) aneurysms

Classical presenting features include:

• headache
  • usually of sudden-onset ('thunderclap' or 'hit with a baseball bat')
  • severe ('worst of my life')
  • occipital
  • typically peaking in intensity within 1 to 5 minutes
  • there may be a history of a less-severe 'sentinel' headache in the weeks prior to presentation
• nausea and vomiting
• meningism
  meningism
  You've never been tested on this concept
  You've not yet rated this concept.
  (photophobia, neck stiffness)
• coma
• seizures
• ECG changes including ST elevation
  ST elevation
  You've never been tested on this concept
  You've not yet rated this concept.
  may be seen
  • this may be secondary to either autonomic neural stimulation from the hypothalamus or elevated levels of circulating catecholamines

Investigation

• non-contrast CT head
  non-contrast CT head
  You've never been tested on this concept
  You've not yet rated this concept.
  is the first-line investigation of choice
  • acute blood (hyperdense/bright on CT) is typically distributed in the basal cisterns, sulci and in severe cases the ventricular system.
• if CT head is done within 6 hours of symptom onset and is normal
  If subarachnoid haemorrhage is suspected but a CT head done within 6 hours of symptom onset is normal, do not do an LP, consider an alternative diagnosis instead
  You've never been tested on this concept
  You've not yet rated this concept.
  Importance: 73
  • new guidelines suggest not doing a lumbar puncture
    If subarachnoid haemorrhage is suspected but a CT head done within 6 hours of symptom onset is normal, do not do an LP, consider an alternative diagnosis instead
    You've never been tested on this concept
    You've not yet rated this concept.
    Importance: 73
  • consider an alternative diagnosis
• if CT head is done more than 6 hours after symptom onset and is normal
  If subarachnoid haemorrhage is suspected but a CT head done > 6 hours after symptom onset is normal, a lumbar puncture should be done to confirm or exclude the diagnosis
  You've never been tested on this concept
  You've not yet rated this concept.
  Importance: 68
  • do a lumber puncture (LP)
    If subarachnoid haemorrhage is suspected but a CT head done > 6 hours after symptom onset is normal, a lumbar puncture should be done to confirm or exclude the diagnosis
    You've never been tested on this concept
    You've not yet rated this concept.
    Importance: 68
  • timing wise the LP should be performed at least 12 hours
    To detect a subarachnoid haemorrhage the LP should be done at least 12 hours after the start of the headache
    You've never been tested on this concept
    You've not yet rated this concept.
    Importance: 85
    following the onset of symptoms to allow the development of xanthochromia (the result of red blood cell breakdown)
    The presence of red blood cells in CSF may be due to traumatic tap. The presence of breakdown products of RBC in CSF is indicative of a SAH
    You've never been tested on this concept
    You've not yet rated this concept.
    Importance: 28
    .
  • xanthochromia helps to distinguish true SAH from a 'traumatic tap' (blood introduced by the LP procedure)
  • xanthochromia is due to red blood cells in the CSF undergoing haemolysis: haemoglobin → oxyhaemoglobin → bilirubin. Spectrophotometry detects bilirubin and oxyhaemoglobin
    Xanthochromia in the CSF of patients with a subarachnoid haemorrhage is due to the development of bilirubin (following haemolysis) and is best detected by spectrophotometry
    You've never been tested on this concept
    You've not yet rated this concept.
    Importance: 33
  • as well as xanthochromia, CSF findings consistent with subarachnoid haemorrhage include a normal or raised opening pressure
    as well as xanthochromia, CSF findings consistent with subarachnoid haemorrhage include a normal or raised opening pressure
    You've never been tested on this concept
    You've not yet rated this concept.
• if the CT shows evidence of a SAH
  • referral to neurosurgery to be made as soon as SAH is confirmed

After spontaneous SAH is confirmed, the aim of investigation is to identify a causative pathology that needs urgent treatment:

• CT intracranial angiogram
  CT intracranial angiogram
  You've never been tested on this concept
  You've not yet rated this concept.
  (to identify a vascular lesion e.g. aneurysm or AVM)
• +/- digital subtraction angiogram (catheter angiogram)

Management of a confirmed aneurysmal subarachnoid haemorrhage

• supportive
  • bed rest
  • analgesia
  • venous thromboembolism prophylaxis
  • discontinuation of antithrombotics (reversal of anticoagulation if present)
• vasospasm is prevented using a course of oral nimodipine
  Nimodipine is used to prevent vasospasm in aneurysmal subarachnoid haemorrhages
  You've never been tested on this concept
  You've not yet rated this concept.
  Importance: 84
• intracranial aneurysms are at risk of rebleeding and therefore require prompt intervention, preferably within 24 hours
  • most intracranial aneurysms are now treated with a coil by interventional neuroradiologists, but a minority require a craniotomy and clipping by a neurosurgeon
    most intracranial aneurysms are now treated with a coil by interventional neuroradiologists, but a minority require a craniotomy and clipping by a neurosurgeon
    You've never been tested on this concept
    You've not yet rated this concept.

