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Subarachnoid haemorrhage

German: Subarachnoidalblutung

1 Definition

A subarachnoid haemorrhage is an arterial bleeding event in the subarachnoid space. The cause is usually the rupture of (an) intracranial aneurysms or more rarely, of an angioma.

2 Epidemiology

The subarachnoid haemorrhage is a relatively common, neurological emergency case. Women are affected on average more frequently. Peak incidence is between the ages of 40 and 60 years. The incidence rate is about 20/100 000 per year. Spontaneous SAH is in about 5-10% of cases the origin of a stroke, representing about 15,000 new patiens per year.

Approximately 1/3 of the patients die before reaching the hospital, another third die during hospitalisation, or remain permanently disabled. Only 1/3 of patients retain a slight deficit or achieved an approximation of their initial state of physical and mental ability.

3 Aetiology

A subarachnoid haemorrhage can originate traumatically, ie. can arise as a result of injury, or can arise non-traumatically. Cause of non-traumatic intracranial haemorrhages is in 80% of cases a ruptured aneurysm of the Circulus arteriosus Willisi or the distal artery/arteries of the pia mater. The most common sites are:

Approximately 85% of aneurysms are at the front, 15% located at the rear portion of the cirulus arteriosus. The majority of aneurysms arises at bifurcation points of the arterial vessels. Its development is favoured by an embryonic malformation of the tunica media.

Acquired aneurysms are mainly caused by atherosclerosis, bacterial embolism and vasculitis, are rather rare. Arterial hypertension and smoking are the most important risk factors.

Other possible causes of subarchnoidal bleeding events are:

4 Risk factors

Risk factors for subarachnoid haemorrhage include:

5 Pathogenesis

After rupture of the aneurysm or of the AVM massive bleeding into the subarachnoid space leads to the acute increase in intracranial pressure, with a simultaneous reduction of perfusion pressure there. Due to the reduced cerebral blood flow, the patient initially loses consciousness. After a short time, blood flow increases again as part of a reactive response (reactive hyperaemia), whereby the patient can re-emerge from the state of unconsciousness.

Larger blood buildup can cause adhesions in the basal cistern and impair the passage of cerebral fluid, which can lead to hydrocephalus. The leaked blood and its breakdown products in the arteries of the pia mater lead to vasospasms. The chronic constriction of the vessels leads to hypoperfusion and further cerebral damage. The greatest risk for vasospasm exists from 4 to 10 days after the SAH event, for which reason operations are in this period also avoided.

6 Symptomatology

Approximately 25% of patients before the acute subarachnoid haemorrhage have a 'warning bleeding' with violent 'headache' ( 'headache like nothing ever before' ) and 'neck pain' , which merge into pain with a dull, less acute character. Within days, the patient undergoes a further, serious subarachnoid haemorrhage with the following symptoms:

7 Diagnostics

The SAH can be determined by CT or, in the absence of evidence there, by examination of cerebral fluids.

8 Differential diagnosis

Sudden heavy ( "annihilating") headache must always be taken to be suggestive a subarachnoid haemorrhage and it needs to be immediately ascertained whether such has occurred. Given the presence of other symptoms including nausea, vomiting, disturbance of consciousness and neck stiffness, a diagnosis of subarachnoid haemorrhage is quite certain.

However using differential diagnosis, various other causes of headache and increased intracranial pressure should come into consideration. A decompensated occlusive hydrocephalus or defective spinal fluid shunt can provoke similar symptoms. In addition poisoning or metabolic disorders (eg diabetes mellitus, liver disease) can rapidly lead to impaired consciousness with antecedent vomiting. Presence of meningism means meningitis needs to be suspected.

9 Treatment

The severity and the appropriate therapeutic option of SAH is categorised by using the Hunt and Hess classification system.

9.1 Conservative therapy

9.2 Neurosurgical treatment

Prevention of rebleeding by clipping or coiling of the aneurysm.

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