Subarachnoid hemorrhage (SAB) (ICD-10 I60.-: Subarachnoid hemorrhage) describes arterial bleeding into the subarachnoid space (i.e., bleeding outside the brain). The subarachnoid space surrounds the brain (Latin cerebrum) and spinal cord (Latin medulla spinalis or medulla dorsalis) and is filled with cerebrospinal fluid (CSF). It is a cleft space between the arachnoid mater (cobweb skin; middle meninges) and the pia mater (delicate meninges that rest directly on the brain).Intracranial pressure (ICP) increases due to the hemorrhage.
Subarachnoid hemorrhage is one of the intracranial hemorrhages (bleeding in the brain inside the skull).Like epidural hematoma and subdural hematoma, subarachnoid hemorrhage is an extracerebral hemorrhage (outside the skull) and thus should be distinguished from intracerebral hemorrhage (ICB; brain hemorrhage).
In about 85% of cases, a rupture (tear) of an intracranial aneurysm (pathological/diseased bulge of an arterial wall inside the skull) is the cause of subarachnoid hemorrhage.
A distinction is made between traumatic and non-traumatic (spontaneous) subarachnoid hemorrhage based on cause (see “Classification”).
Approximately 5% of apoplectic strokes are caused by a non-traumatic (spontaneous) subarachnoid hemorrhage.
Sex ratio: Women are affected by non-traumatic SAB slightly more often than men.
Frequency peak: non-traumatic SAB occurs in 60% of cases in the age range of 40 to 60 years.
The prevalence (disease incidence) of intracranial aneurysms is 2%.The prevalence for recurrence of SAB over 10 years is approximately 2-3%.
The incidence (frequency of new cases) of nontraumatic SAB is approximately 6-9 cases per 100,000 population per year (in Central Europe and the United States). Traumatic SAB is found in approximately 40% of all severe traumatic brain injuries.
Course and prognosis: Subarachnoid hemorrhage represents a frequent neurological emergency! Characteristic are severe annihilation headaches, which the patient has never experienced before (maximum headache is reached within seconds). If SAB is suspected, the patient must be hospitalized immediately so that appropriate diagnostic measures can be taken.The most significant complication is recurrent bleeding (rebleeding) – within the first 24 hours – as well as pulmonary (affecting the lungs) and cardiogenic (affecting the heart) complications. The patient should be transferred promptly to a neurovascular center with neurosurgical care options after confirmation of SAB.Prognosis depends on age, severity of hemorrhage, location and size of the aneurysm and is usually unfavorable.10-25 % of those affected die before reaching the hospital. Approximately one-third of survivors subsequently require nursing care and only one-third are able to live independently.
The 30-day lethality (mortality based on the total number of people with the disease) is approximately 35%.The risk of rerupture of an unexpiated aneurysm is 4% on the first day and approximately 1-2% in the first month. The lethality for re-rupture of an untreated cerebral aneurysm and second hemorrhage is 70-90%.
