Intracranial Aneurysm and Subarachnoid Haemorrhage (SAH)
Essentials
Subarachnoid haemorrhage (SAH) should be suspected however slight the symptoms, and the diagnosis confirmed with an urgent CT scan.
The patient should be transferred without delay to an appropriate hospital for neurosurgical treatment, relevant intensive care and cerebral angiography.
A ruptured intracranial aneurysm must be closed (microsurgical clipping or an endovascular approach) during the acute phase to prevent rebleeding.
Patients with SAH often have sequelae in the form of neurological, psychiatric and psychosocial problems.
In general
An aneurysm is almost always a saccular pouch in a branch of the large cerebral arteries in the region of the circle of Willis.
The aneurysm is located on the brain surface in the cerebrospinal fluid space and primarily bleeds into this space (subarachnoid haemorrhage).
A patient who survives a primary bleed is immediately at risk of a new bleed because there is a threat that the brittle thrombus that obstructs the bleeding site may yield.
SAH may damage the brain by, e.g.
acute damage (bleed into the parenchyma, acute hydrocephalus, increased intracranial pressure, brain ischaemia)
subacute ischaemic brain damage (”vasospasm”)
late damage (communicating hydrocephalus).
An inflammatory reaction may develop in the aneurysm wall, leading to rupture.
Epidemiology
The lifetime incidence of intracranial aneurysms in the general population is 2-3%.
In Finland (population 5.5 million), about 100 000 individuals have unruptured intracranial aneurysms, the majority of which will never cause any symptoms (median diameter only 4 mm) and will not be detected.
About 40% of the patients die of the sequelae of the bleed within 12 months.
In Finland, the median diameter of ruptured aneurysms is 7 mm.
Large size and irregular shape of the aneurysm increase the bleeding risk.
The prevalence of SAH is focused on the working-age population (median age 55 years), unlike in cerebral infarction and haemorrhage.
Particularly young patients diagnosed with aneurysm may develop new aneurysms during long-term follow-up.
Acquired risk factors include
age
smoking (45% of unruptured and 42% of ruptured patients at the time of diagnosis)
excessive alcohol intake
hypertension (73% of unruptured and 63% of ruptured patients).
Congenital risk factors include
family history of aneurysms (28% of unruptured and 14% of ruptured patients)
polycystic kidney disease (1% of all SAH cases).
The concordance of monozygotic twins in relation to SAH is low.
Signs and symptoms
The characteristic symptom of SAH is a sudden explosive, severe and relentless headache which
is often associated with nausea and vomiting, nuchal rigidity and photosensitivity
may be associated with localising symptoms (limb paralysis, speech difficulties, diplopia)
may be associated with convulsions and loss of consciousness.
The bleed only last for a few seconds but the blood released to the CSF circulation irritates the meninges and causes headache that may last up to several days.
On presentation the patient's condition may range from being alert and orientated to deeply unconscious.
A patient with mild symptoms may seek medical appointment several days after the event.
Up to one third of patients have had an earlier, usually initially undiagnosed, premonitory minor leak (”a sentinel bleed”) with few symptoms.
SAH in a patient known to have migraines, or whose symptoms are mild, might remain undiagnosed at the first appointment.
SAH and other causes of blood in the cerebrospinal fluid
Primary SAH
Ruptured intracranial aneurysm (80%)
Perimesencephalic haemorrhage (10%) - good prognosis and quick recovery
Bleed from an arteriovenous or other blood vessel malformation (5%)
Spinal SAH (rare)
No site of bleeding identified by neuroradiology (15%)
Angiography is usually repeated within one week - an aneurysm that has bled may then become visible, although in the initial examination it did not fill with contrast medium.
Secondary SAH
Spontaneous intracerebral haemorrhage (ICH) may bleed into the ventricles of the brain and the cerebrospinal fluid space.
Even mild brain contusion may be the cause of blood in the cerebrospinal fluid.
In an acute brain injury, lumbar puncture is contraindicated and of no benefit.
Other causes:
Any condition with bleeding diathesis and anticoagulant treatment
Vascular diseases
Inflammatory diseases
CNS tumours (rarely)
Lumbar puncture induced bleeding
Lumbar puncture is technically difficult and a small vein may be punctured Lumbar Puncture
Detecting SAH by CT scanning
SAH should be diagnosed or excluded by emergency CT scanning.
In a CT scan, an acute bleed will show up as light areas in the cerebrospinal fluid spaces in the sellar region, Sylvian fissure, interhemispheric spaces or the posterior cranial fossa.