Complications of aneurysmal SAH:

• re-bleeding
  • happens in around 10% of cases and most common in the first 12 hours
  • if rebleeding is suspected (e.g. sudden worsening of neurological symptoms) then a repeat CT
    Subarachnoid haemorrhage: if rebleeding is suspected (e.g. sudden worsening of neurological symptoms) --> repeat CT
    You've never been tested on this concept
    You've not yet rated this concept.
    Importance: 90
    should be arranged
  • associated with a high mortality (up to 70%)
• hydrocephalus
  hydrocephalus
  You've never been tested on this concept
  You've not yet rated this concept.
  • hydrocephalus is temporarily treated with an external ventricular drain (CSF diverted into a bag at the bedside) or, if required, a long-term ventriculoperitoneal shunt
• vasospasm
  vasospasm
  You've never been tested on this concept
  You've not yet rated this concept.
  (also termed delayed cerebral ischaemia), typically 7-14 days after onset
  • ensure euvolaemia (normal blood volume)
  • consider treatment with a vasopressor if symptoms persist
• hyponatraemia
  hyponatraemia
  You've never been tested on this concept
  You've not yet rated this concept.
  (most typically due to syndrome inappropriate anti-diuretic hormone (SIADH
  SIADH is a common consequence of subarachnoid haemorrhage
  You've never been tested on this concept
  You've not yet rated this concept.
  Importance: 74
  ))
• seizures

Important predictive factors in SAH:

• conscious level on admission
• age
• amount of blood visible on CT head

+PassMedicine Notes

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 most common cause of SAH is head injury and this is called traumatic SAH . In the absence of trauma, SAH is termed spontaneous SAH . The rest of this note focuses on spontaneous SAH.

Causes of spontaneous SAH include:

• intracranial aneurysm (saccular 'berry' aneurysms)
• accounts for around 85% of cases
• conditions associated with berry aneurysms include hypertension,adult polycystic kidney disease, Ehlers-Danlos syndrome and coarctation of the aorta
• arteriovenous malformation
• pituitary apoplexy
• mycotic (infective) aneurysms

Classical presenting features include:

• headache
• usually of sudden-onset ('thunderclap' or 'hit with a baseball bat')
• severe ('worst of my life')
• occipital
• typically peaking in intensity within 1 to 5 minutes
• there may be a history of a less-severe 'sentinel' headache in the weeks prior to presentation
• nausea and vomiting
• meningism (photophobia, neck stiffness)
• coma
• seizures
• ECG changes including ST elevation may be seen
• this may be secondary to either autonomic neural stimulation from the hypothalamus or elevated levels of circulating catecholamines

Investigation

• non-contrast CT head is the first-line investigation of choice
• acute blood (hyperdense/bright on CT) is typically distributed in the basal cisterns, sulci and in severe cases the ventricular system.
• if CT head is done within 6 hours of symptom onset and is normal
• new guidelines suggest not doing a lumbar puncture
• consider an alternative diagnosis
• if CT head is done more than 6 hours after symptom onset and is normal
• do a lumber puncture (LP)
• timing wise the LP should be performed at least 12 hours following the onset of symptoms to allow the development of xanthochromia (the result of red blood cell breakdown).
• xanthochromia helps to distinguish true SAH from a 'traumatic tap' (blood introduced by the LP procedure)
• xanthochromia is due to red blood cells in the CSF undergoing haemolysis: haemoglobin → oxyhaemoglobin → bilirubin. Spectrophotometry detects bilirubin and oxyhaemoglobin
• as well as xanthochromia, CSF findings consistent with subarachnoid haemorrhage include a normal or raised opening pressure
• if the CT shows evidence of a SAH
• referral to neurosurgery to be made as soon as SAH is confirmed

After spontaneous SAH is confirmed, the aim of investigation is to identify a causative pathology that needs urgent treatment:

• CT intracranial angiogram (to identify a vascular lesion e.g. aneurysm or AVM)
• +/- digital subtraction angiogram (catheter angiogram)

Management of a confirmed aneurysmal subarachnoid haemorrhage

• supportive
• bed rest
• analgesia
• venous thromboembolism prophylaxis
• discontinuation of antithrombotics (reversal of anticoagulation if present)
• vasospasm is prevented using a course of oral nimodipine
• intracranial aneurysms are at risk of rebleeding and therefore require prompt intervention, preferably within 24 hours
• most intracranial aneurysms are now treated with a coil by interventional neuroradiologists, but a minority require a craniotomy and clipping by a neurosurgeon

Complications of aneurysmal SAH:

• re-bleeding
• happens in around 10% of cases and most common in the first 12 hours
• if rebleeding is suspected (e.g. sudden worsening of neurological symptoms) then a repeat CT should be arranged
• associated with a high mortality (up to 70%)
• hydrocephalus
• hydrocephalus is temporarily treated with an external ventricular drain (CSF diverted into a bag at the bedside) or, if required, a long-term ventriculoperitoneal shunt
• vasospasm (also termed delayed cerebral ischaemia), typically 7-14 days after onset
• ensure euvolaemia (normal blood volume)
• consider treatment with a vasopressor if symptoms persist
• hyponatraemia (most typically due to syndrome inappropriate anti-diuretic hormone (SIADH))
• seizures

Important predictive factors in SAH:

• conscious level on admission
• age
• amount of blood visible on CT head