Blood may also be noted in the ventricles.
The bleeding may extend to the brain parenchyma or under the dura mater.
A normal CT scan does not exclude SAH - particularly if several days or weeks have lapsed from the bleed.
A lumbar puncture should be carried out if SAH is clinically possible but the CT scan result is negative.
Spectroscopic (degradation products of haemoglobin) or cytological analysis of cerebrospinal fluid (siderophages) may reveal a previous SAH.
Treatment in the acute phase and transfer of the patient
Clinical suspicion of SAH will indicate an immediate referral to a hospital for CT scanning.
If SAH is confirmed, a neurosurgical unit is to be consulted immediately.
A patient with SAH should be admitted to a neurointensive care unit. The patient must not be treated on a general ward.
The neurosurgeon on call should be contacted by telephone, and the CT images sent to him/her electronically.
The patient should be transferred immediately (especially in the case of a large haematoma, poor general condition, hydrocephalus) to the neurosurgical unit and neurointensive care.
Medical care during transfer should be discussed with the accident and emergency doctor or the doctor responsible for the intensive care unit at the receiving hospital, particularly if the patient's conscious level is affected or is deteriorating.
The escort must have sufficient skills in emergency medical care.
Optimal airway management
Aneurysm(s) must be identified or excluded with four-vessel angiography at the neurosurgical unit.
CT angiography is the examination of choice.
Catheter angiography (digital subtraction angiography DSA), if indicated
The Kuopio Intracranial Aneurysm Database http://www.uef.fi/ns maintained by the University of Eastern Finland (UEF) and Neurosurgery of NeuroCenter, Kuopio University Hospital (KUH) in Kuopio, Finland, includes data of 4 500 patients living in Central and Eastern Finland. Data collection was started in 1980.
27% of the SAH patients admitted to the Kuopio University Hospital died of their disease within 12 months.
Risk factors included unconsciousness, high age, intracerebral haemorrhage, intraventricular haemorrhage, acute hydrocephalus
Mortality was 92% among patients who were unconscious and responded to pain with extension at arrival.
Mortality was as low as 3.5% among patients who were fully conscious and in good condition at arrival.
In long-term follow-up after 12 months there still was a clear over-mortality among the SAH survivors as compared to the general population.
The risk of hydrocephalus requiring placement of a shunt was 18%.
The risk of epilepsy was 13%.
Risk factors included acute onset, poor condition at arrival, intracerebral haemorrhage.
The risk of depression is about 29%.
Vitreous haemorrhage (Terson syndrome) may occur during the acute phase with a subsequent effect on the patient's eyesight.
The psychological and socio-economical well-being of those suffering from sequelae of SAH has not been properly researched.
Of patients living independently after recovery from SAH, 67% report of fatigue, 32% of anxiety and 23% of depression.
Screening of relatives
Cerebral aneurysm belongs to multifactorial illnesses that typically accumulate to varying extent in a family.
18% of patients have a family history of aneurysms.
For the moment there is no genetic test to assess the aneurysm risk (except for polycystic kidney disease).
A clinical geneticist may be consulted if required for providing information and for relieving anxiety.
Screening of family members (siblings, children, parents)
If two first-degree family members have a history of an unruptured aneurysm or aneurysmatic SAH
The primary imaging method being MR angiography.
Treatment of unruptured aneurysm
An unruptured aneurysm will not close on its own.
The number of patients referred for treatment evaluation is significant because
28% of patients with SAH are found to have additional, unruptured aneurysms
the screening of families with a history of aneurysms is increasing
aneurysms are found in brain imaging carried out for other reasons.
A team of specialists will consider the expected benefit of prophylactic closing of the aneurysm. Aspects relevant for the decision include the patient's life expectancy, other illnesses, the size of the aneurysm and its location in the arterial tree of the brain, irregularity of its shape, growth during follow-up, psychological factors, etc.
Being aware of an unruptured aneurysm may cause the patient a mental burden that is difficult to bear without closing the aneurysm.
Prophylactic treatment
Cessation of smoking
Treatment of hypertension
73% of unruptured and 63% of ruptured patients used antihypertensive medication before the aneurysm diagnosis or thereafter
10% have secondary hypertension, which should be taken into account if conventional pharmacotherapy is not effective.
Avoidance of excessive alcohol consumption
No specific prophylactic treatment exists as either to prevent the generation, growth or rupture of intracranial aneurysms.
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